Teses / dissertações sobre o tema "Thermoplastic composite"
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1
Li, Min-Chung. "Thermoplastic composite consolidation". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40036.
Resumo:
Fabrication of high-quality composites from thennoplastic prepregs requires careful selection of the processing cycles so that intimate contact at the ply interfaces is achieved resulting in the formation of strong interply bonds and the process-induced residual stress is minimized to ensure superior mechanical performance. The void formation and the consolidation mechanism were studied experimentally. A refined model was developed to relate the processing parameters of pressure, temperature and time to the interply intimate contact of thermoplastic composites. The model was developed by integrating a prepreg surface topology characterization with a resin flow analysis. Both unidirectional and cross-ply lay-ups were modeled. Two-ply unidirectional laminae fabricated from graphite-polysulfone and graphite-PEEK prepregs and [0/90/0]T laminates were consolidated using different processing cycles. Optical microscopy and scanning acoustic microscopy were used to obtain the degree of intimate contact data. Agreement between the measured and calculated degree of intimate contact was good. A finite element model was developed to analyze residual stresses in thermoplastic composites by combining a plane-strain elasticity analysis and a temperature-dependent matrix properties. The residual stress model takes into account the mismatch of the thermal expansion coefficients and the crystallization shrinkage of the matrix. [O₁₀/90₆]T graphite-PEEK laminates were manufactured at different cooling rates to verify the model. The induced residual thermal defonnations were measured by a shadow moire system. The model accurately estimated the out-of-plane displacement of the non-symmetrical laminates.Ph. D.
2
Wu, Xiang. "Thermoforming continuous fiber reinforced thermoplastic composites". Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/9383.
3
Yang, Heechun. "Modeling the processing science of thermoplastic composite tow prepreg materials". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/17217.
4
Norpoth, Lawrence R. "Processing parameters for the consolidation of thermoplastic composites". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/19099.
5
ABDU, ALINE AMARAL QUINTELLA. "ELONGATIONAL BEHAVIOR OF COMPOSITE THERMOPLASTIC MATERIALS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11520@1.
Resumo:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOOs materiais termoplásticos compósitos, tais como o polipropileno reforçado com fibras de vidro curtas, são usados cada vez mais em diversos setores industriais. O reforço da fibra de vidro é uma forma utilizada para melhorar as propriedades mecânicas dos termoplásticos, devido ao elevado módulo das fibras e à melhor adesão entre as fibras e a matriz polimérica. No entanto, há poucas informações referentes às propriedades desses fluidos na literatura. No presente trabalho, um estudo das propriedades cisalhantes e elongacionais do polipropileno reforçado com fibras de vidros curtas é apresentado. As viscosidades cisalhantes e elongacionais foram obtidas em um reômetro capilar através da medição da queda de pressão na entrada convergente de um capilar axissimétrico. Utilizaram-se duas geometrias diferentes na entrada do capilar, para a obtenção dos dados experimentais: as geometrias semi-hiperbólica convergente e cônica convergente. Neste último, a viscosidade elongacional foi obtida a partir da queda de pressão na entrada, utilizando as análises de Cogswell e Binding. Simulações numéricas foram realizadas com o objetivo de investigar o comportamento do polipropileno em um processo de extrusão. As equações de conservação de massa e quantidade de movimento foram resolvidas utilizando o método dos elementos finitos a partir do programa comercial Polyflow (Ansys). Para modelar o comportamento da mecânico viscoelástico do polipropileno foram utilizados os modelos de Maxwell, Oldroyd-B e Phan-Thien Tanner (PTT), no entanto a comparação entre os resultados numéricos e os experimentais obtidos no reômetro capilar não apresentaram concordância satisfatória.
Composite thermoplastic materials, like glass fiber reforced polypropropylene, are used increasingly in several industries. In particular, glass fiber reinforcement is used to improve the mechanical properties of thermoplastics, due to the high fiber modulous and to the better adesion between the fibers and the polymeric matrix. However, few data of material properties of these fluids are avaiable in the literature. In this work, a study of shear and elongational properties of a commercial short glass fiber reinforced polypropylene is presented. The shear and elongational viscosities were obtained using the pressure drop measured at a capillary rheometer, with axisymmetric converging dies. Two different die geometries were used: semihyperbolically convergent dies and conical convergent dies. In the last case, the elongational viscosity was obtained using the Cogswell and Binding analysis. Numerical simulations were also performed, to investigate the flow field through the extrusion die process, and to evaluate the pressure drop and elongational viscosity. The conservation equations of mass and momentum were solved via the finite element method, using the commercial program POLYFLOW (Ansys). The Maxwell, Oldroyd B and Phan Thien-Tanner (PTT) constitutive equations were used to model the viscoelastic mechanical behavior of Polypropylene, but the comparison between numerical results and experimental data obtained from the capillary rheometer did not show good agreement.
6
Sandusky, Donald Allan. "Fabrication of thermoplastic polymer composite ribbon". W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539616840.
Resumo:
The goal of this research was to develop a controllable process to convert a thermoplastic powder-coated carbon-fiber towpreg into uniform and consolidated ribbon. The approach comprised four primary activities. (1) The patent and processing literature was studied to evaluate the state of the art. (2) A functional ribbon fabrication technique was developed by scaling-up, in a novel configuration, hardware components found in the literature. (3) The ex parte ribbonizing process was characterized by calibrating equipment, determining steady state and studying cause and effect between process parameters and ribbon quality. (4) Process design and control methods were derived from heat transfer and pulling force analyses. The ex parte ribbonizer process comprises a material handling system, a preheat region, a heated stationary bar assembly, and a cooled nip roller assembly. Appropriate timing of important contacts is key to fabricating quality ribbon. Process characterization and analyses revealed key flow mechanisms. Ribbon microstructure changes most at the bars. Ribbon macrostructure changes most at the nip. An isothermal bar contact is a practical processing constraint for ensuring uniform squeeze flow bar spreading. All bar drag force is attributed to shear stress in the interfacial viscous boundary layer between the towpreg and the stationary bar surface. Continually sensing pulling force is a good indication of process control. The research goal was achieved because the ex parte ribbonizer can be used to convert polymer powder towpreg into uniform and fully-consolidated ribbon in a controllable manner.
7
Song, Xiaolan. "Modeling of Thermoplastic Composite Filament Winding". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35370.
Resumo:
Thermoplastic composite filament winding is an on-line consolidation process, where the composite experiences a complex temperature history and undergoes a number of temperature history affected microstructural changes that influence the structure's subsequent properties. These changes include melting, crystallization, void formation, degradation and consolidation. In the present study, models of the thermoplastic filament winding process were developed to identify and understand the relationships between process variables and the structure quality. These include models that describe the heat transfer, consolidation and crystallization processes that occur during fabrication of a filament wound composites structure.
A comprehensive thermal model of the thermoplastic filament winding process was developed to calculate the temperature profiles in the composite substrate and the towpreg temperature before entering the nippoint. A two-dimensional finite element heat transfer analysis for the composite-mandrel assembly was formulated in the polar coordinate system, which facilitates the description of the geometry and the boundary conditions. A four-node 'sector element' was used to describe the domain of interest. Sector elements were selected to give a better representation of the curved boundary shape which should improve accuracy with fewer elements compared to a finite element solution in the Cartesian-coordinate system. Hence the computational cost will be reduced. The second thermal analysis was a two-dimensional, Cartesian coordinate, finite element model of the towpreg as it enters the nippoint. The results show that the calculated temperature distribution in the composite substrate compared well with temperature data measured during winding and consolidation. The analysis also agrees with the experimental observation that the melt region is formed on the surface of the incoming towpreg in the nippoint and not on the substrate.
Incorporated with the heat transfer analysis were the consolidation and crystallization models. These models were used to calculate the degree of interply bonding and the crystallinity achieved during composite manufacture. Bonding and crystallinity developments during the winding process were investigated using the model. It is concluded that lower winding speed, higher hot-air heater nozzle temperature, and higher substrate preheating temperature yield higher nippoint temperature, better consolidation and a higher degree of crystallization. Complete consolidation and higher matrix crystallization will result in higher interlaminar strength of the wound composite structure.
Master of Science
8
Rohm, Kristen Nicole. "Thermoplastic Polyurethane: A Complex Composite System". Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1625604511143102.
9
Talbot, Edith. "Manufacturing process modelling of thermoplastic composite resistance welding". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83934.
Resumo:
One-, two- and three-dimensional transient heat transfer finite element models are developed to simulate the resistance welding process of pre-consolidated unidirectional AS4 carbon fibre reinforced Poly-ether-ether-ketone (APC-2/AS4) laminates with a metal mesh heating element, in a lap-shear configuration. The finite element models are used to investigate the effect of process and material parameters on the thermal behaviour of the coupon size welds, yielding to a better understanding of the process. The 1-D model determines: (a) the importance of including the latent heat of PEEK, and (b) the through-thickness temperature gradient away from the edges, for different tooling plate materials. The 2-D model simulates the cross-section of the process, considering the convective and irradiative heat losses from the areas of the heating element exposed to air. The 3-D model includes the heat conduction along the length of the laminates, to fully depict the thermal behaviour of the welds. Finally, the models are compared with experimental data.
10
Peterson, Nels Royal. "Wood-thermoplastic composites manufactured using beetle-killed spruce from Alaska's Kenai Peninsula". Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/N_Peterson_060508.pdf.
11
Schmitt, Ron R. "Viscoelastic relaxation in bolted thermoplastic composite joints". Thesis, Wichita State University, 1991. http://hdl.handle.net/10057/3988.
Resumo:
Results from a research program to investigate the long term effects of
through-the-thickness fastener clamp-up force (preload) relaxation on the
strength of mechanically fastened joints for two graphite/thermoplastic
composite materials (Dupont's IM6/KIII and ICI-Fiberite's IM8/APC(HTA)) are
summarized and compared with analytical methods. An experimental program
was conducted in which 56 mechanically fastened single-shear joints were
tested. Phase I static tests established joint bearing strength as a function of
clamp-up force for two types of fasteners (protruding head and countersink) with
no relaxation of preload. Phase II testing monitored short-term fastener preload
relaxation (up to 1 ,000 hours), with special bolt force sensor washers. Inservice
parameters included were temperature, in-plane loads, and torque. The
jOints were tested to failure at the end of the relaxation time period to determine
any subsequent effect on joint strength.
Phase I test results indicated that joint bearing strength increased by as
much as twenty-eight percent over the clamp-up force range of a Ibs (fingertight)
to 3,500 Ibs for both materials. Fastener head type, material, and
temperature also affected the resultant bearing strength. For Phase II, fastener
clamp-up force at room temperature (78°F) relaxed an average of six percent
from the initial value during the short-term test period. The relaxation was
projected to be as high as fourteen and sixteen percent at 100,000 hours for
HTA and Kill, respectively. The elevated temperature condition (250°F)
significantly increased the relaxation rate with the projected 100,000 hour
relaxation amount being as high as thirty-seven percent for HTA and sixty
percent for Kill. Comparison of the Phase II bearing strengths to the Phase I
results indicated that portions of the data correlated well, while others did not. It
was concluded that relaxation of the clamp-up force over the short-term time
period did not significantly lower the bearing strength of either material,
however an extended exposure to 250°F could affect the bearing strength.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.
12
Åkermo, Malin. "Compression moulding of thermoplastic composite sandwich components /". Stockholm, 1999. http://www.lib.kth.se/abs99/aker0422.pdf.
13
Butt, Arif. "Resin flow characterization during thermoplastic composite consolidation". Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12010.
14
Lee, Jaewoo. "Thermoplastic Composite with Vapor Grown Carbon Fiber". Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1127335929.
15
Howes, Jeremy C. "Interfacial strength development in thermoplastic resins and fiber-reinforced thermoplastic composites". Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/77899.
Resumo:
The objective of this study was to develop tests that could be used to characterize autohesive strength development in amorphous thermoplastic resins and fiber-reinforced thermoplastic prepregs. All tests were performed using polysulfone P1700 thermoplastic resin and AS4/P1700 graphite-polysulfone prepreg.
Two test methods were examined to measure autohesion in neat resin samples. These included an interfacial tension test based on the ASTM tensile adhesion test (ASTM D897) and a fracture toughness test using a compact tension (CT) specimen (based on the ASTM toughness test for metals ASTM E399-83). The interfacial tensile test proved to be very difficult to perform and with an unacceptable amount of data scatter. The data obtained using the compact tension test were repeatable and could be correlated with temperature and contact time.
Autohesive strength development in fiber-reinforced prepreg samples was measured using a double cantilever beam (DCB) interlaminar fracture toughness test. The fracture mechanisms were determined to be different in the healed DCB specimen than the virgin specimen due to resin flow at the crack plane during the healing tests.
The CT test was found suitable for use in determining the autohesive properties and self-diffusion coefficient of neat resin. The DCB test, although not suitable for autohesive testing, indicated that repair of thermoplastic matrix composites is possible; however, the repair will not be as tough as the virgin material.Master of Science
16
Stevanović, Dejan. "Delamination properties of a vinyl-ester/glass fibre composite toughened by particle-modified interlayers /". View thesis entry in Australian Digital Theses Program, 2001. http://thesis.anu.edu.au/public/adt-ANU20030421.212730/index.html.
17
Otheguy, Mariano E. "Manufacture, repair and recycling of thermoplastic composite boats". Thesis, University of Newcastle Upon Tyne, 2010. http://hdl.handle.net/10443/889.
Resumo:
The design and construction of boats using thermoplastic composites (TPCs) is an emerging industry derived from the advantages these materials offer. Short manufacturing cycle times, virtually infinite shelf life, increased toughness, no volatiles emission, and the ability to be re‐processed and recycled, lead to improved processes and open new and more sustainable manufacturing possibilities for boats and other structures. However, the manufacture, repair and actual recycling of TPCs still present a number of technical challenges. This thesis addresses the five most important of these challenges, from both the academic and industrial points of view. The manufacturing of TPC structures involves the impregnation of reinforcing fibres with melted resin. This process, known as consolidation, is still to be fully understood. In order to contribute to this understanding, a consolidation model based on existing and newly developed sub‐models was developed and applied to experimental data. The results obtained proved that the non‐isothermal consolidation of laminates of a thickness typical of boatbuilding, can be approached by applying this model locally on a discretised laminate, fitting well experimental data. The choice of a cost‐effective moulding material is one of the factors currently preventing the widespread use of TPCs in boatbuilding. The vacuum forming of TPCs requires moulds which have considerable strength, and allow high service temperatures and the shape freedom which is typical of boat moulds. A review of commercial and experimental materials and laboratory experimentation on a novel glass‐reinforced ceramic composite was carried out, showing that a range of metals and composites are useful for TPC‐capable moulds, and that a cost‐effective free‐shape mould capable of processing any TPC is achievable. After hull shell manufacturing stiffeners and other internal structure are often required. The manufacturing of such a reinforced and subdivided hull involves the use of a joining technology. Adhesive joining, widely used in thermosetting resin composite boats, cannot be easily used on TPCs due to their low energy surfaces. However, the re‐melting ability of thermoplastic resins enables the use of welding, fusion bonding and other joining methods involving molecular diffusion at the bond line. Experiments carried out on lap and T‐joints showed that vacuum‐assisted local heating can be used for structural assemblies such as reinforced boat hulls, obtaining strengths that are comparable to existing thermosetting designs. A TPC boat manufactured and assembled in such way would still require a suitable repair technique that provides a long product life. An emergency repair method capable to return the boat to the water in less than 24 hours without using any mould was devised and tested on a prototype TPC rigid inflatable boat. This was achieved by fusion bonding the edges of a pre‐manufactured flat panel to the hull. The flat panel adapted to the hull double curvature by means of vacuum pressure, delivering the required bond quality and strength. Finally, the disposal of a TPC boat must be addressed after the end of its service life. Current policies and innovative business thinking are leading companies into reusing and recycling instead of landfilling materials. While the mechanical recycling of TPCs, achieved by means of resin re‐melting, has been largely studied, the recycling of a real boat containing paint and core material raise questions on how these materials would affect the recyclate. An experimental study on the recycling of a TPC real boat was carried out to answer these questions, revealing that despite the deleterious effect of core and paint, the final properties of injection moulded samples were in the region of those of virgin materials.
18
Liu, Xiao Bin. "Finite element analysis of hybrid thermoplastic composite structures". Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493330.
Resumo:
A wide range of thermoplastic composites (TPC) are now being used in automotive applications including vehicle front-end structures, load floors, seat backs, door cassettes and instrument panels. Long fibre thermoplastics (LFT), glass mat thermoplastics (GMT) and fully structural materials such as woven commingled fabric TPCs, e.g. Twintex®, provide a range of properties and mouldability appropriate to specific applications.
19
Kulandaival, Palanivel Palaniathevar. "Manufacturing and performance of thermoplastic composite sandwich structures". Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438298.
20
Ekström, Lars Johan. "Welding of bistable fibre-reinforced thermoplastic composite pipelines". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614933.
21
Derisi, Bijan. "Development of thermoplastic composite tubes for large deformation". Thesis, Connect to online version, 2008. http://proquest.umi.com/pqdweb?did=1675143241&sid=1&Fmt=2&clientId=10306&RQT=309&VName=PQD.
22
Choupin, Tanguy. "Mechanical performances of PEKK thermoplastic composites linked to their processing parameters". Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0043/document.
Resumo:
Les thermoplastiques hautes performances poly(éther-cétone-cétone) (PEKK) sont actuellement étudiés avec un grand intérêt dans l’industrie aéronautique comme matrice pour la fabrication de pièces de structure composites renforcées par des fibres de carbone. En effet, les composites thermoplastiques PEKK ont l’avantage d’être consolidables hors autoclave et ont des températures de mise en œuvre plus faibles que les composites PEEK.L’objectif de cette étude est de comprendre et prédire l’évolution des propriétés mécaniques des composites PEKK suivant le cycle thermique de mise en œuvre pour déterminer les paramètres de mise en œuvre optimaux pour la fabrication des pièces composites PEKK concernant les temps de mise en œuvre et les performances mécaniques finales.Une première partie traite de la modélisation des cinétiques de cristallisation des matrices PEKK ainsi que l’influence de la cristallinité et des morphologies cristallines sur les propriétés mécaniques des matrices PEKK. Une deuxième partie se concentre sur les modifications macromoléculaires des matrices PEKK pour des hautes températures de mise en œuvre sous air et sous azote et leurs impacts sur la cristallisation et les performances mécaniques des matrices PEKK. Enfin une dernière partie présente l’influence des fibres de carbones sur les morphologies cristallines et les cinétiques de cristallisation, la fabrication de composites PEKK unidirectionnels et tissés à ± 45° sous presse et sous autoclave et enfin l’impact de la cristallinité et des morphologies cristallines sur les performances mécaniques finales des composites PEKKPoly(ether-ketone-ketone) (PEKK) high performance thermoplastics are currently studied with a great interest by the aeronautic industry as matrix for carbon fiber reinforced structural parts. In fact, PEKK composites can be consolidated out of autoclave and they have lower processing temperatures than PEEK composites.The aim of the study was to investigate and predict the evolution of PEKK composite mechanical properties depending on the processing thermal cycle to determine the best processing parameters for PEKK composite part manufacturing regarding processing times and final mechanical performances.A first part investigates the crystallization kinetics modelling of PEKK matrices and the influence of crystallinity and crystalline morphologies on PEKK matrix mechanical properties. A second part focuses on the macromolecular modifications of PEKK matrices at high processing temperatures under air and nitrogen and their impact on PEKK matrices crystallization and mechanical properties. A last part presents the influence of carbon fibers on crystalline morphologies and crystallization kinetics, the manufacturing of unidirectional and ± 45° PEKK composites under press and autoclave and finally the impact of crystallinity and crystalline morphologies on PEKK composite mechanical properties
23
Kuriger, Rex J. "Improved thermoplastic composite by alignment of vapor grown carbon fiber". Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1179254413.
24
Chazerain, Aurélie. "Characterization of resistance-welded thermoplastic composite double-lap joints". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67019.
Resumo:
An investigation of resistance welding of thermoplastic composite double-lap shear joints is presented. Double-lap shear specimens consisting of carbon fibre/poly-etherether-ketone (PEEK/CF), carbon fibre/poly-etherketone-ketone (PEKK/CF), carbon fibre/poly-ether-imide (PEI/CF) and glassfibre/poly-ether-imide (PEI/GF) were resistance-welded using a stainless steel mesh heating element. The objective of this work was to study the mechanical performances of the double lap shear resistance-welded joints and to compare them with the single lap shear resistance-welded joints. The welded specimens were analyzed using static and dynamic lap shear tests and optical and scanning electron microscopy. Lap shear strengths of 53 MPa, 49 MPa, 45 MPa and an extrapolated value of 34 MPa were obtained for PEEK/CF, PEKK/CF, PEI/CF and PEI/GF double-lap joints, respectively. Infinite fatigue lives were obtained at 30% for PEEK/CF and PEKK/CF, 25% for PEI/CF and 20% for PEI/GF. Resistance-welded double-lap joints were found to have equivalent static and fatigue mechanical properties compared with single-lap joints, for all materials tested.Ce travail présente une étude des joints à recouvrement double de matériaux composites à matrice thermoplastique assemblés par soudage par résistance. Des échantillons de joints à recouvrement double constitués de fibre de carbone/polyéther éther cétone (PEEK/CF), fibre de carbone/polyéther cétone cétone (PEKK/CF), fibre de carbone/polyéther imide (PEI/CF) et fibre de verre/polyéther imide (PEI/CF), ont été assemblés pas soudage par résistance à l'aide d'un élément chauffant en acier inoxydable. L'objectif de ce travail est d'étudier les performances mécaniques des joints à recouvrement double soudés pas résistance et de les comparer avec celles des joints à recouvrement simple. Les échantillons soudés ont été analysés à l'aide de tests de chargement statiques et dynamiques, ainsi que pas microscopie optique et par microscopie électronique à balayage. Une résistance au cisaillement de 53 MPa, 49 MPa, 45M Pa, et une valeur extrapolée de 34 MPa ont été obtenues pour les joints à recouvrement double de PEEK/CF, PEKK/CF, PEI/CF et PEI/GF, respectivement. Une durée de vie indéterminée en fatigue de 30% du chargement statique pour les joints de PEEK/CF et PEKK/CF, de 25% pour les joints de PEI/CF, et de 20% pour les joints de PEI/GF ont été obtenues. Pour chacun des matériaux testés, les joints à recouvrement double soudés par résistance ont donné lieu à des propriétés mécaniques en statique et en fatigue équivalentes à celles des joints à recouvrement simple.
25
Yang, Bing. "Thermoplastic and Thermoset Natural Fiber Composite and Sandwich Performance". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500002/.
Resumo:
The objective of this thesis is to investigate the effects of adding natural fiber (kenaf fiber, retted kenaf fiber, and sugarcane fiber) into polymer materials. The effects are obtained by considering three main parts. 1. Performance in thermoplastic composites. The effect of fiber retting on polymer composite crystallization and mechanical performance was investigated. PHBV/PBAT in 80/20 blend ratio was modified using 5% by weight kenaf fiber. Dynamic mechanical analysis of the composites was done to investigate the glass transition and the modulus at sub-ambient and ambient temperatures. ESEM was conducted to analyze fiber topography which revealed smoother surfaces on the pectinase retted fibers. 2. Performance in thermoset composites. The effect of the incorporation of natural fibers of kenaf and of sugarcane combined with the polyester resin matrix is investigated. A comparison of mechanical properties of kenaf polyester composite, sugarcane polyester composite and pure polyester in tensile, bending, dynamic mechanical thermal analysis (DMA) and moisture test on performance is measured.. 3. Performance in sandwich composites. The comparison of the performance characteristics and mechanical properties of natural fiber composites panels with soft and rigid foam cores are evaluated. A thorough test of the mechanical behavior of composites sandwich materials in tensile, bending and DCB is presented here.
26
Jackson, Mitchell L. "Modeling the microwave frequency permittivity of thermoplastic composite materials". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06232009-063055/.
27
Van, der Westhuizen Artho Otto. "Impact response of a continuous fibre reinforced thermoplastic from a soft bodied projectile". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80095.
Resumo:
Thesis (MScEng)--Stellenbosch University, 2013.AFRIKAANSE OPSOMMING: Saamgestelde materiale het baie gewilde materiale in die lugvaart- en motor industrië geword as gevolg van die gewigsbesparende voordele wat dit inhou. Kostes en ander verwerkingsprobleme het tradisioneel die wydverspreide gebruik van spesifiek termoplasties-versterkte vesels in hierdie areas verhinder. Baie van die vervaardigingsprobleme (spesifiek lang siklusse) is aangespreek met die aanvang van termoplastiese matriks materiaal soos Polyphenolien Sulfied (PPS). Hierdie materiaal voldoen ook aan die lugvaart-industrie se brand-, rook- en giftigheidstandaarde. Termoplastiese saamgestelde materiale kan byvoorbeeld gevind word op komponente in vliegtuie se binneruimtes en ook die voorste rand van die vlerke. Hierdie komponente is hoogs vatbaar vir impakskade. Die hoë sterkte en styfheid tot gewig verhoudings van saamgestelde materiale laat toe vir dun materiaal dwarssnitte. Komponente is dus kwesbaar vir uit-vlakkige impak beladings. Saamgestelde materiale kan ook intern deur hierdie beladings beskadig word en kan nie met die blote oog waargeneem kan word nie. Dit is dus nodig om die skade weens hierdie beladings tydens normale gebruik akkuraat te voorspel. Verder sal dit nuttig wees om die struktuur se gedrag te bepaal in toepassings waar byvoorbeeld passasier veiligheid krities is, soos op vliegtuig ruglenings tydens noodlandings. In hierdie studie is die potensiële vervaardigingsvoordele van termoplastiese saamgestelde materiale gedemonstreer. Daarbenewens is 'n uit-vlakkige impak deur 'n sagte liggaam herbou in 'n laboratorium omgewing. Die primêre doelwit van hierdie studie was om die impak numeries te modelleer. Vervaardigingsvoordele van `n vesel versterkte termoplastiese laminaat is gedemonstreer deur die vervaardiging van 'n konkawe, agt laag laminaat uit 'n vooraf gekonsolideerde geweefde doek. Die totale verwerkingstyd van die plat laminaat na 'n konkawe laminaat was minder as vyf minute. 'n Eenvoudige plat laminaat en 'n konkawe laminaat is onderwerp aan 'n lae snelheid impak deur 'n sagte projektiel. Die impak is gemodelleer deur die evaluering van drie modelleringsmetodes vir die saamgestelde paneel. Die evalueringskriteria het o.a. ingesluit of laminaat se volle gedrag suksesvol gemodelleer kon word met behulp van slegs 2D dop elemente. Die reaksie van die saamgestelde paneel en gepaardgaande faling is met wisselende vlakke van sukses deur die drie geëvalueerde modelle voorspel. Die faling van tussen-laminêre bindings (verwys na as delaminasie) kon nie deur enige van die modelle voorspel word nie. Twee van die modelle het egter in-vlak faling met redelike akkuraatheid voorspel.
ENGLISH ABSTRACT: Due to weight saving advantages composite materials have become a highly popular material in the aerospace and automotive industries. Traditionally processing difficulties and costs have been a barrier to widespread composite material use in these industries. With the advent of thermoplastic matrix materials such as Polyphenoline Sulphide (PPS) the processing difficulties (especially long cycle times) experienced with traditional thermosetting resins can be addressed while maintaining aerospace Fire-Smoke and Toxicity (FST) approval. Thermoplastic composites can for example be found on aircraft interior components and leading edges of the wings. These areas are highly susceptible to impact damage. The high strength- and stiffness to weight ratios of composites allows for thin material cross sections. This leaves the components vulnerable to out-of-plane impact loads. Composite materials may also be damaged internally by these loads, leaving the damage undetectable through visual inspections. It may therefore be necessary to predict the amount of damage a component would sustain during normal operation. Additionally, it would be useful to predict structural response of these materials in applications where passenger safety is crucial, such as aircraft seat backrests during emergency landings. In this study the potential processing benefits of thermoplastic composite materials were demonstrated. Additionally an out-of-plane impact from a soft bodied projectile was reconstructed in a laboratory environment. The primary objective was to numerically model the impact event. Processing benefits of thermoplastics were demonstrated by producing a single curvature eight layered laminate from a pre-consolidated woven sheet. The total processing time from flat panel to a single curvature panel was below five minutes. A simple flat laminate and a single curvature laminate were subjected to a low velocity drop weight impact load from a soft bodied projectile. These impact events were modelled by evaluating three modelling methods for the composite panel structural response and damage evolution. Part of the evaluation criteria included whether laminate failure could be modelled successfully using only 2D shell elements. The response of the composite panel and accompanying failure were predicted with varying levels of success by the three evaluated models. The failure of interlaminar bonds (referred to as delamination) could not be predicted by either model. However two of the models predicted in-plane failure with reasonable accuracy.
28
Andersen, Bruce Jacob. "An experimental study of the automation of thermoplastic composite processing". Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/19668.
29
Umberger, Pierce David. "Characterization and Response of Thermoplastic Composites and Constituents". Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/33574.
Resumo:
The research presented herein is an effort to support computational modeling of ultra-high molecular weight polyethylene (UHMWPE) composites. An effort is made to characterize the composites and their constituents. UHMWPE, as a polymer, is time and temperature dependent. Using time-temperature superposition (tTSP), the constituent properties are studied as a function of strain rate. Properties that are believed to be significant are fiber tensile properties as a function of strain rate, as well as the through-thickness shear behavior of composite laminates. Obtaining fiber properties proved to be a challenge. The high strength and low surface energy of the fibers makes gripping specimens difficult. Several different methods of fixturing and gripping are investigated, eventually leading to a combination of friction and adhesion approaches where a fiber was wrapped on an adhesive coated cardboard mandrel and then gripped in the test fixture. Fiber strength is estimated using tTSP to equivalent strain rates approaching 10^6 sec^-1. Punch-shear testing of UHMWPE laminates is conducted at quasi-static strain rates and the dependence of the results on thickness and test geometry is investigated.Master of Science
30
Adams, Daniel O'Hare. "Effects of layer waviness on compression-loaded thermoplastic composite laminates". Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08252008-161903/.
31
Michael, Steven Gerard. "Thermoplastic encapsulation of wood strand composite using a tie-layer". Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/S_Michael_120108.pdf.
Resumo:
Thesis (M.S. in civil engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Mar. 10, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references.
32
Brunnacker, Lena. "Short Carbon Fiber-Reinforced Thermoplastic Composites for Jet Engine Components". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76733.
Resumo:
State-of-the-art aircraft engine manufactures aim to reduce theirenvironmental impact steadily. Thereby they attempt to increase engineefficiency, use new renewable fuel sources and most importantly aim toreduce component weight. While Titanium, Aluminum and continuousfiber reinforced thermosetting composites and superalloys prevail in thecurrent material selection, the present work desires to raise awareness fora novel group of materials; short carbon fiber reinforced thermoplasticcomposites (SCFRTPs). In this kind of composite short fibers givedimensional stability and strength while the thermoplastic matrix ensuresthe physical properties, even at temperatures up to 300°C.Even though in some applications these materials offer great potential tosave weight and cost, it is not clear if their properties suffice to be used indemanding areas of the aero engine and if they are still able provide costand weight reductions there.The present work therefore investigated potential aero-engine componentsthat could be replaced by SCFRTPs. With literature, manufacturer data andmaterial and process modelling approaches, it is shown that SCFRTPsmechanical and physical properties suffice for the selected component.Further it is shown that cost reductions up to 77% and weight savings upto 67% compared to the Ti-6Al-4V baseline component are possible.
33
Aramphongphun, Chuckaphun. "In-mold coating of thermoplastic and composite parts microfluidics and rheology /". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1141759615.
34
McGarva, Lance. "Thermoplastic Composite Sandwich Components : Experimental and Numerical Investigation of Manufacturing Issues". Doctoral thesis, KTH, Aeronautical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3345.
35
Leach, David W. "An experimental study of the processing parameters in thermoplastic filament winding". Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/16030.
36
Paine, Jeffrey Steven Nelson. "The performance of nitinol shape memory alloy actuators embedded in thermoplastic composite material systems /". This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10102009-020117/.
37
Zoller, Alexander. "Development and kinetic modeling of resins for advanced thermoplastic polymer composite materials". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4728.
Resumo:
L’objectif de cette thèse est de développer un matériau à base de polyméthacrylate de méthyle (PMMA) amorcé par une réaction redox à température ambiante pour produire des composites thermoplastiques. Plus particulièrement, notre travail a consisté à étudier le mécanisme d’amorçage afin d’améliorer la formulation de la résine en terme de cinétique de polymérisation. Afin d’atteindre cet objectif, les paramètres d’Arrhenius de la décomposition d’amorceur ont été déterminés et intégrés dans un modèle de simulation numérique décrivant la polymérisation du MMA à température ambiante développé à l’aide du logiciel PREDICI. Basé sur cette simulation, des différents paramètres ont été testés dans le but de diminuer le temps de polymérisation. En complément de la détermination des paramètres du système d’amorçage, une étude de copolymérisation avec un grand nombre de comonomères a été effectuée. Cette étude a conduit à l’identification d’un monomère permettant d’accélérer la vitesse de polymérisation : le méthacrylate d’acetoacetoxyethyle (AAEMA). Une étude cinétique de ce monomère a été réalisée avec l’identification du coefficient de la vitesse de propagation kp ainsi que les paramètres de copolymérisation avec MMA, rMMA et rAAEMA. Les paramètres cinétiques, qui ont été déterminés expérimentalement, ont été vérifiés par une simulation numérique de copolymérisation de MMA et AAEMAComposite materials are used for decades as high-performance materials in industry. Up to date these materials were based on non-recyclable thermoset polymers. Nowadays, environmental and economical restrictions enhance the development of recyclable composite materials. For answering that demand, research focuses on the development of recyclable thermoplastic polymer composites. Within this context, the work of this thesis focuses on the development of a material based on a poly(methyl methacrylate) (PMMA) resin initiated with a redox initiation system at room temperature in order to prepare thermoplastic composites. More precisely, our work consisted of studying this initiation system and to improve the kinetics of the resin formulation. For that purpose, the Arrhenius parameters of the initiator decomposition reaction were determined and implemented in a simulation model that describes the polymerization of MMA at room temperature. Based on the simulation carried out on the software PREDICI, several conditions were tested aiming in the decrease of the polymerization times. Besides investigating parameters concerning the initiation system, a copolymerization study, using a large variety of comonomers, was conducted. This study led to the identification of an interesting fast polymerizing methacrylate: acetoacetoxyethyl methacrylate (AAEMA). The kinetics of this monomer were studied including the determination of the propagation rate coefficient kp and the copolymerization parameters with MMA rMMA and rAAEMA. The determined kinetic parameters were finally verified by a copolymerization simulation of MMA and AAEMA
38
Dubé, Martine. "Static and fatigue behaviour of thermoplastic composite laminates joined by resistance welding". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18695.
Resumo:
This work investigates the mechanical behaviour of resistance-welded thermoplastic composites under both static and fatigue conditions for skin/stringer and lap shear welds. The first configuration was chosen in order to represent a typical reinforced aerospace composite structure. It consists of a flange laminate, representing a stringer or frame, welded onto a skin laminate. The effects of various resistance welding parameters on the weld quality and mechanical performance of a carbon fibre/poly-ether-ether-ketone (APC-2/AS4) composite skin/stringer are first investigated. The results show that the input power level and clamping distance, i.e., the distance between the connector to the power supply and the edge of the weld, have a significant influence on the weld quality. Then, the mechanical performance and the failure modes of the skin/stringer specimen are studied using the optimum welding conditions. Failure modes typically encountered with adhesively bonded thermosetting resin composites skin/stringer configuration are obtained. Diverse stress concentration reduction methods at the flange tip are also investigated. The most efficient one is to machine a taper angle at the flange tip after the welding operation. A novel solution to prevent current leakage in carbon fibre composites is developed where a ceramic (TiO2) coating is applied to the heating element. Excellent electrical insulation is obtained which results in a more uniform temperature distribution at the weld interface. Furthermore, the coating does not affect the weld static mechanical performance. The fatigue properties are then investigated and the APC-2/AS4 skin/stringer joints present indefinite fatigue lives at 40% and 35% of their static damage initiation loads, for unidirectional and quasi-isotropic specimens, respectively. The previously developed ceramic coating does not affect the fatigue properties of the welds. The heating element mesh size is optimised for carbon fibre/poly-ether-kCe travail présente une étude de la performance mécanique statique et dynamique de matériaux composites à matrice thermoplastique assemblés par soudage par résistance pour des géométries de joints de type « revêtement/raidisseur » et « joint recouvrement ». La première géométrie représente une structure typique rencontrée dans l'industrie aérospatiale. Elle consiste en un laminé, représentant un raidisseur, soudé sur un autre laminé, représentant un revêtement. L'effet des différents paramètres de soudage sur la qualité des joints est d'abord étudié pour le joint revêtement/raidisseur composé de fibre de carbone/poly-éther-éther-kétone (APC-2/AS4). Les résultats montrent que la puissance électrique fournie à l'élément chauffant et la distance de connexion, soit la distance entre le connecteur et le côté du joint, ont des effets significatifs sur la qualité des joints produits. La condition de soudage optimale est ensuite utilisée pour étudier la performance mécanique et les modes de rupture des échantillons revêtement/raidisseur. Un mode de rupture semblable à des joints revêtement/raidisseur faits de composites thermodurcissables collés est observé. Diverses méthodes de réduction de la concentration de contraintes sur les côtés du raidisseur sont étudiées. La méthode la plus efficace consiste à machiner des angles de chaque côté du raidisseur après que l'opération de soudage soit complétée. Une solution, qui consiste en l'application d'un revêtement de céramique (TiO2) sur l'élément chauffant est ensuite proposée pour contrer le problème de court circuit. Cette solution offre une bonne isolation électrique, améliore l'uniformité de la température à l'interface du joint et n'influence pas les propriétés mécaniques des joints sous chargement statique. Finalement, les propriétés des joints soudés en fatigue sont étudiées. Les échantillons revêtement/raidisseur faits de APC-2/AS4
39
Grünewald, Jonas [Verfasser], e Volker [Akademischer Betreuer] Altstädt. "Thermoplastic composite sandwiches for structural helicopter applications / Jonas Grünewald ; Betreuer: Volker Altstädt". Bayreuth : Universität Bayreuth, 2018. http://d-nb.info/1156920655/34.
40
Papadakis, Nikolaos. "Strain rate dependency of the properties of a unidirectional thermoplastic composite material". Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396872.
41
Fallon, Jake Jeffrey. "Structure-Process-Property Relationships of Cellulose Nanocrystal Thermoplastic Urethane Composites". Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/103053.
Resumo:
Nanomaterials are becoming increasingly prevalent in final use products as we continue to improve our understanding of their structure and properties and optimize their processing. The useful applications for these materials extend from new drug delivery systems to improved materials for various transport industries and many more. Nanoscale materials which are commonly used include but are not limited to carbon nanotubes, graphene, silica, nanoclays, and cellulose nanocrystals. The literature presented herein aims to investigate structure-process-property relationships of cellulose nanocrystal (CNC) polymer composites. These CNC nanocomposites are unique in that they provide a dynamic mechanical response when exposed to H2O. Currently, these nanocomposite systems are most commonly solvent cast into their final geometry. In order to enable the use of these materials in more commercial processing methods such as extrusion, we must understand their inherent structure-process-property relationships. To do this, we first characterize the influence of temperature and shear orientation on the unique mechanical adaptive response. Next, the melt processability of the nanocomposite was characterized using material extrusion (MatEx) additive manufacturing (AM). Additionally, the diffusion behavior of water within the film, which controls the dynamic mechanical response, was probed to better predict the concentration dependent behavior. Finally, a literature review is presented which outlines the state of the art for melt extrusion AM of fiber filled polymer composite materials and provides insight into how we can further improve mechanical properties through further addition of composite filler materials.
The initial focus of the dissertation is on the influence of melt processing CNC thermoplastic urethane (TPU) composites and the resulting impact on the mechanical adaptive response. Dynamic mechanical analysis (DMA) fitted with a submersion clamp was used to measure the mechanical softening of the composite while submerged in water. Small angle x-ray scattering (SAXS) and polarized raman spectroscopy were used to qualify the orientation of the various CNC/TPU composite samples. The results of the orientation measurements show that solvent casting the films orient CNCs into a mostly random state and melt extrusion induces some degree of uniaxial orientation. The DMA results indicate that at the processing conditions tested, the uniaxial orientation and thermal exposure from the melt processing do not significantly impact the mechanical responsiveness of the material.
The next objective of this work was to expand upon the aforementioned learnings and determine the CNC composite material processability using MatEx. The ability to process mechanically dynamic CNC/TPU composites with a selective deposition process capable of generating complex geometries may enable new functionality and design freedom. To realize this potential, a two factor (extrusion temperature and extrusion speed) three level (240, 250 and 260 ℃/ 600, 1100 and 1600 mm/min) design of experiments (DOE) was utilized. The resulting printed parts were characterized by DMA to determine their respective mechanical adaptivity. Processing conditions did prove to have a significant impact on the mechanical adaptivity of the printed part. A correlation between applied energy and mechanical adaptivity demonstrates how increasing residence time and temperature can reduce mechanical performance. The shape fixity of the printed parts was calculated to be 80.4% and shape recovery was 44.2%. A 3D prototype part was also produced to demonstrate the unique properties of this material.
Although the understanding of the melt processing behavior of these CNC composites had been improved, a stronger understanding of the moisture diffusion behavior within the composite is required to fully realize and control their potential. Therefore, a study was undertaken to capture the diffusion behavior and correlate it to the mechanical responsive mechanism. To do this, a thermogravimetric sorption analysis (TGA-SA) instrument was used to monitor the mass uptake as a function of time exposed to a humid environment. These data were then compared to DMA data collected for the same samples exposed to a similar degree of humidity. All studies were conducted as a function of concentration in order to better elucidate the influence that percolating network structures may have on the resultant properties. Interestingly, the results show how increasing addition of CNCs results in a decrease in the rate of diffusivity, which is counter to what has been commonly hypothesized. It is hypothesized that increasing CNC content restricts the mobility of surrounding amorphous matrix material, thus increasing the resistance for diffusion of a water molecule. However, the rate of mechanical adaptation was found to increase with increasing CNC content, which is believed to be a result of the increased connectivity, enabling further transport of water molecules.Doctor of Philosophy
42
Hastie, Robert L. "The effect of physical aging on the creep response of a thermoplastic composite". Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-07282008-134037/.
43
Chatterjee, Sanjukta. "Structural and Physical Effects of Carbon Nanofillers in Thermoplastic and Thermosetting Polymer Systems". Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-171449.
Resumo:
Ever since the discovery of carbon nano materials like carbon nanotube (CNT) and graphene, this class of materials has gained significant attention due to their exotic properties. The principle idea of my present research project is to understand the novel improvements induced in polymer matrices with inclusion of the nanofillers. This thesis is thematically divided into three parts. In the first part we introduce principle materials that we use for preparation of composites. Methods of nanofiller preparation and different nanocomposites as previously reported in literature are discussed to formulate the basis of our study. Different dispersion techniques are discussed which facilitate uniform nanofiller distribution. A variety of experimental methods are described which were employed to investigate the structure and properties of the composites. In the second part we discuss in details polyamide-12 (PA12) composites using CNT and graphene as fillers. A marked improvement is recorded in the toughness of the films with incorporation of CNT, dispersed in PA12 using a surfactant. Electrical percolation is also achieved in the otherwise insulating matrix. With PA-12 fibers we explored the effect of fiber processing and CNT incorporation in the mechanical properties. Extensive wide angle x-ray diffraction was carried out to interpret the structural modifications brought about by CNT in the matrix. The final part of the thesis deals with a thermosetting polymer, epoxy composites. CNT, Graphene and also a mixture of the two nanofillers were used as reinforcing agents. Appreciable improvement was recorded in the mechanical properties, electrical and thermal conductivity of the composites. Detailed optical and electron microscopy was carried out to get a vivid idea of the micro-structure and dispersion. The presented work demonstrates the significant ability of carbon nanofillers to reinforce polymer matrices enhancing their mechanical, electrical and thermal properties and opening a wide horizon for a variety of applications.
44
Damadzadeh, Behzad, e Hamideh Jabari. "Biodegradable Composites : Processing of thermoplastic polymers for medical applications". Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19329.
Resumo:
Despite the recent development in PLA and PLGA based medical devices, there are still needs to further improve the mechanical performance of bioresorbable medical implants and their bioactivity. This is normally done by optimizing the filler compositions in selected groups ofbiodegradable polymer matrices. In this study, the effects of various filler levels on mechanical strength and thermal properties of PLA and PLGA composites were investigated. Composites containing different dosage of osteoconductive HAp with various particles size (0-5μm, 0-50 μm, nano size), β-TCP, bioactive glass and biodegradable Poly-L-lactide and Polylactide-glycolic acid was manufactured with melt blending, using a twin-screw extruder.The samples were investigated by Differential Scanning Calorimetry (DSC), thermo gravimetric analysis (TGA), Scanning Electron Microscopy (SEM), viscometer, three points bending machine, and Optical Microscopy (OM). The Extruder produced a porous profile. The result from TGA and SEM indicated that there was homogenous filler dispersion in the matrix after compounding.The result from DSC and Viscometer shows that there was some degradation duringcompounding. Mechanical properties of composites were modified by adding filler to matrix. The addition of Bioactive glass, as a filler, increases the degradation of the polymer matrix. The best filler that was applied is 0-5μm and nano HAp. Also in in-vitro degradation part of this thesis work, the effects of calcium phosphate materialsare investigated on degradation process.
45
Umberger, Pierce David. "Modeling the High Strain Rate Tensile Response and Shear Failure of Thermoplastic Composites". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23846.
Resumo:
The high strain rate fiber direction tensile response of Ultra High Molecular Weight Polyethylene (UHMWPE) composites is of interest in applications where impact damage may occur. This response varies substantially with strain rate. However, physical testing of these composites is difficult at strain rates above 10^-1/s. A Monte Carlo simulation of composite tensile strength is constructed to estimate the tensile behavior of these composites. Load redistribution in the vicinity of fiber breaks varies according to fiber and matrix properties, which are in turn strain rate dependent. The distribution of fiber strengths is obtained from single fiber tests at strain rates ranging from 10^-4/s to 10^-1/s and shifted using the time-Temperature Superposition Principle (tTSP) to strain rates of 10^-4/s to 10^6/s. Other fiber properties are obtained from the same tests, but are assumed to be deterministic. Matrix properties are also assumed to be deterministic and are obtained from mechanical testing of neat matrix material samples. Simulation results are compared to experimental data for unidirectional lamina at strain rates up to 10^-1/s.
Above 10^-1/s, simulation results are compared to experimental data shifted using tTSP. Similarly, through-thickness shear response of UHMWPE composites is of interest to support computational modeling of impact damage. In this study, punch shear testing of UHMWPE composites is conducted to determine shear properties. Two test fixtures, one allowing, and one preventing backplane curvature are used in conjunction with finite element modeling to investigate the stress state under punch shear loading and the resulting shear strength of the composite.Ph. D.
46
Margossian, Alexane [Verfasser]. "Forming of tailored thermoplastic composite blanks: material characterisation, simulation and validation / Alexane Margossian". München : Verlag Dr. Hut, 2017. http://d-nb.info/1137024399/34.
47
Masi, Barbara Ann. "Fabrication methods and costs for thermoset and thermoplastic composite processing for aerospace applications". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/72739.
48
Claassen, Marius. "A reconfigurable manufacturing system for thermoplastic fibre-reinforced composite parts : a feasibility assessment". Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97045.
Resumo:
Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The South African manufacturing industry plays a pivotal role in the growth of its local economy. Modern manufacturing requirements include the ability to respond quickly to product variability, fluctuations in product demand and new process technologies. The reconfigurable manufacturing paradigm has been proposed to meet the demands of the new manufacturing requirements. In order to assess the feasibility of incorporating automated, reconfigurable manufacturing technologies into the production process of thermoplastic fibre-reinforced composite parts, a system, based on the thermoforming process, that implements these technologies was developed and evaluated. The assessment uses a seat pan for commercial aircraft as case study. Aspects that were addressed include the architecture, configuration and control of the system. The architecture and configuration addressed the sheet cutting, fixturing, reinforcing, heating, forming, quality assurance and transportation. The control, implemented using agents and based on the ADACOR holonic reference architecture, addresses the cell control requirements of the thermoforming process. An evaluation of the system’s reconfigurability and throughput is performed using KUKA Sim Pro. The evaluation of the system’s throughput is compared to the predicted throughput of the conventional technique for manufacturing thermoplastic fibre reinforced composite parts in a thermoforming process. The evaluation of the system’s performance show that the system designed in this thesis for the manufacture of a thermoplastic fibre-reinforced composite seat pan sports a significant advantage in terms of throughput rate, which demonstrates its technical feasibility. The evaluation of the system’s reconfigurability show that, through its ability to handle new hardware and product changes, it exhibits the reconfigurability characteristics of modularity, convertibility, integrability and scalability.
AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse vervaardigingsbedryf speel 'n sentrale rol in die groei van die plaaslike ekonomie. Moderne vervaardiging vereistes sluit in die vermoë om vinnig te reageer op die produk veranderlikheid, skommelinge in die produk aanvraag en nuwe proses tegnologieë. Die herkonfigureerbare vervaardiging paradigma is voorgestel om te voldoen aan die nuwe produksie vereistes. Ten einde die uitvoerbaarheid van die integrasie van outomatiese, herkonfigureerbare vervaardiging-tegnologieë in die produksieproses van veselversterkte saamgestelde onderdele te evalueer, is 'n stelsel, gebaseer op die termo-vormingsproses, wat sulke tegnologieë implementeer, ontwikkel. Die assessering gebruik 'n sitplek pan vir kommersiële vliegtuie as gevallestudie. Aspekte wat aangespreek is sluit in die argitektuur, konfigurasie en beheer van die vervaardigingstelsel. Die argitektuur en konfigurasie spreek aan die sny, setmate, versterking, verwarming, vorm, gehalteversekering en vervoer van n veselversterkte saamgestelde sitplek pan in 'n termo-vormingsproses. Die beheer, geïmplementeer deur die gebruik van agente en gebaseer op die ADACOR holoniese verwysing argitektuur, spreek die selbeheervereistes van die termo-vormingsproses aan. 'n Evaluering van die stelsel se herkonfigureerbaarheid en deurvoer word gedoen met die behulp van KUKA Sim Pro. Die evaluering van die stelsel se deurvoer word vergelyk met die deurvoer van die konvensionele vervaardigingsproses vir termoplastiese vessel-versterkte saamgestelde onderdele in 'n termo-vormingsproses. Die evaluering van die stelsel se prestasie toon dat die stelsel wat in hierdie tesis ontwerp is vir die vervaardiging van 'n termoplastiese vessel-versterkte saamgestelde sitplek pan, hou 'n beduidende voordeel, in terme van deurvloeikoers, in wat die stelsel se tegniese haalbaarheid toon. Die evaluering van die stelsel se herkonfigureerbaarheid wys dat, deur middel van sy vermoë om nuwe hardeware en produk veranderinge te hanteer, die stelsel herkonfigureerbare einskappe van modulariteit, inwisselbaarheid, integreerbaarheid en skaalbaarheid vertoon.
49
Tufail, Muhammad. "Effects of textile and process parameters on the properties of hybrid thermoplastic composites". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287237.
50
Gray, Robert Williamson IV. "The Effects of Processing Conditions on Thermoplastic Prototypes Reinforced with Thermotropic Liquid Crystalline Polymers". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/46512.
Resumo:
This work is concerned with preliminary studies on
developing thermoplastic composite materials suitable for
use in fused deposition modeling (FDM). Polypropylene (PP)
strands reinforced with continuous thermotropic liquid
crystalline polymer (TLCP) fibrils were generated in a
novel dual extruder process. Strands were then re-extruded
to form short fiber composite monofilaments that were used
as feed stock in the FDM 1600 rapid prototyping system.
Prototypes containing 40 wt% Vectra A were shown to have
tensile properties twice those of parts built using
acrylonitrile butadiene styrene copolymer (ABS), a
commercially available material used in the FDM 1600 rapid
prototyping system. It was also shown that the final
mechanical properties of a composite prototype can be
tailored to a specific application by adjusting the
lay-down pattern, increasing the functionality of the
prototype. In order to obtain the maximum tensile
properties in these composite prototype, additional
studies were performed to determine the effects of thermal
and deformation histories on the mechanical properties of
monofilaments that were re-extruded from long fiber TLCP
reinforced strands. Strands were consolidated uniaxially
at temperatures just above the melting point of the matrix
in order to determine the effects of thermal history, and
an approximate 20% reduction in tensile modulus relative
to the modulus of the strands was observed. Monofilaments
that could be used as feed stock in FDM were extruded from
long fiber TLCP reinforced strands using a capillary
rheometer in order to study the effects of capillary
diameter, capillary L/D, and apparent shear rate on the
tensile properties.Master of Science