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Freitas, Ricardo Luiz Barros de [UNESP]. "Fabricação, caracterização e aplicações do compósito PZT/PVDF." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/100281.
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freitas_rlb_dr_ilha.pdf: 3147438 bytes, checksum: 01acb2a6a67b2e11009fd170fd595861 (MD5)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>Um material compósito é constituído pela combinação de dois ou mais materiais, onde se procura sintetizar um novo material multifásico, e que abrigue as melhores características individuais de cada um de seus constituintes. Compósitos de polímeros (matriz) e ferroelétricos (inclusões) podem manifestar piezoeletricidade, ou seja, a produção de uma resposta elétrica devido a uma excitação mecânica, e vice-versa. Nesta tese o material polimérico usado para preparar os filmes ou lâminas de nanocompósitos é o PVDF, e, o material cerâmico é formado por nanopartículas de PZT. Ambos os materiais são dielétricos, porém, com características muito distintas (por exemplo, o PVDF tem aproximadamente 1/4 da densidade e 1/250 da constante dielétrica do PZT). O PZT é muito utilizado em transdutores, principalmente devido aos seus elevados coeficientes piezoelétricos, contudo, é quebradiço e sofre desgaste quando empregado na forma de filmes ou lâminas. Por outro lado, o PVDF é um polímero piezoelétrico que apresenta grande flexibilidade e excelentes resistências mecânica e química, porém, seus coeficientes piezoelétricos são apenas moderados. A fim de se aumentar a flexibilidade do PZT, mistura-se o pó cerâmico, na forma de nanopartículas, com o PVDF, também pulverizado. Na tese, evidencia-se que o compósito constituído por esta combinação cerâmica-polímero proporciona uma nova classe de materiais funcionais com grande potencial de aplicação, por terem combinadas a resistência e rigidez das cerâmicas, e, a elasticidade, flexibilidade, baixa densidade e elevada resistência a ruptura mecânica dos polímeros. O novo material tem grande resistência a choques mecânicos, flexibilidade, maleabilidade, e, principalmente, coeficientes piezoelétricos relativamente elevados. Amostras do compósito...<br>A composite material is constituted by the combination of two or more materials, which synthesizes a new multiphase material, and has the best individual characteristics of each of its constituents. Polymer composites (matrix) and ferroelectric (inclusions) can express piezoelectricity, i.e. the production of an electrical response due to a mechanical excitation, and vice versa. In this thesis the polymeric material used to prepare the films or slides of nanocomposites is the PVDF, and, ceramic material is formed by PZT nanoparticles. Both materials are dielectrics, however, with very different characteristics (for example, the PVDF is approximately 1/4 density and 1/250 relative permittivity from PZT). The PZT is widely used in transducers, mainly due to their high piezoelectric coefficients, however, is brittle and suffers wear and tear when employed in the form of films or slides. On the other hand, the PVDF is a piezoelectric polymer that offers great flexibility and excellent mechanical and chemical resistances, however, its piezoelectric coefficients are only moderate. In order to increase the flexibility of PZT, ceramic powder is mix, in the form of nanoparticles, with PVDF, also sprayed. In theory, it becomes evident that composite consisting of this ceramic- polymer combination delivers a new class of functional materials with great potential for application, because they combine the strength and rigidity of ceramics, and elasticity, flexibility, low density and high resistance to mechanical disruption of polymers. The new material has great resistance to mechanical shock, flexibility, suppleness, and, primarily, relatively high piezoelectric coefficients. PZT/PVDF composite samples were fabricated and characterized aiming to applications such as: piezoelectric actuators, acoustic emission detectors, and energy... (Complete abstract click electronic access below)
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Karlsson, Johan. "Composite material in car hood : Investigation of possible sandwich materials." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-45633.
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Maman, Shmuel. "Composite material repair and reliability." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25759.
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Composite structure repair methodology has been developed to specific applications (typically in small area and limited to secondary structure) and is being extended to Large Area Composite Structure Repair (with target extension to primary structures). Therefore, the repair becomes more critical because we get redistribution of stresses that can also affect the zones outside of the repair area. For this reason, an analytic evaluation of the repair's reliability has to be performed to define a parameter which reflects on the effectiveness of the repair. In this work, we establish a principal guideline to evaluate the redundancy and compare the reliability of the repair to the reliability of the parent structure (i.e., the structure in the undamaged state). The approach adopted is to utilize structural finite element analysis to compute the state and of the candidate repaired state. The reliability of these two spatially non-uniform stresses is computed by a probabilistic failure criterion. Thus, we can optimize the repair configuration by varying the strength and the stiffness of any element in the repair site by varying the lamination angles, and selectively using hybrid materials. Keywords: Theses, Jet fighters, Airframes, Fixed wing aircraft
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Ghaemi, Hamid. "The effective properties of composite material." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/MQ58036.pdf.
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Goel, Anjali 1978. "Economics of composite material manufacturing equipment." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/31096.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.<br>Includes bibliographical references (p. 43).<br>Composite materials are used for products needing high strength-to-weight ratios and good corrosion resistance. For these materials, various composite manufacturing processes have been developed such as Automated Tow Placement, Braiding, Diaphragm Forming, Resin Transfer Molding, Pultrusion, Autoclave Curing and Hand Lay Up. The aim of this paper is to examine the equipment used for these seven processes and to produce a cost analysis for each of the processes equipment. Since many of these processes are relatively new or are fairly costly and specified to the customers need, much of the equipment is custom made to meet the requirements of the part being produced. Current pricing information for individual custom-built machines, as well as standard machinery has been provided here.<br>by Anjali Goel.<br>S.B.
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Lloyd, Rachel Louise. "Recycling of carbon fibre composite material." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/11356.
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Different routes for recycling carbon fibre composites from the aircraft industry were
investigated for feasibility., Literature analysis revealed little previous ·work in this area,
with most composite recycling investigations concentrating on automotive industry
wastes.
The magnitude of disposal of carbon fibre composite materials from the aircraft industry
is estimated to be in the region of 350,000 tonnes between the years 2000 and 2050.
Landfill cost investigations concluded that the corresponding disposal cost will be in the
region of £52 million. Experimentation indicated that the material was stable in landfill
conditions, whilst investigations into the health and safety aspects of composite
recycling revealed that the materials were harmless unless reduced diameter fibres were
released.
Activation experiments concluded that the production of commercially viable active
carbons was not possible - although the resins activated the carbon fibres did not.
Maximum BET surface areas of 170 m2 g-
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were achieved, despite employing different
activation methods and pre-treatments.
Therefore, alternative recycling routes were investigated. Two brainstorming sessions
generated over forty options. After analysis for of these options were considered most
likely to succeed and were investigated in more depth. .
Fragment mitigation trials showed a significant reduction in fragment velocity (-20 %)
using composite plates of 10.5 mm thickness, liquid-holding boxes resulted in fragment
velocity reductions of up to 75 %. Delamination was localised to the area of impact.
Literature based investigations of fibre recovery methods identified fluidised bed and
high-pressure steam as the most likely to be viable, with fluidised bed plants breaking
even at throughputs under 9,000 t/yr. Chemical digestion and resin burn off produced
significantly weakened fibres, swelling resulted in the freeing of pre-preg layers.
Artificial reef investigations showed that although the material did not appear to
degrade in marine environments, it was unsuitable for organism growth. No organisms
were attached after a period of 1 year.
Pyrolysis appeared to be a viable option, with plants breaking even at throughputs of
approximately 6,000 t/yr.
Fragment mitigation, fluidised bed fibre recovery and pyrolysis were considered most
likely to offer technically and economically viable recycling 1"9utes, and it is
recommended that these routes should be investigated further.
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Counts, William Arthur. "Mechanical behavior of bolted composite joints at elevated temperature." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17315.
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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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Sinclair, Chad. "Co-deformation of a two-phase FCC/BCC material /." *McMaster only, 2001.
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Pacheco, João Felipe Mota. "Influencia do tratamento superficial na resistencia a tração da união polimero de vidro-cimento resinoso." [s.n.], 1997. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288172.
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Orientador: Mario Fernando de Goes<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba<br>Made available in DSpace on 2018-07-23T01:41:39Z (GMT). No. of bitstreams: 1
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Previous issue date: 1997<br>Resumo: O objetivo deste estudo foi avaliar a influência de diferentes tratamentos na superfície do polímero de vidro Artglass (HERAEUS, Kulzer - Germany). Foi verificado também o efeito do agente de silanização (Porcelain Primer - BISCO, lnc. ltasca IL), do ativador superficial de compósitos (Composite Activator BISCO, lnc. ltasca IL) e do líquido para reparos do sistema Artglass na resistência à tração com o sistema adesivo All Bond 2 (BISCO, lnc. ltasca IL) associado ao cimento Choice Porcelain Venner System (BISCO, lnc. ltasca IL). Foram confeccionadas duzentos e quarenta amostras e divididas em 12 grupos com 20 amostras cada. Cada grupo foi submetido aos seguintes tratamentos: grupo 1 - jateamento com óxido de alumínio; grupo 2 - jateamento com óxido de alumínio e aplicação do Porcelain Primer; grupo 3 jateamento com óxido de alumínio e aplicação do Composite Activator; grupo 4 - jateamento com óxido de alumínio e aplicação do Artglass Liquid; grupo 5 - condicionamento com ácido fosfórico; grupo 6 - condicionamento com ácido fosfórico e aplicação do Porcelain Primer; grupo 7 - condicionamento com ácido fosfórico e aplicação do Composite Activator; grupo 8 condicionamento com ácido fosfórico e aplicação do Artglass Liquid; grupo 9 - condicionamento com ácido fluorídrico; grupo 10 - condicionamento COIIJ ácido fluorídrico e aplicação do Porcelain Primer; grupo 11 - condicionamento com ácido fluorídrico e aplicação do Composite Activator; grupo 12 - condicionamento com ácido fluorídrico e aplicação do Artglass Liquid. Após o tratamento, as amostras foram unidas em pares com auxílio do sistema adesivo e do cimento resinoso manipulados de acordo com as instruções do fabricante. Em seguida, os corpos-de-prova foram armazenados a 37 'GRAUS'C com umidade relativa do ar em 100%, durante 24 horas e, logo após, foram submetidos a 500 ciclos térmicos ajustados às temperaturas de 5'GRAUS'C, 37°C e 60°C, com duração de 30 segundos cada. Decorrido o período de 48 horas, os corpos-de-prova foram submetidos ao ensaio de tração em uma máquina de ensaio universal (Otto Wolpert Werke, Germany), a uma velocidade de 6 mm/minuto. As médias dos resultados obtidos foram: grupo 1 - 11,46 MPa; grupo 2 - 12,28 MPa; grupo 3 - 9,45 MPa, grupo 4 - 11,53 MPa; grupo 5 - 3,83 MPa; grupo 6 - 4,84 MPa; grupo 7 - 3,94 MPa; grupo 8 - 5,67 MPa; grupo 9 - 6,51 MPa; grupo 10 - 6,36 MPa; grupo 11 - 7,86 MPa; grupo 12 - 8,34 MPa. A seguir os resultados foram submetidos análise de variância e ao Teste de Tukey. Após os testes de resistência à tração as amostras foram examinadas em lupa estereoscópica com aumento de 16 vezes, onde foi verificado predomínio de fraturas coesivas do polímero de vidro para os grupos tratados com jateamento com óxido de alumínio. O efeito dos tratamentos de superfície foi analisado com auxílio de um microscópio eletrônico de varredura (Zeiss DSM 960, Germany). Os resultados indicaram que o maior valor de resistência de união foi obtido através do jateamento com óxido de alumínio associado ao agente de silanização. Nos demais grupos onde também foi realizado o jateamento com óxido de alumínio os valores de resistência de união foram superiores e diferentes estatisticamente, quando comparados aos outros grupos, com exceção da associação do ácido fluorídrico com o Composite Activator, que não diferiu do grupo 3. A análise através de M.E.V. das superfícies tratadas demonstrou um padrão morfológico mais favorável ao imbricamento micromecânico produzido com o jateamento com óxido de alumínio<br>Abstract: The purpose of this study was to evaluate the influence of different superficial treatment of glass polymeric material Artglass (Heraeus, Kulzer). The effect of the silane agent application (Porcelain Primer - Bisco, lnc., ltasca, IL), a superficial Composite activator mixture (Composite Activator - Disco, Inc., ltasca, lL) and also the Artglass Liquid was verified in the tensile strength with adhesive system AllBond 2 (Bisco, lnc., !tasca, lL) associated with the resin cement Choice Porcelain Venner System (Bisco, lnc., !tasca, IL). Two hundred and torty samples were made and divided into 12 groups. Each group contained 20 samples submitted to treatments: Group 1 sandblasting with aluminum oxide; Group 2 - sandblasting with aluminum oxide and Porcelain Primer application; Group 3 - sandblasting with aluminum oxide and Composite Activator application; Group 4 - sandblasting with aluminum oxide and Artglass liquid application; Group 5 - acid etching with phosphoric acid; Group 6 - acid etching with phosphoric acid and Porcelain Primer application; Group 7 - acid etching with phosphoric acid and Composite Activator application; Group 8 acid etching with phosphoric acid and Artglass Liquid application; Group 9 acid etching with hydrofluoridric acid; Group 10 - acid etching with hydrofluoridric acid and Porcelain Primer application; Group 11 - acid etching with hydrotluoridric acid and Composite Activator application; Group 12 - acid etching with. hydrofluoridric acid and Artglass Liquid application. Following the treatment, the samples were bonded into pairs with the adhesive system and the resin cement, applied according with the manufacturer's instructions. Then, the samples were stored in 37° with a relative humidity of 100% during 24 hours. Submitted into 500 thermal circles, adjusted to 5 'DEGREE'C, 37 'DEGREE'C and 60'DEGREE'C, lasting 30 second each. After 48 hours, the samples were submitted to a tensile strength test in a Universal test machine (Otto Wolpert Werke, Germany) with a crosshead speed 6 mm / minute. The average results were : Group 1 - 11,46 MPa; Group 2 - 12,28 MPa; Group 3 - 9,45 MPa; Group 4 - 11,53 MPa; Group 5 - 3,83 MPa; Group 6 - 4,84 MPa; Group 7 - 3.94 MPa; Group 8 - 5,67 MPA; Group 9 - 6,51 MPA; Group 10 6,36 MPa; Group 11 - 7,86 MPa; Group 12 - 8,34 MPa. ThereFore, the results were submitted to Anova and Tukey Test. Then the samples were examined in a stereoscopic magnifying glass (x16), where it was verified the prevailing of cohesive rupture of the Glass Polymer in the groups treated with aluminum oxide sandblasting. The efFect of the superficial treatments was analyzed by a Scanning Electron Microscopy. The results indicated that sandblasting with aluminum oxide associated with the silane agent attained the biggest value of the bond strength. ln groups where the aluminum oxide sandblasting was performed the values presented were higher and statistically significant comparing with the others groups, except the association between hydrotluoridric acid and Composite Activator, which did not differ from group 3. The analysis of the treated surface was made using the Scanning Electron Microscopy and showed a more suitable morphologic pattem to the micromechanic retention produced with aluminum oxide sandblasting<br>Doutorado<br>Doutor em Materiais Dentários
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Forconi, Mattia. "Experimental analysis of a hybrid composite material." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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The main aim of this thesis is to investigate the mechanical properties of a hybrid composite material under static loadings. The material is a composite laminate made by layers of carbon bars and a rubber layer. The thesis can be split into three main parts. In the first part a background about carbon bar composite is given and, subsequently, the research and main results on hybrid composites is introduced. The objective of this section is to provide a base on which built the main results of this work. In the second part it is explained how the test activities have been performed and the main results obtained. In particular, the effect of the introduction
of a rubber layer has been highlighted in each type of tests. In the last part, a finite element dynamical analysis is presented. A very simple transient analysis has been performed in order to foresee the dynamic behaviour of the hybrid. In conclusion, it has been demonstrated a relevant hybrid effect in the compressive and flexural properties. Those effects can be roughly reassumed in anincreasing specific stiffness for the compressive properties and in a large improvement of flexibility in the bending test. The numerical simulation shows that an increased damping effect is present, corresponding to an increase of rubber layer thickness.
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Weibel, Nicolas. "Industrial implementation of novel composite material technologies /." Lausanne, 2002. http://library.epfl.ch/theses/?nr=2567.
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Thèse sciences techniques, EPF Lausanne en collab. avec IMD Lausanne, no 2567 (2002), Faculté des Sciences et Techniques de l'Ingénieur, Section Matériaux. Directeurs: J.-A. E. Månson (EPFL), T. E. Vollmann (IMD) ; rapporteurs: D. Bonner, S. Catsicas, P. Lorange.
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Ahmadi, Hoda. "Cellulose-Mycelia foam : novel bio-composite material." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59970.
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Demand for sustainable products is growing faster than ever before. Because of this, the development of novel sustainable materials is crucial to leverage our environmental resources and to ensure future growth of Canada's economy. In this study, we propose a technology to develop the use of fungal mycelium, the vegetative part of a fungus, through a porous scaffold of cellulose-based foam. A methodology for producing cellulose-mycelia foam (CMF) has been developed by mixing a surfactant with pulp suspension of 1% consistency and Pleurotus djamor spawn, mixing at high velocity to entrain air, filtering the suspension, and then holding at incubation conditions suitable for mycelium growth. During the incubation period, temperature (20-25 °C), pH (5-8), humidity (80-100%), ventilation and exposure to light were controlled. Simplicity of production, biodegradability, and 3-D porous structure of the product position this biocomposite as a green alternative to polymeric foams. The structure of the CMF was characterized through fluorescent microscopy during the incubation period. The effect of mycelial growth on the mechanical behavior of the CMF including compressibility, thermal decomposition, dry and wet strength was investigated during 25 days of mycelial growth. The results indicated that all tested mechanical properties improved after 25 days of mycelial growth. The second set of experiments was run to specify the application of the CMF in a hydraulic filtration system. The pressure drop, permeability, and filtration efficiency of the product were studied. The experimental results showed that the permeability of the CMF decreases by an increase in mycelial growth. The hydraulic filtration efficiency of the product improved from 74% for cellulosic foam to 99.9% for 25 days CMF for removing 20 µm and larger particles. Bioremediation tests also were performed to evaluate the detoxification capability of mycelia in the CMF. Detoxification tests demonstrated that the living mycelia are able to detoxify potassium hydroxide from waste alkaline batteries.<br>Applied Science, Faculty of<br>Graduate
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Phillips, Steven. "Bio-composite material applications to musical instruments." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66668.
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Bio-composite materials suitable for replacing wood for use in musical instruments were developed. The mechanical properties of Sitka spruce, the most widely used wood species for this application, were taken as a benchmark when developing the new materials. The materials were characterized by static and dynamic methods to determine the dynamic Young's modulus, shear modulus, internal friction and static mechanical properties. Based on the material characterization, a hand layup process with a two-part closed mould and internal pressure bladder was developed and a total of six prototype ukuleles were manufactured. The results show that the bio-composite material can meet all the necessary criteria for a soundboard material and that an efficient manufacturing process can be developed for producing composite musical instruments.<br>Des matériaux bio-composites dans le but de remplacer le bois pour les instruments de musique ont été développés. Les propriétés mécaniques de l'épinette de Sitka, une espèce de bois couramment utilisée pour cette application, ont été utilisées comme référence dans l'élaboration de nouveaux matériaux. Ces derniers ont été caractérisés par des tests mécaniques statiques et dynamiques afin de déterminer le module d'élasticité, le module de cisaillement, la friction interne et les propriétés mécaniques statiques. Les résultats de caractérisation ont permis de développer un procédé de fabrication avec un moule en deux parties et un sac pressurisé. Six prototypes de ukulélés ont été fabriqués. Les résultats montrent que le bio-composite peut répondre aux critères nécessaires pour un matériel de table d'harmonie et qu'un processus de fabrication efficace peut être développé pour produire des instruments de musique en matériaux composites.
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Yao, Lining. "Shape changing composite material design for interactions." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109657.
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Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 258-274).<br>This thesis is about designing shape change composite material for interactions. Interaction has gone beyond computer screens and electronics to enter the realm of physical materials. Shape changes at the micro level will cause shape changes and other physical property changes at the macro level. A design strategy for bioinspired shape-changing composite materials includes two development steps: a shape-changing material unit (SCMUnit), followed by a shape-changing matrix composite (SCMC). SCMC contains the matrix phase and the dispersion phase, one of which is composed of SCMUnits. In addition, SCMC can be hierarchical, while SCMC and SCMUnits have a relationship of recursive embodiment. Two major projects exemplify how water-responsive shape-changing material can be used to design interactions based on the outlined design strategy. bioLogic is about hygromorphic bacteria-based SCMC, while Transformative Appetite is about water-driven edible SCMC material. Programmable transformations, multilayer composites and sequential-foldings were engineered with these materials. A customized fabrication strategy, combining wet lab processes and additive manufacturing, was introduced, while applications were presented to exemplify various interaction scenarios. In addition, the SCMC design strategy has been adapted to develop shape-changing materials beyond water responses. Stimuli and responsive behaviors are used to categorize these materials. A design space for nature-inspired responsive material design for shape-changing interfaces was outlined from two aspects: the technical aspects and the conceptual aspects. The technical aspects are identified with the interplays of three features of nature: natural structural mechanisms, natural stimuli and natural transformation mechanisms. The conceptual aspects is summarized in two conceptual spaces: microscale shape changes for macroscale shape changes, and microscale shape changes for macroscale material property changes.<br>by Lining Yao.<br>Ph. D.
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Bastidas, Erazo Pablo Daniel. "Degradation of composite insulators at material interfaces." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/degradation-of-composite-insulators-at-material-interfaces(69477a7e-9cc1-496e-a527-4bb64488493d).html.
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High-voltage (HV) outdoor composite insulators used in transmission lines are made of two polymers, comprising the core and housing, bonded together with metallic end-connections. The interface between these polymers is parallel to the electric field, which makes the insulators more prone to interfacial problems at these common points [1]. If interfacial ageing occurs, degradation and catastrophic breakdown can result [2]. Therefore, the design reliability of outdoor composite insulators depends on the high-strength bond between the core and the housing [3],[4]. Research findings by Kutil and Froshlic [5] indicate that delaminated areas, cavities and/or micro cracks in the medium are enough to initiate streamer discharges along the interface that are capable of degrading both insulating materials. The heat, UV radiation, and high-energy electrons produced from such discharge activity resulted in the growth of carbon paths along the interface, known as âtrackingâ, ultimately causing failure [6]. This investigation focuses on the development of tracking between silicone rubber and epoxy resin, with a view to replicating the tracking phenomena seen within composite insulators in service. A fine wire is placed between the dielectrics materials to enhance the local electric field magnitude and initiate discharge processes. The resulting partial discharge (PD) activity has been monitored. This Information has been used to understand the inception and propagation of the interfacial tracking. A strong relationship was found between maximum PD magnitude and track length. PD patterns and unique detailed images of the interfacial tracking development, allowed identification of the growth characteristics of interfacial channels and phases of tracking growth. Furthermore, a correlation in the mechanisms of interfacial degradation was found between the lab-fabricated samples and commercial composite rods. Finally, a growth model of interfacial ageing has been developed with the information from FEA models, PD patterns and the detailed images of tracking growth. The physical structure and chemical analysis of interfacial tracking is also disclosed to provide an insight into interfacial ageing mechanisms that occur in the composite insulators under electrical stress.
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Szpieg, Magdalena. "A novel composite material from recycled constituents /." Luleå : Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3350732.
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Freitas, Ricardo Luiz Barros de. "Fabricação, caracterização e aplicações do compósito PZT/PVDF /." Ilha Solteira, [s.n.], 2012. http://hdl.handle.net/11449/100281.
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Orientador: Aparecido Augusto de Carvalho<br>Coorientador: Antônio de Pádua Lima Filho<br>Banca: Cláudio Kitano<br>Banca: João Antonio Pereira<br>Banca: Adriano Rogério Bruno Tech<br>Resumo: Um material compósito é constituído pela combinação de dois ou mais materiais, onde se procura sintetizar um novo material multifásico, e que abrigue as melhores características individuais de cada um de seus constituintes. Compósitos de polímeros (matriz) e ferroelétricos (inclusões) podem manifestar piezoeletricidade, ou seja, a produção de uma resposta elétrica devido a uma excitação mecânica, e vice-versa. Nesta tese o material polimérico usado para preparar os filmes ou lâminas de nanocompósitos é o PVDF, e, o material cerâmico é formado por nanopartículas de PZT. Ambos os materiais são dielétricos, porém, com características muito distintas (por exemplo, o PVDF tem aproximadamente 1/4 da densidade e 1/250 da constante dielétrica do PZT). O PZT é muito utilizado em transdutores, principalmente devido aos seus elevados coeficientes piezoelétricos, contudo, é quebradiço e sofre desgaste quando empregado na forma de filmes ou lâminas. Por outro lado, o PVDF é um polímero piezoelétrico que apresenta grande flexibilidade e excelentes resistências mecânica e química, porém, seus coeficientes piezoelétricos são apenas moderados. A fim de se aumentar a flexibilidade do PZT, mistura-se o pó cerâmico, na forma de nanopartículas, com o PVDF, também pulverizado. Na tese, evidencia-se que o compósito constituído por esta combinação cerâmica-polímero proporciona uma nova classe de materiais funcionais com grande potencial de aplicação, por terem combinadas a resistência e rigidez das cerâmicas, e, a elasticidade, flexibilidade, baixa densidade e elevada resistência a ruptura mecânica dos polímeros. O novo material tem grande resistência a choques mecânicos, flexibilidade, maleabilidade, e, principalmente, coeficientes piezoelétricos relativamente elevados. Amostras do compósito... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: A composite material is constituted by the combination of two or more materials, which synthesizes a new multiphase material, and has the best individual characteristics of each of its constituents. Polymer composites (matrix) and ferroelectric (inclusions) can express piezoelectricity, i.e. the production of an electrical response due to a mechanical excitation, and vice versa. In this thesis the polymeric material used to prepare the films or slides of nanocomposites is the PVDF, and, ceramic material is formed by PZT nanoparticles. Both materials are dielectrics, however, with very different characteristics (for example, the PVDF is approximately 1/4 density and 1/250 relative permittivity from PZT). The PZT is widely used in transducers, mainly due to their high piezoelectric coefficients, however, is brittle and suffers wear and tear when employed in the form of films or slides. On the other hand, the PVDF is a piezoelectric polymer that offers great flexibility and excellent mechanical and chemical resistances, however, its piezoelectric coefficients are only moderate. In order to increase the flexibility of PZT, ceramic powder is mix, in the form of nanoparticles, with PVDF, also sprayed. In theory, it becomes evident that composite consisting of this ceramic- polymer combination delivers a new class of functional materials with great potential for application, because they combine the strength and rigidity of ceramics, and elasticity, flexibility, low density and high resistance to mechanical disruption of polymers. The new material has great resistance to mechanical shock, flexibility, suppleness, and, primarily, relatively high piezoelectric coefficients. PZT/PVDF composite samples were fabricated and characterized aiming to applications such as: piezoelectric actuators, acoustic emission detectors, and energy... (Complete abstract click electronic access below)<br>Doutor
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Sacks, Serena. "Effects of thermal aging on the mechanical behavior of K3B matrix material and its relationship to composite behavior." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18865.
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Zhang, Bo. "Locally resonant composite material : analytical models and experiments /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20ZHANGB.
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Lee, Sang Jin. "Active, polymer-based composite material implementing simple shear." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2349.
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Kinard, Janet. "Material systems for rapid manufacture of composite structures." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/16844.
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Manolakis, Ioannis. "Chemical modification of PEEK for composite material applications." Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518223.
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Priston, Ann-Marie. "Evaluation of stress induced damage in composite material." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389766.
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Kim, Sungmin Mech E. Massachusetts Institute of Technology. "A study on cork-based plastic composite material." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68899.
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Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 115-116).<br>Sandwich panels are mainly used in construction for lightweight structures since their concept is appropriate due to extremely high in-plane and flexural stiffness to weight ratios. However, low structural freedom and high environmental burdens of core material in sandwich panels such as fiberglass, and chemically synthesized foams have retarded a wide use in various areas. Recently it has been suggested that the better performance and economic, environmental benefits could be possibly achieved by using hybrid sandwich panels comprising non-traditional pairs of materials for sandwich panels. Therefore, in this paper, a cork-based plastic composite material has been proposed as a new core material and the possibility for substituting existing core materials have been explored by investigation on its mechanical properties, economic benefit, and environmental impact. Several mechanical testing were carried out on the cork composite and Glass Fiber Reinforced Plastic (GFRP) to determine the mechanical properties and compare their relative performances. By conducting property-limited design cases with the obtained mechanical properties, how they will perform in light, stiff panel application was investigated. Economic analysis was demonstrated with a table top application by using rigidity equality condition. Finally, Eco-impact of the cork composite was investigated by conducting Life Cycle Assessment. The result proved that the cork composite is competitive with other core materials.<br>by Sungmin Kim.<br>Mech.E.
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Holt, Michael Dana. "Fatigue Microcracking of Composite Material IM7/977-2." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/1071.
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The application of an ultralight linerless composite fuel tank to a man-rated, reusable launch vehicle requires greater understanding of the micro-fracture behavior which can lead to propellant permeation through the tank wall. Transverse matrix cracks in unidirectional wound, or placed, plies can provide a path for permeation of pressurized fluid if the cracks interlink from the interior to the exterior of the tank wall. Following research on an energy based fracture mechanics approach to composite microcracking, experiments in fatigue were run on IM7/977-2 cross-ply laminates. Using a modified Paris Law approach, microcracking fatigue data is presented over a wide range of applied cyclic stresses. This Paris Law plot shows an "A" value of 6.40x10-25 and a "B" value of 8.07 and provides a complete characterization of composite IM7/977-2 material's resistance to microcrack formation during fatigue loading.
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Grosskopf, Paul P. "Mechanical behavior of a ceramic matrix composite material." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42214.
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<p>Monolithic ceramic materials have been used in industry for hundreds of years. These
materials have proven their usefulness in many applications, yet, their potential for
critical structural applications is limited. The existence of an imperfection in a monolithic
ceramic on the order of several microns in size may be critical, resulting in catastrophic
failure. To overcome this extreme sensitivity to sman material imperfections, reinforced
ceramic materials have been developed. A ceramic matrix which has been reinforced with
continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain
significant damage without suffering catastrophic failure.</p>
<p>
A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth
(Nicalon) has been studied. The mechanical testing which was performed included both
flexural and tensile loading configurations. This testing was done not only to determine the
material properties, but also to initiate a controlled amount of damage within each specimen.</p>
<p>
Several nondestructive testing techniques, including acousto-ultrasonics (AU), were
performed on the specimens periodically during testing. The AU signals were monitored
through the use of an IBM compatible personal computer with a high speed data acquisition
board. Software has been written which manipulates the AU signals in both the time and
frequency domains, resulting in quantitative measures of the mechanical response of the
material.</p>
<p>
This paper will compare the measured AU parameters to both the mechanical test results
and data from other nondestructive methods including ultrasonic C-scans and penetrant
enhanced X-ray radiography.</p><br>Master of Science
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Hozić, Dženan. "Composite Structure Optimization using a Homogenized Material Approach." Licentiate thesis, Linköpings universitet, Mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102316.
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The increasing use of bre-reinforced composite materials in the manufacturing of high performance structures is primarily driven by their superior strength-toweight ratio when compared to traditional metallic alloys. This provides the ability to design and manufacture lighter structures with improved mechanical properties. However, the specic manufacturing process of composite structures, along with the orthotropic material properties exhibited by bre-reinforced composite materials, result in a complex structural design process where a number of dierent design parameters and manufacturing issues, which aect the mechanical properties of the composite structure, have to be considered. An ecient way to do this is to implement structural optimization techniques in the structural design process thus improving the ability of the design process to nd design solutions which satisfy the structural requirements imposed on the composite structure. This thesis describes a two phase composite structure optimization method based on a novel material homogenization approach. The proposed method consists of a stiness optimization problem and a lay-up optimization problem, respectively, with the aim to obtain a manufacturable composite structure with maximized stiness properties. The homogenization material approach is applied in both optimization problems, such that the material properties of the composite structure are homogenized. In the proposed method the stiness optimization problem provides a composite structure with maximized stiness properties by nding the optimal distribution of composite material across the design domain. The aim of the lay-up optimization problem is to obtain a manufacturable lay-up sequence of bre-reinforced composite plies for the composite structure which, as far as possible, retains the stiness properties given by the stiness optimization problem. The ability of the composite structure optimization method to obtain manufacturable composite structures is tested and conrmed by a number of numerical tests.
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Weber, Tobias [Verfasser]. "Numerical Field Simulations of Composite Material / Tobias Weber." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1216877734/34.
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Tremaine, Kellie Michelle. "MODAL ANALYSIS OF COMPOSITE STRUCTURES WITH DAMPING MATERIAL." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/823.
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The purpose of this study is to develop an analytical solution for modal analysis of actively damped orthotropic composite plates in bending and to verify it with experimental analysis.
The analytical modal analysis solution for composite plate dynamics is derived using Euler theory. This analysis applies to structures with orthotropic lamina of uniform material properties at any lamination angle. The bending-extensional coupling can be neglected for plates that are symmetric or approximately symmetric, which allows an exact solution for natural frequency and mode shape to be obtained. An exact solution can be found for natural vibration and in general.
The active control is modeled analytically by combining the Lagrange equation with the Ritz Assumed Mode method. This analysis produces a generalized coordinate vector that correlates the assumed mode to the particular amplitude of a particular case. The kinetic energy dissipated by the piezoelectric actuator from the system over one oscillation can be calculated from the generalized coordinate vector and the assumed mode. The equivalent damping ratio of the active control system is calculated as the ratio between the kinetic energy absorbed by the piezoelectric actuator from the system in one oscillation and the maximum strain energy of the system during that oscillation.
A point mass on the plate, such as an accelerometer mass, can also be modeled as a single layer of uniform mass, that is an isotropic layer, by equating the potential energy of the point mass with the potential energy of the uniform mass layer. It is important to note that the mass of the isotropic layer is frequency dependent, and it has no effect on the plate stiffness.
The analytical model is validated by comparison to experimental work. The samples studied were aluminum and composite plates of various lengths. The active control predictions were also validated using previous experimental work completed at California Polytechnic State University in San Luis Obispo. These cases included active control of an aluminum beam with a patch of piezoelectric material and an aluminum sailplane with a patch of piezoelectric material.
Results indicate that while the analytical mode solutions are in good agreement with the experimental results, they are also systematically higher than the experimental results. The analytical active control solutions match previous work when the piezoelectric effects are linear. The main result of adding an active control system is approximately a 5-10% increase in modal frequencies and a 200-800% increase of damping ratio.
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Al-Taee, Shaymaa. "Evaluation of thermal and mechanical properties of the composite material of LignoBoost- lignin and recycled polyurethan : A preliminary feasibility study for a novel composite material from waste materials." Thesis, Karlstads universitet, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-65194.
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The purpose of this study was to investigate the possibility of producing a composite material of lignoBoost- lignin and recycled polyurethane. Also, the study evaluated the thermal and mechanical properties of the composite materials. These properties were investigated in a number of steps by applying different: additives, concentrations, conditions (temperature, time, and pressure), and equipment. The results from the preliminary trials show that it was impossible to produce a composite material from lignin/polyurethane blends. Hence, the blends were modified by adding acrylate and glycerol as a copolymer and plasticizer, respectively, to improve the compatibility of the blends. Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), and tensile tests were carried out to study the thermal and mechanical properties of (lignin/ polyurethane/ acrylate/ glycerol) composite materials. The FTIR results indicated the existence of intermolecular interactions between the components in the blends. The DSC analysis revealed the existence of two glass transition temperature (Tg) values, indicative of an immiscible blend. However, the first Tg and melting temperature (Tm) of composite material decreased with increased lignin content up to 40%. As a result of interactions, the maximum strength and Young’s modulus increased with increased lignin content up to 40 %. Meanwhile, elongation at break decreased with increased lignin content.<br>Syftet med denna studie var att undersöka möjligheten att producera ett kompositmaterial av LignoBoost- lignin och återvunnet polyuretan. Studien utvärderade också de termiska och mekaniska egenskaperna hos kompositmaterialen. Dessa egenskaper undersöktes i ett antal steg genom att använda olika tillsatser, koncentrationer, förhållanden (temperatur, tid och tryck) och utrustning. Resultaten från de preliminära försöken visar att det var omöjligt att framställa ett kompositmaterial från enbart lignin och polyuretan. För att förbättra kompatibiliteten hos blandningarna tillsattes akrylat, som extra polymer och glycerol som mjukgörare. Fourier Transform Infrared Spectroscopy (FTIR), differentialscanning kalorimetri (DSC) och dragprov utfördes för att studera de termiska och mekaniska egenskaperna hos kompositmaterialet av (lignin / polyuretan / akrylat / glycerol). FTIRresultaten indikerade förekomsten av intermolekylära interaktioner mellan komponenterna i blandningarna. DSC-analyserna visade att det förekom två glasövergångstemperaturer (Tg), vilket indikerar att komponenterna inte är helt blandade. Det första Tg och smälttemperaturen (Tm) för kompositmaterialen minskade med ökande ligninhalt upp till 40 %. Den maximala hållfastheten och Youngs modul ökade med ökad ligninhalt upp till 40 % på grund av interaktioner mellan polymererna i blandningarna. Samtidigt minskade brottöjningen med ökad ligninhalt.
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Foston, Marcus Bernard. "Cyclic, tethered and nanoparticulate silicones for material modification." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24762.
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Thesis (Ph.D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Dr. Haskell W. Beckham; Committee Member: Dr. Anselm Griffin; Committee Member: Dr. Johannes Leisen; Committee Member: Dr. Sankar Nair; Committee Member: Dr. Uwe Bunz.
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Cheuk, Ming Wai. "Study of composite material filler with different surface treatment /." access abstract and table of contents access full-text, 2004. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174106a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2004.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
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Jack, David Abram. "Advanced analysis of short-fiber polymer composite material behavior." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4363.
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Thesis (Ph. D.) University of Missouri-Columbia, 2006.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 2, 2007) Includes bibliographical references.
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Buggy, Stephen J. "Composite material process monitoring using optical fibre grating sensors." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/4035.
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In this thesis a long period grating (LPG) based sensor is investigated as a possible
alternative to current process monitoring sensors used in the manufacture of composites
to monitor cure. An LPG is demonstrated as a means of monitoring the cure of a UVcured
epoxy resin. The wavelength shift of the attenuation bands were measured during
the cure of the resin and compared with measurements made using a fibre optic Fresnel
based refractometer. The results showed a good correlation (6 x 10
-3
rius) and illustrate
the potential of the techniques for non-invasive composite material cure monitoring.
Alternative fibre grating methods; a chirped LPG sensor, an in-fire Mach-Zehnder
interferometer and a tilted fibre Bragg grating sensor, are also presented to demonstrate
the versatility of grating based sensors for flow, high sensitivity refractive index and
multi-parameter sensing, respectively. Demonstrations of LPG sensors in industrial
applications are also presented and highlight the technical issues of integrating such
devices in composite components and composite manufacturing processes.
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Hirst, Edward A. J. "Characterisation of hemp-line as a composite building material." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636516.
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Hemp-lime is a comparatively novel renewable insulation material in the construction industry. Its use was first documented in the 1980’s, however, recent increased interest and the release of popular publications has resulted in an increased need for scientific investigation into the material. The research conducted in this investigation firstly focussed on furthering the empirical characterisation of hemp-lime and its constituents with particular attention paid to minimising fabrication variables and increasing the accuracy of final specimen bulk densities. Secondly attempts were made to quantify the degree of carbon sequestration that occurs as a result of the carbonation of the lime binder. A total of 196 specimens were fabricated for the main programme of work. It has been demonstrated that the novel fabrication methodology developed and tested in this investigation allows for reliable and consistent fabrication of specimens with almost identical final bulk densities. An average intrinsic empirical variability of 0.8% was determined for hemp-lime composites. It has been shown that the values of CO2 sequestration varied between 151- 192kg/m3 for the current formulated binders and composite bulk densities being used or considered in the UK construction industry. This resulted in a minimum 100% increase above the lowest estimated sequestration value from previous investigations. Preliminary carbonation constant values for hemp-lime have been determined, however, further testing is required to establish definite values based on a wider sample of testing.
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Ambrogio, Simone. "Finite Element Modeling of Short, Randomized Fiber Composite Material." Thesis, KTH, Lättkonstruktioner, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290039.
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With the advent of hybrids and electric vehicles, the need for lightweight and highperformancematerials is growing. Sheet molding compound (SMC) is a compositemade of short and randomized bers that o ers a substantial weight reduction andgood mechanical properties while meeting the demand for large volume production.This thesis aims to develop a constitutive FE model of the SMC used in the bodyin black of an autonomous vehicle.To extract its properties, several physical tests were performed on specimens madeof the above-mentioned material. Both the tensile and three point bending testsresults show that the material is not homogeneous and that its properties vary fordi erent directions. The damping ratio extracted from the vibration test is muchlower than in conventional structural materials like aluminum and steel.In the FE analysis, the material was modeled both as isotropic and orthotropic.After adjusting the Young's modulus, the isotropic model shows accurate resultsuntil 1200 Hz. On the other hand, without knowing in which directions the propertiesoccur, the orthotropic model is very limited.In conclusion, even though the properties were tailored speci cally for the specimen,the model might not correctly represent the material's behavior, being itsproperties not the same for di erent components. Therefore, it is more reasonableto use average data instead.<br>Tack vare en okad efterfragan av hybrid och eldrivna fordon, kommer ett storrebehov av lattvikts-och hogpresterande material. Sheet Molding Compound (SMC)ar en komposit av korta, randomiserade brer som ger en vasentlig viktreduktion,liksom goda mekaniska egenskaper, samtidigt som det moter kraven fran hogvolymsproduktioner. Malet med detta examensarbete ar att utveckla en FE-modell for detSMC material som anvands for chassit pa ett sjalvkorande, eldrivet fordon.For att ta reda pa dess egenskaper, har era fysiska tester utforts pa prover gjort avovannamnda material. Bade dragprov och bojprov visar att materialet inte ar homogentoch att materialets egenskaper varierar i olika riktningar. Dampningsfaktornsom ar extraherad fran vibrationstesterna ar mycket lagre an for konventionella material,sa som aluminium och stal.I FE-analysen, var materialet modellerat som bade isotropt och ortotropt. Efteratt ha justerat E-modulen, visade den isotropa modellen mer korrekta resultat, upptill 1200 Hz. Dock ar den ortotropa modellen valdigt begransad, eftersom riktningarnafor de olika egenskaperna ar okanda.Som slutsats, aven om egenskaperna var justerade speci kt for detta prov, kan dethanda att modellen inte representerar materialets beteende korrekt, eftersom egenskapernainte kommer vara samma for alla komponenter. Darfor ar det mer rimligtatt anvanda genomsnittliga data istallet.
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Rezaizadeh, Mohammad Ali. "Pulsed-Laser Ultrasound Generation in Fiber-Reinforced Composite Material." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/26010.
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A laser-based ultrasonic technique using a pulsed laser for stimulating ultrasonic waves in fiber-reinforced composite materials is the subject of investigation. For convenience, the material is chosen to be homogeneous transversely isotropic. The study is strictly limited to the laser power regimes that are suitable for nondestructive evaluation. An elastodynamic methodology is presented based on integral formulation in order to develop a representation for the dynamic responses in terms of the characteristics of the source that originated the motion. This requires a computation of elastodynamic Green function which represents the displacement field from the idealized synthetic sources localized precisely in both space and time. A two-dimensional numerical analysis utilizing a finite difference method for computation of the Green function in a finite plate is developed which provides the basis for quantitative nondestructive evaluation of fiber reinforced composite materials. Numerical results are presented for the surface displacement at the epicenter. Prediction based on numerical simulations are compared with experimental results.<br>Ph. D.
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Lane, Ryan Jeffrey. "Study of Wave Propagation in Damaged Composite Material Laminates." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/86366.
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The characteristics of carbon fiber composites have enabled these materials to be accepted as replacements for metal parts in industry. However, due to their unsymmetrical material properties, carbon fiber composites are susceptible to damage, such as a delamination, which can cause premature failure in the structure. This has resulted in the need for nondestructive testing methods that can provide quick, reliable results so that these parts can be tested while in service. In this study, an approach was examined that involved a pencil lead break to excite multiple wave modes in a composite plate in an effort to identify key characteristics based on the wavespeed and frequency. These characteristics were then compared to models based on boundary conditions to generate dispersion curves using the transfer matrix method for whole composite plates that were either undamaged or damaged. To first test this approach, experiments were performed on multilayer isotropic plates and then on a composite plate. The results for all cases showed that modes could be excited by the pencil lead break in the undamaged region of the plates that were not theoretical possible in a delaminated region. Also modes that were specific to the delaminated region were excited and this allowed for a clear comparison between the two regions. This approach could be placed into practice to provide routine testing to detect delamination for in-service, carbon fiber composite parts.<br>Master of Science<br>The physical properties of high strength and low weight and the economic benefits of carbon fiber composites has resulted in these materials replacing metals in several industries. It is important, however, to be aware that the change in materials used impacts the different types of damage composites experience compared to conventional metals. One type of damage that could cause a composite part to fail is a delamination or a separation of layers. In order to identify if this damage has occurred, it is beneficial to have an inspection technique that will not damage the part. In this study, a technique was tested that involved breaking a piece of pencil lead on a plate in order to generate multiple wave modes that would propagate in the plate. Based on boundary conditions caused by the damage in the plate, the speed of the wave and frequency content could be compared to an undamaged plate to identify a delamination. A model was created to compare experimental results and demonstrated that using wavespeed and frequency could identify a delamination. The experimental results compared well with the model dispersion curves for a plate with and without a delamination suggesting this approach could be placed into practice to provide routine testing to detect delamination for in-service, carbon fiber composite parts.
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Zhang, Yanhong. "An investigation of shear response of composite material systems." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10042006-143846/.
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Lin, Chih-Hung, and 林志宏. "Identification of Material Constants of Composite Materials." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/23415884646084014541.
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碩士<br>國立交通大學<br>機械工程系<br>87<br>A method for nondestructive evaluation of material properties of composite materials is presented. A multi-start algorithm for global constrained minimization is presented. In this algorithm the search trajectories are derived from the equation of motion of a particle in a conservative force field and the objective function which is the difference between the theoretically and experimentally predicted strains is treated as the potential energy of the particle. The applications of the proposed method are demonstrated by means of several examples on the identification of material properties of laminated composite plates, laminated composite cylindrical pressure vessels and filament wound composite pressure vessels.
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Guan, Ji Kong, and 管繼孔. "Composite material backed antennas." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/94237815567742139234.
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Chi, Shyang-Ho, and 紀翔和. "The Study of Functional Gradient Material in composite Materials." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/87870331266188623113.
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碩士<br>國立臺灣科技大學<br>營建工程系<br>87<br>The subject of this thesis mainly discusses the stress behaviors and stress intensity factors of cracks of composite material with functionally gradient material subjected to thermal loading by finite element method. There are five parts included in this thesis: (1)one material coating problem. (2)multi-layered homogeneous coating problem. (3)S-curve functionally gradient material problem. (4) anti-S-curve functionally gradient material problem. (5) the problem of FGM coating with a crack.
This study indicates that the use of functionally gradient material can efficiently reduce stress concentration at the edge of the interface of the composite material. The different functionally gradient materials led to different stress distributions. Results showed that the S-curve of p=2 and metal rich functionally gradient result in better stress distribution in which there is no stress singularity and lower stress concentrations. Consequently, the debonding of the undercoat can be efficiently reduced.
Moreover, in the aspect of crack problem, stress intensity factor of crack tip in S-curve functionally gradient material was concerned with Dundurs'' constants and . When α>0 and , stress intensity factor appears S-curve character by the influence of functionally gradient material disposition. While when α<0 and , the SIF of a crack in the functionally gradient material is similar with that in homogeneous material.
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Umesh, K. "On The Effect Of Material Uncertainty And Matrix Cracks On Smart Composite Plate." Thesis, 2013. https://etd.iisc.ac.in/handle/2005/2603.
Full textAbstract:
Recent developments show the applications of smart structure in different engineering fields. Smart structures can be used for shape and vibration control, structural health monitoring etc. Smart materials can be integrated to composite structure to enhance its abilities. Fiber reinforced composites are the advanced materials of choice in aerospace applications due to its high strength and stiffness, light weight and ability to tailor according to the design requirements. Due to complex manufacturing process and varying operating conditions, composites are susceptible to variation in material properties and damages. The present study focuses on the effect of uncertainties in material properties and damages on a smart composite structure.
A cantilevered composite plate with surface mounted piezoelectric sensor/ actuator is considered in this study. The sensors and the actuators are connected through a conventional feedback controller and the controller is configured for vibration control application. Matrix cracks are considered as damage in the composite plate. To study the effect of material uncertainty, probabilistic analysis is performed considering composite material properties and piezoelectric coefficients as independent Gaussian random variables. Numerical results show that there is substantial change in dynamic response of the smart composite plate due to material uncertainties and damage. Deviation due to material uncertainty and damage can be compensated by actively tuning the feedback control system. Feedback control parameters can be properly adjusted to match the baseline response. Here baseline case represents the response of the undamaged smart composite plate with deterministic material properties. The change in feedback control parameters are identified as damage indicator. Feedback control based damage detection method is proposed for structural health monitoring in smart composite structure and robustness of the method is studied considering material uncertainties.
Fractal dimension based damage detection method is proposed to detect localized matrix cracks in a composite plate with spatially varying material properties. Variation in material properties follows a two dimensional homogeneous Gaussian random field. Fractal dimension is used to extract the damage information from the static response of composite plate with localized matrix cracks. It is found that fractal dimension based approach is capable of detecting the location of the single and multiple damages from the static deflection curve. Robustness of the fractal dimension based damage detection method is studied considering spatial uncertainties in material properties.
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Umesh, K. "On The Effect Of Material Uncertainty And Matrix Cracks On Smart Composite Plate." Thesis, 2013. http://etd.iisc.ernet.in/handle/2005/2603.
Full textAbstract:
Recent developments show the applications of smart structure in different engineering fields. Smart structures can be used for shape and vibration control, structural health monitoring etc. Smart materials can be integrated to composite structure to enhance its abilities. Fiber reinforced composites are the advanced materials of choice in aerospace applications due to its high strength and stiffness, light weight and ability to tailor according to the design requirements. Due to complex manufacturing process and varying operating conditions, composites are susceptible to variation in material properties and damages. The present study focuses on the effect of uncertainties in material properties and damages on a smart composite structure.
A cantilevered composite plate with surface mounted piezoelectric sensor/ actuator is considered in this study. The sensors and the actuators are connected through a conventional feedback controller and the controller is configured for vibration control application. Matrix cracks are considered as damage in the composite plate. To study the effect of material uncertainty, probabilistic analysis is performed considering composite material properties and piezoelectric coefficients as independent Gaussian random variables. Numerical results show that there is substantial change in dynamic response of the smart composite plate due to material uncertainties and damage. Deviation due to material uncertainty and damage can be compensated by actively tuning the feedback control system. Feedback control parameters can be properly adjusted to match the baseline response. Here baseline case represents the response of the undamaged smart composite plate with deterministic material properties. The change in feedback control parameters are identified as damage indicator. Feedback control based damage detection method is proposed for structural health monitoring in smart composite structure and robustness of the method is studied considering material uncertainties.
Fractal dimension based damage detection method is proposed to detect localized matrix cracks in a composite plate with spatially varying material properties. Variation in material properties follows a two dimensional homogeneous Gaussian random field. Fractal dimension is used to extract the damage information from the static response of composite plate with localized matrix cracks. It is found that fractal dimension based approach is capable of detecting the location of the single and multiple damages from the static deflection curve. Robustness of the fractal dimension based damage detection method is studied considering spatial uncertainties in material properties.
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WTWANG and 王文庭. "MATERIAL CONSTANTS IDENTIFICATION COMPOSITE STRUCTURES." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/84179988213169077428.
Full textAbstract:
博士<br>國立交通大學<br>機械工程系<br>88<br>Composite laminates have been used extensively in the mechanical and aerospace industries for fabricating high performance structures. To ensure high reliability of the structures, the actual behaviors of the laminated composite parts in service must be accurately predicted and carefully monitored. It has also been pointed out that accurate determination of current stiffness or material properties of a laminated composite structure can help prevent sudden failure of the structure. The attainment of the actual behavioral predictions of the structures depends on the correctness of the elastic constants of the structures. Therefore, the determination of realistic material or mechanical properties of laminated composite components has become an important topic of research.
In this paper, a method for nondestructive evaluation of elastic constants of composite structures is presented. An error function is established to measure the differences between the theoretically and experimentally predicted system deformations and/or natural frequencies. The identification of the elastic constants is formulated as a constrained minimization problem in which the elastic constants are determined to make the error function a global minimum. A global minimization method together with an appropriate bounding technique for constraining the variations of the elastic constants are used to solve the above minimization problem. The applications of the proposed method are demonstrated by means of several examples on the elastic constants identification of laminated composite plates.
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Lee, Jun-Yih, and 李俊毅. "MECHANICS PROPERTIES OF HYBRID COMPOSITE MATERIALS AND ESTABLISHMENT OF MATERIAL DATABASE." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/90672414581916048690.
Full textAbstract:
碩士<br>國立臺灣大學<br>造船工程學系<br>85<br>The primary object of this paper is to study the mechanical
properties of FRP composite materials which are frequently used
in the ship-building yards of Taiwan. The properties are
obtained via experiments of material test. Then the data
obtained from the experiments is calculated by the principle of
composite to predict the bending and tension properties of
hybrid laminates . Another achievement of this paper is that the
data base of FRP composite materials‘ mechanical properties is
established by computer . Users can use computer to consult the
data of FRP composite materials’ mechanics properties and to
calculate the properties of hybrid laminates . In addition ,
this paper also concerns about the static strengths of hybrid
laminates . Four kinds of hybrid laminates are measured here .
The results of experiment are compared with the values of
calculating to ensure the precision of the prediction methods.
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Chen, Juen-Chuen, and 陳俊村. "Composite Material Impact and Repair Study." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/50182169071611732910.
Full textAbstract:
碩士<br>中華科技大學<br>飛機系統工程研究所在職專班<br>100<br>ABSTRACT
Materials industry has become more important as the progress of technology. Composite materials are widely applied in high-tech products nowadays. However, the panels with the sandwich structure of composite materials would be destroyed by the external loads or strikes. The purpose of this study is to explore whether composite materials used as materials of repairing structure would recover the original strength. This article discusses its impact behavior of composite glass fiber sandwich structure and structure performance after repair, design using high density styrofoam core material mixed with epoxy resin and glass fiber made from different types of composite sandwich structures test piece, exploring the bending resistance of composite sandwich structure and ability to resist pressure and tensile strength. The experiment used a self design shocks equipment to simulate energy impacts with different levels of damage energy caused by different impacts angle and mass of weight. On the other hand, the impact damaged patch characteristics, and performance analysis of bending strength of composite sandwich structures will be discussed. The results indicated repaired test pieces enhanced the bending strength from 0.01 Mpa to 0.06 Mpa. It is suggested that repairing can enhanced the strength of material to the original strength and even better than the original one. The study implicated the repair of composite materials of structure by using glass fibers would cause the economic benefits in materials industry.
Keywords： sandwich structure、 impact test、composite repair、 bending test
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Gu, Rong-Yao, and 古榮耀. "Nondestructive Evaluation for Sandwich Composite Material." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/98414161263548416529.
Full textAbstract:
碩士<br>中華科技大學<br>飛機系統工程研究所在職專班<br>100<br>ABSTRACT
In this study, take composite materials as sample; evaluate the reliability of non-destructive testing and certification. Use the thermal imaging method to exam its internal defects by heat transfer characteristics of sandwich composite material. The detection method is to use an instantly heating device adding on a composite material, as well as infra-red thermal imaging apparatus. The infrared issued by the observation of the thermal imaging, from it can be identified by the detection of composite materials within the defects and normal area. With a simple, fast, economic, checking the location is less restricted and immediately review the composite defects can be achieved. Besides, it can be safety upgrading and checking business-driven applied to composites structural. On the other hand, this article and take advantage of digital imaging in Omni-directional image synthesis and processing of, was reversed by original material difficult to analyze, measure, you can try this method and system, more real-time and accurate results, significantly shortened testing time. Furthermore, through real-time dynamic or static images more shooting, more detailed analysis of the material in each of the torsion angles of rotation or when you each time, marked changes in the material above and through computerized fast calculation of real-time results. Not only on the material test can be applied in the future, but can be used for load monitoring, that is, through a change of control material marking on the surface of, warning may have been closer to the yield point of the material.
Keywords: sandwich structure,non-destructive inspection, thermal image, image analysis, full range image.
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Liu, Ren-Wei, and 劉人維. "Measurements of conductivity of composite material." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/43937929502427658253.
Full textAbstract:
碩士<br>國立臺灣大學<br>電機工程研究所<br>84<br>The main point of this paper is the measurement of the
attenuation of the microstripline that contains composite
material and finding a method for estimating the conductivity
of the composite material.The composite material that is under
test is put under the dielectric slab of the microstripline
,regarded as the second medium .The attenuation constant of
composite material is estimated by the S parameter of the two
layer medium microstripline .It is the experimental value.The
frequency range of the measurement is 50MHz-10GHz.By numerical
method computing the attenuation of composite material of
different conductivities ,we can compare the experimental
values with the theoretical values then estimate the
conductivity of of the composite material.