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Structural and dielectric properties of polyvinyl alcohol/barium zirconium titanate polymer-ceramic composite

Badapanda, T.; Senthil, V.; Anwar, S.; Cavalcante, L. S.; Batista, N. C.; Longo, Elson
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
48.49141%
The polyvinyl alcohol (PVA)/barium zirconium titanate Ba[Zr0.1Ti0.9]O3 (BZT) polymer-ceramic composites with different volume percentage are obtained from solution mixing and hot-pressing method. Their structural and electrical properties are characterized by X-ray diffraction (XRD), Rietveld refinement, cluster modeling, scanning electron microscope and dielectric study. XRD patterns of PVA/BZT polymer-ceramics composite (with 50% volume fractions) indicate no obvious differences than the XRD patterns of pure BZT which shows that the crystal structure is still stable in the composite. The scanning electron micrograph indicates that the BZT ceramic is dispersed homogeneously in the polymer matrix without agglomeration. The dielectric permittivity (ε r) and the dielectric loss (tan δ) of the composites increase with the increase of the volume fraction of BZT ceramic. Theoretical models are employed to rationalize the dielectric behavior of the polymer composites. The dielectric properties of the composites display good stability within a wide range of temperature and frequency. The excellent dielectric properties of these polymer-ceramic composites indicate that the BZT/PVA composites can be a candidate for embedded capacitors. © 2013 Elsevier B.V.

Compósitos poliméricos de poli (éter imida)/polianilina : preparação e caracterização; Polymer composites of poly (ether imide) polyaniline : preparation and characterization

Evandro Mendes Alexandrino
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/02/2012 PT
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A combinação de polianilina (PAni) com termoplásticos, elastômeros e termorrígidos na forma de compósitos e blendas tem sido amplamente estudada nas últimas duas décadas. Entretanto, a utilização de termoplásticos de alto desempenho térmico em compósitos ou blendas com polianilina tem sido pouco explorada devido às altas temperaturas de processamento destes termoplásticos e no fato de que, nestas condições, a PAni se apresenta termicamente instável de acordo com a natureza do dopante utilizado. A poli(éter imida) (PEI) é um termoplástico de engenharia que apresenta boas propriedades térmicas e mecânicas, porém apresenta altas temperaturas de processamento. Nesta dissertação de Mestrado, PAni foi sintetizada em escala laboratorial através de oxidação química, gerando a PAni dopada com ácido clorídrico (PAni HCl). A PAni HCl foi desdopada e redopada para obtenção de PAni dopada com ácido p-tolueno sulfônico (PAni APTS) ou com um complexo de cobalto com acetonitrila (PAni CoAcn). Foram preparados compósitos de PEI com PAni APTS, com teor de PAni entre 2,5 a 20% em massa, por extrusão em uma mini-extrusora dupla rosca. Compósitos de PEI plastificada (PEIR) com resorcinol bis(difenil fosfato) (RDP) também foram preparados com PAni APTS ou PAni CoAcn...

Structure–properties relationship in single polymer composites based on polyamide 6 prepared by in-mold anionic polymerization

Dencheva, Nadya Vasileva; Denchev, Z.; Pouzada, A. S.; Sampaio, Ana Sofia; Rocha, A. M.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
68.04487%
Single polymer composites (SPCs) based on polyamide 6 (PA6) were prepared by in-mold activated anionic ring-opening polymerization (AAROP) of capro- lactam in the presence of PA6 textile fibers. The influence of the reinforcing fibers content, their surface treatment, as well as of the temperature of AAROP upon the morphol- ogy, crystalline structure, and mechanical properties of the resulting SPCs was followed. The presence of oriented transcrystalline layer (TCL) on the surface of the rein- forcing fibers was demonstrated by means of microscopy methods. Its orientation and polymorph structure were determined by synchrotron wide-angle X-ray scattering. Studies on the mechanical behavior in tension of the SPCs showed a well-expressed growth of the stress at break (70–80 %) and deformation at break (up to 150–190 %) in composites with 15–20 wt% of reinforcements. The best mechanical properties were found in SPCs whose rein- forcing fibers were solvent-pretreated prior to AAROP in order to remove the original finish. In these samples a stronger adhesion at the fiber/matrix interface was proved by scanning electron microscopy of cryofractured samples. This effect was related to a thinner TCL in which the α-to-γ polymorph transition is impeded.; HASYLAB at DESY (Grant Number II-07- 011EC); Strategic Project LA 25-2011-2012 financed by Fundação para a Ciência e a Tecnologia (FCT) - Portugal; FCT post-doctoral award SFRH/BPD/45252/2008...

Properties and processing by extrusion of electrically conductive multilayer filaments comprising polymer composites

Martins, R. S.; Gonçalves, Renato Ferreira; Azevedo, Tiago; Nóbrega, J. M.; Carvalho, Helder; Lanceros-Méndez, S.; Rocha, J. G.
Fonte: Sociedade Portuguesa de Materiais (SPM) Publicador: Sociedade Portuguesa de Materiais (SPM)
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
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57.82196%
This work describes the production and characterization of three-layer piezoelectric filaments using two different electrically conductive polymers. The filaments were produced in a filament extrusion line, equipped with a coextrusion die that enabled a coaxial arrangement for a three-layer filament. For the inner and outer layers two different electrically conductive compounds were used, and the middle layer was made of the electroactive polymer PVDF. The produced filament can be used as a piezoelectric sensor, as described in other work [1]. A commercial conductive polymer grade of polypropylene compounded with carbon black and a commercial polypropylene containing 7 wt% of carbon nanotubes were studied and compared when employed as the filament conductive layers under various processing conditions, namely different process temperatures and drawing ratio. For evaluation purposes measurements of the electrical resistance of the inner and outer conductive layers were performed and correlated with the composition and processing conditions. The polypropylene based composite containing 7 wt% carbon nanotubes revealed to be the most effective material to be used in the production of three-layer piezoelectric filaments since it presents higher electrical conductivity and easier processing...

Functionalized cork-polymer composites (CPC) by reactive extrusion using suberin and lignin from cork as coupling agents

Fernandes, E. M.; Aroso, Ivo; Mano, J. F.; Covas, J. A.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /11/2014 ENG
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58.188936%
High density polyethylene (HDPE) and cork powder were compounded in a co-rotating twin-screw extruder to obtain cork-polymer composites (CPC) with improved properties. Benzoyl peroxide (BPO) was used as initiator agent, and suberin or lignin isolated from cork enhanced filler-matrix bonding and promoted mechanical reinforcement with environmental benefits. The novel composites were characterised in terms of dimensional stability, evolution of morphology, thermal and mechanical properties and their performance was compared with that of composites containing polyethylene-grafted maleic anhydride (PE-g-MA) as coupling agent. As expected, composites with coupling agent present higher mechanical properties, lower water uptake and thickness swelling variation. Suberin acts as plasticizer with antioxidant benefits, while lignin works as a coupling agent, improving tensile modulus and maximum strength. Increasing lignin content does not improve the mechanical properties but improves thermal stability.

Effect of particle morphology on the mechanical and thermo-mechanical behavior of polymer composites

Oréfice,R. L.; Hench,L. L.; Brennan,A. B.
Fonte: The Brazilian Society of Mechanical Sciences Publicador: The Brazilian Society of Mechanical Sciences
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 EN
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58.52901%
Fiber reinforced polymer composites have been used in many applications, such as in automobile, aerospace and naval industries, due basically to their high strength-to-weight and modulus-to-weight, among other properties. Even though particles are usually not able to lead to the level of reinforcement of fibers, particle reinforced polymer composites have been proposed for many new applications due to their low cost, easy fabrication and isotropic properties. In this work, polymer composites were prepared by incorporating glass particles of different morphologies on poly(aryl sulfones) matrices. Particles with aspect ratios equal to 1, 2.5 and 10 were used. The prepared composites were characterized using electron microscopy and thermal analysis. Mechanical properties of the composites were evaluated using a four-point bending test. The thermo-mechanical behavior of the obtained composites was also investigated. The results showed that the morphology of the particles alter significantly the mechanical properties of composites. Particles with larger values of aspect ratio led to large elastic modulus but low levels of strain at failure. This result was explained by modeling the thermo-mechanical behavior of the composites using a viscoelastic model. Parameters of the model...

Natural rubber: leather composites

Ravichandran,K.; Natchimuthu,N.
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
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57.88036%
Leather is a fibrous protein consisting of collagen in a three dimensionally crosslinked network. Chrome tanning of leather improves the appearance of leather but at the same time emits both solid and liquid chrome leather wastes. Scrap rubber recycling using untreated and neutralized leather fibrous particles in natural rubber has been studied. Vulcanization, mechanical, morphological and swelling properties of the natural rubber - scrap rubber composites containing neutralized leather have been discussed. Use of chrome leather particles has been found to improve the consumption of scrap rubber powder in natural rubber formulations. Polymer composites based on leather wastes as fillers are reported to be useful for many applications such as in construction materials, automobile interior moldings, heat and sound insulating boards, shoe soles, flooring materials and moldings with good anti-static properties, air permeability and good appearances.

Transcrystallization at the interface of polyethylene single-polymer composites

Kestenbach,H.-J.; Loos,J.; Petermann,J.
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/1999 EN
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57.756875%
The phenomenon of transcrystallization was studied at the interface of UHMWPE fibers embedded in an HDPE matrix. It was hoped that epitaxial crystallization in such model composites could eventually be used to improve adhesion between these high-strength fibers and the thermoplastic matrix material. Matrix crystallization was induced and accompanied on a specially designed hot stage which made the crystallization front advance slowly along a thermal gradient. Transcrystalline interfacial layers were observed without regard to temperature conditions, but with widely varying dimensions. Lamellar resolution within these layers was achieved by low voltage scanning electron microscopy, and the very beginning of transcrystallization was observed in sample areas where UHMWPE fiber segments were only partially embedded into the HDPE matrix. Lamellar alignment on the fiber surface indicated that transcrystallization in this system was associated with epitaxial nucleation.

Properties of SBS and sisal fiber composites: ecological material for shoe manufacturing

Verney,José Carlos Krause de; Lima,Martha Fogliato Santos; Lenz,Denise Maria
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
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58.12852%
The worldwide trend toward using cheap, atoxic and durable materials from renewable resources contributes to sustainable development. Thus, the investigation of the potential use of vegetal fibers as reinforcing agent in polymeric composites has gained new significance. Sisal fiber has emerged as a reinforcing material for polymers used in automobile, footwear and civil industries. In this work, properties such as hardness, tensile strength and tear strength of polymer composites composed by block copolymer styrene-butadiene-styrene (SBS) and 5, 10 and 20% by weight of sisal fiber were evaluated. The influence of conventional polymer processing techniques such as single-screw and double-screw extrusion, as well as the addition of coupling agent on the composite mechanical performance was investigated. Also, the morphology and thermal stability of the composites were analyzed. The addition of 2 wt. (%) maleic anhydride as coupling agent between sisal fiber and SBS has improved the composite mechanical performance and the processing in a double-screw extruder has favored the sisal fiber distribution in the SBS matrix.

Rheological and mechanical characterization of poly (methyl methacrylate)/silica (PMMA/SiO2) composites

Silva,Erik dos Santos; Ribeiro,Lourdes Aparecida; Nascimento,Maria Carolina Burgos Costa do; Ito,Edson Noriyuki
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2014 EN
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58.2991%
The search for new materials with properties suitable for specific applications has increased the number of research studies to fill the market demands. The development of polymer composites by the addition of inorganic fillers to the poly(methyl methacrylate) (PMMA) increases the potential use of this polymer in various application fields. The main objective of this work was to study the rheological and mechanical behavior of composites obtained from the addition of silica in two different types of PMMA matrix: a common (PMMAc) and an elastomeric copolymer (PMMAel). The results showed that the addition of silica particles to the PMMA matrix promoted an increase in torque, a decrease in the melt flow index of composites and an increase in hardness compared to pure polymers. The composites also showed a reduction of the maximum tensile strength for composites with PMMAc matrix and maintenance of tensile strength for composites with PMMAel matrix. The average width of scratch decreased due to a change in wear mechanism, attributed to the increase of hardness in the composites obtained.

The chemical modification of tropical wood polymer composites

Islam, M.S.; Hamdan, S.; Hassan, A.; Talib, Z.A.; Sobuz, M.D.H.R.
Fonte: Sage Publicador: Sage
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
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58.264214%
Wood polymer composites were manufactured from several types of tropical wood species by impregnating the woods with acrylonitrile monomer solution. The physical and mechanical properties of wood polymer composites were then investigated in this study. The vacuum-pressure method was employed to impregnate wood samples with monomer and in situ polymerization. Acrylonitrile reacted and incorporated with wood, which was confirmed through Fourier transform infrared spectroscopy and scanning electron microscopy test analysis. The mechanical properties of wood samples in terms of modulus of elasticity and compressive modulus were found to be improved on acrylonitrile treatment. Besides, the fabricated wood polymer composite samples had lower water absorption and higher surface hardness (Shore D) value as compared to their corresponding raw one. For wood polymer composites, a significant improvement was found in physical and mechanical properties compared to the raw woods.; Md. Saiful Islam, Sinin Hamdan, Azman Hassan, Zainal Abidin Talib, and HR Sobuz

Modeling of setting stresses in particle-reinforced polymer composites using finite element analysis

Boriek, Aladin Mohamed
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
48.687646%
This work uses three-dimensional Finite Element Analysis (FEA) to investigate the effect of geometric arrangement of particulate reinforcement in highly filled polymer composites (such as polymer concrete) on the setting stresses that develop in these materials during cure due to resin shrinkage during polymerization. These composites were initially modeled by systems reinforced with spherical particles packed in simple cubic (SC) and face-centered cubic (FCC) arrangements within the polymer matrix. A pronounced decrease in setting stresses was observed in the FCC system, which has a greater aggregate to resin ratio and more of resin domains per unit cell. A hexagonal-close-packed arrangement of hexagonal, prism-shaped aggregate was also analyzed and found to develop higher stresses, indicating that aggregate shape has an effect on setting stresses. A second set of models investigated the effect of size gradation and geometric arrangement of spherical reinforcing particles on setting stresses. The maximum stresses occur at the particle-resin interface, underlining the importance of resin/aggregate adhesion. Reduction of setting stresses by a factor of two was observed in systems with efficient packing, achieved with proper size gradation and close-packed geometry. A microstructural model for a polymer composite system based on a fairly random arrangement (FRA) of aggregate particles was also developed. This model gives a realistic representation of actual particle reinforced polymer composites. FEA results were used to develop an empirical equation for maximum setting stresses for Particle reinforced polymer composites. A probabilistic model for the distribution of voids in polymer composites was developed by solving a non-linear constrained optimization problem. The probability distributions of voids was used with a specially developed algorithm to generate the voids distributions in specific composites. The effect of voids on setting stresses in FRA models was discussed. In polymer composites voids tend to act as stress relief. This effect is more pronounced in poorly packed systems. This study provides an understanding of setting stress distribution in polymer composites. This work provides guidelines for optimizing the amount...

Carbon Nanotubes Filled Polymer Composites: A Comprehensive Study on Improving Dispersion, Network Formation and Electrical Conductivity

Chakravarthi, Divya Kannan
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
58.556465%
In this dissertation, we determine how the dispersion, network formation and alignment of carbon nanotubes in polymer nanocomposites affect the electrical properties of two different polymer composite systems: high temperature bismaleimide (BMI) and polyethylene. The knowledge gained from this study will facilitate optimization of the above mentioned parameters, which would further enhance the electrical properties of polymer nanocomposites. BMI carbon fiber composites filled with nickel-coated single walled carbon nanotubes (Ni-SWNTs) were processed using high temperature vacuum assisted resin transfer molding (VARTM) to study the effect of lightning strike mitigation. Coating the SWNTs with nickel resulted in enhanced dispersions confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS). An improved interface between the carbon fiber and Ni-SWNTs resulted in better surface coverage on the carbon plies. These hybrid composites were tested for Zone 2A lightning strike mitigation. The electrical resistivity of the composite system was reduced by ten orders of magnitude with the addition of 4 weight percent Ni-SWNTs (calculated with respect to the weight of a single carbon ply). The Ni-SWNTs - filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts indicated by the minimal carbon fiber pull out. Methods to reduce the electrical resistivity of 10 weight percent SWNTs -- medium density polyethylene (MDPE) composites were studied. The composites processed by hot coagulation method were subjected to low DC electric fields (10 V) at polymer melt temperatures to study the effect of viscosity...

Single-Walled Carbon Nanotubes (SWNT) polymer composites & composite fibers

Chen, Zheyi
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: 122 p.; application/pdf
ENG
Relevância na Pesquisa
58.45396%
With their potentially extraordinary mechanical, thermal, and electrical properties, Single-Walled Carbon Nanotubes (SWNT)/polymer composites and composite fibers may be the ultimate building blocks for next generation ultra-light-weight, ultra-high performance structural applications. However, the dispersity and processibility of SWNT in polymer matrices have been a challenge because of the strong van der Waal attraction between individual nanotubes and their chemical inertness. Predicated on oleum's (100% H2SO 4 with excess SO3) ability to intercalate between individual SWNT inside SWNT ropes, two types of reinforcing SWNT with much improved solubility and dispersity in common solvents were developed: supra-roped SWNT (SWNT-R) and soluble, ultra-short (length<60 nm), carboxylated SWNT(US-SWNT). SWNT-R hold much improved dispersity in super acid and other solvents, and can facilitate the processing of SWNT/polylmer composites and composites fibers. US-SWNT exhibit up to 2 wt% solubility in common solvents. The availability of SWNT-R and US-SWNT open the opportunities for forming high performance composites, blends, and copolymers without inhibiting their processibility. Studies on the synthesis, processing, properties, and morphology of SWNT-R or US-SWNT/polymer composites and composite fibers have demonstrated the reinforcement efficacy of these SWNT in typical thermoset...

Produtos têxteis inteligentes incorporando filamentos compósitos com nanotubos de carbono; Monofilament composites with carbon nanotubes for the production of smart textiles

Ferreira, Alexandre
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 13/02/2015 POR
Relevância na Pesquisa
58.214688%
Programa Doutoral em Engenharia Têxtil.; Atualmente é possível encontrar compósitos de polímero e nanotubos de carbono (NTC) aplicados em diversas áreas. Existe um particular interesse neste tipo de materiais quando aplicados como compósitos eletricamente condutores. Este crescimento é fruto do desenvolvimento do conhecimento nos métodos de processamento e produção, assim como da redução significativa do preço dos materiais. A condutividade elétrica de um compósito polímero/nanotubos de carbono é fruto de uma rede contínua de ligações entre o reforço e o polímero. Esta rede de ligações é também normalmente sensível a estímulos como variações térmicas, tensões mecânicas, ou presença de vapor ou gases. É por estas razões que os compósitos poliméricos são bons candidatos para integração em têxteis inteligentes. Durante este estudo, foram estudados os comportamentos sensoriais de misturas de poliácido láctico (PLA), de polipropileno (PP)/policaprolactona (PCL) e de poliuretano termoplástico (TPU) reforçadas com nanotubos de carbono de parede múltipla (MWNT), tendo sido analisadas a variação da resistividade elétrica na presença de estímulos, em particular a presença e variação de humidade para o compósito baseado em PLA...

Mechanical properties of PET composites using multi-walled carbon nanotubes functionalized by inorganic and itaconic acids

Cauich Rodríguez, J. V.; Toro, P.; Aviles, F.; Yazdani-Pedram Zobeiri, Mehrdad; May-Pat, A.
Fonte: BUDAPEST UNIV TECHNOL & ECON, DEPT POLYMER ENG Publicador: BUDAPEST UNIV TECHNOL & ECON, DEPT POLYMER ENG
Tipo: Artículo de revista
EN
Relevância na Pesquisa
57.96401%
Artículo de publicación ISI; Multi-walled carbon nanotubes (MWCNTs) were oxidized by two different acid treatments and further functionalized with itaconic acid (IA). The functionalized MWCNTs were used to fabricate Poly(ethylene terephthalate) (PET) composites by melt mixing. The presence of functional groups on the surface of the treated MWCNTs was confirmed by infrared spectroscopy and thermogravimetric analysis. The MWCNTs oxidized with a concentrated mixture of HNO(3) and H(2)SO(4) exhibited more oxygen containing functional groups (OH, COOH) but also suffer larger structural degradation than those oxidized by a mild treatment based on diluted HNO(3) followed by H(2)O(2). PET composites were fabricated using the oxidized-only and oxidized followed by functionalization with IA MWCNTs. PET composites fabricated with MWCNT oxidized by mild conditions showed improved tensile strength and failure strain, while harsh MWCNT oxidation render them overly brittle.; CONACYT-Mexico 105567 79609 CONICYT-Chile 1090260

Energy Transfer Dynamics of Nanocrystal−Polymer Composites

Warner, Jamie H.; Watt, Andrew; Thomsen, Elizabeth; Heckenberg, Norman Richard; Meredith, Paul; Rubinsztein-Dunlop, Halina
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
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67.92138%
Steady-state and time-resolved photoluminescence spectroscopy are used to examine the photoluminescent properties of nanocrystal-polymer composites consisting of colloidal PbS nanocrystals blended with poly(2-methoxy-5(2- ethylhexyloxy)-p-phenylene vinyle

Using glass-fibre reinforced polymer composites in the production of sustainable water storage vessels

Simões, C. L.; Vasconcelos, M.; Nunes, J. P.; Bernardo, C. A.
Fonte: Inderscience Publicador: Inderscience
Tipo: Artigo de Revista Científica
Publicado em 18/08/2015 ENG
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58.02262%
The present work focuses on the use of the life cycle assessment (LCA) and life cycle costing (LCC)methodologies to evaluate environmental and economic impacts of polymers and polymer composites materials and products. Initially a literature review is performed in order to assess the scope and limitations of existing LCA and LCC studies on these topics. Then, a case study, based on the production of a water storage glass-fibre reinforced polymer (GFRP) composite storage tank, is presented. The storage tank was evaluated via a LCA/LCC integrated model, a novel way of analysing the life cycle (LC) environmental and economic performances of structural products. The overarching conclusion of the review is that the environmental and economic performances of polymers composites in non-mobile applications are seldom assessed and never in a combined integrated way.; This work was funded by FEDER, through the COMPETE 2020 program, and by FCT, the Portuguese Foundation for Science and Technology, under project UID/CTM/50025/2013. The authors acknowledge the data provided by Vidropol SA, which was essential for its completion. Carla L. Simões also thanks FCT for a personal research grant (SFRH/BD/60852/2009).

Methods to characterize and enhance the through-thickness thermal conductivity of three dimensional polymer composites

Yu, Hang
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
58.489707%
Advani, Suresh G.; Increased polymer composites are being used to replace traditional materials in modern structures and industrial applications due to their light weight and corrosion resistant features. However some of these devices and components are subjected to increasing thermal load and as polymer composites are poor conductors of heat, thermal management is critical. Thermal transport mechanisms are investigated and characterized when highly conductive fibers are embedded in three-dimensional polymer composites. Improved out-of-plane thermal conductivity of fiber reinforced polymer (FRP) composite materials will enable lightweight structures to integrate efficient thermal management. Different approaches have been explored to enhance out-of-plane thermal conductivity and address measurement issues associated with this class of composites, including Z-pin insertion and distribution, particle-fabric reinforcement and laminate stacking sequence design and some combinations of above factors. An approach in which a conductive coating is applied on the surface of composite samples to improve the through-thickness thermal conductivity of composites containing a small percentage of conductive fibers in the thickness direction is explored. A parametric study revealed that the thickness of the coating and the distribution of the conductive fibers play a crucial role in augmenting the heat transfer across the thickness of the polymer composite. For the enhancement of through-thickness thermal conductivity of nonwoven laminated composites...

Predicting the piezoresistance contribution of carbon nanotubes in a polymer matrix through finite element modeling

Oliva-Avilés,A. I.; Sosa,V.; Avilés,F.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2013 EN
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58.214688%
The change in electrical resistance due to mechanical deformation of carbon nanotube (CNT)/polymer composites can be rationalized in terms of two main effects: i) changes in the composite electrical resistivity due to changes in the CNT network configuration, and ii) deformation of the CNTs themselves. The contribution of CNT dimensional changes (ii) to the piezoresistivity of CNT/polymer composites is investigated here. A model based on a representative volume element which describes the CNT geometrical contribution to the composite electromechanical response (piezoresistivity) in terms of the CNT and matrix deformations is proposed. Finite element analysis is performed to correlate the macroscale composite strain to the individual CNT strain. The CNT geometric contribution to the piezoresistivity of the composite is quantified for a range of matrix elastic modulus and different CNT orientations. Based on the model predictions and previous experimental results, it is estimated that the contribution of the CNT deformation to the composite piezoresistivity is only about 5%, indicating that the dominant effect in the piezoresistivity of CNT/polymer composites is the change in the CNT network configuration.