Tesi: "3D woven organic composites"

1

Orenes, Balaciart Salvador. "In Situ Characterization by Acoustic Emission and X-Ray μ-Computed-Tomography of the Effects of Temperature, Aging, and Multi-Axial Loads on Damage Onset in 3D Woven Organic Matrix Composites for Aeronautical Applications". Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2024. http://www.theses.fr/2024ESMA0010.

Testo completo

Abstract (sommario):

Le domaine du génie aéronautique a connu des avancées considérables au cours des dernières décennies en science des matériaux. Les composites organiques tissés en trois dimensions à matrice de carbone (3DOMC) sont de plus en plus utilisés comme éléments de parties structurelles proches des moteurs d'avions et dans les pales de ventilateur de moteurs aéronautiques Ces matériaux sont donc sollicités pour fonctionner dans des gammes de haute performance, soumis à des sollicitations mécaniques multi-axiales à différentes températures et exposés à des cycles thermiques chaud/froid. Bien qu'il existe une littérature substantielle sur les effets de telles sollicitations sur le comportement à la fracture et les mécanismes d'endommagement ultime des 3DOMC, les études sur les mécanismes de l’amorçage de l’endommagement sont limitées. Cette lacune est particulièrement critique puisque l’amorçage de l’endommagement dicte l'usabilité de ces composants ; du point de vue opérationnel, aucun dommage n'est permis en service dans ces parties. Ce travail vise à développer une nouvelle méthodologie expérimentale pour caractériser le début de l’endommagement dans les 3DOMC pour différentes sollicitations multi-axiales rencontrées en service. Pour ce faire, un test in situ a été conçu couplant la Micro-Tomographie (μ-CT) et l'Émission Acoustique (AE), identifiant avec succès l'initiation de l’endommagement multi-axial lors d'un test de traction et de flexion-compression excentrique (ECB) sur des échantillons en axe et hors axe. L'effet de la température a été abordé via un test in situ mettant en œuvre la nouvelle méthodologie développée à haute température (120ºC) et basse température (-30ºC) ; il a été constaté que les mécanismes d'initiation de dommage dépendent fortement de la température. L'effet du cyclage thermique entre 120ºC et -55ºC sur le début du dommage a été caractérisé par AE et ex situ (μ-CT). De plus, la propagation du dommage jusqu'à 1000 cycles a été caractérisée en détail dans la méso-structure tissée en 3D. Enfin, la dégradation par cyclage thermique et le vieillissement sur le début du dommage sont étudiés dans un test de traction in situ statique
The field of aeronautical engineering has seen considerable advancements over the past decades in materials science. Carbon fibre Three-Dimensional Woven Organic Matrix composites (3DOMC) are increasingly used as elements of structural parts close to aircraft engines and in aero-engine fan blades. These materials are therefore requested to operate in high-performance ranges subjected to multi-axial mechanical solicitations at different temperatures and exposed to cold/hot thermal cycling. Although there is substantial literature on the effects of such solicitations on the fracture behavior and ultimate damage mechanisms of 3DOMC, there is a limited study on the initial damage mechanisms. This gap is particularly critical since the onset of damage dictates the usability of such components; from operational standpoint, no damage is permissible in service in these parts. This work aims to develop a novel experimental methodology to characterize the onset of damage in 3DOMC for different multi-axial solicitations encountered in-service.To achieve this, an in situ test has been designed coupling μ-Computed Tomography (μ-CT) and Acoustic Emission (AE), successfully identifying multi-axial damage initiation during tensile test and Eccentric Compression Bending (ECB) in in-axis and off-axis specimens. The effect of temperature has been addressed via in situ test implementing the new developed methodology test at high (120ºC) and low (-30ºC) temperature; it has been found damage initiation mechanisms are strongly dependent on temperature.The effect of thermal cycling between 120ºC and -55ºC on damage onset has been characterized by AE and ex situ (μ-CT). Further, damage propagation up to 1000 cycles has been characterized in detail in the 3D woven meso-structure. Finally, thermal cycling degradation and ageing on damage onset is investigated in static in situ tensile test

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Stig, Fredrik. "3D-woven Reinforcement in Composites". Doctoral thesis, KTH, Lättkonstruktioner, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-70438.

Testo completo

Abstract (sommario):

Composites made from three-dimensional (3D) textile preforms can reduce both the weight and manufacturing cost of advanced composite structures within e.g. aircraft, naval vessels and blades of wind turbines. In this thesis composite beams reinforced with 3D weave are studied, which are intended for use as joining elements in a boltless modular design. In practice, there are a few obstacles on the way to realise the modular boltless design. There is lack of experimental data and more importantly, lack of experience and tools to predict the properties of composites reinforced with 3D-weaves. The novel material will not be accepted and used in engineering applications unless proper design methods are available. The overall aim of this thesis is to remedy these deﬁciencies by generating data, experience and a foundation for the development of adequate design methods. In Paper A, an initial experimental study is presented where the mechanical properties of 3D-weave reinforced composites are compared with corresponding properties of 2D-laminates. The conclusion from Paper A is that the out- of-plane properties are enhanced, while the in-plane stiffness and strength is reduced. In Paper B the inﬂuential crimp parameter is investigated and three analytical models are proposed. The warp yarns exhibit 3D crimp which had a large effect the predicted Young’s modulus as expected. The three models have different levels of detail, and the more sophisticated models generate more reliable predictions. However, the overall trends are consistent for all models. A novel framework for constitutive modelling of composites reinforced with 3D-woven preforms is presented in Papers C and D. The framework enables predictive modelling of both internal architecture and mechanical properties of composites containing 3D textiles using a minimum of input parameters. The result is geometry models which are near authentic with a high level of detail in features compared with real composite specimens. The proposed methodology is therefore the main contribution of this thesis to the field of composite material simulation. Paper E addresses the eﬀect of crimp and diﬀerent textile architectures on the mechanical properties of the ﬁnal composite material. Both stiﬀness and strength decreases non-linearly with increasing crimp. Furthermore specimens containing 3D-woven reinforcement exhibit non-linear stress-strain behaviour in tension, believed to be associated with relatively early onset of matrix shear cracks.

QC 20120131

Gli stili APA, Harvard, Vancouver, ISO e altri

3

El, Said Bassam Sabry Fawzy. "Integrated multi-scale modelling of 3D woven composites". Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720811.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

King, Robert Scott. "Damage tolerant 3D woven technical textiles in reinforced composites". Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516537.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Dai, Shuo. "Mechanical characterisation and numerical modelling of 3D woven composites". Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16221.

Testo completo

Abstract (sommario):

Three-dimensional woven composites were developed to improve the through-thickness properties which conventional two-dimensional laminate composites currently lack. However, these textile composites generally show lower in-plane mechanical properties due to fibre crimping, and also encounter modelling difficulties due to the complex geometries. In this thesis, the static and fatigue mechanical behaviour of several types of 3D woven composites were experimentally characterised, the influence of the weave architecture on the mechanical performance was revealed, and meso/macro scale numerical models with improved failure criteria were developed to simulate the tensile behaviour of the 3D woven composites. The mechanical characterisation was conducted on six woven structures under tension, compression, and flexural loading, and were also carried out on two weaves under open-hole quasi-static tensile and fatigue loading. Digital image correlation and thermoelastic stress analysis were used to characterise the strain and damage development during static and fatigue loading. The testing results showed that the angle-interlock weave W-3 had higher in-plane quasi-static properties, lower notch sensitivity, higher fatigue damage resistance, but lower delamination resistance. The meso-scale model was developed on the unit cell of the woven structure and the macro-scale model (mosaic model) was created on the testing samples. Both un-notched and notched tensile behaviour were modelled for the angle-interlock weave W-3 and a one-by-one orthogonal weave W-1, and the difference between the predicted and experimental results was within 16% for the unit cell models and within 21% for the mosaic models. A modified failure criterion was developed to better simulate the damage behaviour of the notched macro-scale model and improved the predicted notched strength by 10-20%. Whilst further experimental investigation and improvement in the modelling techniques are still required, the data presented in this thesis provided an essential update for the current 3D woven composites research, and the presented models offered the potential to predict the damage behaviour of large 3D woven structures.

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Arshad, Mubeen. "Damage tolerance of 3D woven composites with weft binders". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/damage-tolerance-of-3d-woven-composites-with-weft-binders(2b1435bc-fdb7-47c3-b555-ca5ea2883b4b).html.

Testo completo

Abstract (sommario):

3D woven composites, due to the presence of through-thickness fibre bridging, have the potential to improve damage tolerance and at the same time to reduce the manufacturing costs. However, the ability to withstand damage depends on weave architecture as well as the geometry of individual tows. A substantial amount of research has been performed to understand in-plane properties as well as the performance of 3D woven composites exposed to impact loads, but there is limited research on the damage tolerance and notch sensitivity of 3D weaves and no work is reported on the damage tolerance of 3D weaves with a weft binding pattern. In view of the recent interest in 3D woven composites, the influence of weft binder on the tensile, open hole tensile, impact resistance and subsequent residual compressive strength properties and failure mechanisms of 3D woven composites was investigated against equivalent UD cross-ply laminate. Four different 3D woven architectures; layer-to-layer, angle interlocked, twill angle interlock and modified angle interlock structures were produced under identical weaving conditions. All the above mentioned tests were performed in both the warp and weft directions on 3D woven and UD cross-ply laminates. Stress concentration and yarn waviness due to through-thickness reinforcement led to lower mechanical properties compared with the UD cross-ply laminate. However, improved in-plane and damage tolerance properties of 3D woven composites under tensile loads were achieved by modifying the weave architecture. The influence of the weave architecture and binder yarn orientation on the notch insensitivity and damage tolerance of 3D woven composites was less significant for compressive loads. Despite the lower undamaged compression strength of 3D woven structures, their residual compressive strength was found to be superior to their equivalent UD cross-ply laminates. The lower rate of strength reduction in the 3D woven fabrics laminates was attributed to a crack bridging mechanism, effectively inhibiting delamination propagation.

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Green, Steven Daniel. "Modelling preform consolidation and its effects in 3D woven composites". Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705451.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Stig, Fredrik. "An Introduction to the Mechanics of 3D-Woven Fibre Reinforced Composites". Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10235.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Manjunath, R. N. "Design and development of 3D woven complex hollow structures and their composites for energy absorbent structures". Thesis, IIT Delhi, 2019. http://eprint.iitd.ac.in:80//handle/2074/8059.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Broderick, John. "Advancement of 3D woven composites through embedded in situ strain measurement". Thesis, University of Ulster, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546738.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Poole, Matthew C. "Fatigue damage development in 3D woven glass and glass/carbon composites". Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845964/.

Testo completo

Abstract (sommario):

A number of studies have been conducted on 3D non-crimp orthogonal woven composites, but their industrial application is still in its infancy. 3D woven composites show increased through-thickness strength, reducing delamination damage, which is often a key failure mechanism for composites under various loading conditions, especially fatigue. This work investigates the fatigue performance and damage development in a 3D non-crimp orthogonal woven composite consisting of three weft tow layers, two warp tow layers, and a through-thickness z-binder that interlaces along the warp-direction. While the properties of carbon fibres are generally superior to glass fibres, they are more expensive. Therefore, it is of interest to see if the fatigue performance of a glass fibre 3D orthogonal weave can be improved via selective hybridisation using a small amount of carbon fibres. Initial work began on a commercial all-glass 3D orthogonal weave called 3D-78, which was produced by 3TEX. It was found that quasi-static tensile mechanical properties were the same for both warp and weft loading directions, but when loaded in tension-tension fatigue, the warp direction had longer fatigue lifetimes than the weft-direction. The crack density was lower in warp-direction specimens as a result of greater micro-delamination growth blunting stress concentrations around the tips of matrix cracks. The micro-delamination damage in warp-direction fatigue specimens showed a shield-like shape (not previously observed), i.e. wider along one side and narrowing to a point on the other side; where delamination was restricted (at the pointed end), fibre fractures occurred in the adjacent warp tow. The pointed portion of the micro-delamination corresponded to proximity to a z-binder crown. Other damage that was common to both loading directions (warp and weft) included: transverse cracks in transverse tow and resin-rich regions, z-binder debonding, and longitudinal tow splitting cracks. No obvious failure sites were noted for weft-direction fatigue loading. The second material used, 3DMG, was manufactured by the University of Manchester. This material was produced with two different z-binder tensions. The initial z-binder tension (3DMG-T1) resulted in a higher tensile modulus and strength-to-failure, and lower strain-to-failure, for the warp-direction, while the tensile fatigue properties of both directions were similar. Increasing the z-binder tension (3DMG-T2) reduced the tensile modulus and increased the strain-to-failure of the warp-direction, with these properties now similar in both loading directions; the tensile strength for both loading directions remained similar. However, the fatigue performance of the warp-direction was observed to increase with increased z-binder tension, while the weft-direction remained the same. The damage that developed in both materials was similar to the damage in 3D-78, and remained practically the same regardless of z-binder tension, though the energy dissipated per cycle for warp-direction specimens was higher in 3DMG-T1, which corresponds well with the lower number of cycles to failure. The final material tested was a University of Manchester hybrid 3D non-crimp orthogonal woven composite, termed 3DMHyb; here the glass fibre z-binder was replaced with carbon fibre; the z-binder tension used here was the same as 3DMG-T2. Generally, the quasi-static properties of this hybrid material were similar in both loading directions, with the exception of the tensile modulus which was approximately 10% higher, indicating that the carbon fibre z-binder may influence low strain properties. Additionally, the properties of 3DMHyb remained similar to 3DMG-T2. For fatigue performance, However, the fatigue lifetime to failure appeared to increase by a factor of just over 2 at lower peak stress/initial peak strains for the hybrid warp-direction specimens. Again, the energy dissipation per cycle was lower for specimens that had larger number of cycles to failure, in this case the hybrid specimens. Damage development also remained similar between the 3DMG-T2 and 3DMhyb specimens, indicating that the extension of fatigue life noted in 3DMHyb may be the result of the carbon fibre z-binder supressing the development of damage mechanisms leading to ultimate failure of the specimens.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Waterton, Taylor Lindsey. "Design and manufacture of 3D nodal structures for advanced textile composites". Thesis, University of Manchester, 2007. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:151244.

Testo completo

Abstract (sommario):

Traditional weaving technologies have been utilised over the past twenty-to-thirty years in producing woven textile components that meet engineering requirements through the interlacement of high performance yarns such as carbon, glass and Kevlar. The end performance properties and lightweight characteristics of these fabrics have been adapted within the development of both flat multilevel and shaped configurations for the composites industry. The purpose of the present research required the employment of conventional weaving technologies with limited modifications for the production of 3D woven textile preforms in a variety of truss like configurations; therefore, generating a generic procedure for all yarn combinations and strut and node dimensions for production on dissimilar jacquard looms. The ultimate driving force behind the research was to produce a truss like configuration for the aerospace industry incorporating the design criterion of solid and hollow woven counterparts. This would enable the end truss configuration to have two functions; the first being a lightweight structure by the elimination of bonding applications, through the utilisation of a fully integrated fabrication process; secondly to incorporate hollow struts for a novel storage solution.

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Fergusson, Alexander D. "Evaluating the mechanical behaviour of orthotropic 3D woven carbon fibre reinforced composites". Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6146.

Testo completo

Abstract (sommario):

Laminated composites are increasingly employed in a variety of industries ranging from Aerospace to Wind Power. The high specific stiffness and strength of these materials renders their wider application advantageous in many fields. However, the broader implementation of such composites is frequently restrained by their poor impact resistance and damage tolerance. Even events as innocuous as a dropped tool can impart significant damage to such materials. Such damage can lead to drops in the strength and stiffness that are unacceptable for many applications, particularly those in Aerospace. 3D woven composites present a possible means of improving the impact resistance and damage tolerance of composite materials. The incorporation of out-of-plane fibres, transversely passing through layers of in-plane fibres, is the means by which this improvement in performance is obtained. This body of work presents an investigation into the behaviour of three dimensionally woven carbon fibre composites. Specifically, the subject composite fabric had an orthogonally woven three dimensional structure. The novelty of these materials is such that knowledge and understanding of their mechanical behaviour is very limited. The purpose of this work was to remedy this through experimental and analytical analysis of these composites. The 3D woven materials were characterized experimentally using a variety of techniques. In addition to evaluating the material experimentally, analytical methods were also used. Current analytical methods were found to be deficient in their incapacity to account for in-plane crimp on a micro scale. As a result a new micro scale approach for predicting the stiffness and strength of these 3D woven materials was developed. The composites used for this thesis were tested using a variety of means. The range of test methodologies used subjected the materials to in-plane, out-of-plane, dynamic and quasi- static loadings. Techniques used included; tension, shear, impact, compression after impact, bolt shear out and bearing pull through. Other means implemented included microscopy, C-scanning and Digital Image Correlation. In addition, conventional composites made from unidirectional pre-pregs or Non-Crimp Fabrics (NCFs) were tested to provide a basis for comparison. Analysis and prediction of the behaviour of conventional laminated composites can be performed using a variety of methods. While the range of methods available is broad, they commonly use individual plies of composite as their fundamental building blocks. This is both convenient analytically and experimentally as the properties of such individual lamina may be found with reasonable ease. However, 3D woven composites are integrated laminates due to the out‐of‐plane fibres they possess. As a result, the accuracy of conventional experimental or analytical methods for evaluating these materials is likely to be poor. In order to gain a better understanding of the behaviour of these 3D woven materials a new micromechanics model was developed. In contrast to other available methods, this micromechanics approach examines the effect of crimp at the fibre level. The method proposed is also distinct in its capability of simultaneously accounting for varying crimp across and along a section of composite.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Buchanan, Saul. "Models to Predict the Geometric and Elastic Stiffness Properties of 3D Woven Composites". Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515431.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Turner, Paul. "Deformation and collapse of orthogonal 3D woven composites : quasi-static and impact loading". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32732/.

Testo completo

Abstract (sommario):

This thesis presents an experimental and numerical investigation undertaken in order to develop the understanding of the behaviour of orthogonal 3D woven composites under quasi-static tension/compression, out-of-plane bending and dynamic soft and multi-hit ballistic impact load cases. Focus is given to the deformed configuration of samples, and to the initiation and propagation of damage within the material. The damage mitigation properties of the through-the-thickness (TTT) reinforcement are highlighted throughout. A pressurised gas gun test system was developed at the University of Nottingham in order to undertake the soft and ballistic impact tests upon 3D woven composite samples. Experimental and numerical comparisons are made to similar UD-laminate composite materials. An established continuum damage mechanics framework is employed for numerical modelling of the quasi-static and soft impact load cases, allowing for further insights into the experimental results. A review of the efficacy of the numerical modelling strategy is presented, alongside a study on the influence of the TTT reinforcement on the out-of-plane static and dynamic response of the material. The numerical modelling strategy is then adapted for ballistic impact events. A numerical study is conducted on the multi-hit ballistic impact properties of orthogonal 3D woven composites, the first of its kind. Comparisons are made between experimental ballistic impact experiments and numerical calculations.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Kong, Weiyi. "Macro-scale modelling of the impact response of 3D woven composites for aerospace applications". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35756/.

Testo completo

Abstract (sommario):

The objective of this work is to develop a reliable simulation methodology that can be applied to predict the impact response of the components made with 3D textile composites in aero engine applications. Textile composites are excellent candidate materials for the design of aero engine fan containment casings, which are required to sustain the high velocity impact during a fan blade out (FBO) event. This work is focused on a particular form of 3D woven textile composites, in which reinforcement through the thickness is provided by the interlocking weft or warp yarns. An extensive experimental characterisation was conducted for the composites with four different types of reinforcement. The in-plane mechanical properties under the quasi-static tensile, compressive and shear loadings were obtained. The compressive properties at high strain rate were determined in split Hopkinson pressure bar tests. In additional to that, ballistic impact tests were conducted with these composite materials to study their response to high velocity impact loads. The properties determined in the mechanical tests were employed to specify the input data for a commercially available material model in the finite element (FE) software, LS-DYNA. The model was validated by simulating the ballistic impact tests. Good agreement between the predictions and the experimental results was ensured. Once validated, the material model was applied in a range of parametric studies. Since the plate impact tests cannot fully represent the complexity of the FBO event, effects of the projectile shape, the impact obliquity, the target size and the target curvature on the impact performance were investigated by means of parametric studies. To ease the simulation cost encountered during the modelling of a large casing structure, mixed element type analysis (META) was employed for its FE models, where the computationally costly solid elements were coupled with simpler shell elements. The predictive capability of the META models was assessed by comparing their predictions with those of the corresponding solid-element-only models. The study has shown that this method can substantially reduce the simulation time without compromising the accuracy of predictions.

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Rudov-Clark, Shoshanna Danielle, e srudov-clark@phmtechnology com. "Experimental Investigation of the Tensile Properties and Failure Mechanisms of Three-Dimensional Woven Composites". RMIT University. AEROSPACE, MECHANICAL AND MANUFACTURING ENGINEERING, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080808.115853.

Testo completo

Abstract (sommario):

This PhD thesis presents an experimental investigation into the tensile properties, strengthening mechanics and failure mechanisms of three-dimensional (3D) woven composites with through-the-thickness (z-binder) reinforcement. 3D composites are being developed for the aerospace industry for structural applications in next-generation aircraft, such as wing panels, joints and stiffened components. The use of 3D woven composites in primary aircraft structures cannot occur until there has been a detailed assessment of their mechanical performance, including under tensile loading conditions. The aim of this PhD project is to provide new insights into the in-plane tensile properties, fatigue life, tensile delamination resistance and failure mechanisms of 3D woven composites with different amounts of z-binder reinforcement. Previous research has revealed that excessive amounts of z-binder reinforcement dramatically improves the tensile delamination toughness, but at the expense of the in-plane structural properties. For this reason, this PhD project aims to evaluate the tensile performance of 3D woven composites with relatively small z-binder contents (less than ~1%). The research aims to provide a better understanding of the manufacture, microstructure and tensile properties of 3D woven composites to assist the process of certification and application of these materials to aircraft structures as well as high performance marine and civil structures.

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Badawi, Said Sobhey. "Development of the Weaving Machine and 3D Woven Spacer Fabric Structures for Lightweight Composites Materials". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1195729741274-93895.

Testo completo

Abstract (sommario):

The need for innovative lightweight materials are rapidly increased in the recent years, owing to their cost-effective, high-strength, environmentally-sound use of materials and process technologies, in addition to that they reduce the weight of a product. The characteristics of 3D-spacer fabrics as one of the most important lightweight materials in future are multifaceted not only owing to its extremely light materials, but also because of exceptionally high stiffness to weight ratio compared to other constructions. It is also one possible method for improving the properties of fabric-reinforced composites. It can enhance the through-the-thickness properties, such as shear strength, dimensional stability, damage, tolerance, and fracture toughness that are critical for many structural applications. Spacer fabric has been employed in high-technology applications because of its critical mechanical properties related to high tensile strength, tear strength and stiffness. Furthermore, its multidirectional structures allow with more reinforcement along the thickness direction leading to an increase in stiffness and strength properties. The fundamental aim of this thesis exists in the development of a new kind of woven spacer fabrics for the light weight composites materials, in an effort to weave spacer fabrics that can not be realized with the old technology which are mentioned above. Therefore, the work in brief focuses on two main goals: 1. Development of a new kind of spacer fabrics for composites in the lightweight constructions. 2. Development of special devices of a narrow weaving machine for standing the process of the new kind of spacer fabrics production. The slippage strength test had to be carried out for the floated warp yarns through the ground fabrics by using different elements of woven fabric structures variables represented in different fabric constructions, different weft densities and different repeats of constructions by using different materials. The importance of this test related to the backward-movement of the floated warp yarns which is the crucial stage in the weaving process of spacer fabrics during the backward-movement. The results of this test determine the required forces for the backward-movement, on the other side it is the best method to observe the behavior of structure elements during the backward movement. The results of the slippage strength had been statistically analyzed, and the weaving process for the spacer fabrics had been achieved. It was concluded that the best properties for the woven spacer fabrics and the optimum case for the weaving process on the test weaving machine had been achieved when the following items are realized: Development of the narrow weaving machine is closed in assisting operations, let-off and take-up and enhancement for take-up processes. Extra let-off and take-up devices must be constructed at the weaving machine. Extra let-off device has to be used for controlling the floated warp yarns of ground fabrics. On the other side, extra take-up and the developed take-up devices have to be used for controlling the woven spacer fabrics. The experimental results give fundamental knowledges for the next steps in research and development of woven spacer fabrics made of high-performance yarns on the wide weaving machine
Die Ziele der Arbeit bestanden in der Entwicklung der Geometrie der Spacer Fabrics und der notwendigen Falteneinrichtung an der Bandwebmaschine. Spacer Fabrics werden ausschließlich aus zwei Deckflächen, die durch eingewebte Stege verbunden sind, gefertigt. Zur Entwicklung der Spacer Fabrics muss eine Doppelnadel-Bandwebmaschine mit zwei Webfächern eingesetzt werden. Für die Faltenwebeinrichtung werden der entwickelte Extra-Kettablass und der Extra-Abzug benötigt. Der Antrieb und die Steuerung des Extra-Abzuges erfolgen durch einen Synchronantrieb und der Antrieb und die Steuerung des Extra-Ablasses durch Pneumatik.Eine frei programmierbare Steuerung der Faltenwebeinrichtung ermöglicht eine sichere und optimierte Synchronisation zwischen Webprozess und Faltenbildung. Im Ergebnis einer systematischen Strukturentwicklung von Spacer Fabrics und der Simulation ihrer günstigen Herstellung mittles eines speziell entwickelten Slippage Strength Tests werden die optimalen Strukturen ermittelt. Die experimentellen Untersuchungen bringen grundlegende Erkenntnisse für die folgenden Forschungsschritte zur Entwicklung von gewebten Spacer Fabrics mit Hochleistungsgarnen auf Doppelgreiferwebmaschinen

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Adluru, Hari Kishore. "A Novel Hip Implant Using 3D Woven Composite Material – Design and Analysis". FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2318.

Testo completo

Abstract (sommario):

The present research focuses on analyzing the possibility of implementing three dimensional woven composite (3DWC) materials in hip implants. The integration of 3DWCs in hip implants has the possibility to both extend the life-time and improve patient outcomes; by spatially varying mechanical properties to meet both biological needs as well as required mechanical loading. In this study, the bulk material properties of 3DWCs were varied based on woven composite architecture and determined using physics based models, which reflect the realistic geometries of fibers in compaction and preform. The multi-digital chain method combined with Extended Finite Elemental Analysis (XFEA) are adopted in this micro-analysis for composite design. Four different woven architectures with a combination of different existing biocompatible fiber and resins are considered in this study. The main objective is to assess the mechanical response of these biocompatible materials in the design of 3D woven architectures and determine their ability to match the required modulus at different regions of a hip implant. Results obtained show 3DWCs are viable candidates for this application. Multiple architectures and materials chosen, were able to achieve the desired mechanical response. Additional studies can use these results as a starting point and framework for further mechanical and biological testing.

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Yu, Bo. "Damage characterisation of 3D woven glass-fibre reinforced composites under fatigue loading using X-ray computed tomography". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/damage-characterisation-of-3d-woven-glassfibrereinforced-composites-under-fatigue-loading-using-xraycomputed-tomography(e4d6ee91-e3f5-4b33-b9e7-4367cbbfcf0c).html.

Testo completo

Abstract (sommario):

In the advanced polymer composites reinforced by 3D woven fibre architectures, tows areinterlaced into through-thickness direction to overcome the problems encountered in theapplications of traditional 2D laminates, such as poor interlaminar toughness anddelamination resistance. The understanding of the influence of fibre architectures on thefatigue performance of 3D woven composites is essential in providing guide for the designof fibre architecture. This PhD project is an in-depth study into the fatigue damagemechanisms of 3D woven composites reinforced by two kinds of fibre architectures,namely, 3D modified layer-to-layer (MLL) and 3D angle-interlocked (AI). 3D X-raycomputed tomography (CT) has been used as the main tool to non-destructively evaluateand quantify the evolution of fatigue damage, with an attempt to link macro behaviour withlocal micro (damage) microstructure. Part I is focused on a post-failure study on both typesof materials to identify their respective failure mechanism, using the combination of 2D(optical surface and SEM cross-sectional) imaging and 3D (X-ray CT) imaging. Somecharacteristic features are found in both materials: firstly, fatigue damage progresses by theinitiation of transverse cracks within weft yarns and subsequent propagation as interfacialdebonding crack until the catastrophic failure occurs in a localised area; secondly, bothmaterials display a high resistance to ultimate failure. However, a distinctive damage modeobserved in MLL composites is the extensive development of debonding cracks, whichresult in larger scale of damage (~10μm) than those in AI composites (1-2 μm). Part IIpresents an investigation of evolution of fatigue damage in 3D woven MLL compositesfollowed by an X-ray time-lapse experiment. An innovative algorithm was developed toenable automatic classification of damage, providing insight into the competition andinteraction of different damage modes. Fatigue damage is regularly distributed throughoutfatigue life, with a geometrical dependency on the repeating unit cells. Damageinteractions have been identified, indicating a high level of damage tolerance. Aquantitative analysis has been carried out to examine and compare the growth of differenttypes of damage as a function of fatigue cycles. Transverse cracks initiate at almost thebeginning the fatigue life (0.1%) and govern the growth of weft/binder debonds, but don’tcompromise fatigue life, whereas interply debonds have a large growth towards the end offatigue life and facilitate the ultimate failure. Other types of damage occurring in the resinhave a trivial effect on the fatigue life. Part III carries out a systematic study to find out thebest approach to detect the fatigue damage in the 3D AI composites. Different strategieshave been employed in each scan, including imaging the cracks with the load applied, withcontrast enhanced by phases contrast and staining. The image contrast was not effectivelyenhanced by applying phase contrast imaging, but significantly improved by staining. Withthe application of in-situ loading, the visibility of transverse cracks is highly improved,while longitudinal debonding cracks still cannot be resolved. Overall, the best approachwas found to be high resolution ROI (region of interest) scanning in combination withstaining, in terms of practical feasibility, scan time and image quality.

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Kearns, Eleanor Rose. "Multi-stimuli Metal-organic frameworks and their composites". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29561.

Testo completo

Abstract (sommario):

Metal-Organic Frameworks (MOFs) are a versatile class of materials. Their high surface area combined with the functionality of their constituent organic ligands make them suitable for a wide range of applications. In their scale-up to industry level uses, MOFs face several roadblocks. The largest of these obstacles are large-scale green syntheses of MOFs and processing the polycrystalline powders into useable forms. This thesis examines structure-activity relationships in a family of TTF-based MOFs, and presents a green synthesis for UiO-66-NH2. Finally, 3D-printing will be examined as a method for preparing MOF-based electrocatalytic electrodes. Chapter 3 and Chapter 4 will examine the structure-activity relationships (SARs) of charge transfer and photocyclization respectively. Herein, a family of photoactive TTF-based MOFs, generated by systematically varying the framework constituents, are used to probe the effect of structure on the intervalence charge-transfer (IVCT) and [2+2] photocyclisation processes. Chapter 5 presents a novel one-step mechanochemical synthesis of UiO-66-NH2. This synthesis proceeds from ZrOCl2.8H2O in a 66% yield. The mechanochemical synthesis presented is more scalable than other benign syntheses of UiO-66-NH2, and importantly yields highly crystalline material with comparable surface area to UiO-66-NH2 synthesized via alternative mechanochemical routes. Chapter 6 presents the first example of 3D-printed MOF electrodes for electrocatalysis, which expands upon previous work on 3-D printed MOF and zeolite-based composite sorbent materials. This represents a new technique for electrochemical analysis of solid analytes, as well as the development of self-supporting solid MOF-based electrodes. This research shows that the properties of the MOF are maintained once printed, and a clear electrochemical response to the analyte of interest is observed.

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Panchal, Dhaval. "Failure and damage progression of 3D woven composite structures subjected to out-of-plane loading". Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/33284.

Testo completo

Abstract (sommario):

Three-dimensionally woven composites are a relatively new class of material that offer improved out-of-plane performance by including through-the-thickness mechanical reinforcement compared to traditional laminated composite structures. The mechanical properties are highly dependent upon the weave architecture as this dictates the nature of the through the thickness reinforcement and its effect in improving out-of-plane shear strength. A comparison of two testing methods, Short Beam Strength, and Five Point Bending was conducted over a range of span to thickness ratios with the latter found to be more consistent at producing shear failure over a greater range of span to thickness ratios, although evidence of matrix crushing was present in both, and flexural failure in the Short Beam Strength test. Two weave architectures, the orthogonal and angle weave were subjected to the Five Point Bending test and the failure and damage progression behaviour of both weave architectures were characterised using Digital Image Correlation analysis to measure the edge strain through the thickness of the specimens. This testing showed the angle weave architecture had in general a higher failure strength, and more gradual failure due to longer debonding cracks. The orthogonal weave architecture showed a characteristic post-failure response indicative of crack bridging with discrete load recovery and load drop phases. A numerical model developed from previous work builds on the mosaic modelling method and was modified to include cohesive elements in order to simulate interface debonding via the maximum stress criterion. The simulations are consistently 15 20% greater in failure loads, and 8 - 12% greater in failure shear stresses than those found from the averaged experimental results over the range of tested span to thickness ratios. Post failure response was not modelled. The work presented in this thesis is another step towards gaining a thorough understanding of the mechanical properties of 3D woven composite structures, focussing in particular on out of plane shear strength. The modified mosaic modelling method used showed it is effective at modelling the out of plane testing of orthogonal 3D woven composite structures, and offer the potential to predict the failure of larger composite structures of the same construction and 3D woven architecture although developments are still needed in modelling the post failure response.

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Guigon, Camille. "Vieillissement par cyclage thermique de composites interlocks 3D à matrice polymère". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2015. http://www.theses.fr/2015ESMA0004.

Testo completo

Abstract (sommario):

L’introduction des composites dans des pièces structurelles critiques pour les aéronefs représente une réelle rupture technologique et nécessite des études spécifiques afin de maîtriser leur comportement et leur durabilité. Ce travail a pour objectifs de caractériser et de comprendre les mécanismes de vieillissement de composites interlock 3D à fibres de carbone et à matrice polymère lorsqu’ils sont soumis à des cycles thermiques.Dans ce but, un essai de cyclage thermique (-55°C/120°C), dont l’environnement thermique et gazeux est totalement maitrisé, a été mis en place pour le vieillissement d’échantillons composites représentatifs du motif interlock élémentaire. L’analyse des mécanismes de dégradation induits a été réalisée grâce i/ à la mise au point d’une méthode de caractérisation quantitative 3D de l’évolution des microfissures au cours du cyclage, basée sur des observations par microtomographie RX et sur le développement d’une procédure de traitement d’images spécifique, ii/ au développement d’un essai de cyclage thermique in situ synchrotron couplé à une technique de corrélation d’images volumiques 3D, et iii/ à des simulations par éléments finis prenant en compte l’architecture réelle des échantillons à l’échelle mésoscopique et le comportement thermo-viscoélastique de la matrice.Les résultats obtenus mettent en évidence des couplages thermo-chimio-mécaniques complexes,qui s’expriment à travers quatre paramètres influents : le temps (et le nombre de cycles),l’architecture de l’interlock, la ténacité de la matrice et sa sensibilité à la thermo-oxydation
The introduction of composite materials in critical structural parts for aircrafts represents a real technological breakthrough and requires specific studies to understand their behavior and durability. This work aims to characterize and understand the ageing mechanisms incarbon/epoxy 3D interlock composites when they are submitted to thermal cycling.For this purpose, a thermal cycle test (-55°C/120°C), whose heat and gaseous environment istotally mastered, was set up for the ageing of composite samples of elemental interlock pattern dimensions. Analysis of induced degradation mechanisms was achieved by i/ the development ofa 3D quantitative characterization method of the evolution of microcracks during cycling, basedon observations by microtomography RX and the development of a specific image processing procedure, ii/ the development of an in situ thermal cycle test under synchrotron light, coupled to a digital volume correlation technique, and iii/finite elements simulations taking into account the actual mesoscopic architecture of the samples and the thermo-viscoelastic behavior of thematrix.The results reveal complex thermo-chemo-mechanical couplings that are linked to four important parameters: time (and the number of cycles), the interlock architecture, the matrix toughness andits sensitivity to thermo-oxidation

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Roirand, Quentin. "Modélisation multiéchelle du comportement et de l'endommagement de composites tissés 3D. Développement d'outils numériques d'aide à la conception des structures tissées". Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM036/document.

Testo completo

Abstract (sommario):

Les composites tissés 3D, à l'aide de leurs grandes libertés de conception, peuvent fournir des propriétés mécaniques adaptées aux besoins spécifiques d'une structure. La complexité architecturale de ces matériaux induit néanmoins des propriétés, des comportements ainsi que des endommagements très difficiles à prédire. Les travaux présentés dans ce manuscrit s'inscrivent directement dans cette problématique et cherchent à développer des outils permettant, par simulation numérique, de prévoir les caractéristiques mécaniques de ce type de matériaux. Afin de répondre à cet objectif, une approche multiéchelle, alliant essais expérimentaux et simulations numériques, a été adoptée. Cette démarche permet, en appliquant des sollicitations réelles, de considérer la géométrie des renforts et les hétérogénéités du matériau, observables à l'échelle mésoscopique, qui sont responsables du comportement macroscopique du composite tissé. Le travail d'investigation expérimentale s'est attaché à caractériser le comportement d'un composite interlock 2,5D et des ses constituants ainsi que les mécanismes et cinétiques de rupture, pour des sollicitations de traction/flexion, grâce à des observations tomographiques aux rayons X et au concept d'interzone. En ce qui concerne la modélisation numérique, un critère de rupture permettant de simuler la dégradation ultime du composite, en coupant les fils de renforts, a été présenté et testé sur une cellule représentative du composite expérimentale. Les résultats en termes de localisations, d'orientations et de cinétiques de l'endommagement sont en accord avec les observations expérimentales. Ensuite, après avoir estimé l'influence des différents paramètres architecturaux sur le critère de rupture avec une campagne de calcul éléments finis, des architectures optimisées, pour les sollicitations considérées, ont pu être proposées et comparées à l'interlock 2,5D. Toujours dans l'optique d'une meilleure prédiction du comportement des composites tissés, les travaux se sont également intéressés à une modélisation plus fine des mécanismes d'endommagement. Une approche fiabiliste a donc été introduite sur le critère de rupture à l'aide d'une distribution statistique de Weibull. De plus, un autre mécanisme d'endommagement a aussi pu être pris en compte dans la modélisation en simulant, avec le modèle GTN (Gurson-Tvergaard-Needleman), la cavitation de la matrice. Enfin, des techniques de réduction de modèle ont été employées pour diminuer le coût calcul de la modélisation multiéchelle afin d'identifier, par exemple, des propriétés matériaux par méthode inverse ou de simuler des essais de fatigue
With their large flexibility of design , 3D woven composites can provide mechanical properties tailored specificially to structural needs. However, the architectural complexity of woven reinforcements presents serious challenges when predicting properties, behaviours and damage processes. The present work deals with these challenges and seeks to develop numerical tools which are able to foresee the mechanical characteristics of this kind of materials. For this purpose, a multiscale approach, which combines experimental tests and numerical simulations, has been adopted. This approach allows, simultaneously, to take into account the loads and composite behavior, at the macroscopic scale, also the reinforcement geometry and the material heterogeneities which are only visible at the mesoscopic scale. The experimental investigation has been carried out to characterize the behaviour of an 2.5D interlock composite and its constituents. Examinations of the damage mechanisms have also been performed, using tomography and the interzone concept, for this woven composite under loadings in tension and combined tension and bending. With regards to the numerical modeling part, the ultimate degradation of the composite was simulated by cutting the reinforcement yarns with a failure criterion, previously reported, on a 3D representative cell of the experimental composite. For the two kinds of macroscopic loadings, the locations, orientations and kinetics of the damage were found to be fully in agreement with the experimental results. The influence of the architectural parameters on the failure criterion was then evaluated by finite element calculation. Consequently, it has been possible to proposed optimized architectures and make a camparison, for the two macroscopic loadings, with the 2.5D interlock woven composite. Still motivated to improve the prediction of the behaviour of woven composites, this work has also been on developing a finer modeling approach to the understanding of damage mechanisms. A stochastic approach was therefore introduced to the failure criterion using a Weibull statistical distribution. In addition, matrix cavitation has also been taken into account in the modelling. This damage mechanism was simulated using the GTN (Gurson-Tvergaard-Needleman) model. Finally, model reduction techniques have been applied to lower the cost of computing multiscale modeling in order to identify, for example, material properties by an inverse method or to simulate fatigue tests

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Médeau, Victor. "Rupture des composites tissés 3D : de la caractérisation expérimentale à la simulation robuste des effets d’échelle". Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0025/document.

Testo completo

Abstract (sommario):

Ces travaux s’attachent à décrire et quantifier les mécanismes de ruptures des compositestissés 3D sous chargement de traction quasi-statique et à mettre en place une méthode de simulationnumérique adaptée et robuste, pouvant à terme être appliquée en bureau d’études.Dans cette optique, une étude expérimentale a été menée afin de quantifier la propagation defissures dans ces matériaux. Celle-ci a permis de mettre en place un scenario de rupture, entirant parti de la multi-instrumentation des essais. L’étude a également été effectuée sur deséprouvettes de géométries et de tailles variées et a mis en évidence d’importantes variations dutaux de restitution d’énergie avec les conditions d’essai. Un formalisme d’analyse et de modélisationintroduisant des longueurs internes a ensuite été présenté et adapté aux mécanismes derupture des composites tissés 3D. Ce formalisme est étayé par la recherche des mécanismes àl’aide de l’analyse des faciès de rupture. Les longueurs introduites ont ainsi été mises en relationavec les paramètres du tissage. Une méthode d’identification des paramètres a été proposée etles conséquences de ce comportement sur le dimensionnement de pièces composites discutées.Enfin, le transfert de ces résultats a été effectué vers des simulations numériques robustes. Desméthodes de régularisation des modèles d’endommagement continu ont été présentées et évaluéesà l’aune de leur capacité à assurer, d’une part, la robustesse des résultats et, d’autre part,la bonne retranscription des effets d’échelle expérimentaux. La prise en compte de ces considérationsnumériques et physiques nous a amené à proposé un modèle d’endommagement Non-Local.Une méthode d’identification des paramètres et de la longueur interne à partir des données expérimentalesa été proposée
This work aims to describe and quantify the failure mechanisms of 3D woven composites underquasi-static tensile loading and to implement an adapted and robust numerical simulationmethod, that can be applied in industry. To this end, an experimental study was carried out toquantify the propagation of cracks in these materials. Thus, a crack propagation scenario wasestablished, thanks to the multi-instrumentation used during the tests. The experimental campaignwas carried out on specimens of various geometries and sizes and highlighted significantvariations in the fracture toughness with the test conditions. A modelisation framework introducinginternal lengths was then presented and adapted to 3D woven composites. This frameworkis supported by the identification of the failure mechanisms subsequent to the analysis of thecrack profile. The introduced lengths were thus related to the weaving parameters. A method foridentifying the parameters was proposed and the consequences of this behaviour on the designof the composite parts discussed. Finally, these results were transferred to robust numerical simulations.Regularisation methods of continuous damage models were presented and evaluatedin terms of their ability to ensure, on the one hand, the robustness of the results and, on theother hand, the correct transcription of experimental size effects. Taking into account these numericaland physical considerations led us to propose a Non-Local damage model. A method foridentifying the parameters and the internal length on experimental data was proposed

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Angrand, Lise. "Modèle d’endommagement incrémental en temps pour la prévision de la durée de vie des composites tissés 3D en fatigue cyclique et en fatigue aléatoire". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN005/document.

Testo completo

Abstract (sommario):

Les travaux présentés dans ce document s’insère dans le cadre du Projet de Recherche Concerté PRC Composites, financé par la DGAC et impliquant le groupe Safran, l’Onera et un grand nombre de laboratoires du CNRS de le LMT Cachan. Un des objectifs principal du PRC est d’établir des modèles pour la simulation du comportement mécanique, de la durabilité et encore des procédés de fabrication des pièces composites CMC & CMO. Ces travaux de thèse se focalisent sur l’étude du comportement des composites tissés 3D aux sollicitations de fatigue mécanique. Ils font suite aux travaux menés à l’Onera sur un modèle d’endommagement en cycles pour la fatigue des composites CMO tissés 3D, nommé ODM-CMO. Nous proposons un modèle dit « temporel », nommé OD ̇M, qui détermine l’évolution de l’endommagement de façon continue, en fonction du temps. Ce modèle est alors capable d’une part de prendre en compte des chargements de fatigue cycliques, et d’autre part les chargements de fatigue complexes, aléatoires. La loi d’endommagement proposée fait intervenir deux contributions, une contribution monotone et une contribution de fatigue. La contribution monotone est totalement équivalente à la loi monotone du modèle initial ODM-CMO, les paramètres sont alors facilement identifiables. La contribution de fatigue n’est pas équivalente à la loi du modèle ODM-CMO, ceci s’explique notamment par le fait qu’il existe différentes façon de prendre en compte la notion de contrainte moyenne, notion primordiale concernant l’étude de la fatigue. Nous avons choisi de prendre en compte l’effet de contrainte moyenne en ajoutant le calcul d’une moyenne originale qui évolue au cours du chargement dans la contribution de fatigue de la loi d’endommagement. L’identification des paramètres de fatigue se déroule en deux étapes. La première étape se base sur une simplification du jeu d’équation du modèle (élasticité et endommagement non couplé) de façon à déterminer une relation simple, en 1D, entre le nombre de cycles à rupture et la contrainte maximale. Cette expression nous permet alors de tracer rapidement les diagrammes de Wöhler (σ_a ou σ_Max vs N_R) ainsi que les diagrammes de Haigh (σ_a vs σ ̅). Ces diagrammes nous permettent de faire une première identification des paramètres de la contribution de fatigue de la loi d’endommagement. La seconde étape consiste à recaler certains paramètres en utilisant le modèle complet, de façon numérique, le modèle ayant été programmé en 3D tant pour un pilotage en déformation que pour un pilotage en contrainte. La méthodologie proposée nécessite néanmoins d’avoir un nombre important de résultats d’essais de fatigue. Elle permet l’identification à d’autres températures dans le but de proposer des modélisations anisothermes. Le modèle d’endommagement est rendu probabiliste grâce à une première approche, pragmatique, en fatigue à grands nombres de cycles. Un paramètre du modèle initialement considéré comme déterministe, prend le statut de variable aléatoire, il s’agit du seuil d’endommagement de fatigue (en déformation) délimitant le domaine d’endurance illimitée. L’idée étant de pouvoir associer à une probabilité de rupture (ou de survie) à une limite de fatigue « asymptotique »
The work presented in this report is part of the Collaborative Research Project PRC Composites, funded by the DGAC involving Safran, Onera and several CNRS laboratories whose LMT Cachan. One of the main objectives of this project PRC is to establish models capable to simulate the mechanical behavior, durability and still manufacturing processes for composite PMC. This thesis focus on the study of the behavior of 3D woven composite to mechanical fatigue stresses. This thesis further to the work developed at Onera on cycle damage models for fatigue on PMC, named ODM-PMC. We propose a kinetic damage model, which calculates the kinetic damage evolution, over time. This model is then able to take into account the cycle fatigue loads, and on the other hand the complex or random fatigue loads. The proposed kinetic damage law involves two damage contributions, a monotonous contribution for static loads and a fatigue contribution for fatigue loads. The monotonous contribution is fully equivalent to the monotonous law of ODM-PMC model, the parameters are easily identifiable. The fatigue contribution is not equivalent to the fatigue damage law of initial model ODM-PMC, this is explained by the fact that there are different ways to take into account the average stress effect, unavoidable concept for the study of fatigue loads. We have chosen to consider the mean stress effect by adding the calculation of a mean that evolves during the loading. The identification of fatigue parameters takes place in two steps. The first step is based on a simplification of the model equation set (elasticity and damage are not coupled) to determine a simple relationship, 1D, between the number of cycles to failure and the maximum stress. This expression allows us then quickly to draw diagrams Wohler (σ_a ou σ_Max vs N_R) as well as Haigh diagram (σ_a vs σ ̅). These diagrams allow us to make an initial identification of fatigue parameters. The second step is to readjust certain parameters using the full model 3D, numerical, the 3D model was been encoded for both strain and stress steering. Nevertheless, the methodology requires having a lot of experimental results. It allows also to identifying fatigue parameters at other temperatures in order to provide isothermal modeling. The damage model is made with a first probabilistic approach, pragmatic, to the great number of cycles fatigue. One parameter (determinist), is defined as a random variable, it is the fatigue damage threshold (strain) delimiting the endurance unlimited domain

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Garcia, Cécile. "Modélisation de l'endommagement et de la rupture des matériaux composites tissés 3D appliquée aux chapes ceinturées". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN035.

Testo completo

Abstract (sommario):

L’enjeu de ces travaux de thèse est de proposer des outils à destination du bureau d’études Safran, pour le dimensionnement de chapes réalisées en matériau composite tissé 3D à matrice organique. L’arrachement du nez de chape par cisaillement, qui est le mode de ruine prédominant sur les chapes composites tissées 3D de par leur géométrie et l’absence de renfort à 45°, est particulièrement investigué. Une caractérisation expérimentale de ce mode de ruine est menée, mettant en évidence une rupture par fissurations matricielles le long des bandes de cisaillement. Le modèle ODM-CMO, déjà validé pour les modes de matage et de rupture en traction nette, est ici enrichi afin de bien décrire le scénario d’endommagement. Plus précisément, la loi d’évolution de l’endommagement matriciel est modifiée pour des niveaux de cisaillement élevés. Le modèle est validé au travers de comparaisons avec les résultats d’essais disponibles sur chapes.Par la suite, une solution innovante de chape basée sur le ceinturage de la pièce est examinée. L’objectif de cette solution de chape est d’orienter les renforts afin de s’affranchir du mode de ruine par cisaillement qui intervient prématurément. Ce concept induit des états de contraintes tridimensionnels complexes, faisant en particulier intervenir les composantes hors-plan du tenseur des contraintes. Les paramètres matériau hors-plan étant difficiles à identifier, une méthode d’identification par mesure de champs est proposée, implémentée, et appliquée au matériau d’intérêt à partir d’essais élémentaires. Un essai technologique multi-instrumenté original permettant de solliciter la ceinture en traction est proposé sur la base de simulations. Trois essais ont été réalisés. Conformément aux prévisions du modèle, les ceintures ont rompu en traction nette, témoignant ainsi d’une augmentation de performance vis-à-vis de la chape monolithique tissée étudiée en première partie
The challenge of this work is to offer tools to the Safran design office for the sizing of lugs made of organic matrix 3D woven composite material. Shear failure is the predominant failure mode on 3D woven composite lugs due to their geometry and the lack of 45° reinforcements. Thus, in this work, special attention is paid to this failure mode. An experimental characterization of the shear failure is carried out, showing matrix cracks along the shear strips. The ODM-CMO model, already validated for bearing and net tensile failure modes, is here enriched to properly describe the shear failure damage scenario. More precisely, the matrix damage evolution law is modified for high shear levels. The model is validated through comparisons with test results available on lugs.Subsequently, an innovative solution of lug is examined, based on the belting of the part. The objective of this design of lug is to provide reinforcements to avoid the shear failure mode that occurs prematurely. This concept induces complex three-dimensional stress states, and particularly off-plane components of the stress tensor. As off-plane material parameters are difficult to identify, an identification method based on full-field measurement is proposed, implemented and applied to the material of interest using elementary tests. An original technological set-up to test the belt in tension with appropriate instrumentation is proposed on the basis of simulations. Three tests have been performed. The belts failed in net tension, reflecting an increase in performance over the monolithic 3D woven composite lug studied in first part

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Navrátil, Libor. "Apports de l'imagerie qualitative infrarouge pour la caractérisation thermomécanique et le dimensionnement en fatigue de composites tissés 3D". Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2021. http://www.theses.fr/2021ENTA0007.

Testo completo

Abstract (sommario):

Les travaux de cette thèse portent sur la caractérisation thermomécanique et le dimensionnement en fatigue d’un composite tissé 3D qui est fabriqué par le groupe Safran à des fins de recherche. La caractérisation expérimentale repose principalement sur des analyses des mesures infrarouges. Les protocoles expérimentaux, utilisés pour la génération des bases de données expérimentales, se basent sur le protocole d’auto-échauffement, qui cherche à relier les variations de température mesurées sous chargements cycliques aux différentes sources thermiques. Pour exploiter au mieux les données expérimentales obtenues, plusieurs outils de post-traitement, permettant de mettre en évidence les mécanismes caractéristiques aux composites tissés, ont été mis en place (détection des événements thermiques, génération des cartographies des amplitudes à 2×f, . . .). Cette caractérisation expérimentale est complétée par des comparaisons issues d’un dialogue essai/calculs. Ce dernier représente une complémentarité aux mesures expérimentales, notamment, parce qu’il permet d’identifier les mécanismes dissipatifs activés sous chargements cycliques relativement faibles. En s’appuyant sur la description des mécanismes dissipatifs, une méthode de caractérisation rapide en fatigue, qui cherche à identifier un critère de dimensionnement à partir des résultats des essais de traction et d’auto-échauffement, a été proposée
This work focuses on the thermomecanical characterisation and design against fatigue of a woven composite that is produced for research purposes by the Safran Group. The experimental characterisation is based mainly on the analyses of infrared measurements. The experimental protocols, used for generating the experimental database, are based on the heat build-up protocol, which seeks to relate the temperature variations measured under cyclic loadings to different heat sources. In order to fully exploit the experimental data, different postprocessing tools that enable to highlight mechanisms characteristic to woven composites were developed (thermal event detection, frequency analyses, ...). This experimental characterisation is then complemented by results coming from simulation/experiment comparisons. The latter enable to identify dissipative mechanisms activated under relatively low cyclic loadings. Furthermore, this dissipative mechanism description was used to introduce a rapid fatigue characterisation method that identifies an S-N curve model based on the results of tensile tests and heat build-up experiments

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Foti, Federico. "Effect of the Environment on the Fatigue Behaviour of Textile Organic Matrix Composite Materials for Aircraft Applications". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0031/document.

Testo completo

Abstract (sommario):

Les composites à matrice organiques (CMO) et fibre de carbone sont de plus en plus employés dans la réalisation de structures « tièdes » (aubes de fan, nacelles …) ; ces pièces peuvent être soumises, en service, à la fatigue mécanique, au cyclage thermique et à la fatigue thermo-mécanique. Bien qu’il existe une littérature consistante sur le comportement en fatigue des composites tissés, l'interaction entre fatigue et la dégradation liée à l'environnement à haute température n’a pas été encore bien exploitée. Le couplage entre les effets de la thermo-oxydation, le comportement mécanique (viscoélastique, viscoplastique) de la matrice organique à températures élevées et la dégradation par fatigue peut être néfaste pour le composite.Le but de ce travail est de caractériser et de modéliser - pour les composites tissés C/matrice organique - le comportement thermomécanique, l'apparition et le développement de l’endommagement liés aux mécanismes mécaniques cycliques (fatigue) sous environnement contrôlé (température et gaz).Une étude préliminaire sur un composite stratifiée [02/902]s a été menée pour pouvoir analyser les effets de l’environnement sur une architecture simple. La corrélation d’image numérique (CIN) et des scans μ-tomographiques (μCT) ont été employés pour le suivi et la caractérisation de l’endommagement de fatigue de composites tissés 2D à architecture complexe pour applications aéronautiques. Les effets de l’environnement sur la dégradation par fatigue ont été également explorés.L'objectif à long terme de cette étude est de fournir des outils expérimentaux et numériques pour renforcer la compréhension et la modélisation du couplage mécanique/endommagement/environnement pour la prédiction de la durée de vie et pour la proposition de protocoles d’essais accélérés réalistes de pièces « tièdes » en CMO
In the next future, the employment of organic matrix/carbon fibre composites (OMC) is foreseen for the realization of “hot” structures: these parts may be subjected, in service, to mechanical fatigue (e.g. fan blades turbo-engines), thermal cycling and thermo-mechanical fatigue (e.g. aircraft structural parts). Though there is a consistent literature concerning the fatigue behaviour of woven composites, the interaction between fatigue and environmental degradation at high temperature has been poorly explored. Coupling between thermo-oxidation effects, mechanical (viscoelastic, viscoplastic) behaviour of the polymer matrix at high temperatures and degradation due to fatigue may be highly detrimental for the material. This work aims at characterizing and modelling - for carbon fibre/organic matrix (polyimide) textile composites – the thermomechanical behaviour, the onset and the development of damage related to cyclic mechanical mechanisms (fatigue) under controlled (temperature and gas) environment.A preliminary study on a cross-ply laminate [02/902]s has been carried out in order to analyse the environmental effect on a model sample. Digital Image Correlation (DIC) and μ-Computed Tomography (μCT) have been used to monitor and characterize the fatigue damage of 2D woven composites for aeronautical applications. The environmental effect on fatigue degradation have been also explored.The long-term aim of the study is to provide experimental and numerical tools to strengthen the understanding and the modelling of mechanics/damage/environment coupling for durability prediction

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Hollette, Matthieu. "Modélisation de la propagation des ondes élastiques dans un milieu composite à microstructure 3D". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00840603.

Testo completo

Abstract (sommario):

En contrôle non-destructif par ultrasons, la simulation présente un intérêt majeur en permettant à la fois d'optimiser les configurations de contrôle des pièces et de simplifier l'analyse des données acquises. Cette thèse traite de la modélisation de la propagation des ultrasons dans les matériaux composites tissés. Ces matériaux sont constitués de fibres de Carbone (micrométriques) regroupées en mèches (millimétriques) qui sont ensuite tissées pour former une couche de matériau : leur structure est donc hétérogène à deux échelles distinctes. L'étude à l'échelle du tissage nécessite la connaissance préalable des propriétés mécaniques des mèches. Nous proposons deux méthodes visant à effectuer l'homogénéisation dynamique du matériau à l'échelle microscopique. Une première consiste à identifier les rigidités complexes d'un milieu effectif représentatif de la mèche en comparant les nombres d'ondes des modes guidés s'y propageant à ceux calculés dans un milieu hétérogène de même géométrie ; nous avons développé un algorithme génétique permettant de faire correspondre les jeux de nombres d'onde, dont l'application permet d'identifier certaine des rigidités recherchées. La seconde consiste à étendre un modèle existant permettant d'homogénéiser la structure de la mèche en tenant compte de la diffraction multiple des ondes de volume par les fibres. Le modèle initial (modèle à trois phases) ne traitant que le cas de l'incidence normale aux fibres est étendu au cas plus complexe de l'incidence oblique : un calcul de la diffraction multiple en incidence oblique par un réseau dense de fibres et tenant compte de l'anisotropie des différents milieux est donc proposé. Comme pour la première méthode, on utilise un algorithme génétique pour effectuer l'identification des rigidités effectives. Les résultats obtenus nous amènent à remettre en cause certaines hypothèses de base faites pour effectuer cette homogénéisation dynamique ; particulièrement, la dépendance des résultats à l'angle d'incidence semble remettre en cause le choix de la loi de Hooke comme loi fondamentale pour effectuer une homogénéisation dynamique des composites à structures complexes.

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Embrey, Leslie. "Three-Dimensional Graphene Foam Reinforced Epoxy Composites". FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3128.

Testo completo

Abstract (sommario):

Three-dimensional graphene foam (3D GrF) is an interconnected, porous structure of graphene sheets with excellent mechanical, electrical and thermal properties, making it a candidate reinforcement for polymer matrices. GrF’s 3D structure eliminates nanoparticle agglomeration and provides seamless pathways for electron travel. The objective of this work is to fabricate low density GrF reinforced epoxy composites with superior mechanical and electrical properties and study the underlying deformation mechanisms. Dip coating and mold casting fabrication methods are employed in order to tailor the microstructure and properties. The composite’s microstructure revealed good interfacial interaction. By adding mere 0.63 wt.% GrF, flexural strength was improved by 56%. The addition of 2 wt.% GrF showed a surge in glass transition temperature (56oC), improvement in damping behavior (150%), and electrical conductivity 11 orders of magnitude higher than pure epoxy. Dip coated and mold casted composites showed a gauge factor of ~2.4 indicating electromechanically robust composite materials.

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Hussain, Muzzamal. "Couplage procédé / propriétés mécaniques des matériaux sandwiches Métal / Composite hybride à base de tissus en jute". Thesis, Lille, 2021. http://www.theses.fr/2021LILUI006.

Testo completo

Abstract (sommario):

Dans cette étude, les propriétés mécaniques des FML renforcés de jute tissé 3D et hybrides de jute tissé 3D renforcé ont été étudiées. Le renfort tissé 3D à quatre couches a été fabriqué avec du fil de jute en utilisant quatre types de motifs imbriqués, par ex. Orthogonal Through Thickness OTT et Orthogonal Layer to Layer OLL imbriqué. La technique d'infusion sous vide a été utilisée pour la fabrication de FML avec renfort en jute tissé 3D. Après l'optimisation du renforcement tissé 3D, les FML renforcés hybrides ont été développés dans lesquels le tissu tissé OTT 3D a été pris en sandwich entre une peau tissée 2D. Quatre types de fibres différents ont été utilisés pour fabriquer une peau tissée 2D, par ex. jute, aramide, carbone et verre tandis que trois types différents de matrice ont été utilisés, par ex. époxy, PVB et PP. La presse à chaud par compression a été utilisée pour développer des FML hybrides renforcés. L'aluminium utilisé pour fabriquer tous les FML a été anodisé avant d'être utilisé pour la fabrication. Les propriétés adhésives ont été étudiées pour vérifier la qualité du traitement de surface, la liaison métal-composites et l'effet des fibres et de la matrice. Les propriétés monotones et dynamiques ont également été étudiées. Les propriétés adhésives ont été caractérisées à l'aide de tests de pelage en T et de pelage au rouleau flottant. Les propriétés monotones ont été analysées à l'aide d'essais de traction et de flexion. Les performances d'impact à faible vitesse ont été déterminées en utilisant un test d'impact à faible vitesse. Les résultats ont montré que la surface en aluminium anodisé avait une énergie libre de surface élevée, de sorte que le meilleur mouillage de l'aluminium peut être obtenu par anodisation par rapport à d'autres types de préparations de surface. Les résultats de l'analyse du collage ont montré que les propriétés de délaminage étaient principalement influencées par la nature du matériau adhésif plutôt que par le type de structures de renforcement. La nature de la matrice influence également le type de défaillance car avec l'époxy, la défaillance dominante était cohésive tandis qu'avec la matrice thermoplastique, elle s'est transformée en défaillance adhésive et intra-laminaire. La plasticité et la ductilité de la matrice ont plus influencé les propriétés finales que le type de rupture, malgré la rupture cohésive de l'époxy, la matrice thermoplastique avait plus de force de délamination. Les propriétés de traction et de flexion des FML renforcées de jute tissé OTT 3D étaient supérieures à celles des FML renforcées tissées OLL 3D en raison de la fraction de volume de métal plus élevée, ce qui était possible grâce à une construction plus serrée du tissu OTT. Les propriétés de traction et de flexion des composites hybrides renforcés et des FML ont été influencées par le type de matrice et le matériau de la peau 2D. Les propriétés globales plus élevées ont été obtenues avec une matrice époxy suivie d'une matrice PVB. Les FML à base de PVB ont montré que leurs propriétés étaient comparables à celles de l'époxy. Le test de flexion a montré que les FML hybrides à base de PP échouaient prématurément en raison d'une délamination entre la peau synthétique et l'âme tissée 3D. L'époxy et le PVB ont montré une meilleure imprégnation du renfort contrairement au PP dans lequel seul un verrouillage mécanique a été observé. Les propriétés d'impact dynamique des composites hybrides et des FML ont montré que les caractéristiques de dissipation d'énergie étaient influencées par la matrice et l'hybridation du renforcement
In current study the mechanical properties of 3D woven jute reinforced and hybrid 3D woven jute reinforced FMLs were investigated. The four-layered 3D woven reinforcement was made with jute yarn using four types of interlocking patterns e.g. Orthogonal Through Thickness OTT and Orthogonal Layer to Layer OLL interlocking. The vacuum infusion technique was used for the fabrication of FMLs made with 3D woven jute reinforcement. After the optimization of 3D woven reinforcement the hybrid reinforced FMLs were developed in which OTT 3D woven fabric was sandwiched between 2D woven skin. Four different kinds of fibres were used to make 2D woven skin e.g. jute, aramid, carbon, and glass while three different kinds of matrix were employed, e.g. epoxy, PVB and PP. The compression hot press was used to develop hybrid reinforced FMLs. Aluminium used to make all FMLs was anodized before using for fabrication. The adhesive properties were investigated to check the quality of surface treatment, metal-composites bonding and effect of fibres and matrix. Both monotonic and dynamic properties were also investigated. The adhesive properties were characterized using t-peel and floating roller peel tests. The monotonic properties were analyzed using tensile and flexural tests. The low velocity impact performance was determined using drop weight low velocity impact test. The results showed that the anodized aluminium surface had high surface free energy so the better wetting of aluminium can be achieved by anodizing as compared to other type of surface preparations. The adhesive bonding analysis results showed that the delamination properties were mainly influenced by the nature of adhesive material rather than the type of structures of reinforcement. The nature of the matrix also influences the type of failure as with the epoxy the dominant failure was cohesive while with thermoplastic matrix it changed to adhesive and intra-laminar failure. The plasticity and ductility of matrix influenced the final properties more than the type of failure, in spite of cohesive failure of epoxy the thermoplastic matrix had more delamination force. The tensile and flexural properties of OTT 3D woven jute reinforced FMLs were higher than the OLL 3D woven reinforced FMLs due to the higher metal volume fraction, this was possible due to tighter construction of OTT fabric. The tensile and flexural properties of hybrid reinforced composites and FMLs were influenced by the type of matrix and material of 2D skin. The overall higher properties were achieved with an epoxy matrix followed by PVB matrix. The PVB-based FMLs showed that their properties were comparable with the epoxy. The flexural test showed that hybrid FMLs based on PP were failed prematurely due to delamination between synthetic skin and 3D woven core. Both epoxy and PVB showed better impregnation of the reinforcement unlike PP in which only mechanical interlocking was seen. The dynamic impact properties of hybrid composites and FMLs showed that the energy dissipation characteristics were influenced by matrix and hybridization of reinforcement

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Vilfayeau, Jérôme. "Modélisation numérique du procédé de tissage des renforts fibreux pour matériaux composites". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0026/document.

Testo completo

Abstract (sommario):

L'industrie aéronautique doit faire face aux nouvelles exigences environnementales, tout particulièrement concernant la réduction de la consommation des énergies fossiles. L'utilisation de matériaux composites plus léger permet de répondre en partie à cette attente. Pour limiter les coûts lors de la fabrication et du développement des composites à renforts tissés 3D, il est nécessaire d'utiliser des outils de simulation performants. En particulier, les outils existants, qui discrétisent à une échelle mésoscopique l'architecture des tissus 3D, ne tiennent pas compte de l'influence du procédé de fabrication sur la constitution de la structure textile. Si des outils numériques dédiés à la modélisation du procédé de tressage et de tricotage sont disponibles, il n'en est rien concernant le tissage. Cette étude avait donc pour but de s'intéresser plus particulièrement à la simulation du prodécé de tissage pour pouvoir obtenir une structure de tissu sèche déformée numériquement. La production de différentes architectures de tissu en verre E dans notre laboratoire nous a permis d'observer les différents éléments en contact avec le fil ou le tissu sur la machine à tisser, par le biais de l'utilisation d'une caméra rapide par exemple. Le développement d'un modèle numérique par éléments finis reproduisant le procédé de tissage a été réalisé. Une loi de comportement isotrope transverse fut utilisée pour modéliser les fils de verre. Des premières simulations numériques encourageantes pour la fabrication d'un tissu d'armure toile et d'un tissu d'armure croisé 2-2 sont présentées et comparées avec les tissus réels produits correspondants
The aeronautical industry faces new challenges regarding the reduction of fossil fuel consumption. One way to address this issue is to use lighter composite materials. The ability to predict the geometry and the mechanical properties of the unit cell is necessary in order to develop 3D reinforcements in composite materials for these aeronautical applications. There is a difficulty to get realistic geometries for these unit cells due to the complexity of their architecture. Currently, existing tools which model 3D fabrics at a meso scale don't take into account manufacturing process influence on the shape modification of the textile structure. There is already some numerical tools that can model the braiding or knitting process, but none have been developed for weaving so far. Consequently, this study deals with the numerical simulation of the weaving process to obtain a deformed dry fabric structure. During the weaving process of E-glass fabrics, achieved in our laboratory, it has been observed that large deformations led to the modification of transverse section of meshes, or local density changes, that can modify the fabrics mechanical resistance. For this reason, a numerical tool of the weaving process, based on finite element modelling, has been developped to predict these major deformations and their influences on the final textile structure. The correlation between numerical results and fabrics produced with glass fibres has been achieved for plain weave and 2-2 twill

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Wendling-Hivet, Audrey. "Simulation à l'échelle mésoscopique de la mise en forme de renforts de composites tissés". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0079.

Testo completo

Abstract (sommario):

De nos jours, l’intégration de pièces composites dans les produits intéresse de plus en plus les industriels, particulièrement dans le domaine des transports. En effet, ces matériaux présentent de nombreux avantages, notamment celui de permettre une diminution de la masse des pièces lorsqu’ils sont correctement exploités. Pour concevoir ces pièces, plusieurs procédés peuvent être utilisés, parmi lesquels le RTM (Resin Transfer Molding) qui consiste en la mise en forme d’un renfort sec (préformage) avant une étape d’injection de résine. Cette étude concerne la première étape du procédé RTM, celle de préformage. L’objectif est de mettre en œuvre une stratégie efficace conduisant à la simulation par éléments finis de la mise en forme des renforts à l’échelle mésoscopique. A cette échelle, le renfort fibreux est modélisé par un enchevêtrement de mèches supposées homogènes. Plusieurs étapes sont alors nécessaires et donc étudiées ici pour atteindre cet objectif. La première consiste à créer un modèle géométrique 3D le plus réaliste possible des cellules élémentaires des renforts considérés. Elle est réalisée grâce à la mise en œuvre d’une stratégie itérative basée sur deux propriétés. D’une part, la cohérence, qui permet d’assurer une bonne description du contact entre les mèches, c'est-à-dire, que le modèle ne contient ni vides ni interpénétrations au niveau de la zone de contact. D’autre part, la variation de la forme des sections de la mèche le long de sa trajectoire qui permet de coller au mieux à la géométrie évolutive des mèches dans le renfort. Grâce à ce modèle et à une définition libre par l’utilisateur de l’architecture tissée, un modèle représentatif de tout type de renfort (2D, interlock) peut être obtenu. La seconde étape consiste à créer un maillage hexaédrique 3D cohérant de ces cellules élémentaires. Basé sur la géométrie obtenue à la première étape. L’outil de maillage créé permet de mailler automatiquement tout type de mèche, quelle que soit sa trajectoire et la forme de ses sections. La troisième étape à franchir consiste, à partir du comportement mécanique du matériau constitutif des fibres et de la structure de la mèche, à mettre en place une loi de comportement du matériau homogène équivalent à un matériau fibreux. Basé sur les récents développements expérimentaux et numériques en matière de loi de comportement de structures fibreuses, un nouveau modèle de comportement est présenté et implémenté. Enfin, une étude des différents paramètres intervenant dans les calculs en dynamique explicite est réalisée. Ces deux derniers points permettent à la fois de faire converger rapidement les calculs et de se rapprocher de la réalité de la déformation des renforts. L’ensemble de la chaîne de modélisation/simulation des renforts fibreux à l’échelle mésoscopique ainsi créée est validée par comparaison d’essais numériques et expérimentaux de renforts sous sollicitations simples
Nowadays, manufacturers, especially in transport, are increasingly interested in integrating composite parts into their products. These materials have, indeed, many benefits, among which allowing parts mass reduction when properly operated. In order to manufacture these parts, several methods can be used, including the RTM (Resin Transfer Molding) process which consists in forming a dry reinforcement (preform) before a resin being injected. This study deals with the first stage of the RTM process, which is the preforming step. It aims to implement an efficient strategy leading to the finite element simulation of fibrous reinforcements at mesoscopic scale. At this scale, the fibrous reinforcement is modeled by an interlacement of yarns assumed to be homogeneous and continuous. Several steps are then necessary and therefore considered here to achieve this goal. The first consists in creating a 3D geometrical model of unit cells as realistic as possible. It is achieved through the implementation of an iterative strategy based on two main properties. On the one hand, consistency, which ensures a good description of the contact between the yarns, that is to say, the model does not contain spurious spaces or interpenetrations at the contact area. On the other hand, the variation of the yarn section shape along its trajectory that enables to stick as much as possible to the evolutive shape of the yarn inside the reinforcement. Using this tool and a woven architecture freely implementable by the user, a model representative of any type of reinforcement (2D, interlock) can be obtained. The second step consists in creating a 3D consistent hexahedral mesh of these unit cells. Based on the geometrical model obtained in the first step, the meshing tool enables to mesh any type of yarn, whatever its trajectory or section shape. The third step consists in establishing a constitutive equation of the homogeneous material equivalent to a fibrous material from the mechanical behavior of the constituent material of fibers and the structure of the yarn. Based on recent experimental and numerical developments in the mechanical behavior of fibrous structures, a new constitutive law is presented and implemented. Finally, a study of the different parameters involved in the dynamic/explicit scheme is performed. These last two points allow both to a quick convergence of the calculations and approach the reality of the deformation of reinforcements. The entire chain modeling/simulation of fibrous reinforcements at mesoscopic scale created is validated by numerical and experimental comparison tests of reinforcements under simple loadings

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Alia, Adem. "Comportement à la rupture d'un composite à fibres végétales". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI016.

Testo completo

Abstract (sommario):

L’objectif de cette thèse est la caractérisation du comportement mécanique et de l’endommagement d’un composite tissé jute/polyester. Les fibres végétales constituent en effet une alternative écologique intéressante à l’utilisation des fibres synthétiques, en particulier les fibres de verre qui sont les plus utilisées pour les pièces composites de grande diffusion. Le composite est développé au sein du laboratoire LMNM à l’IOMP, Sétif, Algérie. Deux orientations ([0]8 et [+45/-45]2S) sont considérées. La caractérisation mécanique est effectuée en traction et compression monotones ainsi qu’en fatigue cyclique. Les caractérisations mécaniques et microstructurales sont réalisées au sein du laboratoire MATEIS. L’étude de l’endommagement des composites est réalisée en combinant cinq techniques : l’évolution des paramètres mécaniques via des essais cyclés et de fatigue, la microscopie, l’émission acoustique (EA), la corrélation d’images et la micro-tomographie RX. L’étude de l’évolution des paramètres mécaniques accompagnée de l’analyse globale de l’EA fournit des premiers indicateurs quant au développement de l’endommagement lors des essais. Les analyses microstructurales permettent d’identifier finement les différents mécanismes d’endommagement qui surviennent lors des sollicitations mécaniques (décohésions fibre/matrice, fissurations matricielles et rupture de fibres). Pour la segmentation des signaux d’émission acoustique en traction et en compression monotones, une classification non-supervisée est utilisée en mettant l’accent sur le choix des descripteurs et sur la labellisation des classes obtenues. Des essais de traction instrumentés par corrélation d’images ainsi que des essais de traction in-situ sous tomographe permettent d’identifier la chronologie d’apparition de l’endommagement. Ces résultats permettent également de labelliser les classes obtenues. Les signaux labellisés servent ensuite à créer une bibliothèques pour identifier la chronologie d’évolution des modes d’endommagement en fatigue cyclique réalisée par classification supervisée. Enfin, toutes ces analyses ont permis d’établir des scénarios d’endommagement pour les différents modes d’endommagement et pour les deux orientations. Il est ainsi possible de reconsidérer l’élaboration pour optimiser les propriétés mécaniques
The objective of this thesis is the characterization of the mechanical behavior and the damage of a woven jute / polyester composite. natural fibers are indeed an interesting ecological alternative to synthetic fibers, in particular glass fibers which are the most used for composite manufacturing. The studied composite is developed in the LMNM laboratory at IOMP, Sétif, Algeria. Two fibre orientations ([0] 8 and [+ 45 / -45] 2S) are considered. The mechanical characterization is carried out in monotonic tensile and compression as well as in cyclic fatigue. Mechanical and microstructural characterizations are carried out in the MATEIS laboratory. The study of the damage is carried out by combining five techniques: the evolution of mechanical parameters via cyclic and fatigue tests, microscopy, acoustic emission (EA), image correlation and micro- RX tomography. The study of the evolution of the mechanical parameters combined with the global analysis of the AE provides first indicators concerning the development of the damage during the tests. Microstructural analyzes allow to finely identify the damage mechanisms that occur during mechanical tests (fiber / matrix decohesions, matrix cracks and fiber breakage). For the segmentation of acoustic emission signals in monotonic tests, an unsupervised classification is used, emphasizing the choice of descriptors and the labeling of the classes obtained. Tensile tests instrumented by image correlation as well as in situ tensile tests under tomography allow to identify the chronology of appearance of the damage. These results are also used to label the obtained classes . The labeled signals are then used to create a library to identify the chronology of evolution of the modes of damage in cyclic fatigue achieved by supervised classification. Finally, all these analyzes made it possible to establish damage scenarios for the different damage modes and for the two orientations. It is thus possible to reconsider the development to optimize the mechanical properties

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Naouar, Naïm. "Analyse mésoscopique par éléments finis de la déformation de renforts fibreux 2D et 3D à partir de microtomographies X". Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0088/document.

Testo completo

Abstract (sommario):

La simulation à l'échelle mésoscopique de la déformation des renforts composites fournit des informations importantes. En particulier, elle donne la direction et la densité de fibres qui conditionne la perméabilité du renfort textile et les propriétés mécaniques du composite final. Ces analyses mésoscopiques par éléments finis dépendent fortement de la qualité de la géométrie initiale du modèle. Certains logiciels ont été développés pour décrire ces géométries de renforts composites. Mais, les géométries obtenues impliquent une simplification (notamment dans la section transversale de mèche) qui peut perturber le calcul de déformation du renfort. Le présent travail présente une méthode directe utilisant la microtomographie à rayon X pour générer des modèles éléments finis, basée sur la géométrie réelle de l'armure textile. Le modèle EF peut être obtenu pour tout type de renfort, plus ou moins complexe. Les problèmes d’interpénétrations de mèches sont évités. Ces modèles sont utilisés avec deux lois de comportement : une loi hypoélastique et une loi hyperélastique. Les propriétés de chacune d'entre elles, ainsi que les grandeurs caractéristiques nécessaires à leur implémentation dans le logiciel ABAQUS sont développées. Enfin, une identification des paramètres matériau à l'aide d'une méthode inverse est proposée. Les résultats obtenus pour les simulations de mise en forme sont comparés avec les résultats expérimentaux et montrent une bonne correspondance entre les deux
The simulation at meso-scale of textile composite reinforcement deformation provides important information. In particular, it gives the direction and density of the fibres that condition the permeability of the textile reinforcement and the mechanical properties of the final composite. These meso FE analyses are highly dependent on the quality of the initial geometry of the model. Some software have been developed to describe composite reinforcement geometries. The obtained geometries imply simplification that can disrupt the reinforcement deformation computation. The present work presents a direct method using computed microtomography to determine finite element models based on the real geometry of the textile reinforcement. The FE model is obtained for any specificity or variability of the textile reinforcement, more or less complex. The yarns interpenetration problems are avoided. These models are used with two constitutive laws : a hypoelastic law and a hyperelastic one. An analysis of their properties is presented and their implementation in the software ABAQUS is detailed. Finally, an identification method is presented and the results of forming simulations are compared to experimental tests, which shows a good fit between the both

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Bai, Renzi. "Modélisation de la mise en forme des renforts fibreux : Nouvelle Approche de coque spécifique et étude expérimentale". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI108.

Testo completo

Abstract (sommario):

La déformation des renforts composites textiles est fortement conditionnée par leur composition fibreuse. Les théories classiques des plaques et des coques sont basées sur des hypothèses cinématiques qui ne sont pas vérifiées pour les renforts textiles. Des expérimentations montrent que le glissement entre fibres (couche) dans l’épaisseur fait la spécificité des matériaux fibreux. Le processus RTM (Resin Transfer Molding) est largement utilisé pour obtenir des pièces composites avec géométrie complexe. La mise en forme est une étape très importante. Afin d’optimiser la fabrication de produit (spécialement le tissu multicouche), des modèles numériques sont nécessaires. Par conséquent une approche de coque 3D spécifique aux renforts fibreux est proposée. Elle est basée sur deux spécificités : la quasi-inextensibilité des fibres et le glissement possible entre les fibres. L'approche est développée dans le cadre « Continuum-based shells ». La nouvelle hypothèse basée sur la conservation d’épaisseur est appliquée dans l’équation cinématique. La forme de puissance virtuelle reflète les spécificités de la déformation des renforts fibreux. Il prend en compte la rigidité de traction et de flexion des fibres et aussi de cisaillement dans le plan. Le frottement entre fibres est pris en compte de manière simple en lien avec la flexion. La présente approche est basée sur la physique réelle de la déformation des renforts textiles. Il permet de simuler les déformations 3D des renforts textiles et fournit des déplacements et déformations pour tous les points dans l'épaisseur du tissu et les bonnes rotations du directeur matériel. Enfin, des expérimentations et simulations réalisées sur des renforts multicouches sont présentées dans ce travail, et une nouvelle méthode d’expérimentation est proposée
The deformation of textile composite reinforcements is strongly conditioned by their fibrous composition. Classic plate and shell theories are based on kinematic assumptions that are not verified for textile reinforcements. Experiments show that the slippage between fiber (layer) in the thickness makes the specificity of fibrous materials. The RTM process (one of the forming process) is widely used to obtain composite parts with complex geometry is with great importance. In order to optimize the manufacturing of product, numerical models are necessary. Therefore, a 3D shell approach specific to fiber reinforcements is proposed which is based on two specificities: the quasi-inextensibility of the fibers and the possible sliding between the fibers. This approach is developed in the frame of continuum-based shell, the new assumption who based on the conservation of the thickness is applied to the kinematic equation. The theory of virtual power reflects the specific deformation of the fibrous reinforcements. It considers the tensile and bending stiffness of the fibers and the in-plan shear stiffness. The friction between fibers is taken into account in a simple way in connection with bending. The present approach is based on the real physics of the deformation of textile reinforcements. It simulates the 3D deformations of textile reinforcements and provides displacements and deformations for all the points along the thickness of the fabric and simulates the correct rotations of the material director. Finally, experiments and simulations performed on multilayer reinforcements are presented in this work, and a new method of experimentation is proposed

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Wendling, Audrey. "Simulation à l'échelle mésoscopique de la mise en forme de renforts de composites tissés". Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00961196.

Testo completo

Abstract (sommario):

De nos jours, l'intégration de pièces composites dans les produits intéresse de plus en plus les industriels, particulièrement dans le domaine des transports. En effet, ces matériaux présentent de nombreux avantages, notamment celui de permettre une diminution de la masse des pièces lorsqu'ils sont correctement exploités. Pour concevoir ces pièces, plusieurs procédés peuvent être utilisés, parmi lesquels le RTM (Resin Transfer Molding) qui consiste en la mise en forme d'un renfort sec (préformage) avant une étape d'injection de résine. Cette étude concerne la première étape du procédé RTM, celle de préformage. L'objectif est de mettre en œuvre une stratégie efficace conduisant à la simulation par éléments finis de la mise en forme des renforts à l'échelle mésoscopique. A cette échelle, le renfort fibreux est modélisé par un enchevêtrement de mèches supposées homogènes. Plusieurs étapes sont alors nécessaires et donc étudiées ici pour atteindre cet objectif. La première consiste à créer un modèle géométrique 3D le plus réaliste possible des cellules élémentaires des renforts considérés. Elle est réalisée grâce à la mise en œuvre d'une stratégie itérative basée sur deux propriétés. D'une part, la cohérence, qui permet d'assurer une bonne description du contact entre les mèches, c'est-à-dire, que le modèle ne contient ni vides ni interpénétrations au niveau de la zone de contact. D'autre part, la variation de la forme des sections de la mèche le long de sa trajectoire qui permet de coller au mieux à la géométrie évolutive des mèches dans le renfort. Grâce à ce modèle et à une définition libre par l'utilisateur de l'architecture tissée, un modèle représentatif de tout type de renfort (2D, interlock) peut être obtenu. La seconde étape consiste à créer un maillage hexaédrique 3D cohérant de ces cellules élémentaires. Basé sur la géométrie obtenue à la première étape. L'outil de maillage créé permet de mailler automatiquement tout type de mèche, quelle que soit sa trajectoire et la forme de ses sections. La troisième étape à franchir consiste, à partir du comportement mécanique du matériau constitutif des fibres et de la structure de la mèche, à mettre en place une loi de comportement du matériau homogène équivalent à un matériau fibreux. Basé sur les récents développements expérimentaux et numériques en matière de loi de comportement de structures fibreuses, un nouveau modèle de comportement est présenté et implémenté. Enfin, une étude des différents paramètres intervenant dans les calculs en dynamique explicite est réalisée. Ces deux derniers points permettent à la fois de faire converger rapidement les calculs et de se rapprocher de la réalité de la déformation des renforts. L'ensemble de la chaîne de modélisation/simulation des renforts fibreux à l'échelle mésoscopique ainsi créée est validée par comparaison d'essais numériques et expérimentaux de renforts sous sollicitations simples.

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Zhang, Chuyang. "Characterization and modeling of 3D woven composites". 2003. http://www.lib.ncsu.edu/theses/available/etd-06112003-210833/unrestricted/etd.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Dash, Bibhu Prasad. "Modelling and characterization of 3D woven solid structures and their composites". Thesis, 2013. http://localhost:8080/xmlui/handle/12345678/6511.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Neje, Ghanshyam Suryakant. "Design and development of 3d woven spacer fabrics for structural composites". Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7988.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

42

陳昆泓. "The Fatigue Behavior of Connected Structures Made with 3D I-Shape Woven Composites". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/01811643126683450112.

Testo completo

Abstract (sommario):

碩士
逢甲大學
紡織工程學系
87
The purpose of this investigation is to study the fatigue behavior of connected structures made with 3D I-shape woven composites. Three different I-shape woven preforms, type I, type II, and type III were used in this work. Two aluminum blocks were bonded to a I-shape composite structures to form a connected rectangular beam. The four-point bending tests under both static loading and cyclic loading were carried out using the Material Testing System (MTS-810). The curves of residual strength versus loading cycles were constructed for those three type composite structures to investigate the variation of fatigue residual strength over cycle numbers. The S/N curves were also drawn to discuss the effect of layer number on the fatigue strength and fatigue sensitivity. From experimental results, typeI was found to have higher strength than type II and type III in both static loading and cyclic loading. The fatigue limit strength of typeI and III were calculated to be respectively 64﹪and 56﹪of their ultimate flexural strength. The residual strength decreased slowly with loading cycles throughout most parts of fatigue life. As approaching final fatigue failure, the residual strength decreased abruptly. The metallographic microscope was employed to investigate the mechanism of fatigue damage growth. The observation indicated that the cracks between the warps and wefts were the major damage occurring during fatigue loading. Such cracks spreaded out with loading cycles resulting in decreasing of the residual strength.

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Badawi, Said Sobhey [Verfasser]. "Development of the weaving machine and 3D woven spacer fabric structures for lightweight composites materials / Badawi, Said Sobhey". 2007. http://d-nb.info/987189700/34.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "3D woven organic composites"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili