Tesi sul tema "Polymer matrix composites"
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1
Foch, Bethany J. (Bethany Joy). "Integrated degradation models for polymer matrix composites". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10520.
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Clark, Richard L. "Altering the fiber-matrix interphase in semicrystalline polymer matrix composites". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020216/.
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Benethuilière, Thibaut. "Phénomènes physico-chimiques aux interfaces fibre/matrice dans des composites SMC structuraux : Du mouillage à l'adhésion". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI151.
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Joffe, Roberts. "Matrix cracking and interfacial debonding in polymer composites". Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26359.
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Vyawahare, Siddharth M. Ahmed Ikram. "Protective thermal spray coatings for polymer matrix composites". Diss., A link to full text of this thesis in SOAR, 2006. http://soar.wichita.edu/dspace/handle/10057/684.
Testo completoAbstract (sommario):
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering."December 2006." Title from PDF title page (viewed on Sept. 18, 2007). Thesis adviser: Ikram Ahmed. Includes bibliographic references (leaves 79-81).
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Goertzen, William Kirby. "Thermosetting polymer-matrix composites for structural repair applications". [Ames, Iowa : Iowa State University], 2007.
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7
Carroll, H. "Fatigue damage mechanisms in advanced polymer matrix composites". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597310.
Testo completoAbstract (sommario):
Recently, advances have been made in the design, manufacture and application of composite materials. A great deal of this progress has been made in the field of Fibre-Reinforced-Plastics (FRP). FRP often have greater strength to weight and stiffness to weight ratios than traditional materials such as metals, which makes them ideal for use in many application especially in aeronautical and aerospace sectors. For example Carbon-Fibre-Reinforced-Plastics (CFRP) are becoming more common in civil and military aircraft structures. However, there remain many unanswered questions regarding the behaviour of these materials especially under in-service conditions such as fatigue. There is an increasingly urgent need to gain an understanding of how FRPs behave. To fully understand the fatigue of a material it is necessary to gain an understanding of how damage initiates and accumulates and how the damage will affect the materials properties. It is also clear that to fully utilise FRPs it is necessary to be able to model the relationship between microstructural damage and the materials mechanical properties. This work has characterised the fatigue life of a quasi-isotropic carbon fibre reinforced composite, HS/919, at four R ratios. These are R=0.1 (tension-tension), R=+10 (compression-compression), R = -0.3 and R=-3.3 (both tension-compression). Those R ratios with a majority compression loading cycle experienced lower fatigue lives than those with a mainly tensile loading cycle. The work also highlighted the delaminations were a major damage mechanism. Post failure analysis of the fatigue specimens showed that the primary delamination, was occurring at different interfaces dependent on the loading cycle. With a mainly tensile loading cycle the delamination was occurring at the 0°/90° interface. While the mainly compressive loading cycle showed delaminations at the 0°/45° interface. This phenomenon was investigated using a modified mixed-mode bending technique developed by Reeder and Crews at Nasa. Static and fatigue tests were carried out on both the highlighted interfaces at three mixed-modes, MI/MII of 1/3, 1/1 and 3/1. Static tests showed that the 0°/45° interface was the weaker. In the fatigue tests two phenomena were observed, 1) that the strain energy release rate steadily decreased with crack length, 2) the strain energy release rate initially increased and then decreased. This is due to fibre bridging which was seen in both interface but was more apparent for the tests at the 0°/90° interface. There was a large amount of scatter in the fatigue data, especially at the 0°/45° interface. This made fitting a Paris type law to crack growth rates impossible for this interface. A Paris law was fitted to the 0°/90° data. It was hoped to transfer this knowledge to fatigue coupons with inserts.
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Cunningham, Ronan A. (Ronan Anthony). "High temperature degradation mechanisms in polymer matrix composites". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10722.
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GUERRIERO, ANDREA. "Development of polymer matrix composites for sensing applications". Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2506254.
Testo completoAbstract (sommario):
The PhD thesis describes the experimental activity concerning the elaboration and characterization of ceramic-polymer nanocomposites for dielectric and piezoelectric applications. In particular,
barium titanate based 0-3 composites were processed by means of the photo-polymerization process and the solvent casting technique.
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Olea, Mejia Oscar Fernando. "Micro and nano composites composed of a polymer matrix and a metal disperse phase". Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5135/.
Testo completoAbstract (sommario):
Low density polyethylene (LDPE) and Hytrel (a thermoplastic elastomer) were used as polymeric matrices in polymer + metal composites. The concentration of micrometric (Al, Ag and Ni) as well as nanometric particles (Al and Ag) was varied from 0 to 10 %. Composites were prepared by blending followed by injection molding. The resulting samples were analyzed by scanning electron microscopy (SEM) and focused ion beam (FIB) in order to determine their microstructure. Certain mechanical properties of the composites were also determined. Static and dynamic friction was measured. The scratch resistance of the specimens was determined. A study of the wear mechanisms in the samples was performed. The Al micro- and nanoparticles as well as Ni microparticles are well dispersed throughout the material while Ag micro and nanoparticles tend to form agglomerates. Generally the presence of microcomposites affects negatively the mechanical properties. For the nanoparticles, composites with a higher elastic modulus than that of the neat materials are achievable. For both micro- and nanocomposites it is feasible to lower the friction values with respective to the neat polymers. The addition of metal particles to polymers also improves the scratch resistance of the composites, particularly so for microcomposites. The inclusion of Ag and Ni particles causes an increase in the wear loss volume while Al can reduce the wear for both polymeric matrices.
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Wright, Richard J. "Bolt bearing creep behavior of highly loaded polymer matrix composites at elevated temperatures". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17362.
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Sudarisman. "Flexural behaviour of hybrid fibre-reinforced polymer (FRP) matrix composites". Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2110.
Testo completoAbstract (sommario):
The flexural behaviour of three different hybrid fibre-reinforced polymer (FRP) matrix composites, i.e. S2-glass/E-glass/epoxy, TR50S carbon/IM7 carbon/epoxy, and E-glass/TR50S carbon/epoxy hybrid FRP composites, has been investigated. The main objectives of this study were to: (i) improve the flexural properties of the parent composite materials, i.e. E-glass/epoxy and TR50S carbon fibre/epoxy composites, through substitution of stronger fibres, i.e. S2-glass and IM7 carbon fibres, for the fibres of the parent composite materials, and (ii) determine the optimum stacking configurations that produced the maximum increase in flexural properties of the resulting hybrid composites. In addition to these, two secondary objectives related to the preliminary investigation of determining the optimum stacking configurations have also been established. The two secondary objectives were to: (i) determine the optimum values of the processing parameters of the composites under investigation, and (ii) determine the compressive strength and compressive modulus of the parent materials.The investigation was carried out experimentally, thus data presented and analysed were obtained from laboratory work. Optimum values of five processing parameters, i.e. (i) the concentration of matrix precursor within the solvent solution utilised to wet the fibres, (ii) the compressive pressure applied during hotpress curing, (iii) the vacuum pressure of the atmosphere inside the curing chamber, (iv) the dwell time during hot-press curing, and (v) the holding temperature during hot-press curing, have been established. The criteria for determining the optimum values of these parameters were optimum fibre content, minimum void content, and optimum flexural properties. Compressive strength and compressive modulus of the parent composite materials have also been determined.Specimens were cut from flat composite plates using a diamond-tipped circular blade saw. The longitudinal edges of the specimens were carefully polished to remove any possible edge damage due to cutting. The composite plates were produced from preforms comprised of a number of glass fibre/epoxy prepregs, carbon fibre/epoxy prepregs or a combination of these. All the fabrication procedures were carried out using manual techniques. Whilst the compressive tests were conducted in accordance with the ASTM D3410-03 standard, flexural tests were carried out according to Procedure A of the ASTM D790-07 standard. Span-to depth ratios, S/d, of 16, 32, and 64 were selected for flexural testing in order to determine the minimum value of S/d required to ensure flexural failure rather than shear failure. Fibre and void contents were evaluated from optical micrograph images of the slices perpendicular to the fibre direction of the samples.It was concluded that the optimum values of the five processing parameters under investigations were: (i) epoxy concentration, C[subscript]e ~ 50 wt%, (ii) compressive pressure, p[subscript]c ~ 1.00 MPa, (iii) vacuum pressure, p[subscript]v ~ 0.035 MPa, (iv) dwell time, t ~ 30 minutes, and (v) holding temperature, T ~ 120 °C. Compressive tests revealed that the order of compressive strength for the parent composite materials were arranged as follows: S2-glass fibre/epoxy (476 MPa), E-glass fibre/epoxy (430 MPa), IM7 carbon fibre/epoxy (426 MPa), and TR50S carbon fibre/epoxy (384 MPa). The compressive modulus of these parent composite materials were found to be ordered as follows: IM7 carbon fibre/epoxy (67.9 GPa), TR50S carbon fibre/epoxy (61.8 GPa), S2-glass fibre/epoxy (45.1 GPa), and E-glass fibre/epoxy (32.9 GPa). After considering these compressive properties, three different hybrid combinations, as mentioned earlier, were manufactured and evaluated with the prepreg layers of the fibre composites possessing higher compressive strength being placed at the compressively loaded side of the flexural specimens.Shorter beam specimens (S/d = 16) of the three hybrid systems exhibited increased flexural strength as the amount of stronger fibre content was increased, but no hybrid effect was noted. The increase appeared to follow the rule of mixtures and this was attributed to their failure mode being shear failure. For beams tested at S/d = 32 and S/d = 64, the three hybrid systems demonstrated three different trends. The S2-glass fibre/E-glass fibre/epoxy hybrid system, where the S2-glass fibre (substituted at the compressive loading face) was slightly stronger and stiffer compared to the E-glass fibre at the tensile side, demonstrated increases in flexural strength together with the presence of a hybrid effect following partial substitution of the S2-glass fibre for E-glass fibres at the compressive side. The IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, where the IM7 carbon fibre (substituted at the compressive side) was slightly stronger but significantly stiffer in compression compared to the TR50S fibre at the tensile side, exhibited a slight increase in flexural strength that appeared to obey the rule of mixtures.This result was attributed to the strength increase in the compressive side introduced by the substituted fibres not being sufficient to suppress the increase of internal compressive stress due to the increase in compressive modulus of the substituted fibres. The E-glass fibre/TR50S carbon fibre/epoxy hybrid system, where the E-glass fibre (substituted at the compressive side) was found to be slightly stronger but significantly less stiff in compression compared to the TR50S fibre at the tensile side, demonstrated a significant increase in flexural modulus and also exhibited a significant hybrid effect. The decrease in internal compressive stresses generated at the compressive side due to the decreased compressive modulus of the substituted fibre, when combined with the increase in compressive strength of the substituted fibre, was thought to led to the significant increase of flexural strength for this hybrid system.General trends observed in flexural modulus for the three hybrid systems were reasonably similar with any change in flexural modulus appearing to obey the rule of mixtures. Whilst an increase in flexural modulus was noted for higher contents of stronger fibre in the case of the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system, a decrease in flexural modulus with increased quantities of stronger fibre was exhibited by the E-glass fibre/TR50S carbon fibre/epoxy hybrid system. The increase or decrease in flexural modulus was attributed to the relative stiffness in compression of the substituted fibre when compared to that of the respective parent composite materials.Unlike the S2-glass fibre/E-glass fibre/epoxy hybrid system and IM7 carbon fibre/TR50S carbon fibre/epoxy hybrid system that did not exhibit any significant trend with regards the effect of the substitution of stronger fibre at the compressive side, the E-glass fibre/TR50S carbon fibre hybrid system demonstrated a significant increase in the energy stored to maximum stress with increasing content of the stronger fibre. This increase was mainly attributed to the increased strain–to-maximum stress of the hybrid system with respect to that of the parent composite material.In addition, for the three hybrid systems under investigation, the most significant change in flexural properties was noticed following substitution of the first layer at the compressive face. The relative position with respect to the neutral plane of the substituted layer was thought to be the reason for this phenomenon. It was also noted that flexural properties increased with the increase in S/d. A change in failure morphology was noted with the change of S/d from 16 to 32. It was thus determined that a S/d ratio of at least 32 was required in order to promote flexural failure (as opposed to shear failure). For the S2-glass fibre/E-glass fibre/epoxy hybrid system, this change appeared more obvious in comparison with that the other two hybrid systems with this change being accompanied by a significant increase in flexural strength.The main general conclusions that could be drawn from this investigation were that, although the flexural modulus appeared to obey the rule of mixture, an increase in flexural strength together with the presence of a hybrid effect, would most probably be observed when the fibre substituted at the compressive side possessed a significantly lower modulus combined with significantly higher compressive strength as demonstrated by the hybrid TR50S carbon - E-glass FRP composites. The most significant change in properties was exhibited by the first layer substitution whilst increasing the value of S/d resulted in an increase of flexural strength, with S/d = 32 being determined to be sufficient in order to promote flexural failure as opposed to shear failure.
13
Slesinger, Nathan Avery. "Thermal modeling validation techniques for thermoset polymer matrix composites". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/26641.
Testo completoAbstract (sommario):
Process modeling is becoming a widely-accepted tool to reduce the time, cost, and risk in producing increasingly large and complicated composite structures. Process modeling reduces the need for physical parts, as it is not practical or economical to design and fabricate large composite structures using a trial-and-error approach. The foundation of the composite manufacturing process, and thus of process models, is the thermal history of the composite part during cure. Improperly curing the composite part will compromise its mechanical properties. Consequently, proper validation of the thermal model input parameters is critical, since the simulation output depends on the accuracy of the input. However, there are no standard methods to validate thermal process model input parameters.
In this work, repeatable and robust methods were developed to isolate and validate the conductive heat transfer, thermochemical, and convective heat transfer sub-models. By validating the sub-models, the uncertainty of the complete thermal simulation was significantly reduced. Conductive and thermochemical material models were validated by comparing the thermal response of a material surrounded by rubber bricks to a 1-D simulation of the same materials. Four composite prepreg systems and their respective material models were tested, with agreement ranging from excellent (errors less than 1.0 °C) to poor (errors greater than 5.0 °C).
Calorimetery, visual monitoring, and CFD were used to characterize the convective heat transfer environment inside the UBC autoclave. The validation methods were also used to better understand the capabilities and limitations of the autoclave. Local variations in airflow patterns and heat transfer coefficients showed that heat transfer can be highly variable in an individual piece of equipment. Simple procedures for characterization of an autoclave or oven were demonstrated.
The developed methods can be used individually, or in combination, to validate thermal models and reduce uncertainties associated with the cure of composites. With further refinement, the demonstrated methods can be developed into validation standards for thermal modeling of composite materials.
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ALFORD, LORENLEYN DE LA HOZ. "TRIDIMENTIONAL CHARACTERIZATION OF POLYMER MATRIX GLASS FIBER REINFORCED COMPOSITES". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29681@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Compósitos são materiais tipicamente não homogêneos e anisotrópicos,tanto do ponto de vista microestrutural quanto de suas propriedadesmecânicas. Os mecanismos de falha são afetados pela distribuição espacial e pela qualidade da adesão na interface reforço-matriz. As técnicas tradicionais de caracterização microscópica são bastante limitadas para caracterizar este tipo de material, já que seções ou projeções bidimensionais podem não revelar completamente a microestrutura anisotrópica. Quando se busca entender a origem de mecanismos de falha, estas limitações são ainda mais importantes. Nesta dissertação foi desenvolvida uma metodologia de caracterização tridimensional baseada em microtomografia de raios-x. O material avaliado foi um compósito de matriz epóxi reforçado com fibras de vidro alinhadas unidirecionalmente. Corpos de prova (CP) foram tomografados antes e depois de ensaios de flexão em diferentes níveis de tensão. As imagens 3D foram analisadas para visualizar e quantificar vazios e trincas, tanto originados no processo de fabricação como gerados durante o ensaio mecânico. Para visualizar a evolução de defeitos com a tensão/deformação, foi estabelecido um procedimento de registro 3D entre as imagens dos CP´s como recebidos, após ensaio no regime elástico e após a falha. Uma avaliação da incerteza do procedimento foi realizada tomografando mais do que uma vez o CP, registrando e comparando as imagens 3D. Os resultados indicaram um crescimento do volume de defeitos após a falha do material. A visualização 3D de regiões específicas das tomografias permitiram identificar a formação e o crescimento de defeitos gerados pelo esforço mecânico.
Composites are typically no homogeneous and anisotropic materials, both from the point of microstructural view as well mechanical properties. The failure mechanisms are affected by the spatial distribution and quality of the adhesion the interface matrix-reinforcement. The traditional techniques of microscopic characterization are enough limited to characterize this type of material since sections or two-dimensional projections may not fully reveal the anisotropic microstructure. When search to understand the origin of failure mechanisms, these limitations are even more important. In the present work, a three-dimensional characterization methodology based on X-ray microtomography was developed. The material evaluated was an epoxy matrix composite reinforced with glass fibers unidirectionally aligned. The samples (CP) were tomographed before and after the bending tests at different loads. The 3D images were analyzed to identify and quantify voids and cracks, both defects were originated in the process of manufacturing as were generated during the mechanical tests. A 3D registration procedure was developed between the sample images obtained before and after the bending tests, in the elastic range and after the failure. An assessment of the uncertainty of the procedure was performed doing more than one tomography of the samples as received, registering and comparing the resulting 3D images. The results showed a clear increase in the volume of the defects after material failure. The 3D visualization of specific regions of the tomographies allowed the identification of the formation and the growth of these defects generated by the mechanical stress.
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Islam, Md Zahirul. "Fatigue Behavior of Flax Fiber Reinforced Polymer Matrix Composites". Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31577.
Testo completoAbstract (sommario):
Bio-based flax fiber polymer composites (FFPC) have the potential to replace metals and synthetic fibers in certain applications due to their unique mechanical properties. However, the long term reliability of FFPC needs to be better understood. In this study, the fatigue limit was evaluated using mathematical, thermographic, and energy-based approaches. Each approach determined fatigue limits around 45% load of ultimate tensile strength at a loading frequency of 5 Hz. Thermographic and energy-based approaches were also implemented at different loading frequencies (5, 7, 10, and 15 Hz) to define the effect of loading frequency on the fatigue life. Fatigue limit was found to decrease slowly with increasing loading frequency. Moreover, two forms of damage energy (thermal and micro-mechanical) during cyclic loading was separated using an experimental approach to pinpoint the main responsible damage energy for decreasing fatigue limit with increasing loading frequency.
16
Ochola, Robert O. "Investigation of strain rate sensitivity of polymer matrix composites". Thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6740.
Testo completoAbstract (sommario):
Includes bibliographical references (leaves 210-219)An investigation into high strain rate behaviour of polymer composites was performed by developing a finite element model for a fibre reinforced polymer (FRP) plates impacted at varying strain rates. The work was divided into three facets, firstly to characterize the FRP material at varying strain rates, to develop a constitutive model to elucidate the relationship between strain rate and ultimate stress and lastly to use the experimental data to develop a finite element model. Experimental work performed in support of this model includes material characterization of unidirectional carbon and glass fibre reinforced epoxy at varying impact strain rates. The data is then used to develop a suite of constitutive equations that relate the strain rate, ultimate stress and material loading type. The model is of a linear and non-linear viscoelastic type, depending on the type of loading and is applicable to a FRP plate undergoing out-of-plane stresses. This model incorporates techniques for approximating the quasi-static and dynamic response to general time-varying loads. The model also accounts for the effects of damage, the linear and non-linear viscoelastic constitutive laws reporting failure by instantaneously reducing the relevant elastic modulus to zero. An explicit solver is therefore utilised in order to ensure stability of the numerical procedure. Glass fibre reinforced plastics (GFRP) was found to be more strain rate sensitive in all directions when compared to carbon fibre reinforced plastics (CFRP). The validation process therefore involves plate impact experimental testing on GFRP plates. The data from these experiments compare to within 8% of the finite element model that incorporates both damage and the developed strain rate sensitivity constitutive equations. For the first time a model that includes progressive damage with built-in strain rate sensitivity is developed for these particular FRP systems. Furthermore, the ultimate stress has been related to strain rate using an empirical technique. This technique allows for the prediction of dynamic ultimate stresses given the quasi-static ultimate stresses, again for this particular material systems.
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Caceres, Arsenio. "Local damage analysis of fiber reinforced polymer matrix composites". Morgantown, W. Va. : [West Virginia University Libraries], 1998. http://etd.wvu.edu/templates/showETD.cfm?recnum=328.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 1998.Title from document title page. Document formatted into pages; contains x, 107 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 104-107).
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Shan, Xiaobing Cheng Zhongyang. "High dielectric constant 0-3 ceramic-polymer composites". Auburn, Ala, 2009. http://hdl.handle.net/10415/1820.
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Bakar, Azhar Abu. "Micro- and macro-mechanical properties in advanced polymer matrix composites". Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301430.
Testo completo
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D'Antino, Tommaso. "Bond behavior in fiber reinforced polymer composites and fiber reinforced cementitious matrix composites". Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423690.
Testo completoAbstract (sommario):
The use of fiber reinforced composites for strengthening reinforced concrete (RC) structures has gained great popularity in the last few decades. Fiber reinforced polymer (FRP) composites represent an effective solution for strengthening existing reinforced concrete structures due to their mechanical properties and relatively low cost. FRP composites have been extensively studied, and design codes/recommendation/guidelines are available. One of the most important concerns regarding the use of FRP for strengthening RC structures is the proper design to preclude debonding failure. The bond behavior of FRP-concrete joints is studied in this thesis by means of a fracture mechanics approach, assuming that the debonding is characterized by a pure Mode II failure. The most important analytical formulations for the evaluation of the bond strength of FRP-concrete joints are analyzed and discussed. The accuracy of each analytical model studied is assessed through the use of a wide experimental database including different test set-ups and composite materials. Furthermore, the accuracy of several analytical models for the evaluation of the effective bond length, i.e. the minimum length needed to fully develop the bond strength of the FRP-concrete joint, is assessed.
A promising alternative to FRP composites is fiber reinforced cementitious matrix (FRCM) composites. FRCM composites are comprised of high strength fibers applied to the concrete substrate through the use of inorganic cementitious matrix. FRCM composites are still in their infancy, and very limited work is available in the literature. In the second part of this thesis, an extensive experimental campaign conducted on PBO FRCM-concrete joints is presented and discussed. Since the weakness of FRCM-concrete joints is located at the matrix-fiber interface, the study of the stress-transfer mechanism between the fibers and the matrix is of particular importance. Specimens with different bonded lengths and bonded widths are presented. The fracture mechanics approach used to study the FRP-concrete joints is extended to the study of FRCM-concrete joints, and the exsistence of an effective bond length similar to that observed for FRP-concrete joints is investigated. The results obtained through the fracture mechanics approach are used for the implementation of numerical models to investigate the fiber-matrix interface bond behavior for FRCM-concrete joints that include more than one layer of matrix.L’utilizzo di compositi fibrorinforzati per il rinforzo e l’adeguamento di strutture esistenti in calcestruzzo armato (c.a.) ha raggiunto una grande popolarità negli ultimi decenni. Tra i materiali compositi, l’utilizzo dei cosiddetti polimeri fibrorinforzati (fiber reinforced polymer, FRP) rappresenta una soluzione efficace per l’intervento su strutture esistenti in c.a. grazie all’elevata resistenza meccanica ed al costo relativamente non elevato del materiale. Gli FRP sono stati largamente studiati negli ultimi anni e sono attualmente disponibili diverse linee guida per la progettazione di questo tipo di rinforzo in tutto il mondo. Uno dei problemi di maggiore importanza nell’utilizzo di compositi FRP è costituito dalla valutazione della resistenza al distacco (debonding) del composito dal supporto su cui è applicato. In questa tesi viene analizzato il comportamento di giunti FRP-calcestruzzo nel contesto della meccanica della frattura, assumendo che la rottura per distacco sia assimilabile ad un modo di rottura di tipo II. Le più importanti formulazioni analitiche per la valutazione della resistenza d’adesione del composito al substrato sono analizzate e discusse. L’accuratezza di ognuno dei modelli analitici considerati è stata valutata per mezzo di un esteso database sperimentali in cui sono presenti i risultati di test condotti su diversi materiali compositi e con diverse configurazioni di prova. Viene inoltre valutata l’accuratezza di alcuni modelli analitici per il calcolo della lunghezza effettiva d’aderenza, cioè della lunghezza minima necessaria per poter sviluppare appieno il meccanismo di adesione FRP-calcestruzzo. Una promettente alternativa all’utilizzo dei compositi FRP è rappresentata dai cosiddetti materiali compositi a matrice cementizia (fiber reinforced cementitious matrix, FRCM), costituiti da fibre lunghe ad alta resistenza applicate a supporti in calcestruzzo per mezzo di matrici cementizie. I compositi FRCM rappresentano una novità nel mondo del rinforzo di strutture esistenti in c.a. e la letteratura disponibile a riguardo è ancora assai limitata. Nella seconda parte di questa tesi viene presentata e discussa una vasta campagna sperimentale condotta su provini di FRCM di diversa lunghezza e larghezza costituiti da fibre in PBO e matrice cementizia applicata su supporti in calcestruzzo. Dal momento che la rottura nei giunti FRCM-calcestruzzo avviene all’interfaccia fibra-matrice, lo studio del meccanismo di trasmissione degli sforzi da fibra a matrice è di particolare importanza in questi compositi. L’approccio di meccanica della frattura applicato nel caso di giunti FRP-calcestruzzo è esteso al caso dei compositi FRCM ed è indagata la possibile esistenza di una lunghezza effettiva d’aderenza simile a quella osservata nei compositi FRP. I risultati ottenuti dall’approccio di meccanica della frattura sono utilizzati per l’implementazione di modelli numerici che permettono di studiare il comportamento di adesione fibra-matrice in compositi che includano più di uno strato di matrice cementizia.
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Pafitis, Demosthenis Georgeou. "Environmental effects on the progressive crushing of composites". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281999.
Testo completo
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Bausano, John Vincent. "Structural Integrity of Polymer Matrix Composites Exposed to Fire Conditions". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31473.
Testo completoAbstract (sommario):
Polymer matrix composites (PMCâ s) perform well under many loading conditions and situations. Exposure of PMCâ s to fire is a concern due to their inherent material degradation at elevated temperatures. The elevated temperature response of PMCâ s to combined thermal and mechanical loads are especially of concern.
PMC thermal and mechanical properties undergo transformations at elevated temperatures. Some of these effects are reversible if the maximum temperatures are lower than approximately 200ºC. The stiffness is significantly reduced at elevated temperatures but if the applied temperature is under the thermal degradation temperature of the matrix, the stiffness should be recoverable upon cooling. Some effects like the endothermic decomposition of the matrix are not reversible effects.
This study focuses on reversible properties in the temperature range from room temperature to about 200ºC. Thermally these effects alter the thermal conductivity and specific heat. Reversible elastic effects considered are the off axis stiffness reductions as functions of temperatures.
Thermal profile predictions were conducted using a finite difference code that included convection and radiation effects on the front and back faces of the composite. These predictions were shown to be in good agreement with experimental data.
A modified classic laminate analysis (CLT) was implemented to predict the failure times of the composites under combined thermal and mechanical loading. The Budiansky-Fleck micro-buckling analysis technique was used as the failure function of the [0º] surface plies. A finite element analysis (FEA) analysis was also performed and showed good agreement with the experimental data.Master of Science
23
Wang, Xufeng Materials Science & Engineering Faculty of Science UNSW. "Application of single-part adhesives as healing agent in self-healing composites". Awarded by:University of New South Wales. Materials Science and Engineering, 2007. http://handle.unsw.edu.au/1959.4/32233.
Testo completoAbstract (sommario):
The aim of this study was to develop a new single-part healing system for self-healing composites. The self-healing approach to composite repair has been developed in the last two decades and means that a damaged area can be repaired by material already housed within the structure. The background and development of self-healing has been reviewed. The two main self-healing mechanisms are discussed. To date only two part self healing systems have been examined. These require diffusion of the separate constituents to a single location in order to effect cure and restore strength. Single part adhesives do not have this disadvantage and are therefore very attractive. Several candidate single-part adhesive or resin systems were considered and discussed according to the critical requirements of a self-healing system. A series of experiments was undertaken to evaluate the possibility of candidate adhesive systems being effective for self-healing by focusing on the determination of storage stability and bonding efficiency. The results of storage stability testing showed that the stability of cyanoacrylate and polyurethane adhesives was poor. However silane and polystyrene cements showed good storage stability. Very low bonding efficiency was achieved with polystyrene cement but a 22% strength recovery was obtained with the silane 3-[tris(trimethylsiloxy)silyl]-propylamine. Suggestions for further research into single-part healing systems are also given.
24
Nam, Jae-Do. "Polymer matrix degradation : characterization and manufacturing process for high temperature composites /". Thesis, Connect to this title online; UW restricted, 1991. http://hdl.handle.net/1773/9867.
Testo completo
25
Uleck, Kevin R. "A hybrid model for fatigue life estimation of polymer matrix composites". College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3312.
Testo completoAbstract (sommario):
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
26
Dinulovic, Mirko. "Assessment of dielectric models and their application to polymer matrix composites". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ39105.pdf.
Testo completo
27
Hu, Yile, e Yile Hu. "Peridynamic Modeling of Fiber-Reinforced Composites with Polymer and Ceramic Matrix". Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625367.
Testo completoAbstract (sommario):
This study focuses on developing novel modeling techniques for fiber-reinforced composites with polymer and ceramic matrix based on Peridynamic approach. To capture the anisotropic material behaviors of composites under quasi-static and dynamic loading conditions, a new peridynamic model for composite laminate and a modified peridynamic approach for non-uniform discretization are proposed in this study. In order to achieve the numerical implementation of the proposed model and approach, a mixed implicit-explicit solver based on GPU parallel computing is developed as well.
The new peridynamic model for composite laminates does not have any limitation in fiber orientation, material properties and stacking sequence. It can capture the expected orthotropic material properties and coupling behaviors in laminates with symmetric and asymmetric layups. Unlike the previous models, the new model enables the evaluation of stress and strain fields in each ply of the laminate. Therefore, it permits the use of existing stress- or strain-based failure criteria for damage prediction. The computation of strain energy stored at material points allows the energy-based failure criteria required for delamination propagation and fatigue crack growth. The capability of this approach is verified against benchmark solutions, and validated by comparison with the available experimental results for three laminate layups with an open hole under tension and compression.
The modified peridynamic approach for non-uniform discretization enables computational efficiency and removes the effect of geometric truncations in the simulation. This approach is a modification to the original peridynamic theory by splitting the strain energy associated with an interaction between two material points according to the volumetric ratio arising from the presence of non-uniform discretization and variable horizon. It also removes the requirement for correction of peridynamic material parameters due to surface effects. The accuracy of this approach is verified against the benchmark solutions, and demonstrated by considering cracking in nuclear fuel pellet subjected to a thermal load with non-uniform discretizations.
Unlike the previous peridynamic simulations which primarily employs explicit algorithm, this study introduces implicit algorithm to achieve peridynamic simulation under quasi-static loading condition. The Preconditioned Conjugate Gradient (PCG) and Generalized Minimal Residual (GMRES) algorithms are implemented with GPU parallel computing technology. Circulant preconditioner provides significant acceleration in the convergence of peridynamic analyses. To predict damage evolution, the simulation is continued with standard explicit algorithms. The validity and performance of this mixed implicit-explicit solver is established and demonstrated with benchmark tests.
28
Lapping, Preston. "ROLE OF CARBONACEOUS MATERIALS IN POLYMER MATRIX COMPOSITES FOR FRICTION APPLICATIONS". OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1568.
Testo completoAbstract (sommario):
The purpose of this research was to study the friction performance characteristics of a Copper, Antimony, and sulfide free environmentally automotive friction material using different allotropes of graphite as a replacement. Model brake friction materials were created and tested on a full scale brake dynamometer using the Society of Automotive Engineers J2430 test and Brake Effectiveness Evaluation Procedure. The dynamometer testing revealed the graphite replacement to have higher average effectiveness values when compared to the baseline friction material currently in production. The model samples generally had higher wear rates but some were comparable to the baseline and would be acceptable in real world applications. Some of the model samples displayed stable characteristics under varying load and linear braking velocity conditions, ultimately passing the criteria required. The model samples (RD18670A/B/C/D/E/F/G) displayed average effectiveness values of 0.425, 0.435, 0.4125, 0.425, 0.475, failed test, and 0.35 respectively, which is on average a substantial gain over the baseline effectiveness value average of 0.3125. Sample RD18670F proved to be the most promising replacement for the baseline 1999 Ford Crown Victoria friction lining. This is due to a higher average effectiveness value of 0.5, during both the high speed and low speed testing, than the baseline friction lining material of 0.325. Also, RD18670F displayed comparable wear rates to the baseline test, with 0.384mm lost inboard and 0.650 lost outboard, representing a difference of only 0.074mm and 0.2mm respectively from the baseline.
29
Olea, Mejía Oscar Fernando Brostow Witold. "Micro and nano composites composed of a polymer matrix and a metal disperse phase". [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5135.
Testo completo
30
Corlay, Charlotte. "Thermal and mechanical analysis of polymer matrix composite materials exposed to a concentrated heat source for a short duration". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 236 p, 2007. http://proquest.umi.com/pqdlink?did=1251905081&Fmt=7&clientId=79356&RQT=309&VName=PQD.
Testo completoAbstract (sommario):
Thesis (M.S.M.E.)--University of Delaware, 2006.Principal faculty advisors: Suresh G. Advani, Dept. of Mechanical Engineering; and Shridhar Yarlagadda, Shridhar Yarlagadda, Dept. of Electrical and Computer Engineering. Includes bibliographical references.
31
Quade, Derek J. "Investigation of Interfacial Bonding Between Shape Memory Alloys and Polymer Matrix Composites". University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1498642782053449.
Testo completo
32
Wood, J. R. "Quantitative process modelling of transport phenomena and bubble dynamics for polymer matrix composite materials". Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/2226/.
Testo completo
33
Pearce, Neil Robert Lewarne. "Process-property-fabric architecture relationships in fibre-reinforced composites". Thesis, University of Plymouth, 2001. http://hdl.handle.net/10026.1/2596.
Testo completoAbstract (sommario):
The use of fibre-reinforced polymer matrix composite materials is growing at a faster rate than GDP in many countries. An improved understanding of their processing and mechanical behaviour would extend the potential applications of these materials. For unidirectional composites, it is predicted that localised absence of fibres is related to longitudinal compression failure. The use of woven reinforcements permits more effective manufacture than for unidirectional fibres. It has been demonstrated experimentally that compression strengths of woven composites are reduced when fibres are clustered. Summerscales predicted that clustering of fibres would increase the permeability of the reinforcement and hence expedite the processing of these materials. Commercial fabrics are available which employ this concept using flow-enhancing bound tows. The net effect of clustering fibres is to enhance processability whilst reducing the mechanical properties. The effects reported above were qualitative correlations. Gross differences in the appearance of laminate sections are apparent for different weave styles. For the quantification of subtle changes in fabric architecture, the use of automated image analysis is essential. Griffm used Voronoi tessellation to measure the microstructures of composites made using flow-enhancing tows. The data was presented as histograms with no single parameter to quantify microstructure. This thesis describes the use of automated image analysis for the measurement of the microstructures of woven fibre-reinforced composites, and pioneers the use of fractal dimensions as a single parameter for their quantification. It further considers the process-property- structure relationships for commercial and experimental fabric reinforcements in an attempt to resolve the processing versus properties dilemma. A new flow-enhancement concept has been developed which has a reduced impact on laminate mechanical properties.
34
Khattab, Ahmed. "Exploratory development of VARIM process for manufacturing high temperature polymer matrix composites". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4186.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (month day, year) Vita. Includes bibliographical references.
35
Verghese, Kandathil Eapen. "Durability of Polymer Matrix Composites for Infrastructure: The Role of the Interphase". Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28817.
Testo completoAbstract (sommario):
As fiber reinforced polymer matrix composites find greater use in markets such as civil infrastructure and ground transportation, the expectations placed on these materials are ever increasing. The overall cost and reliability have become the drivers of these high performance materials and have led to the disappearance of resins such as bismaleimides (BMI), cyanate esters and other high performance polyimides and epoxys. In their place polymers, such polyester and vinylester have arisen. The reinforcing fiber scenario has also undergone changes from the high quality and performance assured IM7 and AS4 to cheaper and hybrid systems consisting of both glass and low cost carbon. Manufacturing processes have had their share of changes too with processes such as pultrusion and other mass production techniques replacing hand lay-up and resin transfer molding. All of this has however come with little or no concession on material performance. The motivation of the present research has therefore been to try to improve the properties of these low cost composites by better understanding the constituent materials (fiber and matrix) and the region that lies in-between them namely the interphase. In order to achieve this, working with controls is necessary and the present discourse therefore deals with the AS4 fiber system from Hexcel Corporation and the vinyl ester resin, Derakane 441-400 from The Dow Chemical Company. The following eight chapters sum up the work done thus far on composites made with sized fibers and the above mentioned resin and fiber systems. They are in the form of publications that have either been accepted, submitted or going to be submitted to various peer reviewed journals. The sizings used have been poly(vinylpyrrolidone) PVP and Polyhydroxyether (Phenoxy) thermoplastic polymers and G' an industrial sizing material supplied by Hexcel. A number of issues have been addressed ranging from viscoelastic relaxation to enviro-mechanical durability.
Chapter 1 deals with the influence of the sizing material on the fatigue response of cross ply composites made with the help of resin infusion molding. Chapter 2 describes the effects of a controlled set of interphase polymers that have the same chemical structure but differ from each other in polarity. The importance of the atomic force microscope (AFM) to view and perform nano-indentations on the interphase regions has been demonstrated. Finally, it attempts to tie everything together with the help of the fatigue response of the different composites. Chapter 3 deals only with the vinyl ester resin and examines the influence of network structure on the molecular relaxation behavior (cooperativity) of the glassy polymer. It also tries to make connections between structural features of the glass and fracture toughness as measured in its glassy state. Chapter 4 extends the results obtained in chapter 3 to examine the cooperativity of pultruded composites made with the different sizings. A correlation between strength and cooperativity is found to exist, with systems having greater cooperativity being stronger. Chapter 5 moves into the area of hygrothermal aging of Derakane 441-400 resin. It looks specifically at identifying a mechanism for the unusual moisture uptake behavior of the polymer subjected to a thermal-spiking environment. This it does by identifying the presence of hydrogen bonding in the resin. Finally, chapters 6 to 8 present experimental and analytical results obtained on PVP K90, Phenoxy and G' sized, AS4/Derakane 411-350 LI vinyl ester composites that were pultruded at Strongwell Inc., on their lab-scale pultruder in Bristol, Virginia.Ph. D.
36
Mahieux, Celine Agnès. "Stress rupture of unidirectional polymer matrix composites in bending at elevated temperatures". Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/45398.
Testo completoAbstract (sommario):
A new method for stress-rupture experiments in bending has been developed and used to characterize unidirectional polymer matrix composites. The method. which makes use of very simple fixtures, led to coherent results. These results have been modeled using the large deflection of buckled bars theory (elastica) and it is possible to predict with good accuracy the strain at each point of the specimen if the end-to-end distance is known. The failure process has been experimentally characterized. The formation and propagation of microbuckles leads to a compressive failure. Based on the elastica and the classical lamination theory, a model for the distribution of the Young's modulus along the length of the specimen has been established. Three different micromechanical models have been applied to analyze the time-to-failure versus strain behavior at two temperatures - one below and one above the glass transition. The first micromechanical model considers the nucleation of the microbuckles as the main cause of failure. In addition, the stiffness and stress distributions at any time before failure are calculated based upon the rotation of the fibers in the damaged region. The second and last models, respectively based upon a Paris Law and energy considerations relate the time-to-failure to the propagation of the main microbuckle. For this last model, a good correlation between experimental and theoretical data has been obtained. Finally the influence of the temperature on these models has been studied.
Master of Science
37
Ouyang, Fengxia. "ABAQUS Implementation of Creep Failure in Polymer Matrix Composites with Transverse Isotropy". University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1131898124.
Testo completo
38
Mahieux, Céline Agnès. "Stress rupture of unidirectional polymer matrix composites in bending at elevated temperatures /". This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11012008-063348/.
Testo completo
39
Bauer, Felix [Verfasser]. "Basalt fibers for high performance applications in polymer matrix composites / Felix Bauer". München : Verlag Dr. Hut, 2020. http://d-nb.info/1219470406/34.
Testo completo
40
Hughes, John Mark. "On the mechanical properties of bast fibre reinforced thermosetting polymer matrix composites". Thesis, Bangor University, 2000. https://research.bangor.ac.uk/portal/en/theses/on-the-mechanical-properties-of-bast-fibre-reinforced-thermosetting-polymer-matrix-composites(0fdca4e4-8d50-4a16-afd0-37d78cfb8a64).html.
Testo completoAbstract (sommario):
Bast fibre reinforced, unsaturated polyester matrix composites were fabricated using non-woven mats of hemp or jute fibre as reinforcement. Composites were also prepared using chopped strand mat glass fibre as reinforcement. The short-term mechanical properties of the laminates were assessed. It was observed that at equivalent fibre volume fractions the stiffness of the glass fibre reinforced material only marginally exceeded that of the two, unmodified bast fibre, reinforced materials. At equivalent fibre volume fractions, however, the strength of the glass fibre reinforced composite was found to be significantly greater than that of the bast fibre reinforced materials. It was noted that in the bast fibre reinforced composites, the onset of non-linear behaviour occurred at relatively low applied stresses. Work of fracture in static three-point flexure and Charpy impact strength tests, indicated that the toughness of the plant fibre reinforced material was as much as an order of magnitude less than that of the glass fibre reinforced material. Fracture mechanics techniques were used to further quantify toughness and confirmed this to be so. Furthermore, these tests indicated that the microstructure of the bast fibre reinforced material should be examined more closely. Microscopy conducted on the fibres revealed that these were often subject to extensive micro-compressive damage. It was postulated that uneven fibre straining characteristics could lead to compromised interfacial properties, which might in turn detrimentally affect the macroscopic behaviour of the composite. A technique known as half fringe photoelasticity was used to investigate the stress-field in the matrix surrounding the fibre defects. It was observed that not only did concentrations of stress occur in the vicinity of these, but also that the shear stress distribution along the length of the fibre was interrupted by the presence of the defects. The implications of fibre defects upon composite properties are discussed.
41
Yang, Jingting. "Carbon Nanotubes Reinforced Composites for Wind Turbine Blades". Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1315410407.
Testo completo
42
Nader, Jacques Walid. "Probabilistic Finite Element Analysis and Size Effects of Polymer Matrix Marine Grade Composites". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/NaderJW2007.pdf.
Testo completo
43
Elmkharram, Hesham Moh A. "Mechanically Processed Alumina Reinforced Ultra-high Molecular Weight Polyethylene (UHMWPE) Matrix Composites". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/31522.
Testo completoAbstract (sommario):
Alumina particles filled Ultra-high Molecular Weight Polyethylene (UHMWPE), with Al2O3 contents 0, 1, and 2.5 wt% were milled for up to 10 hours by the mechanical alloying (MA) process performed at room temperature to produce composite powders. Compression molding was utilized to produce sheets out of the milled powders. A partial phase transformation from orthorhombic and amorphous phases to monoclinic phase was observed to occur for both the un-reinforced and reinforced UHMWPE in the solid state, which disappeared after using compression molding to produce composite sheets. The volume fraction of the monoclinic phase increased with milling time, mostly at the expense of the amorphous phase. The melting temperature decreased as a function of milling time as a result of modifications in the UHMWPE molecular structure caused by the milling. At the same time, for a given alumina composition the activation energy of melting increased with milling time. Generally, the crystallinity of the molded sheets increased with milling time, and this caused the yield strength and elastic modulus to increase with milling time for a given alumina composition. However, the tensile strength and ductility remained about the same.Master of Science
44
Melcher, Ryan James. "Characterization of polymer matrix composites and adhesively bonded joints in a cryotank environment". Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/16035.
Testo completo
45
Dissanayake, Nilmini P. J. "Life cycle assessment of flax fibres for the reinforcement of polymer matrix composites". Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/969.
Testo completoAbstract (sommario):
This thesis aims to investigate the sustainability of bast fibres specifically flax fibres as the reinforcement for polymer matrix composites (referenced to glass fibres) by undertaking a quantitative Life Cycle Assessment using the eight environmental impact classification factors of global warming, acidification, eutrophication, human toxicity, aquatic toxicity, ozone depletion, photochemical oxidants creation and non-renewable/abiotic resource depletion. A data set was compiled from numerous literature sources to complete the Life Cycle Inventory for the production of flax fibres. Three scenarios were studied for the production of either flax sliver (pre-spun fibre) or yarn (post-spun fibre): low (no-till combined with warm water retting), average (conservation tillage with stand/dew retting) and high (conventional tillage with bio-retting) energy routes considering different agricultural and fibre preparation (retting) methods. The best agricultural practice for the flax fibre production is identified from this study as the no-till method combined with warm water retting. The environmental credentials for flax fibre can be further improved by using organic fertilisers and biological control of pests. Spinning is the most energy intensive fibre processing operation hence by eliminating this operation energy use and the associated environmental impacts could be reduced. Based on the energy analysis continuous glass fibre reinforcement appears to be superior to spun flax yarn but glass fibre mat and flax sliver are equivalent and embody similar quantities of energy per tonne. The environmental benefit arising from substitution of glass fibres by natural fibre is dependent on the chosen reinforcement format. The key consideration is to use sliver (pre-spun fibres) as reinforcement in polymer matrix composites instead of yarn.
46
Hart, Robert James. "Electrical resistance based damage modeling of multifunctional carbon fiber reinforced polymer matrix composites". Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5493.
Testo completoAbstract (sommario):
In the current thesis, the 4-probe electrical resistance of carbon fiber-reinforced polymer (CFRP) composites is utilized as a metric for sensing low-velocity impact damage. A robust method has been developed for recovering the directionally dependent electrical resistivities using an experimental line-type 4-probe resistance method. Next, the concept of effective conducting thickness was uniquely applied in the development of a brand new point-type 4-probe method for applications with electrically anisotropic materials. An extensive experimental study was completed to characterize the 4-probe electrical resistance of CFRP specimens using both the traditional line-type and new point-type methods. Leveraging the concept of effective conducting thickness, a novel method was developed for building 4-probe electrical finite element (FE) models in COMSOL. The electrical models were validated against experimental resistance measurements and the FE models demonstrated predictive capabilities when applied to CFRP specimens with varying thickness and layup. These new models demonstrated a significant improvement in accuracy compared to previous literature and could provide a framework for future advancements in FE modeling of electrically anisotropic materials. FE models were then developed in ABAQUS for evaluating the influence of prescribed localized damage on the 4-probe resistance. Experimental data was compiled on the impact response of various CFRP laminates, and was used in the development of quasi- static FE models for predicting presence of impact-induced delamination.
The simulation-based delamination predictions were then integrated into the electrical FE models for the purpose of studying the influence of realistic damage patterns on electrical resistance. When the size of the delamination damage was moderate compared to the electrode spacing, the electrical resistance increased by less than 1% due to the delamination damage. However, for a specimen with large delamination extending beyond the electrode locations, the oblique resistance increased by 30%. This result suggests that for damage sensing applications, the spacing of electrodes relative to the size of the delamination is important. Finally CT image data was used to model 3-D void distributions and the electrical response of such specimens were compared to models with no voids. As the void content increased, the electrical resistance increased non-linearly. The relationship between void content and electrical resistance was attributed to a combination of three factors: (i) size and shape, (ii) orientation, and (iii) distribution of voids. As a whole, the current thesis provides a comprehensive framework for developing predictive, resistance-based damage sensing models for CFRP laminates of various layup and thickness.
47
Schöneich, Marc. "Charakterisierung und Modellierung viskoelastischer Eigenschaften von kurzglasfaserverstärkten Thermoplasten mit Faser-Matrix Interphase". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0234/document.
Testo completoAbstract (sommario):
L’influence des propriétés microscopiques de l’interphase entre la matrice et les fibres sur le comportement mécanique macroscopique n’est pas suffisamment connue dans le domaine des polymères renforcés par fibres courtes. Dans le cadre de cette thèse, une étude systématique des propriétés géométriques et mécaniques de l’interphase est réalisée concernant la description des effets sur la réponse viscoélastique linéaire du composite. Dans ce contexte, les résultats présentés mettent l’accent sur l’interaction entre la modélisation micromécanique et la caractérisation expérimentale. D’une part, un nouveau modèle micromécanique en deux étapes est développé pour la description d’un composite anisotrope à trois phases avec interphases. D’autre part, les paramètres du matériau utilisés pour la modélisation micromécanique sont identifiés avec des méthodes expérimentales aux échelles micro- et macroscopiques. En comparaison des résultats expérimentaux avec les propriétés effectives calculées de matériau composite, une inférence peut être faite sur les propriétés mécaniques du composite à partir de celles de l’interphase. Par conséquent, une méthode inverse est proposée offrant un accès aux propriétés inconnues de l’interphase. Enfin, la combinaison de la modélisation micromécanique et des résultats expérimentaux permet une meilleure compréhension des propriétés mécaniques de l’interphase, qui n’étaient auparavant pas accessibles au moyen de seules approches expérimentalesIn order to improve the mechanical properties of short fiber composites, the fiber-matrix adhesion is decisive and depends strongly on the intersection region between the fiber and the matrix material. However, no perspicuous information about the influence or mechanical properties of the fiber-matrix interphase in short fiber reinforced thermoplastic composites is available. Thus, the present thesis aims for a systematic identification of the geometrical and mechanical impacts of an interphase on the linear-viscoelastic behavior in short glass fiber reinforced thermoplastics. Thereby, the performed investigations are focused on the interaction between micromechanical material modeling and experimental testing. On the one hand, a two-step modeling approach is developed for the realistic description of an entire three phase composite with interphase including anisotropic and linear-viscoelastic effects. On the other hand, the input of this model is provided by different experimental testing methods ranging from the micro- to the macroscale characterization of the composite and matrix material. By comparing these experimental results with the linear-viscoelastic modeling output, the impact of the interphase on the mechanical properties of the composite is accessible. Thus, it is shown that a realistic material modeling and experimental investigations are closely interlinked
48
Stackpoole, Margaret Mary. "Reactive processing and mechanical properties of polymer derived silicon nitride matrix composites and their use in coating and joining ceramics and ceramic matrix composites /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10564.
Testo completo
49
Hutten, Victoria Elizabeth. "Process Modeling of Thermoplastics and Thermosetting Polymer Matrix Composites (PMCs) Manufactured Using Fused Deposition Modeling (FDM)". University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1513073294210094.
Testo completo
50
Baci, Francesca M. "Heat transfer during consolidation of metal matrix composites by the hip process". Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177612557.
Testo completo