Dissertations / Theses on the topic 'Dynamic composites'
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Kandan, Karthikeyan. "Dynamic response of polyethylene composites." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608106.
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Gopalan, Sriram. "Quasi-static and dynamic mechanical characterization of reinforced polyurethane foam /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p1418024.
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Gardham, Louise Marie. "Dynamic mechanical properties of polymer composites." Thesis, University of Leeds, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395322.
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Klintworth, John Wilhelm. "Dynamic crushing of cellular solids." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304395.
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Stewart, Alistair. "Dynamic nanoindentation of various polymer nano-composites." Thesis, University of Ulster, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593883.
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There is a strong rationale for replacing traditional carbon fibre and glass fibre composites with nano-composites as smaller size and higher aspect ratio reinforcement can lead to improved mechanical properties, via improved load transfer from reinforcement to polymer matrix but also increased dissipation of mechanical energy within the material, an advantage for maximising toughness and fatigue resistance. This project focuses on using dynamic nanoindentation to characterise polymer nano-composites made with graphene and carbon nanotubes (CNT), namely, CNT-polymethylmethacrylate (PMMA) composites, CNT-polydymethylsiloxane (PDMS) and graphene-polyamide composites. Melt-processed PMMA nano-composites studied by optical microscopy show a gradual increase in aggregate size for the functionaLized CNT/PMMA composites, the results for the nonfu nctionalised CNT/PMMA composite showing a poorer dispersion of CNT. Thermogravimetric analysis (TGA) also indicates that the functionalized-CNT are better dispersed into the polymer. These results are consistent with those obtained by nanoindentation and Rockwell hardness testing; higher storage modulus, lower loss tangent and higher HR value for the composites made with functionalized-CNT, sign of a better interfacial load transfer. The addition of solvent, the use of tip sonication as well as the e NT aspect ratio were all found to have an influence on the CNT dispersion within in-situ cured CNTIPDMS nano-composites. TGA showed a lowering of the degradation temperature upon CNT addition, indicative of CNT inhibiting the cure process, in accordance with recently reported results. Nanoindentation resu lts indicate that the specimen made with the better dispersed CNT exhibit the larger storage modu lus. Generally, these stiffness values increase at low CNT content and then decrease, possibly because of the effect that CNT have upon the PDMS cross-linking. In these nanocomposites, the loss tangent is large, dominated by the elastomeric matrix and not sensitive to the interfacial energy dissipation. Finally. in situ-polymerised graphene-polyamide nano-composites were investigated. TGA showed that the graphene was oxidised in these composites. Optical microscopy indicates that the fine-dispersion of the reinforcement disappear at higher graphene content. Nanoindentation showed that the storage modulus peaked at low graphene content and then decreased at higher percentages, while tested at a larger scale (mm\ the mechanical properties of these composites only saturates with graphene content. This result may be due to the processing of the high graphene content specimen, made by solvent evaporation, during which aggregates may reform, as observed by optical microscopy. Overall, this investigation has shown that dynamic nanoindentation is a valuable tool for studying the dispersion of reinforcement in polymer nanocomposites.
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Tirtom, İsmail Güden Mustafa. "Modeling Dynamic Behavior of Metal Matrix Composites/." [s.l.]: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000141.rar.
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Tan, Kian Sing. "Dynamic loading characteristics in metals and composites." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FTan_Kian_Sing.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Kwon, Young. Second Reader: Didoszak, Jarema. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: Tensile tests, Strain rate effects, Dynamic loading, Failure criterion. Includes bibliographical references (p. 37-38). Also available in print.
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Elmore, Jennifer Susan. "Dynamic mechanical analysis of graphite/epoxy composites with varied interphases." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10312009-020414/.
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Nazhat, Showan Najdat. "Dynamic mechanical characterisation of hydroxyapatite reinforced biomedical composites." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267610.
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Attwood, Julia Patton. "Static and dynamic properties of polyethylene fibre composites." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709355.
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Bohn, Clayton Claverie. "Dynamic antifouling structures and actuators using EAP composites." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006640.
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Singh, Mary Margaret. "Dynamic properties of fibre-reinforced polymers exposed to aqueous conditions." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385659.
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Shanmugam, Arun Kumar. "Dynamic mechanical analysis and impact testing of phenolic composites." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ31638.pdf.
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Kwon, Young W. "A numerical study of dynamic crack propagation in composites." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23735.
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Wang, J., S. Dong, Ashraf F. Ashour, X. Wang, and B. Han. "Dynamic mechanical properties of cementitious composites with carbon nanotubes." Elsevier, 2019. http://hdl.handle.net/10454/17465.
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YesThis paper studied the effect of different types of multi-walled carbon nanotubes (MWCNTs) on the dynamic mechanical properties of cementitious composites. Impact compression test was conducted on various specimens to obtain the dynamic stress-strain curves and dynamic compressive strength as well as deformation of cementitious composites. The dynamic impact toughness and impact dissipation energy were, then, estimated. Furthermore, the microscopic morphology of cementitious composites was identified by using the scanning electron microscope to show the reinforcing mechanisms of MWCNTs on cementitious composites. Experimental results show that all types of MWCNTs can increase the dynamic compressive strength and ultimate strain of the composite, but the dynamic peak strain of the composite presents deviations with the MWCNT incorporation. The composite with thick-short MWCNTs has a 100.8% increase in the impact toughness, and the composite with thin-long MWCNTs presents an increased dissipation energy up to 93.8%. MWCNTs with special structure or coating treatment have higher reinforcing effect to strength of the composite against untreated MWCNTs. The modifying mechanisms of MWCNTs on cementitious composite are mainly attributed to their nucleation and bridging effects, which prevent the micro-crack generation and delay the macro-crack propagation through increasing the energy consumption.
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Herlocker, Jon Alan. "Dynamic response and material processing of photorefractive polymer composites." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284284.
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This dissertation describes advances in the photorefractive dynamic response, and in the understanding of response limitations. In a PVK/ECZ based composite using a tolane chromophore and TNFDM sensitization, a photorefractive response time constant of 4 ms was observed at an applied field (Eₐ) of 95 V/μm with a writing fluence of 0.5 W/cm², while the birefringence response time was under a millisecond. This showed that the chromophore orientational response does not limit speed, and suggests further investigation of photogeneration and transport processes to improve dynamic response. Another segment of research investigated performance changes by exposure under working conditions. Photorefractive properties for composites using chromophores of varied ionization potential (I(p)) were characterized as a function of exposure at Eₐ = 80 V/um, up to 10⁴ J/cm² total optical field exposure. The response time and photoconductivity were found to fatigue for all samples, but a higher chromophore I(p) was correlated to greater stability. The four-wave mixing dependence upon E a showed a variation in trap density with exposure which verifies the role of the C₆₀ anion, the ionized sensitizer, as a photorefractive trap. The third segment of research was the proof-of-principle of a photorefractive injection molding process. Photorefractive properties of molded materials were verified by four-wave mixing and two-beam coupling measurements. At Eₐ = 95 V/μm a diffraction efficiency of 25-30% and a gain coefficient near 50 cm⁻¹ was observed. This shows industrial processing potential of these materials and provides a path from hand crafted devices to mass-production techniques, promoting commercial acceptance.
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Loveless, Thomas A. "Mechanical Properties of Kenaf Composites Using Dynamic Mechanical Analysis." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4310.
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Natural fibers show potential to replace glass fibers in thermoset and thermoplastic composites. Kenaf is a bast-type fiber with high specific strength and great potential to compete with glass fibers.
In this research kenaf/epoxy composites were analyzed using Dynamic Mechanical Analysis (DMA). A three-point bend apparatus was used in the DMA testing. The samples were tested at 1 hertz, at a displacement of 10 μm, and at room temperature.
The fiber volume content of the kenaf was varied from 20%-40% in 5% increments. Ten samples of each fiber volume fraction were manufactured and tested. The flexural storage modulus, the flexural loss modulus, and the loss factor were reported. Generally as the fiber volume fraction of kenaf increased, the flexural storage and flexural loss modulus increased. The loss factor remained relatively constant with increasing fiber volume fraction.
Woven and chopped fiberglass/epoxy composites were manufactured and tested to be compared with the kanaf/epoxy composites were manufactured and tested to be compared with the kenaf/epoxy composites. Both of the fiberglass/epoxy composites reported higher flexural storage and flexural loss modulus values. The kenaf/epoxy composites reported higher loss factor values. The specific flexural storage and specific flexural loss modulus were calculated for both the fiberglass and kenaf fiber composites. Even though the kenaf composites reported a lower density, the fiberglass composites reported higher specific mechanical properties.
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Knowles, Stephen. "Dynamic analysis and the use of composite materials in cricket bat design." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270102.
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CHEN, Yiqing. "POLISHING OF POLYCRYSTALLINE DIAMOND COMPOSITES." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/3682.
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This thesis aims to establish a sound scientific methodology for the effective and efficient polishing of thermally stable PCD composites (consisting of diamond and SiC) for cutting tools applications. The surface roughness of industrial PCD cutting tools, 0.06 μm Ra is currently achieved by mechanical polishing which is time consuming and costly because it takes about three hours to polish a 12.7 mm diameter PCD surface. An alternative technique, dynamic friction polishing (DFP) which utilizes the thermo-chemical reactions between the PCD surfaces and a catalytic metal disk rotating at high peripheral speed has been comprehensively investigated for highly efficient abrasive-free polishing of PCD composites. A special polishing machine was designed and manufactured in-house to carry out the DFP of PCD composites efficiently and in a controllable manner according to the requirements of DFP. The PCD polishing process and material removal mechanism were comprehensively investigated by using a combination of the various characterization techniques: optical microscopy, SEM and EDX, AFM, XRD, Raman spectroscopy, TEM, STEM and EELS, etc. A theoretical model was developed to predict temperature rise at the interface of the polishing disk and PCD asperities. On-line temperature measurements were carried out to determine subsurface temperatures for a range of polishing conditions. A method was also developed to extrapolate these measured temperatures to the PCD surface, which were compared with the theoretical results. The material removal mechanism was further explored by theoretical study of the interface reactions under these polishing conditions, with particular emphasis on temperature, contact with catalytic metals and polishing environment. Based on the experimental results and theoretical analyses, the material removal mechanism of dynamic friction polishing can be described as follows: conversion of diamond into non-diamond carbon takes place due to the frictional heating and the interaction of diamond with catalyst metal disk; then a part of the transformed material is detached from the PCD surface as it is weakly bonded; another part of the non-diamond carbon oxidizes and escapes as CO or CO2 gas and the rest diffuses into the metal disk. Meanwhile, another component of PCD, SiC also chemically reacted and transformed to amorphous silicon oxide/carbide, which is then mechanically or chemically removed. Finally an attempt was made to optimise the polishing process by investigating the effect of polishing parameters on material removal rate, surface characteristics and cracking /fracture of PCD to achieve the surface roughness requirement. It was found that combining dynamic friction polishing and mechanical abrasive polishing, a very high polishing rate and good quality surface could be obtained. The final surface roughness could be reduced to 50 nm Ra for two types of PCD specimens considered from pre-polishing value of 0.7 or 1.5 μm Ra. The polishing time required was 18 minutes, a ten fold reduction compared with the mechanical abrasive polishing currently used in industry.
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CHEN, Yiqing. "POLISHING OF POLYCRYSTALLINE DIAMOND COMPOSITES." University of Sydney, 2007. http://hdl.handle.net/2123/3682.
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Doctor of Philosophy (PhD)This thesis aims to establish a sound scientific methodology for the effective and efficient polishing of thermally stable PCD composites (consisting of diamond and SiC) for cutting tools applications. The surface roughness of industrial PCD cutting tools, 0.06 μm Ra is currently achieved by mechanical polishing which is time consuming and costly because it takes about three hours to polish a 12.7 mm diameter PCD surface. An alternative technique, dynamic friction polishing (DFP) which utilizes the thermo-chemical reactions between the PCD surfaces and a catalytic metal disk rotating at high peripheral speed has been comprehensively investigated for highly efficient abrasive-free polishing of PCD composites. A special polishing machine was designed and manufactured in-house to carry out the DFP of PCD composites efficiently and in a controllable manner according to the requirements of DFP. The PCD polishing process and material removal mechanism were comprehensively investigated by using a combination of the various characterization techniques: optical microscopy, SEM and EDX, AFM, XRD, Raman spectroscopy, TEM, STEM and EELS, etc. A theoretical model was developed to predict temperature rise at the interface of the polishing disk and PCD asperities. On-line temperature measurements were carried out to determine subsurface temperatures for a range of polishing conditions. A method was also developed to extrapolate these measured temperatures to the PCD surface, which were compared with the theoretical results. The material removal mechanism was further explored by theoretical study of the interface reactions under these polishing conditions, with particular emphasis on temperature, contact with catalytic metals and polishing environment. Based on the experimental results and theoretical analyses, the material removal mechanism of dynamic friction polishing can be described as follows: conversion of diamond into non-diamond carbon takes place due to the frictional heating and the interaction of diamond with catalyst metal disk; then a part of the transformed material is detached from the PCD surface as it is weakly bonded; another part of the non-diamond carbon oxidizes and escapes as CO or CO2 gas and the rest diffuses into the metal disk. Meanwhile, another component of PCD, SiC also chemically reacted and transformed to amorphous silicon oxide/carbide, which is then mechanically or chemically removed. Finally an attempt was made to optimise the polishing process by investigating the effect of polishing parameters on material removal rate, surface characteristics and cracking /fracture of PCD to achieve the surface roughness requirement. It was found that combining dynamic friction polishing and mechanical abrasive polishing, a very high polishing rate and good quality surface could be obtained. The final surface roughness could be reduced to 50 nm Ra for two types of PCD specimens considered from pre-polishing value of 0.7 or 1.5 μm Ra. The polishing time required was 18 minutes, a ten fold reduction compared with the mechanical abrasive polishing currently used in industry.
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Yalcin, Omer Fatih. "A Dynamic Theory For Laminated Composites Consisting Of Anisotropic Layers." Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607116/index.pdf.
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In this thesis, first a higher order dynamic theory for anisotropic thermoelastic plates is developed. Then, based on this plate theory, two dynamic models, discrete and continuum models (DM and CM), are proposed for layered composites consisting of anisotropic thermoelastic layers. Of the two models, CM is more important, which is established in the study of periodic layered composites using smoothing operations. CM has the properties: it contains inherently the interface and Floquet conditions and facilitates the analysis of the composite, in particular, when the number of laminae in the composite is largeit contains all kinds of deformation modes of the layered composite
its validity range for frequencies and wave numbers may be enlarged by increasing, respectively, the orders of the theory and interface conditions. CM is assessed by comparing its prediction with the exact for the spectra of harmonic waves propagating in various directions of a two-phase periodic layered composite, as well as, for transient dynamic response of a composite slab induced by waves propagating perpendicular to layering. A good comparison is observed in the results and it is found that the model predicts very well the periodic structure of spectra with passing and stopping bands for harmonic waves propagating perpendicular to layering. In view of the results, the physical significance of Floquet wave number is also discussed in the study.
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Chalivendra, Vijaya Bhaskar. "Static and dynamic constitutive behavior and fracture of particulate composites /." View online ; access limited to URI, 2003. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3112114.
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Xiaozhuang, Zhou [Verfasser]. "Dynamic polydimethylsiloxane based polymer composites for functional materials / Zhou Xiaozhuang." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1224474864/34.
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Mudigonda, Ashwin. "Static and Dynamic Characterization of Ionic Polymer Metal Composites - 'Artificial Muscles'." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1142538201.
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Barker, Daniel Keith. "Active dynamic response tuning of adaptive composites utilizing embedded nitinol actuators." Thesis, This resource online, 1989. http://scholar.lib.vt.edu/theses/available/etd-03042009-041038/.
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Okoli, Okenwa Obinna Ifeanyichukwu-Izejiora. "Experimental determination of transient dynamic response of fibre reinforced polymer composites." Thesis, University of Warwick, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273471.
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Willoughby, Natasha. "Dynamic homogenization for the elastic properties of periodic and random composites." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/dynamic-homogenization-for-the-elastic-properties-of-periodic-and-random-composites(da82e607-bc1f-40e9-8e62-ec5fbca1f68f).html.
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In this thesis we are interested in the propagation of low-frequency linear elastic waves through composite materials. We use a variety of dynamic homogenization techniques to find the effective elastic properties of some composites. We consider composites with isotropic phases for ease of exposition but the theory could easily be extended to anisotropic inclusions or host.We use a Representative Volume Element approach with the Method of Asymptotic Homogenization to model a random fibre-reinforced composite. The fibres are all aligned in the same direction and are taken to be of infinite extent, so the composite is essentially two-dimensional. For a random composite we have considered the anti-plane case for SH wave propagation and the in-plane case for P and SV elastic wave propagation, extending the previous published work of Parnell and Abrahams (2006), (2008a), in which a periodic fibre-reinforced composite was studied. We also show, for a simple example, that it is possible to extend the Representative Volume Element method to a three-dimensional particulate composite.In this thesis an Integral Equation Method for homogenization is also studied, with application to periodic fibre-reinforced composites. We have extended the work of Parnell and Abrahams (2008b), which considered SH wave propagation only, to the case of P and SV wave propagation.
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Bhutta, Salman Ahmed. "Analytical modeling of hybrid composite beams." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020112/.
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Nie, Zifeng. "Advanced Mesomechanical Modeling of Triaxially Braided Composites for Dynamic Impact Analysis with Failure." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1407129124.
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Sen, Ozge. "Transient Dynamic Response Of Viscoelastic Cylinders Enclosed In Filament Wound Cylindrical Composites." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606412/index.pdf.
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In this study, transient dynamic response of viscoelastic cylinders enclosed in filament wound cylindrical composites is investigated. Thermal effects, in addition to mechanical effects, are taken into consideration. A generalized thermoelasticity theory which incorporates the temperature rate among the constitutive variables and is referred to as temperature-rate dependent thermoelasticity theory is employed. This theory predicts finite heat propagation speeds.
The body considered in this thesis consists of n+1-layers, the inner layer being viscoelastic, while the outer fiber reinforced composite medium consist of n-different generally orthotropic, homogeneous and elastic layers. In each ply, the fiber orientation angle may be different. The body is a hollow circular cylinder with a finite thickness in the radial direction, whereas it extends to infinity in the axial direction. The multilayered medium is subjected to uniform time-dependent dynamic inputs at the inner and/or outer surfaces. The body is assumed to be initially at rest. The layers are assumed to be perfectly bonded to each other.
The case in which the inner surface of the viscoelastic cylinder is a moving boundary is further investigated in this study. This is similar to the solid
propellant rocket motor cases. The solid propellant is modelled as a viscoelastic material which in turn is modelled as standard linear solidwhereas, the rocket motor case is a fiber-reinforced filament wound cylindrical composite. Method of characteristics is employed to obtain the solutions. Method of characteristics is suitable because the governing equations are hyperbolic. The method is amenable to numerical integration and different boundary, interface and initial conditions can be handled easily.
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Samur, Algan. "Flexible piezoelectric composites and concepts for bio-inspired dynamic bending-twisting actuation." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47680.
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Al-Khodairi, Fahad Abdul Aziz. "Static and dynamic properties of unidirectional hybrid resin and hybrid fibre composites." Thesis, Brunel University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296214.
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Barakati, Amir. "Dynamic interactions of electromagnetic and mechanical fields in electrically conductive anisotropic composites." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3562.
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Recent advances in manufacturing of multifunctional materials have provided opportunities to develop structures that possess superior mechanical properties with other concurrent capabilities such as sensing, self-healing, electromagnetic and heat functionality. The idea is to fabricate components that can integrate multiple capabilities in order to develop lighter and more efficient structures. In this regard, due to their combined structural and electrical functionalities, electrically conductive carbon fiber reinforced polymer (CFRP) matrix composites have been used in a wide variety of applications in most of which they are exposed to unwanted impact-like mechanical loads. Experimental data have suggested that the application of an electromagnetic field at the moment of the impact can significantly reduce the damage in CFRP composites. However, the observations still need to be investigated carefully for practical applications. Furthermore, as the nature of the interactions between the electro-magneto-thermo-mechanical fields is very complicated, no analytical solutions can be found in the literature for the problem.
In the present thesis, the effects of coupling between the electromagnetic and mechanical fields in electrically conductive anisotropic composite plates are studied. In particular, carbon fiber polymer matrix (CFRP) composites subjected to an impact-like mechanical load, pulsed electric current, and immersed in the magnetic field of constant magnitude are considered. The analysis is based on simultaneous solving of the system of nonlinear partial differential equations, including equations of motion and Maxwell's equations. Physics-based hypotheses for electro-magneto-mechanical coupling in transversely isotropic composite plates and dimension reduction solution procedures for the nonlinear system of the governing equations have been used to reduce the three-dimensional system to a two-dimensional (2D) form. A numerical solution procedure for the resulting 2D nonlinear mixed system of hyperbolic and parabolic partial differential equations has been developed, which consists of a sequential application of time and spatial integrations and quasilinearization. Extensive computational analysis of the response of the CFRP composite plates subjected to concurrent applications of different electromagnetic and mechanical loads has been conducted. The results of this work verify the results of the previous experimental studies on the subject and yield some suggestions for the characteristics of the electromagnetic load to create an optimum impact response of the composite.
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Lin, Jun. "Nonlinear transient analysis of isotropic and composite shell structures under dynamic loading by SPH method." Phd thesis, Université de Technologie de Compiègne, 2014. http://tel.archives-ouvertes.fr/tel-00997702.
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The objective of this thesis is the development and the extension of the SPH method for the analysis of isotropic and multilayered composite shell structures, undergoing dynamic loading. Major defects of the classical SPH method such as the lack of consistency, the tensile instability are solved by "Corrective Smoothed Particle Method", the use of the Total Lagrangian Formulation and artificial viscosity. Mindlin-Reissner Theory is employed for the modeling of thick shells, by using only one layer of particles in the mid-plane. The strong form of the governing equations for shell structures are discretized directly by the modified SPH method and solved using the central difference time integration scheme. An extension of the method has been introduced for the modeling of low-velocity impact of shells by rigid impactors. The contact force is calculated based on the Hertzian contact law. A last extension of the SPH method concerns the integration of Tsai-Wu failure criterion for the modeling of progressive degradation of multilayered structures.
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Keller, Andrew R. "An experimental analysis of the dynamic failure resistance of TiB₂/A1₂O₃ composites." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16657.
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Teh, Kuen Tat. "Impact damage resistance and tolerance of advanced composite material systems." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06062008-170512/.
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Marquina, Edgar Alberto. "Use of Dynamic Mechanical Testing, WAXD and SEM Image Analysis to Study the Properties of Polypropylene/Calcium Carbonate Nanocomposites." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1269363578.
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Angelini, Nicholas Alexander. "Simulating Dynamic Vehicle Maneuvers Using Finite Elements For Use In Design Of Integrated Composite Structure." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/46995.
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Formula SAE (FSAE) chassis systems are increasing being manufactured with integrated composite structures in an effort to increase the performance of the system while decreasing weight. The increased use of composite structures requires more details of the loading conditions and evaluation metrics than the mild steel structures they are replacing. The prototypical FSAE steel space frame chassis designs are heavily structured around the mandated safety rules that doubled as mostly satisfactory structures for vehicle loads. The use of composite structures and the directionality of their material properties has created a need for more detailed loading scenarios to evaluate their ability to transfer load.
This thesis presents a framework for evaluating the chassis structure not only through the standard static twist analysis, but increased use of modal analysis and dynamic vehicle maneuvers using an attached suspension. The suspension joints and springs/dampers are modeled using Abaqus Connector Elements, allowing for the use of complex kinematic degrees of freedom definitions required to accurately model the suspension behavior. The elements used to represent the joints and springs are detailed as well as their superiority over traditional multi-point constraints in this context.
The use of modal analysis is used for a more direct comparison of not only the efficiency of stiffness in the chassis alone, but also how the chassis interacts with the suspension. The natural frequencies from the modal analysis along with the static twist distribution along the chassis are presented as a replacement for the static torsional stiffness performance metric.
By using dynamic vehicle maneuvers the chassis-suspension structure can be evaluated based on loads developed during the typical use of the FSAE vehicle. The dynamic nature of the analysis also allows for the inclusion of mass in the loading profile as well as the load variation with time that can be hard to achieve with static analysis. The framework for a bump event as well as a constant-speed-constant-radius turn are presented. The bump analysis is designed to evaluate the system's response to straight line dynamic events, while the turning maneuver evaluates the lateral components of the suspension load transfer capabilities. For the turn analysis both a spring/damper tire model using connector elements and a rolling tire model are presented. Intermediate checks on suspension and chassis behavior are evaluated to verify the modeling techniques; while the maneuver results are evaluated based on trends and overall motion rather than magnitudes due to lack of data at the time of the analysis.Master of Science
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Slater, Carl. "The static and dynamic behaviour of carbon fibre composites used in golf club shafts." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3476/.
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The static and dynamic properties of carbon fibre composites of varying orientation, stacking sequence and geometry has been analysed in terms of modulus and material loss factor up to strain rates applicable to golf club shafts. No noticeable change in modulus or damping was seen at strain rate applicable to golf club shafts. All panels tested strain rate sensitivity onset occurred at around 0.4 s\(^{-1}\), which is above the maximum observed during a golf swing (0.1 s\(^{-1}\)). The strain rate sensitivity was found to be sensitive to aspect ratio (for strain rates above 0.4 s\(^{-1}\)). Two 20° panels of the same fibre interfacial area, but with different aspect ratios (length/width) showed different strain rate sensitivities. The short wide panel (aspect ratio 1.5) showed a higher stiffness and lower strain rate sensitivity when compared to a panel with an aspect ratio of 2.6. A model was created to predict the modulus and damping of lay-ups for laminates and golf club shafts. The model was validated against three composite systems at varying orientations and stacking sequences. The software agreed well with laminate experimental data (data sets showed a RMSD of less than 5 %). From this an optimising software was developed to provide the user with a stacking sequence that will optimise modulus, damping or the product of both. This thesis also evaluated commercial shafts in order to determine the models applicability to this application. Commercial shafts were tested for both stiffness and damping, where a number of aspects such as inter-ply resin rich regions and seam were observed as possible areas for discrepancy with the models prediction. Shafts were fabricated in order to analyse these aspects in greater deal, and to determine the models limits for this application. The model accurately predicted the stiffness of the shafts however the model failed to predict the damping of the shafts when comparing to the average values taken. When damping was compared to the areas where no seams were present, the model agreed well except for in two cases, which have been attributed to shafts flaws (cracks or excess inter ply resin). The model presented in this research consistently characterised the stiffness of fabricated shafts, however the seams proved too dominant a feature to be neglected in the prediction of damping.
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Roy, Saroj K. (Saroj Kumar). "Dynamic mechanical relaxations of ultradrawn polyethylene and polypropylene films." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72813.
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Kendall, Peter K. "Numerical study of effects of fluid-structure interaction on dynamic responses of composite plates." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Sep/09Sep%5FKendall.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, September 2009.Thesis Advisor(s): Kwon, Young W. "September 2009." Description based on title screen as viewed on 6 November 2009. Author(s) subject terms: Fluid-structure interaction, composite, carbon fiber composite, dynamic response, finite element. Includes bibliographical references (p. 95-96). Also available in print.
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Coussa, Fabien. "Du comportement dynamique de matériaux composites tissés à matrice polyamide." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM063/document.
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Contraint de respecter les réglementations environnementales concernant les émissions de CO2, les industriels du secteur automobile se doivent de lever certains verrous technologiques associés à l’allègement des structures au sein de leur véhicule. L’introduction des matériaux composites dans le développement et la production de pièces structurantes est envisagée comme étant une des solutions les plus efficaces à moyen et long terme. L’optimisation des coûts matière, caractéristique de cette industrie de masse, nécessite de maîtriser le comportement physique de matériaux composites à matrice thermoplastique et à fibres de verre continues tissées. En termes de coût et de variétés d’applications, ces derniers sont considérés aujourd’hui comme une alternative pertinente aux onéreux composites utilisés dans l’aéronautique. Un renfort de porte pour crash latéral a été ainsi développé et les travaux présentés dans cette thèse sont une contribution à la compréhension, la caractérisation et à la prédiction numérique du comportement jusqu’à rupture de cette pièce, qui lors d’un crash est soumise à de forts gradients de vitesses. Au regard de l’absence de normalisation ou de consensus liés aux essais dynamiques sur matériaux composites, nous proposons une procédure expérimentale robuste, garantissant la représentativité de la caractérisation du comportement sur un spectre de vitesses quasi-statiques et dynamiques. La validation des étapes de la procédure et l’utilisation d’un montage d’essais dynamiques développé dans ces travaux permettent d’aboutir à une base de données riche, et utile à une procédure d’identification des paramètres d’un modèle phénoménologique prenant en compte l’influence de la vitesse sur l’évolution des phénomènes dissipatifs jusqu’à rupture. Fort d’une identification majoritairement directe, la précision de la réponse numérique issue de la loi de comportement identifiée est évaluée et validée à l’aide de calculs de structures faisant intervenir d’importants gradients matériels et structurelsCar manufacturers are looking for solutions to lighten their vehicles in order to meet pollutant emission requirements – for thermal engines – or to extend their range – for electric vehicles. Composite materials, among other solutions, offer excellent strength and durability. However increased per unit cost and manufacturing time are among the main drawbacks material producers have to overcome in order to make composite solutions viable for mass-market production. In that prospect, woven glass fibers and thermoplastic matrices respectively are more serious contenders than aeronautic-grade composites. The objective application is a door reinforcement module, whose main function is to act as a safety net, adding its own stiffness and strength to that of the steel door and preventing any foreign object from entering the passenger compartment. A main preoccupation is therefore the constitutive behavior of that material under strain rates varying from 10-3 s-1 to approximately 50 s-1. The study objective is to develop a physically-based constitutive law modelling in order to take into account strain-rate sensitivity on behavior. A new and consistent experimental procedure aiming at capturing the influence of speed solicitation on non-linear internal mechanisms is developed and allows identifying non-linear constitutive law parameters over a wide range of strain rates until failure. Resulting mainly from direct evaluations and direct identification procedure, the accuracy of the implemented constitutive law is guaranteed through numerical computations involving effects of material and structural heterogeneities
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Yilmaz, Faris Sad. "Polyaniline: Synthesis, Characterization, Solution Properties, And Composites." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608598/index.pdf.
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Polyaniline was chemically synthesized at three different temperatures of 25, 0, and -25oC, by oxidative polymerization with ammonium peroxidisulfate at equimolar of aniline to oxidant ratio and 1M HCl. The resulted polyaniline was in a powder form which was characterized by several techniques such as: electrical conductivity, elemental analysis, thermal analysis, wide-angle X-Ray diffraction, and scanning electron microscope. The solution properties of the reduced polymer were studied by viscometry, static and dynamic light scattering.
It was found that as the polymerization temperature decreased, the molecular weight, crystallinity, and thermal stability of polyaniline increased, while the electrical conductivity was independent of the polymerization temperature. Moreover, the morphology of the polymer was changed from granular to tubular with reducing polymerization temperature. Viscometry and static light scattering showed that polyaniline has a flexible random coil conformation when dissolved in N-methyl-2-pyrrolidinone which proved to be a good solvent for this polymer. Dynamic light scattering indicated that the polymer solution is a polyelectrolyte with high hydrodynamic radius at low polymer concentrations.
All mechanical features except Young's modulus of polyaniline-filled low density polyethylene composites became poorer as polyaniline content increased. Moreover, a sudden increase in the electrical conductivity with increasing polyaniline contents was also observed. The conductivity of the tubular composites of multi wall nanotubes (MWNTs)-filled polyaniline increased with increasing MWNTs loading, and became weakly temperature dependent. The morphological analysis indicated that the MWNTs were well dispersed and isolated, and the tubes became crowded proportionally to MWNTs weight percent used in the composites.
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Chitrakar, Rojer. "Fabrication and Performance Evaluation of Porous Microsphere Filled Epoxy Composites." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2882.
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Syntactic foams are hollow particles-filled lightweight composites that are widely used in areas that require high strength while maintaining low weight and density. These foams are highly tailorable materials whose properties can be altered during the manufacturing process by changing various parameters like matrix and microballoon material type, size, distribution, as well as the volume fraction and wall thickness of microballoons. Therefore, understanding the effect of these parameter changes in the behavior of syntactic foams is very important to manufacture the foam for different applications. In the present study, syntactic foams of various volume fractions of microballoons were fabricated and different mechanical testing was conducted to study their elastic and viscoelastic behavior. Moreover, density, void content, and microstructure of the syntactic foam with varying volume fractions of microballoons were also studied to better characterize these foams. Results show that changes in the volume fraction of the microballoons had a significant impact on the elastic and viscoelastic behavior of the foams. The introduction of the microballoons into the epoxy resin decreased the density of the epoxy resin by up to 43.36% and at the same time increasing the specific modulus by up to 21.059%. In addition, representative 3D models of these syntactic foams were also developed to further study the elastic behavior of these materials which were found to be in good agreement with the experimental results. These findings will help in designing and optimizing the material properties of the syntactic foam required for different applications.
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Legrand, Aurélie. "Nanocharges fonctionnelles pour Vitrimères et Catalyse." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066427/document.
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En Science des colloïdes, il est fondamental de contrôler les interactions entre les particules et leur environnement pour obtenir les propriétés souhaitées. Dans ce travail de thèse, pour former des systèmes innovants, nous avons utilisé la chimie covalente réversible à l'interface particule/polymère dans deux domaines différents : les composites vitrimères et la nanocatalyse. Dans les composites, les liens réversibles permettent d'améliorer les propriétés mécaniques tout en limitant l'impact des charges sur les propriétés vitrimères des matériaux. Deux matrices vitrimères reposant sur des réactions d'échange de nature différente, la transestérification et la transimination, ont été étudiées. L'avantage du lien imine est d'être également dissociable dans certaines conditions douces, ce qui facilite le recyclage des matériaux. La réversibilité du lien imine peut aussi être exploitée pour contrôler la dispersion/agrégation de particules en solvant. Lorsqu'elles sont liées, les chaines polymères se déploient en bon solvant et confèrent aux particules une stabilisation stérique, stabilisation qui disparait lorsqu'elles sont détachées : les particules s'agrègent et peuvent être récupérées facilement. Ce concept a été développé sur un système catalytique composé de nanoparticules de palladium supportées sur des particules de silice. Les chaines greffées améliorent non seulement la dispersion des nanocatalyseurs et les taux de conversion du système catalytique, mais aussi stabilisent les nanoparticules de palladium à la surface de la silice, limitant leur lessivage et leur agrégation. L'efficacité catalytique du système est ainsi conservée sur plusieurs cyclesThe control of the interactions between particles and their environment is essential when dealing with colloids in order to reach desired properties. In this study, reversible covalent bonds were used as interfacial interactions in two systems: vitrimer composite materials and nanocatalysis in solution. The aim of this work was to develop materials which present original properties thanks to interfacial dynamic bonds. In composites, the introduction of dynamic covalent bonds between a vitrimer matrix and the fillers enables to improve mechanical properties while preserving vitrimer properties. Two vitrimer matrices based on two different exchange reactions, transesterification or transimination, have been studied. Imine bonds are reversible bonds that can dissociate in presence of water. We demonstrate that polyimine vitrimers can be reshaped and recycled under mild conditions. The reversibility of the imine bond can also be used to control the stability of a colloidal dispersion. Indeed, grafting of polymers on particles surface through reversible covalent bonds give them steric stabilization in good solvent of the chains. Dissocation of these bonds triggers detachment of the polymer chains and induces particle aggregation. This concept was applied to a catalytic system composed of palladium nanoparticles adsorbed onto silica particles. Polymer chains not only improve the dispersion of the whole catalytic system but also limit the leaching and aggregation of the palladium nanoparticles. As a consequence, the catalytic efficiency of the particles can be preserved over several cycles
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Shirinbayan, Mohammadali. "Étude du comportement mécanique et de l’endommagement de divers matériaux composites smc soumis à des chargements de type dynamique, fatigue et dynamique post-fatigue." Thesis, Paris, ENSAM, 2017. http://www.theses.fr/2017ENAM0013/document.
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Le dimensionnement au crash des structures automobiles en matériaux composites à renforts discontinus tels que les SMC est généralement réalisé sur la base de données expérimentales recueillies sur des matériaux vierges n’ayant subi aucun chargement depuis leur mise en œuvre. Or, les accidents proviennent après quelques années de mise en service durant lesquelles la structure composite est soumise généralement à des sollicitations de type fatigue à plus ou moins grande amplitude. La prise en compte d’un pré-endommagement éventuel en fatigue devient alors essentielle si l’on veut rester réaliste. Par ailleurs, de nouvelles formulations de matériaux composites SMC ont été récemment développées. Leur comportement en fatigue et sous sollicitation rapide étaient jusqu’à lors inexplorés. Cette étude à caractère fortement expérimentale a donc pour but d’apporter la connaissance nécessaire au dimensionnement de structures en matériaux SMC de diverses formulations, notamment le A-SMC et le LD-SMC. Le premier correspond à une matrice vinylester fortement renforcée de mèches de fibres de verre (50%). Le second correspond à une formulation proche de celle d’un SMC standard dans laquelle on a rajouté un fort taux de billes de verre creuse afin de réduire la densité. Une analyse multi-échelle permet de mettre en évidence l’influence de la microstructure sur les phénomènes d’endommagement sous sollicitation quasi-statique, dynamique et fatigue. Des méthodes originales d’analyse expérimentale sont développées afin de corréler ces mécanismes aux comportements macroscopiques observés. Les essais dynamiques rapides optimisés sont réalisés jusqu’à des vitesses de déformation de l’ordre de 80 s-1 et mettent en évidence un comportement visco-endommageable pour les deux matériaux SMC étudiés. Le décalage du seuil d’endommagement et la baisse de la cinétique d’endommagement observés à l’échelle macroscopique sont directement corrélés au seuil et cinétique des mécanismes d’endommagement observés à l’échelle locale telles que la rupture à l’interface fibre-matrice ou bille-matrice, la microfissuration de la matrice et le pseudo-délaminage entre les mèches de fibres de verre. Par ailleurs, une analyse multi-échelle du même type est également réalisée sous sollicitation de type fatigue dans laquelle les fréquences varient de 10 à 100 Hz. Une étude de l’influence des phénomènes d’auto-échauffement sur l’endommagement et le comportement du A-SMC est proposée. Enfin, une analyse originale des propriétés résiduelles sous sollicitation rapide d’échantillons préalablement fatigués à différents niveaux de fraction de durée de vie met en évidence une forte influence de l’histoire du chargement sur la sensibilité du A-SMC à la vitesse de sollicitation. L’ensemble des résultats de cette étude, de par son apport de compréhension des phénomènes mis en jeu, constitue la base expérimentale nécessaire à la construction d’outils de dimensionnement adaptés aux structures SMC sous sollicitations cycliques et dynamiquesClassically, crash design of automotive composite structures made of discontinuous reinforcements such as SMC is usually based on experimental data obtained from virgin materials without any history of loading. However, crash events always occur after a few years of use during which composite structure is generally subjected to more or less important fatigue loading. Taking into account of a potential pre-damage in fatigue becomes essential if we want to stay realistic. Moreover, new formulations of SMC composites have been developed recently. Up to now, their fatigue and dynamic behavior were never being explored. This study, of a mostly experimental nature, aims to provide the knowledge necessary for design of structures made of various SMC formulations including A-SMC and LD-SMC. The first one is a vinylester matrix reinforced with a high content of glass fibers (50%). The second corresponds to a standard SMC formulation in which we added a high content of hollow glass micro-sphere in order to reduce density. A systematic multi-scale analysis allows to highlight the influence of the microstructure on damage phenomena under quasi-static, dynamic and fatigue loading. Original experimental methods are developed to correlate these mechanisms to the observed macroscopic behavior. Optimized dynamic tests are performed at strain rate up to 80 s-1 and highlight a visco-damageable behavior for the two SMC materials in study. Damage threshold delay and reduction of damage kinetics observed at the macroscopic scale are directly correlated to the threshold and kinetic of damage development observed at the local scale such as fiber-matrix or matrix-microsphere interfaces, matrix micro-cracking and pseudo-delamination between the bundles of glass fiber. Moreover, a similar multi-scale analysis is also performed under fatigue loading in which the frequency ranges from 10 to 100 Hz. A study of the influence of the self-heating phenomenon on the fatigue damage behavior of A-SMC is proposed. Finally, an original analysis of the remaining dynamic properties of samples which were previously submitted to fatigue loading until different levels of lifetime highlights a strong influence of the history of the loading on the strain rate sensitivity of the A-SMC. Considering the high contribution of this study in term of comprehension of the phenomena involved in the mechanical response of SMC materials, all of the experimental findings of this study provide the physical background crucial to build structural design tools for SMC subjected to cyclic and dynamic loading
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Samant, Gajanan Balkrishna. "Verification of the "Energy Accumulation in Waves Travelling through a Checkerboard Dielectric Material Structure in Space-time" Using Spice Simulations." Digital WPI, 2009. https://digitalcommons.wpi.edu/etd-theses/1210.
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"Recently, there has been some good interest in the field of Dynamic Materials, also referred to as Spatio-Temporal Composites. These materials have been theoretically attributed to show ability to switch their electromagnetic properties in time, as contrast to the spatial variations shown by regular materials of non-dynamic nature, existing naturally. Though there is no exhibition of dynamic material in nature yet, there are suggestions for its synthesis. This paper follows the idea of using standard lossless transmission line model approximating a material substance. Such a material though not truly homogeneous, could be made to vary its properties in time. The aim of this work is to test this idea for its functional efficiency in comparison to analytical results obtained from earlier works on the subject. We make use of Spice simulation for this. An important aspect of this work is to facilitate the dynamic operations in a static environment. Almost all the simulators available today like Spice, ADS, etc intrinsically provide no ability for parameter variations in time. Nonetheless, we make use of certain popular tricks to implement circuits imitating the dynamic circuit components we need. Such implementations are separately tested to demonstrate their success in providing us with the dynamic environment we desire. Finally, within the limitations of the computing capabilities, we could successfully show an agreement between the results obtained and the existing theory. "
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Meftah, Hassen. "Etude du comportement dynamique couplé au vieillissement des composites totalement recyclés à renfort carbone : de la caractérisation à la modélisation." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0014/document.
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Dans le domaine automobile, intégrer de plus en plus de matériaux composites recyclés tout en améliorant les performances initiales et en diminuant les masses emportées devient un compromis auquel il faut répondre. Par ailleurs, les pièces de structures en matériaux composites destinées au crash sont souvent soumises à des conditions environnementales, notamment des températures modérément élevées, pouvant produire une dégradation physico-chimique progressive. Ainsi, pour assurer une meilleure conception et une durabilité des pièces, il est primordial de bien cerner l’influence du vieillissement thermique sur les propriétés dynamiques des matériaux. Dans ce but, ce travail vise à coupler la physique de la cinétique de dégradation par oxydation et le comportement mécanique multi-échelles d’un nouveau matériau composite totalement issu du recyclage à renfort carbone et matrice à base polypropylène. Le premier axe de l’étude est dédié à l’élaboration, la caractérisation physicochimique, microstructurale et mécanique de plusieurs formulations de composites. Une fois le composite optimal sélectionné, une méthodologie hybride, expérimentale et numérique, visant à caractériser les propriétés dynamiques rapides allant jusqu’à des vitesses de déformation de 100 s-1 est développée. Le deuxième axe de ce travail est focalisé sur l’étude de l’influence de la thermo-oxydation sur les propriétés physico-chimique et mécaniques à différentes vitesses de sollicitation du composite optimal et sa matrice. L’ensemble des données expérimentales issues du vieillissement a permis l’identification d’un modèle cinétique basé sur un schéma mécanistique de l’oxydation des matériaux vieillis. D’autre part, une étude qualitative et quantitative de l’effet du vieillissement sur les mécanismes d’endommagement a été réalisée à l’échelle microscopique visant à mettre en place une loi d’endommagement reliant, pour une déformation imposée donnée, le taux d’endommagement local à la concentration des produits d’oxydation. Les résultats de cette étude mettent en évidence la possibilité de développer des lois de comportement affectés par les paramètres de modèles cinétiques décrivant l’évolution de l’état physico-chimique du composite au cours du vieillissementIn the automotive sector, integrating more and more recycled composite materials while improving the initial performance and decreasing the carried masses becomes a compromise that needs to be addressed. Moreover, structural parts made of composite materials intended for crash are often subjected to environmental conditions, including moderately high temperatures, capable of causing gradual physico-chemical degradation. Thus, to ensure better design and durability of parts, it is important to understand the influence of thermal aging on the dynamic properties of materials. To this end, this work aims to couple the physics of oxidative degradation kinetics and the multi-scales mechanical behavior of a new fully recycled composite based on a polypropylene matrix and carbon fibers. The first axis of the study is dedicated to the elaboration, the physicochemical, microstructural and mechanical characterization of several formulations of composites. Once the optimal composite is selected, a hybrid experimental and numerical methodology is s is developed in order to characterize the dynamic properties at high strain rates reaching 100 s-1. The second axis of this work is focused on the study of the influence of thermo-oxidation on the physicochemical and mechanical properties at different strain rates of the optimal composite and its matrix. The resulting experimental has allowed the identification of a kinetic model parameters based on a mechanistic scheme. Furthermore, a qualitative and quantitative study of the effect of aging on the damage mechanisms has been carried out at a microscopic scale in order to establish a damage law linking, for a given imposed strain, the local damage density to the concentration of the oxidation products. The results of this study highlight the possibility of developing behavioral laws affected by the parameters of kinetic models describing the evolution of the physicochemical state of the composite during aging
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Zedde, Nicola. "Dynamic mechanical-thermal, microstructural and mechanical analysis of ultra-light polymer-metal composites: influence of forming." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
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A really particular and innovative metal-polymer sandwich material is Hybrix. Hybrix is a product developed and manufactured by Lamera AB, Gothenburg, Sweden. This innovative hybrid material is composed by two relatively thin metal layers if compared to the core thickness. The most used metals are aluminum and stainless steel and are separated by a core of nylon fibres oriented perpendicularly to the metal plates. The core is then completed by adhesive layers applied at the PA66-metal interface that once cured maintain the nylon fibres in position. This special material is very light and formable. Moreover Hybrix, depending on the specific metal which is used, can achieve a good corrosion resistance and it can be cut and punched easily. Hybrix architecture itself provides extremely good bending stiffness, damping properties, insulation capability, etc., which again, of course, change in magnitude depending in the metal alloy which is used, its thickness and core thickness. For these reasons nowadays it shows potential for all the applications which have the above mentioned characteristic as a requirement. Finally Hybrix can be processed with tools used in regular metal sheet industry and can be handled as solid metal sheets.
In this master thesis project, pre-formed parts of Hybrix were studied and characterized. Previous work on Hybrix was focused on analyze its market potential and different adhesive to be used in the core. All the tests were carried out on flat unformed specimens. However, in order to have a complete description of this material also the effect of the forming process must be taken into account. Thus the main activities of the present master thesis are the following: Dynamic Mechanical-Thermal Analysis (DMTA) on unformed Hybrix samples of different thickness and on pre-strained Hybrix samples, pure epoxy adhesive samples analysis and finally moisture effects evaluation on Hybrix composite structure.
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Tan, Ke Khieng. "Low Strain Rates Behaviour of Carbon Nanotube Enhanced Bagasse-Epoxy Polymer Composites for Dynamic Structure Applications." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/84126.
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The demand for the high-performance natural fibre reinforced polymer composite is growing day by day.
However, uneven micro-sized natural fibre like bagasse has causes low performance due to sensitive
crack initiation and propagation in composite at higher tensile cross-head speed. In this research, further
reinforcement using single-wall carbon nanotube was able to enhance tensile properties of bagasse
composite to certain extend and achieving high strength to weight ratio at higher tensile crosshead speed.