Tesi sul tema "Matériaux composites sandwichs"
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Salloum, Joulia. "Comportement mécanique de Matériaux Sandwichs Innovants pour application nautique". Electronic Thesis or Diss., IMT Mines Alès, 2023. http://www.theses.fr/2023EMAL0017.
Testo completoThis work consists of an experimental and numerical study of the mechanical behaviour of sandwich composite materials used in the nautical industry, up to damage occurrence and its evolution. For eco-design purposes, the facings are made of NCF triaxial basalt fibre laminates and a partially bio-sourced resin (greenpoxy), and the core consists of recycled PET foam. In addition to preparing these materials via vacuum infusion and conducting their microstructural and mechanical characterisation, the main goal of this study is to develop a robust model capable of predicting the response of these sandwich materials under static loading. It is worth noting that all conducted mechanical tests, including compression of the foam alone, simple traction of the monolithic in different directions, or bending of the sandwich composite, are instrumented by image correlation on multiple sides of the specimen to monitor the real-time damage evolution. Furthermore, a 3D finite element study of the mechanical response of the single components (foam and monolithic) and the sandwich is carried out based on Abaqus® simulations to assess the applicability of failure criteria and damage evolution methods. For instance, regarding the foam, the "crushable foam" model was used to predict its collapse within the sandwich structure. As for the monolithic, a progressive damage model of the fibre/matrix constituents is adopted within each ply, and cohesive elements between adjacent plies are used to account for delamination on a mesoscopic scale. This methodology aims to predict the initiation and accumulation of damage in the laminate. The proposed methodology is generic and provides an evolving basis for introducing the concept of cohesion between fibre and matrix, the effectiveness of which is intended for evaluation
Khawar, Farooq Muhammad. "Comportement mécanique des composites sandwichs en statique et fatigue cyclique". Le Mans, 2003. http://cyberdoc.univ-lemans.fr/theses/2003/2003LEMA1006.pdf.
Testo completoThe aim of the this study is to investigate the mechanical behaviour of sandwich composite materials under static and fatigue. Initially, static and fatigue testing of cores in compression, indentation, shear and three-point bending tests and skins in flexural tests are conducted to derive the mechanical behaviour and the characteristics for the constituants of the sandwich composites. Detailed investigations have been carried out to study the performance of sandwich specimens of different core thickness and densities at various span lengths in static flexural tests. Phenomena of pure bending and shear are characterised at different span lengths and compared to the results obtained by the sandwich beam theory. Damage initiation, progression, coalescence and failure are observed in sandwich specimens during fatigue testing and correlated with stiffness degradation. Mechanical behaviour of sandwich composites is highly affected by the core thickness and the density of the foams and depends on the type of loading, the frequency, as well as the applied loading levels and ratios. Fatigue life is characterised by Wohler curves using N10 criterion for different types of sandwich composites. Finally, analytical models are developed on the basis of a stiffness degradation approach to predict the fatigue life and damage development in sandwich composite materials. A good agreement is found between experimental and analytical results
Tran, Van Luan. "Etude du comportement hygro-thermo-mécanique d'un matériau composite sandwich avec âme balsa utilisé en applications navales". Nantes, 2013. http://www.theses.fr/2013NANT2001.
Testo completoSandwich composite structures have been widely adopted in the naval field because they exhibit both lightness and good mechanical strength. However, their resistance to moisture in the marine environment is difficult to predict, and their fire resistance is one of the main limitations to their use in a greater number of cases. In this work, we focus on the behavior of a composite sandwich composed with glass-polyester skins and balsa core. Balsa, which is the main constituent, can absorb a large amount of water which may affect its mechanical properties. Moreover, the presence of moisture can influence the fire resistance of the material. Thus, in order to highlight the material durability and the physical phenomena encountered, several experiments were performed in miscellaneous conditions of humidity, temperature and mechanical loadings. In addition to classical results obtained on the balsa, testing of fire resistance combined with bending tests on sandwich composite materials were achieved to estimate the residual strength as a function of the combustion time. Finally, from experimental results related to the water uptake of balsa and of sandwich composite, modelling was computed to better understand and predict the mechanical state of the studied sandwich structure
Rizk, Georgio. "Durabilité des matériaux composites sandwichs en conditions extrêmes : tenue au feu et évolution des propriétés mécaniques". Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4098/document.
Testo completoComposite materials play an increasingly important role in our society in many fields (aeronautics, naval, civil engineering), because of their advantages in terms of lightness, unalterability and rigidity. It is therefore essential to understand and evaluate their properties in the long term (durability). However, the use of this type of material requires special precautions, particularly with regard to fire resistance. Indeed, sandwich composites are highly flammable and poorly heat resistant. The aim of this thesis project is to study in a combined way the thermomechanical durability (fire resistance) of polymer matrix composite sandwich materials by means of experimental measurements with a calorimeter cone. It is also a question of modeling the variations of mechanical properties induced as a function of the temperature and the combustion time, using a multiphysical model based on a finite element approach (Abaqus). The processes of thermal degradation of these materials are presented as a function of temperature and time, as well as behavior laws and of thermal and mechanical properties predictions. An improved thermal numerical model is programmed and validated in relation to experimental fire resistance measurements (oven, calorimeter cone). Confrontations between experimental measurements and numerical model, performed under several fire resistance scenario configurations, are carried out in order to understand and predict the behavior and thermomechanical properties of composite sandwich materials
Lascoup, Bertrand. "Analyse et modélisation du comportement mécanique de structures composites sandwichs multi-D". Compiègne, 2005. http://www.theses.fr/2005COMP1585.
Testo completoThe objective of this work is to apprehend the damaging modes of an original sandwich structure strengthened by stitches and to propose a predictive tool for the choice of the geometrical and material parameters. This objective requires both an experimental and a theoretical approach. The experimental part enables to determine the behavior of this type of structure under static and dynamic stresses. A R TM device was created in order to control the implementation parameters and to highlight the influence of the microstructure of the reinforcements. The analysis of the damage mechanisms highlights the influence of the geometrical parameters of stitches on the behavior of the structure. The problems resulting from the inter-laminar efforts are attenuated: the brittleness of the core/skin interface and delamination into the skins is reduced. The modelling part allows to represent the material behavior by using simple and adapted theories and seeks to predict the rigidity and the maximum stress in the three directions. A data-processing tool named SANDTEX brings a predictive tool to the industrial world
Ben, Ammar Imen. "Contrôle de santé vibro-acoustique de l'endommagement des matériaux composites à base polymère pour l'aéronautique". Thesis, Le Mans, 2014. http://www.theses.fr/2014LEMA1014/document.
Testo completoThe present study investigates the mechanical behavior under static, fatigue, linear and non linear vibration and assesses damage by the acoustic emission method of laminated composite materials (tensile and buckling) and of sandwich composite materials (4 points bending)
Idriss, Moustapha. "Analyse expérimentale et par élément finis du comportement statique et vibratoire des matériaux composites sandwichs sains et endommagés". Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00808603.
Testo completoHoang, Minh Phuc. "Homogénéisation analytique de structures de nid d'abeille pour des plaques composites sandwich". Thesis, Reims, 2015. http://www.theses.fr/2015REIMS011/document.
Testo completoThe aim of this thesis is to develop an analytical homogenization model for the honeycomb core sandwich panels. Unlike conventional methods, the skin effects are taken into account, leading to a very different mechanical properties. In the cases of extensions, bendings, in-plane shear, transverse shears andtorsion, different analytical function series are proposed to consider the stress redistribution between the honeycomb walls. We have studied the influence of the height of the core on its homogenized properties. The moduli curves obtained by the present H-models are well bounded by the moduli values obtained by the beam theory. The interface stresses are also studied to compare with existing models for stretching problem. Many numerical computations with our H-models have been done for the problems of stretching, bending, in-plan and transverse shearing, as well as torsion. Very good agreement has been achieved between the results of the H-models and the results obtained by finite element simulations by completely meshing thesandwich panel with shell elements. Our H-models have been applied to the computations of industrial large sandwich panels with honeycomb core. The comparison of the results between the H-models and the simulations with Abaqus shell elements are in very good agreement
Min, Kyung-Tak. "Optimisation d'un cylindre en sandwich composite soumis à des sollicitations combinées". Compiègne, 1985. http://www.theses.fr/1985COMPI201.
Testo completoKail, Renaud. "Modélisation asymptotique et numérique de plaques et de coques stratifiées". Paris 6, 1994. http://www.theses.fr/1994PA066606.
Testo completoKhalfallah, Moussa. "Etude expérimentale et modélisation numérique du comportement thermomécanique d’un sandwich agrocomposite à base de fibres longues de lin". Thesis, Reims, 2015. http://www.theses.fr/2015REIMS003.
Testo completoTo reduce waste and CO2 emissions, car manufacturers use more and more new bio-sourced materials to lighten vehicles and reduce fuel consumption. In this context, this thesis aimed at processing a lightweight sandwich panel reinforced by long flax fibers for automotive semi-structural applications.In addition to the literature state of the art, the work is divided into three parts: the material processing, characterization and modeling of the mechanical behavior of the sandwich panel. The composite skins are reinforced by a new reinforcing material "Flaxtape", which is a veil of long unidirectional flaxfibers withouth any weft spinning. The matrix is an aqueous thermosetting resin with a very short cure time and good processability. The composite skins and derived sandwich panels are processed by a thermocompression technique respecting industrial production cycles. Thermomechanical and physicochemical characterizations are used to understand and optimize the parameters involved in their development (cooking cycle, temperature, drying, densification, fiber volume fraction, degree of crosslinking and stacking sequence). Our results highlight good specific mechanical properties of the sandwich panels at different temperatures.Furthermore, the Flaxpreg sandwich panel has been used for the achievement of a vehicle compartment floor. Numerical modeling of the mechanical behavior of the sandwich panel was used to predict the sandwich panel mechanical response at different positions in the trunk. To simplify the geometry of the sandwich panel and reduce the computation time, an analytical model of the homogenized honeycomb was used in this study
Del, Broccolo Simone. "Effets de la topologie des cellules d'une structure en nid d'abeille". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCD001.
Testo completoHoneycomb sandwich panels are well known to provide interesting static out of plane properties because of their high equivalent stiffness whilst containing mass and for this reason, they are widely used as a ‘building brick’ in the Aerospace, Automotive and Naval industries. The environment in which these materials operate involve external forces which excites them in the mid-low frequency range. However, while a high stiffness/mass ratio is a desirable static property, the vibration frequency domain is usually in the high range and therefore they become poor mechanical and acoustic insulators within the frequency range they are usually subjected to. The question addressed then is simple: how periodic concepts can improve the broadband vibroacoustic signatures and performances of those structures? Most of vibroacoustic solutions are frequency band limited, specific and usually include the addition of mass, which for certain engineering segments is disadvantageous. Including vibroacoustic design rules at early stage of product development is one of the main research targets to improve their performance and would allow to design tuned structures without any later intervention or mass increment. This work focuses on investigating existing sandwich panel core topologies and attempt to create novel improved structures. The research was carried out trying to maintain the desired structural properties which justifies the usage of such solution in the first place but also considering its potential use as a platform for Multiphysics resonating periodic material inserts. Such cellular cores were manufactured using Kirigami, which is a variation of Origami, an ancient Japanese technique that consists in creating 3D structures by folding a 2D sheet of material. This manufacturing technique can be used as a systematic way to produce general honeycomb configurations with off-the-shelf long fibre composites by thermoforming and/or autoclaving. The main indicator on which I will focus to evaluate the vibroacoustic performance of the proposed innovative topologies will be the number and range of stopbands, also known as a bandgaps, which describe the frequency ranges in which elastic waves are not transmitted within the structure, in combination with the constituent material and its damping properties. This manuscript is organised in five chapters. The first one consists of a brief overview on periodic structures in the various engineering domains. Emphasis on Sandwich panels and their most popular manufacturing techniques will also be described. The second chapter will introduce the reader to the concept of elastic wave propagation in periodic media. Also, phenomena like Bragg or resonant bandgaps will be explained as well as the Floquet-Bloch theory applied to macro-scale structures such as aeronautical cellular cores.[...]
Afaq, Kamran Sheikh. "Développement d'un nouveau modèle pour les structures composites "multicouches et sandwiches" avec prise en compte du cisaillement transverse et des effets de bord". Toulouse 3, 2003. http://www.theses.fr/2003TOU30203.
Testo completoEssassi, Khawla. "Développement et caractérisation statique et dynamique d'un composite sandwich à âme auxétique et à constituants naturels". Thesis, Le Mans, 2020. http://cyberdoc-int.univ-lemans.fr/Theses/2020/2020LEMA1025.pdf.
Testo completoIn recent years, bio-based composite materials have been used in different industrial sectors due to their environmental interests. The use of a biological matrix reinforced with vegetable fibers makes it possible to improve not only environmental protection but also mechanical performance. On the other hand, auxetic structures have emerged as a result of their high specific properties and especially their great energy absorption capacities. In this context, this study proposes to develop a composite sandwich material with a re-entrant honeycomb core and a purely natural constituent. In order to build this structure, the additive manufacturing method was used. First, the static tensile behavior of the skins is analyzed. The elastic characteristics of the printed specimens in different directions are determined. Subsequently, the mechanical properties of auxetic cores in tension and in compression as well as those of sandwiches in bending and indentation were developed. An analysis of damage mechanisms during indentation tests is performed using the acoustic emission technique. Then, experimental tests and analytical models were carried out to determine the fatigue behavior of the sandwiches. Finally, a study of the vibration behavior of the skin, cores and sandwiches is carried out using an experimental and numerical study by finite element. The contribution of each component in the global damping properties is discussed
Junes, Angel. "Approche théorico-expérimentale du comportement de panneaux sandwichs à parements composites textile-mortier dans le cadre de la construction durable". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10127.
Testo completoThis work fits in the context of the structural design under new sustainable development, health and safety criteria through material recovery to reduced environmental damage and promoting energy savings. This thesis focuses on the theoretical and experimental study of sandwich panels taking advantage of new generation textile - cement matrix composites: TRC ( Textile Reinforced Concrete). It is specifically the establishment of an analytical-numerical approach to predict the behavior of sandwich panels incorporating material non-linear behavior and compatible with different and complex loading combinations. Based on an experimental campaign both at the material and structure level, it was possible to validate the model by several criteria such as the ability approximate the global behavior (load deflection) but also the ability to reproduce the local deformations and failure modes. Finally, based on the experimental identification of the mechanical properties of aged sandwich panel components, by an accelerated aging procedure, simulations were made based on the previously validated model to assess the impact on the behavior and damage mechanisms of the studied structural element. It was possible to demonstrate the probability of the failure mode change accompanied with significant losses of the global properties such as the initial stiffness and bearing and deflection capacity. These results will be eventually subject of validation on natural-aged panels but are likely to inform the design approach
Gulla-Cazenave, Jean. "Étude de l'influence des paramètres d'élaboration par infusion de résine liquide sur l'endommagement et le comportement à l'impact de matériaux composites à structure sandwich". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30313.
Testo completoIn a previous study, prototypes for heavy military equipment (>600kg) transportation by helicopters were developed. Based on sandwich composite structures, these materials showed promising results in terms of weight reduction and load bearing capabilities, but weaknesses were observed during low velocity/low energy impact solicitations. During this PhD project, we aimed at optimizing sandwich structure's resistance to impacts, by studying elaboration parameter's influences of an industrial production method on impact behaviors. A bibliographic review showed critical parameters for this project's feasibility. We chose to use the Liquid Resin Infusion as the elaboration process; this technique is commonly used in the industry, and is suited for small production structures. State of the art also showed impact resistance improving methods for sandwich structures, in terms of processing conditions. A particular elaboration method was designed, to produce sandwich structures in a one-shot process. In this study, and with this method, four sets of parameters were selected: elaboration temperatures, matrix types, core's surface nature, and whether or not the matrix contained nanoscaled additives. Several combinations of these parameters were used to produce sandwich panels, which were cut in samples, to be impacted on a drop-weight tower. Preliminary testing allowed to determine representative impact conditions, similar to real-life situations, the observation and characterization techniques of damages, and behavior observation methods during impact. Based on that, we were able to identify three behaviors during impact, and four damage types, over all tested samples. These behaviors and damages were linked to the selected elaboration conditions and one set appeared very promising. The analysis of the parameters allowed us to understand the mechanisms occurring during the production of the panel. Residual resistance after impact was characterized by subjecting the samples to consecutive impacts. Four behaviors were observed, directly linked to the damages initially observed. The choice of an optimal structure was confirmed
Essid, Safa. "Sandwiches à fibres de lin et anas de lin : optimisation structure-imprégnation-propriétés". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMLH05.
Testo completoFor different reasons including ecological ones, the weight reduction of structures and valorization of lignocellulosic biomass are considered as possible solutions towards ustainable innovation. In this context, the work of this thesis focuses on the manufacturing and optimization of sandwich structures with skins reinforced with flax fibers with mechanical, economic and environmental goals. A flax plant by-product called flax shives is valued by the development of agglomerated panels. These panels will serve as a core for the sandwich structures. To reach the optimization stage, experimental characterizations of the matrix and core materials are carried out first. Subsequently, joint work between the production processes and the desired properties of sandwich structures is undertaken. All the characteristics determined are compared with those of a non-bio-sourced reference material. Finally, analytical, graphic and numerical approaches are developed in order to answer the main question related to the optimization of the design of flax based sandwich structures with imposed rigidity and resistance to rupture. This optimization procedure should systematically control the desired characteristics of flax sandwiches
Lainé, Cyril. "Contribution à la modélisation du comportement mécanique de structures sandwichs 3D par homogénéisation périodique". Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10013.
Testo completo3D composite sandwichs have superior mechanical characteristics compared to usual composite sandwichs, in particular in the through-thickness direction. The structures studied in this work are 3D reinforced sandwichs using the Napco® technology which is based on transverse needling. In a first step, a complete experimental study is realized (creation of the through-thickness reinforcements, composite manufacturing by infusion process, experimental tests, measurement of geometric and material parameters) lead to better understanding of the sandwich architecture and their mechanical behaviour. In a second step, an interest is carried on the determination of the effective mechanical properties of this structures, using different homogenization techniques (periodic), analytical and numerical, in order to assess an equivalent plate model. An interest is devoted to the out-of-plane behaviour such as buckling of the reinforcements during compressive loading in the thickness direction and the importance to take into account the effects of transverse shear. Analytical models have been developed in 2D and a PythonPM program (using Abaqus software) have been created, allowing a fully parameterized modelling and mechanical analysis. The results are finally validated, using numerical computations on 3D heterogeneous structures or by experimental results, for several sandwichs considering different density of reinforcements
Audibert, Clément. "Contribution à la caractérisation des mécanismes dissipatifs sous sollicitation d'impact de structures composites sandwichs intégrant des fibres naturelles. Proposition d'une zone d'absorption pour siège pilote". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0030/document.
Testo completoThis work is part of the problem of mass reduction, safety inherent in the aeronautical field, it concerns more specifically the seats of pilots of airliner. A new multi-functional sandwich composite seat pan is proposed, composed by a carbon skin, a Nomex honeycomb core and a Kevlar/flax hybrid skin. The assembly of several materials generates complex behaviors and makes the ruin of the structure difficult to predict. An experimental/numerical approach is used to understand the damage mechanism of the seat and to create a pre-dimensioning numerical tool.Firstly, characterization tests allow identifying the mechanical behaviors of each material and constituting a database for the creation of material laws. The hybrid composite shows an elastoplastic-damaging-anisotropic behavior. The honeycomb is represented by a spring network and a law coupling the compression and shear behavior is implemented. Impact tests are used to evaluate the failure modes and the energy dissipated by the different concepts. The impact tests are correlates by numerical simulation using the identified material behaviors. The analysis of the experimental and numerical results makes it possible to identify the coupling between the different mechanisms. Finally, the model is used to design a new composite seat pan. This one is comparable to the existing aluminum seat pan without optimization phase
Li, Nan. "Identification des paramètres mécaniques de plaque sandwich cousue par essais vibratoires". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2361.
Testo completoThe sandwich structures are well known for their high bending stiffness. This type of structure is also capable of including acoustic and thermal functionalities. However, they also have weaknesses such as the connection between the faceplate and the core and the weakness in the transverse direction due to the property of the core. The core is usually made of soft materials like foam for acoustic functionality. To overcome these weaknesses, it is possible to connect the different layers of the sandwich by transverse stitches. This is the concept of ‘stitched sandwich’. The stitch will deeply change the behavior of the structure and complicate the determination of its properties. The objective of this thesis is to identify the properties of the constituents of the stitched sandwich in situ. These properties are essential to simulate the behavior of this type of composite material under static or dynamic excitation. The identification of the properties of the constituents by mechanical tests is difficult for various reasons: the heterogeneity makes it complex to extract representative specimen; the behaviors of the constituents may change in non-in-situ tests; several different types of mechanical test, such as tensile-compression and torsion, are necessary to determine all the engineering constants in the case of orthotropic material which is common for composite materials. To overcome all these difficulties, we propose in this thesis a dynamic identification method conducted on the structure (the whole plate for example). Compared to mechanical test which is based on a sample, this method takes into account the heterogeneity and complexity of the structure. This method is based on the correlation between the vibration test and a finite element model of stitched sandwich. The parameters are identified by minimizing a cost function which can measure the gap between the experimental frequencies and the calculated frequencies. The correspondence of experimental mode and calculated mode is guaranteed by MAC (Modal Assurance Criterion). Before the optimization, we propose firstly a sensitivity analysis to classify the parameters according to their importance. Then the identification process is only conducted on a reduced number of parameters. We have applied this dynamic identification method to both a stitched sandwich beam and a stitched sandwich plate. 9 parameters of different constituents are identified in the case of plate. In the second part of this thesis, based on the theorem of Floquet-Bloch, we have profited from the periodic characteristic of the stitched sandwich structures in two aspects: in the numerical aspect, the periodicity has served to reduce the calculation of forced response of periodic structure; in the physical aspect, we have studied the stop band of stitched structures
Barnoncel, David. "Etude d'un système de contrôle santé intègré pour structures sandwich composites utilisant des transducteurs piézo-électriques minces". Paris, CNAM, 2006. http://www.theses.fr/2006CNAM0501.
Testo completoThis PhD is a study of a Integrated Health Monitoring System (IHMS) for a sandwich structure : Rafale nose. The goal of the IHMS is to detect, localize and estimate the size of damages appearing during the life. The characterization of the damages is made with Lamb waves that propagate in the structure. In order to have an integrated system we use slim piezo-electric devices. The use of the flexural wave at low frequencies is adapted to the shape of the damages. The method used with the IHMS needs to knowledge of the sandwich Lamb waves with charateristics (dissipation, Phases speed). In order to measure theses characteistics which have build a NDE system. That have also give a visualisation of the interaction of the waves with damages. The use of special signal processing method and a base references made by simulation with the IHMS signal gives a method to detect, localise and estimate the size of a real damage
Monti, Arthur. "Élaboration et caractérisation mécanique d'une structure composite sandwiche à base de constituants naturels". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1023/document.
Testo completoBio-based composites appear to be very promising alternatives to traditional composites. The use of natural fibres as reinforcement reduces the environmental impact of these materials and their specific properties are significantly increased. In this context, this work focuses on the manufacturing and the mechanical characterization of a bio-based sandwich structure. The skins are made of an innovative thermoplastic resin associated with flax fibres. The core is made of balsa wood. First, quasi-static analyses are performed on the different components. Then, the tensile properties of the composite skins are studied. Moreover, the main damage mechanisms are identified and described by means of the acoustic emission technique. Next, the flexural behavior of the whole sandwich structure is studied. Particular attention is paid to the detection and prediction of the main fracture modes. Moreover, the statistical spreads of the material properties of the balsa core are taken into account. In addition, cyclic fatigue and impact tests are performed to investigate the behavior of this structure under dynamic loads, and to discuss whether or not this material could be suitable for potential semi-structural applications. Finally, experimental analyses of the vibration behavior of composite and sandwich beams are performed. The contributions of the different components to the global damping properties of the sandwich structure are analyzed by means of a finite elements model. This work also compares the properties of this bio-based sandwich to those of traditional materials, in order to benchmark its mechanical performances with a view to further industrial usage
Geoffroy, Laura. "Design of new fire protective multi-materials". Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R014.
Testo completoFire can cause severe material damage as well as human casualties. The development of new fire protective systems is thus of prime importance. In order to conceive new and more efficient systems, an innovative scientific approach has been considered within this PhD work. It consists in combining various concepts and materials while changing their design rather than their chemistry to achieve superior fire protection. In this way, two novel fireproofing multi-materials were developed and aimed on the one hand to limit the reaction to fire, and on the other hand to increase the fire resistance of a substrate. In the first part, additive manufacturing was selected as a process of choice for designing a material with a low reaction to fire. An original bio-inspired sandwich design (honeycomb-like structure) was elaborated, 3D printed and optimized by the combination of numerous concepts (oxygen inhibitor system, physical barrier, low emissivity coating). Thanks to this association of design and concepts, the multi-material exposed to an external radiant heat flux of 50 kW/m2 based on the ISO 13927 standard of the mass loss cone calorimeter has shown a very low reaction to fire with a fast flame extinguishment and an extremely low total rate of heat release rate (less than 10 kW/m2) evidencing its outstanding efficiency. In a second part, a system acting as a fire barrier was developed to protect a substrate against a fire exposure of 116 kW/m2 (burn-through fire testing mimicking the aeronautical standard ISO2685). Intumescence and delamination phenomena were combined within the same design to elaborate this barrier. This new and optimized assembly dramatically reduces heat propagation and protects the substrate, its backside temperature remaining below 250°C after more than 15 minutes of fire exposure. The effectiveness of this fire barrier was finally tested on other substrates to extend its use. This study proves that modifying the design of various materials can be a promising way to design new and very effective fire protective systems
Geoffroy, Laura. "Design of new fire protective multi-materials". Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR014.
Testo completoFire can cause severe material damage as well as human casualties. The development of new fire protective systems is thus of prime importance. In order to conceive new and more efficient systems, an innovative scientific approach has been considered within this PhD work. It consists in combining various concepts and materials while changing their design rather than their chemistry to achieve superior fire protection. In this way, two novel fireproofing multi-materials were developed and aimed on the one hand to limit the reaction to fire, and on the other hand to increase the fire resistance of a substrate. In the first part, additive manufacturing was selected as a process of choice for designing a material with a low reaction to fire. An original bio-inspired sandwich design (honeycomb-like structure) was elaborated, 3D printed and optimized by the combination of numerous concepts (oxygen inhibitor system, physical barrier, low emissivity coating). Thanks to this association of design and concepts, the multi-material exposed to an external radiant heat flux of 50 kW/m2 based on the ISO 13927 standard of the mass loss cone calorimeter has shown a very low reaction to fire with a fast flame extinguishment and an extremely low total rate of heat release rate (less than 10 kW/m2) evidencing its outstanding efficiency. In a second part, a system acting as a fire barrier was developed to protect a substrate against a fire exposure of 116 kW/m2 (burn-through fire testing mimicking the aeronautical standard ISO2685). Intumescence and delamination phenomena were combined within the same design to elaborate this barrier. This new and optimized assembly dramatically reduces heat propagation and protects the substrate, its backside temperature remaining below 250°C after more than 15 minutes of fire exposure. The effectiveness of this fire barrier was finally tested on other substrates to extend its use. This study proves that modifying the design of various materials can be a promising way to design new and very effective fire protective systems
Haddad, Mohamed. "Développement d'un procédé d'enroulement filamentaire adapté aux matériaux composites sandwich et caractérisation mécanique des matériaux". Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0031.
Testo completoComposite materials, and especially sandwich structures, have been studied for decades. Indeed, the association between lightness and resistance of these structures leads to the development of their use. Their manufacturing method and their characterization remain as essential points in most studies. This work is part of the FUI SOLLICITERN project, which aims to design a composite water treatment tank for vehicles intended for this purpose. As a first step, and based on the classical filament winding principal, we aim to search designs that are best adapted to the fabrication of a curved sandwich material on a cylindrical mandrel, while respecting the process parameters of and their influence on structural properties. Since an optimal solution was validated, the constituent materials were studied by measuring mechanical properties. The objective is to help our industrial partner to validate a manufacturing solution and verify that such properties are the expected ones. For that, several static and dynamic characterizations were carried out on curved samples manufactured by the optimized process designed for our application. This part includes various experimental tests in order to validate the structure behavior with the most appropriate dimensions and material combinations, taking into account the manufacturing process. At the end, the best structural configuration is retained for the first tank prototype fabrication
Akoussan, Komlan. "Modélisation et conception de structures composites viscoélastiques à haut pouvoir amortissant". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0188/document.
Testo completoModeling and design of composite viscoelastic structures with high damping powerThe aim of this thesis is to develop numerical tools to determine accurately damping properties of composite sandwich structures for the design of lightweight viscoelastic sandwichs structures with high damping power. In a first step, we developed a generic tool implemented in Matlab for determining damping properties in free vibration of viscoelastic sandwich plates with laminate faces composed of multilayers. The advantage of this tool, which is based on a finite element formulation, is its ability to take into account the anisotropy of composite layers, the material non-linearity of the viscoelastic core induiced by the frequency-dependent viscoelastic laws and various boundary conditions . The nonlinear complex eigenvalues problem is solved by coupling homotopy technic, asymptotic numerical method and automatic differentiation. Then for the continuous study of a modeling parameter on damping properties of viscoelastic sandwichs, we proposed a generic method to solve the nonlinear residual complex eigenvalues problem which has in addition to the frequency dependence introduced by the viscoelastic core, a modeling parameter dependence that describes a very specific study interval. This resolution is based on asymptotic numerical method, automatic differentiation, homotopy technique and continuation technic and takes into account various viscoelastic laws. We propose after that, two separate formulations to study effects on the damping properties according to two modeling parameters which are important in the design of high viscoelastic sandwichs with high damping power. The first is laminate fibers orientation in the sandwich reference and the second is layers thickness which when they are well defined allow to obtain not only sandwich structures with high damping power but also very light. The highly nonlinear complex eigenvalues problems obtained in these formulations are solved by the new method of resolution of eigenvalue residual problem with two nonlinearity developed before. Comparisons with discrete results and computation time are made to show the usefulness of these two formulations and of the new method of solving nonlinear complex eigenvalues residual problem of two dependances
Junker, Nicolas. "Conception et dimensionnement de pièces de robinetterie en matériaux composites". Paris, ENMP, 2001. http://www.theses.fr/2001ENMP1053.
Testo completoGoupil, Anne-Charlotte. "Contribution à l'étude numérique du comportement au feu d'un panneau composite pour l'industrie navale". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1003/document.
Testo completoStructural panels used in naval industry such as bulkheads and decks must succeed in standard certification testssuch as ISO 834 to be commercialized and settled on board. As these tests are long and expensive, panel manufacturerswish to maximize chances of success for their panels when submitted to certification tests especially when it comes toalternative designs such as composite sandwich panels.Finite elements analyses are used to model thermo-mechanical behavior. Industrial software such as SAMCEF,which was used to conduct this work, are able to solve thermal analyses with degradation and mechanical analyses involvingcontact conditions, degradation of mechanical properties and loss of structures due to failure.The objective in this study is to first identify characteristics of these structures. They are special due to their size andtheir manufacturing. This study aims also to determine thermal and mechanical data required for numerical modeling.When necessary some data can be computed from results coming from the results of the materials’ reaction to fire.Numerical models are developed to determine thermo-mechanical behavior and are designed to be robust and used inindustrial context. They include the evolution of thermal and mechanical properties during the degradation process. Thesemodels must enable to estimate the performances of innovative designs during an ISO 834 certification test
Kpeky, Fessal. "Formulation et modélisation des vibrations par éléments finis de type solide-coque : application aux structures sandwichs viscoélastiques et piézoélectriques". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0008/document.
Testo completoThis thesis deals with the development of solid–shell finite elements for vibration modeling of multilayer structures. Indeed, most of multilayer models in the literature show some limitations in certain geometric and material configurations. Considering these restrictions and in order to develop a more efficient calculation tool, we proposed an approach based on the solid–shell concept. This consists of three-dimensional finite elements enhanced through the Assumed Strain Method. First of all, we have formulated the problem of vibrations of sandwich structures with viscoelastic core. The frequency dependence has been taken into account by using a complex constitutive law. To solve the discretized problem, the Asymptotic Numerical Method, coupled with the homotopy technique and the DIAMANT toolbox approach, was adopted due to the excellent results it provides compared to other methods. Benchmark tests have validated the models and highlighted their advantages over existing elements having the same kinematics. In order to increase damping properties, we directed our attention towards an active vibration control. For this purpose, two piezoelectric finite elements have been developed. These finite elements SHB8PSE and SHB20E are extensions, of the elements SHB8PS and SHB20, respectively. The electromechanical coupling consisted in adding an electrical degree of freedom to each node of these elements. A variety of test problems both in static and vibration analysis conducted on multilayer structures ranging from simple beams to structures involving geometric nonlinearities allowed validating the proposed solid–shell elements. Finally, combining the achievements made in chapters 2 and 3, we proposed a modeling approach for multilayer structures composed of elastic, viscoelastic and piezoelectric layers. Active control is introduced using the piezoelectric properties in order to improve the reduction in vibration amplitudes. Thus, a filter has been mounted between the sensors and actuators. This filter allows amplifying or attenuating the generated electric potential in order to reduce the vibration amplitudes. To solve the resulting problem, we extended the resolution method used in chapter 2. To validate the proposed models, active–passive control tests have been conducted on multilayer plate structures. Finally, some control laws, associated with filters, have shown how this procedure can allow reducing or even avoiding amplification of vibrations
Nguyen, Duc Thai. "Benchmark d'un modèle layer wise de multicouches et implémentation du modèle dans Abaqus". Phd thesis, Université Paris-Est, 2012. http://pastel.archives-ouvertes.fr/pastel-00730740.
Testo completoLolive, Eric. "Analyse du comportement non linéaire de poutres en matériaux sandwiches avec âme en mousse". Nantes, 2000. http://www.theses.fr/2000NANT2119.
Testo completoThe purpose of this work is to analyse the non-linear behaviour of sandwich materials, made of a foam core and glass fibre-epoxy laminated skins. The non-linear behaviour has been investigated in indentation tests and 3-points bending tests. Besides the induced phenomena, the principal object was to implement a simulation of the non-linear behaviour as a function of the constituents : foam core, layer of the skins, foam-skins interfaces. The effect of localised loading has been studied through the indentation tests. The results deduced from the simulations have been compared with the experimental results in indentation and 3-points bending tests. Furthermore, experimental investigation of the displacement field allowed to derive a complementary validation of the results obtained by the simulation
Alila, Fahmi. "Analyse de la tenue en fatigue de structures composites sandwich". Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4082/document.
Testo completoSandwich structures are widely used in marines and aeronautic constructions. In this work, the fatigue behaviour of composites sandwich structures is apprehended. However, little knowledge of their failure modes and their fatigue behaviour has slow their development. The literature reports results of fatigue tests based on standard that is considered to be reviewed. In the first part of this document, a first approach of a classic fatigue test on a sandwich beam is proposed with reducing edge effects. This allows to better characterise the structure. Results shows that the fatigue lifetime issued from the standard geometry is twice less than the fatigue lifetime of the developed geometry. In the second part of this work, a self-heating modelling is developed based on the generalized Maxwell approach in order to simulate the viscoelastic behaviour of a PVC foam material in tensile and 4 point bending fatigue test. The numerical results correlate with the experimental results. This viscoelastic model allow to analyse physic phenomenon that are not easily found experimentally
Al, Bachi Lama. "Modélisation numérique et expérimentale du comportement de matériaux sandwiches appliqués à l'aéronautique". Toulouse, INPT, 2002. http://www.theses.fr/2002INPT010H.
Testo completoDerré, Jérémie. "Conception vibro-acoustique de panneaux composites intégrant des structures fractales". Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0019/document.
Testo completoSandwich structures with honeycomb core cells have been widely used within the aerospace industry, because of their high static bending stiffness at a lesser mass cost. The weight reduction is unfortunately responsible for a decrease in the acoustic transmission and a rise of the radiation of such structures. Therefore, a new passive strategy of structural vibration and acoustic radiation reduction is investigated. The founding idea is to used the geometrical network of the honeycomb core by filling some cells with small heterogeneities, in order to create obstacles for the structural waves, creating wave reflection, transmission or even dissipation of the mechanical energy. That results in localization of some modes, which is modifying their acoustic radiation. This study implies modeling, numerical simulation and experimental validation of sandwich structures locally overloaded by fractal distributions
Almusawi, Aqil mousa. "Mise en œuvre et optimisation des propriétés d'une structure sandwich en matériaux biosourcés (fibres et bois de chanvre) avec une matrice en polystyrène expansé pour le bâtiment". Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCA009/document.
Testo completoDue to the rapidly improving functionality of building materials, and increasingly complicated human resource management issues, the traditional cement-based building materials of the past are becoming less and less desirable.These outdated materials are being replaced by new structures of wall that better optimize choices of materials and their layouts. In this study, we propose a multi-function structure to be the unit of a typical wall (individual house), which can be produced via the use of inexpensive materials and classic manufacturing processes. To achieve this, we chose the renewable agricultural source of the hemp plant (hemp yarns and hemp shive particles), along with recycled expanded polystyrene, to manufacture a fully recyclable composite. We established a relationship between the physical-mechanical properties of the resulting composite and the parameters of the manufacturing process, particularly in the zone of high load reinforcement, we successfully manufactured a composite of 100% hemp shive particles. In addition, we have also prepared the numerical optimization phase of an alveolar sandwich structure by modeling the process and the obtained structure
Shahdin, Amir. "Surveillance vibratoire de l'endommagement dû à l'impact sur poutres en matériaux composites stratifiés, sandwiches et matériaux enchevêtrés par variations des paramètres modaux". Toulouse, ISAE, 2009. http://www.theses.fr/2009ESAE0019.
Testo completoAbakar, Malloum. "Analyse des mécanismes d'endommagement et du comportement vibratoire d'un composite à constituants naturels dans un environnement hydrique". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1020/document.
Testo completoIn recent decades, polymer composites reinforced with plant fibers have received significant attention from scientists. The use of reinforcing vegetable fibers makes it possible to improve the environmental performance of these materials reaching higher specific properties. Nevertheless, a major lock still hinders the development of these materials. Indeed, their sensitivity to water ageing, due to their hydrophilic nature, restricts their use. In this context, we propose, as part of this thesis, to analyze the effect of water ageing on static and dynamic behavior, to identify and monitoring the damage mechanisms of a sandwich structure biobased and its constituents. The composites used consist of a greenpoxy resin associated with flax fibers and a cork core for sandwich materials. In the first part of this work, we studied the static an dynamic behavior of the resin, the composites, cores and sandwich structures. This study led on the one hand to the determination of the mechanical characteristics and to the identification and the follow-up of the mechanisms of damage by acoustic emission and microscopic observations and on the other hand to the determination of the dynamic characteristics. In the second part, we first analyzed the kinetics of water diffusion in resin, skins, cores and sandwichs by identification of their diffusion parameters by the Fick model approach. Then, we are interested in the impact of water ageing on the behavior and mechanical properties iof sandwichs and its constituents
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 completoIn 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
Jean-St-Laurent, Mathilde. "Effet des températures froides sur le comportement à l'impact à basse vitesse de panneaux sandwiches en matériaux composites". Doctoral thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/70264.
Testo completoThe thesis project is focused on the effect of extreme cold temperatures on the low-velocity impact behavior of woven carbon/epoxy composite sandwich panels with Nomex honeycomb core forlunar exploration rovers. The project is divided into an experimental campaign and a numerical investigation. The experimental campaign developed includes the study of the effect of extreme cold temperatureson the mechanical behavior of the constituents of the sandwich panel individually, the study of the low velocity impact behavior of the sandwich panel under extreme cold temperatures and the investigation of the effect of impact temperature on the compression after impact behavior of the damaged panels. The sandwich panel studied is made of plain-weave carbon/epoxy composite skins[(±45)(0/90)(0/90)(±45)] with a Nomex honeycomb core. For the experimental campaign, tests are performed at room temperature, -70°C, and -150°C. The study of the effect of temperature on the mechanical behavior of the composite material used for the skins of the sandwich panel shows that the tensile strength decreases at low temperatures, while the compressive strength increases. The inplane shear behavior is characterized by an increase in the in-plane shear modulus and the in-plane shear strength at low temperatures, while the maximum in-plane shear strain diminishes. At cold temperatures, the out-of-plane compressive behavior of the Nomex honeycomb core is characterized by an increase of rigidity and maximum compressive strength. Impact of the sandwich panels at cold temperatures leads to an increase of damage for most impact conditions tested. The conjoint study of the absorbed energy and the damage induced by impact loadings shows that it requires less energy to produce damages at cold temperatures. Finally, the results of the impact tests show that the size of the impactor has an influence on the effect of temperature on the impact behavior of the sandwich panel. Compression after impact (CAI) tests show that the effect of impact temperature on the residual compressive strength is almost negligible, although impact temperature has an effect on the damage induced. For some impact conditions, a slight decrease of the residual compressive strength was measured for specimens impacted at low temperatures, while for the other impact conditions, impact temperature has simply no effect on the residual compressive strength.The effect of impact temperature on the residual compressive strength is negligible with regard to the reduction of the residual compressive strength between the undamaged panels and the panels with the least amount of damage in this study.The second part of the project is focused on the development of a numerical model using the finite element method for the simulation of impact loadings at room temperature, -70°C, and -150°C. The model for the composite material includes the use of three damage variables combined with aplasticity model. The in-plane failure is predicted with the maximum strain criteria. The post failure evolution of the damage variables is defined to have a linear softening. For the Nomex honeycomb core model, the cellular geometry of the Nomex core is modelled with each cell represented as aperfect hexagon. The material behavior of the cell wall is isotropic elastic perfectly plastic. The majority of the properties required for the composite and Nomex honeycomb core models comes from experimental investigations or the literature for all three temperatures. Results of the numerical simulations are validated with experimental data. It shows that the model can predict theoverall behavior of the sandwich panel under impact loading. The effects of temperature on the impact behavior of the sandwich panel are overall well captured by the model.
Lagardère, Émeric. "Comportement au fluage de structures sandwich thermoplastiques". Lille 1, 2006. http://www.theses.fr/2006LIL10156.
Testo completoThis work aims at investigating the creep behaviour of commingled yarn glass/polypropylene unidirectional and cross-ply composites and at predicting the long term behaviour (creep deformation and failure) of tubular industrial parts made of a peculiar sandwich structure (association of a glass/polypropylene composite core with two neat polypropylene skins) and manufactured by the extrusion-winding process. Two ways have been considered to reach this goal, both based on the well-established laminate theory. The first approach takes into account the linear viscoelastic behaviour of the skin and core materials. It has required the determination of the materials creep moduli and life curves over a quite long period of 6 months to one year. The second one is based on modelling the creep strain of the different sandwich layers. Short-term creep or creep-recovery tests (over 1 to 5 days) have allowed the identification of the parameters of various models describing the linear or non-linear viscoelastic and/or viscoplastic creep behaviours: Burgers (linear viscoelasticity + viscoplasticity), Findley (non-linear viscoelasticity), Shapery (non-linear viscoelasticity) coupled to Zapas-Crissman (viscoplasticity). The consistency and application range of both approaches have been experimentally validated on prototype industrial parts for some loading cases (internal hydraulic pressure without end effects) close to in-service conditions
Colis, Silviu-Mihail. "Magnétisme, transport et structure des systèmes de type "spin-valve" utilisant comme couche magnétique dure un sandwich couplé antiferromagnétiquement à base d'iridium". Université Louis Pasteur (Strasbourg) (1971-2008), 2001. http://www.theses.fr/2001STR13103.
Testo completoTom, Louis-Georges. "Contribution à l'étude numérique de la propagation d'un défaut de collage dans une structure sandwich Nida". Thesis, Le Mans, 2014. http://www.theses.fr/2014LEMA1036/document.
Testo completoSAFRAN Aircelle manufactures sandwich structures made of composite skins bonded to aluminium honeycomb core for aircraft’s engines nacelles applications. Local disbonds may occur at the skins/core interface and lead to significant strength reduction under in-service loadings. The present work was done with ISMANS and SAFRAN Aircelle and deals with the introduction of a “Virtual Testing” approach in order to reduce substantiation and validation cost of sandwiches structures with embedded disbond.In this study we have two kinds of models at two scales to describe the sandwich behaviour: the “homogeneized” model, which provide an industrial tool for design offices and the “detailed” model, which provide a specific tool for accurate analysis of disbond growth initiation at skin/core interface. Due to the numerical cost of the second type of model, the superelement technique has been successfully used which permits to gain computational costs without altering the result quality.Damage mechanics, with cohesive zone elements, have been chosen to numerically determine the disbond growth threshold after a comparative study with linear fracture mechanics and a full experimental method. Inputs data for industrial code using cohesive zone elements have been studied through an experimental investigation. DCB type tests on reinforced sandwiches were perfomed in order to determine the energy release rate at the skin/core interface. Various mode-mixity and pure opening mode are available using the same testing tool. The latter has been successfully modelled
Philippe, Marie-Hélène. "Etudes de quelques modélisations de structures en composite à haute rigidité en flexion". Phd thesis, Marne-la-vallée, ENPC, 1997. http://www.theses.fr/1997ENPC9709.
Testo completoThis work is devoted to the development of new modellings of composite structures with high specitif bending stiffness. The purpose is to propose suitable tools for the analysis of flexural stiffness. In the first part of the thesis, new plate modellings (2D modellings) are proposed to describe sandwich structures which core is homogeneous (foams) or can be considered as homogeneous (honeycombs). A new formulation of the classical sandwich theory based upon the REISSNER6Mindlin kinematic assumptions (the Sab’s theory), and multiparticle sandwih modellings based upon the M4 theory (Multiparticle Modelling of the Multilayered Materials), are developped. The second part is devoted to a modelling of a new sandwich structure called « hollow-core composite », with an heterogeneous core made of a serie of diagonal stiffeners, and which technology was developed at the CERAM laboratory of the ENPC. The hollow-core heterogeneous 3D medium was turn into an equivalent homogeneous 2D medium by using an homogeneization process. Assessments of thise modelling were conducted by comparing results from analytical exact solutions or finite-element meshes of the software SAMCEF. The accuracy of the different modellings developed in this thesis were shown. Thzy should be used to develop 2D finite-element meshes integrated in a market software, which will simplify the design of the sandwich and hollow-core structures
Sokolova, Olga. "Systèmes hybrides pour application automobile". Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE027.
Testo completoIn this thesis the investigation focused on the mechanical and forming properties of non-reinforced and locally reinforced metal/polymer/metal sandwiches, used for the further manufacturing of automotive parts. The physical-chemical properties for bonding as well as the deep drawing and stretching behaviour of such sandwiches were studied too. It was observed, that the preliminary surface treatment as corona and/or plasma strongly influence the surface morphology of the PP-PE foil by activating the polymer surface. A new method to insert local reinforcements in the pre-fabricated sandwich was developed after optimizing the conditions for bonding in the roll-bonding process. The sandwiches without the local plate inlays show the high formability compared to the seel mono-materials. The deformation behaviour of sandwiches depends strongly on the size, shape and the position of the inlays to forming
Philippe, Marie-Hélène. "Etudes de quelques modélisations de structures en composite à haute rigidité en flexion". Phd thesis, Ecole Nationale des Ponts et Chaussées, 1997. http://tel.archives-ouvertes.fr/tel-00529473.
Testo completoMárquez, Costa Juan Pablo. "Caractérisation et modélisation des interfaces dans les composites organiques stratifiés à haute température : Application à la tenue au feu des structures aéronautiques PhyFire LOT 2 - Développement de modèles de comportement du composite Caractérisation en température de la ténacité en mode II des interfaces des CMO en utilisant l’effet Joule Caractérisation du comportement visqueux des interfaces CMO et influence sur la propagation de délaminage Convention PhyFIRE 2 - LOT 2 : Développement d’un cadre de modélisation pour les matériaux composites Durabilité des matériaux composites en conditions extrêmes : vers la prédiction des propriétés de tenue au feu Durability of Composite Materials under Severe Temperature Conditions : Influence of Moisture Content and Prediction of Thermo- Mechanical Properties During a Fire Towards the Prediction of Sandwich Composites Durability in Severe Condition of Temperature : A New Numerical Model Describing the Influence of Material Water Content during a Fire Scenario". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2021. http://www.theses.fr/2021ESMA0004.
Testo completoWithin the framework of the fire resistance of composite materials, it is necessary to assess the degradation of their thermal and mechanical properties due to mass losses, matrix cracking and/or delamination cracks. Nevertheless, few studies in the literature about the temperature resistance of aeronautical composites concern the mechanical behaviour and the rupture of interfaces before any thermal degradation,subject which is the main topic of this work. Thus, the objective is to propose a failure model concerning both the delamination crack initiation and growth under thermomechanical loads. Much of this work has focused on the characterisation of interface properties using an analysis of mode II crack propagation tests for Joule heated specimens. These numerical analyses show that the ply behaviour does not explain the macroscopic pseudo-ductile response observed experimentally. Thus, a test-calculation dialog method, comparing the kinematic fields measured by digital images correlation and those simulated by finite elements, underlines the importance of the viscous behaviour at the interface scale. By a similar FEMU approach the parameters of a cohesive-type fracture law have been identified in temperature and taking into account the different sources of uncertainty. This work highlights the similarity between plane and out-of-plane shearing, both on behaviour and on failure. In parallel, the analysis of temperature resistance tests by laser impact made it possible to establish a crack initiation criterion by a coupled stress and energy approach. A comparison of this criterion with the parameters of the cohesive zone law previously identified makes it possible to discuss about the modeling scale of the interface
Haddad, Mohamed. "Développement d'un procédé d'enroulement filamentaire adapté aux matériaux composites sandwichs et caractérisation mécanique des matériaux". Thesis, 2017. http://www.theses.fr/2017ENAM0031/document.
Testo completoComposite materials, and especially sandwich structures, have been studied for decades. Indeed, the association between lightness and resistance of these structures leads to the development of their use. Their manufacturing method and their characterization remain as essential points in most studies. This work is part of the FUI SOLLICITERN project, which aims to design a composite water treatment tank for vehicles intended for this purpose. As a first step, and based on the classical filament winding principal, we aim to search designs that are best adapted to the fabrication of a curved sandwich material on a cylindrical mandrel, while respecting the process parameters of and their influence on structural properties. Since an optimal solution was validated, the constituent materials were studied by measuring mechanical properties. The objective is to help our industrial partner to validate a manufacturing solution and verify that such properties are the expected ones. For that, several static and dynamic characterizations were carried out on curved samples manufactured by the optimized process designed for our application. This part includes various experimental tests in order to validate the structure behavior with the most appropriate dimensions and material combinations, taking into account the manufacturing process. At the end, the best structural configuration is retained for the first tank prototype fabrication