Mechanical Properties of Polymer Composite

Fibre-reinforced plastics (FRP) are susceptible to damage resulting from impacts, even non-penetrating ones. This damage, even without outright destruction, may lead to reduction of fibre-reinforced plastics strength and static load-bearing abilities. This paper presents the results of three-point flexural tests on glass fibre/polyester composites after non-penetrating ballistic impact, where the word “ballistic” refers to a high-speed free-flying impactor (projectile). This is a continuation of previous studies, during which the extent of damage in glass/polyester composites after non-penetrating ballistic impact was evaluated. Materials used in the study were laminated composites produced via the Resin Transfer Moulding (RTM) technology. This laminates were produced using Polimal 1094 AWTP-1 unsaturated polyester resin and E-glass reinforcement in the form of multiple perpendicular layers of chopped-strand mats, continuous-filament mats, twisted-yarn fabrics and woven rovings. Composites with varying thickness, number of layers and fibre content were produced. The impactor is a free-flying 3 g steel ball propelled from a gas gun. Two striking velocities were tested - 60 and 70 m/s, producing impact energies of 5.4 and 7.35 J accordingly. After the impact, the extent of damage in samples (100x100 mm square plates) was evaluated through digital image analysis. The as-impacted samples were then subjected to three-point bending under set conditions. The results were compared to the results of identical examination of undamaged samples and the reduction in mechanical properties was determined. In all cases, the reduction in strength and load-at-break value was noticed. Thicker, more reinforced laminates show lower loss of mechanical properties, than thinner ones. Difference between strength and load-at-break approach for load-bearing abilities reduction was discussed, and the conclusion is that the latter is preferred to the former in laminated composites due to high thickness dependence of strength. Comparing reinforcement types, continuous-filament mat is superior to chopped-strand mat and woven-rovings. Tightly woven twisted-yarn fabric compares favourably to the woven rovings.

Composites are superior to conventional materials due to their high strength to weight ratio. Of late, because of environmental concerns, natural fibres are finding their places in composites. However, their hygroscopic nature affects the mechanical properties of the composites adversely. Applications of composites for decking, flooring and outdoor facilities have made it necessary to evaluate the water uptake characteristics of natural fibre composites. The objective of this paper is to review the water absorption behavior, its effect on mechanical properties and the efforts to reduce the absorption of various natural fibre reinforced composites.

Abstract and figures
A composite in the present context is a multiphase material that is artificially made as opposed to one that occurs naturally. The constituent phases must be chemically dissimilar and separated by a distinct interface. A lot of research has been undertaken with artificial fiber-reinforced polymeric composites like glass/aramid/carbon etc. However, due to the higher cost and non-eco-friendly nature of such fibers, natural fiber reinforced composites are taking the place of artificial fiber-reinforced composites. These composites are having a low cost, easy availability, or may be available in the form of waste. Therefore, waste utilization and application of these composites in engineering have significance in the present scenario. Under circumstances, it has been thought proper to utilize coconut shells that are thrown away as waste in the form of dust and fly ash another industrial waste to fabricate composites of lightweight and reasonable strength for engineering applications like in automotive, interior decorations, space technology, and navigation, etc. In this study, a polymeric composite has been prepared by using epoxy resin as matrix and fly ash and coconut shell dust as filler and reinforcements. Fabrication of composite laminates has been done with different weight fractions of coconut shell dust and constant percentage of fly ash by hand lay-up technique. The mechanical properties of the composite laminate so prepared with a random distribution of reinforcements have been investigated such as microstructure, tensile strength, hardness, water absorption as per standards. From the tensile test, it is observed that as the percentage of coconut shell dust increases the tensile strength of the samples increases by up to 15% & then decreases by 20%. The Vickers hardness test gave the values as 15.884VHN, 16.098VHN, and 16.88VHN for 10%, 15%, and 20% CSP reinforcement respectively. From the water absorption test as the gain in weight is less than 2% hence moisture absorption is negligible. It is also seen from the microstructure analysis that the shell dust is evenly distributed in the matrix. Because of this even distribution of filler in the epoxy matrix probably the hardness and strength values are quite optimum and the composite can be a promising material for future applications

Coraz szerzej stosowane kompozyty polimerowe narażone są na różnorakie obciążenia statyczne i dynamiczne. Obciążenia udarowe powodują kruche pękanie żywic reaktywnych, takich jak np. poliestrowe. Aby poprawić odporność żywic poliestrowych na kruche pękanie można zastosować do nich dodatki modyfikujące, m.in. żywice elastyczne oraz kauczuki reaktywne. Praca przedstawia wyniki porównawczych badań wytrzymałościowych laminatów poliestrowo-szklanych wytworzonych z użyciem żywicy modyfikowanej żywicą elastyczną, kauczukiem ETBN i VTBN oraz żywicy niemodyfikowanej. Przeprowadzone badania wskazują, że już niewielki dodatek środka modyfikującego może znacząco poprawić odporność na kruche pękanie i udarność. Poprawa ta zachodzi bez istotnego pogorszenia pozostałych badanych parametrów wytrzymałościowych, zwłaszcza wytrzymałości i sztywności przy zginaniu.

Polymer composites, increasingly wider used, are subjected to various static and dynamic loads. Impact loading causes brittle fracture of reactive resins, such as unsaturated polyester (UP). In order to improve toughness of UP resins some addition of modifiers, such as elastic resin or reactive rubbers, may be used. The paper presents the results of comparative mechanical tests of glass/polyester laminates produced using UP resin modified with an addition of elastic resin and ETBN and VTBN rubbers, as well as resin unmodified. Conducted tests show, that even small amount of modifier may significantly improve toughness and impact strength. This improvement occurs without significant deterioration of other mechanical parameters,
especially flexural strength and stiffness.

In this work, the effect of graphene nanoplatelets (GNPs) on the physico-mechnaical properties of short carbon fiber (SCF) reinforced polyamide 66/thermoplastic copolyester elastomer composites was investigated. The composites were fabricated with extrusion followed by injection molding method. The host matrix, fiber plus host matrix and graphene nanoplatelets loaded hybrid composites were examined for density, hardness, tensile, flexural and impact properties according to the governing ASTM standard. Fiber reinforcement decreased void content to < 1% but GNPs were able to keep void content under limits. Hardness and impact strength augmented with 2 wt. % graphene nanoplatelets loading, owing to superficial dispersion developing the relationship between the hardness and impact strength. Graphene nanoplatelets loading benefitted the tensile property. However, the same has a deteriorating effect on flexural strength. Flexural modulus increases until 2 wt. %. Improvement in mechanical properties upon GNPs loading is very feeble when compared to the enhancement with SCFs loading to the host. Upon comparing the properties, it was observed that 2 wt. % of graphene nanoplatelets performed admirably and was recognized as an optimum filler loading. Morphology of fractured surfaces was studied by analyzing the scanning electron microscope images to understand the various features and mechanisms.

The equilibrium shape of plain weave fabric, accounting for yarn to yarn contact and incorporating the transverse compressibility, is presently investigated, relying on an energetic analysis of the textile. Each yarn is modeled as an undulated beam at a mesoscopic level, with a shape modeled by a Fourier series. In order to get an accurate description of the contact between yarns, we have considered the contact occurring on a surface (distributed contact) of finite extent according to Hertz contact theory. This method allows evaluating the reaction forces between weft and warp from the pressure distribution in the contact zone between yarns, and the evolution of the contact area versus the applied tension. The overall response of fabric under uniaxial and biaxial tension is computed as the minimum of the total potential energy of the set of interwoven yarns, including the work of reaction forces on the contact zones. The calculated nonlinear response for two important materials (glass, carbon) is due to the change of the geometry, namely the crimp variation and the change of contact area during increased loading. The contact area increases with the applied tensile force and is comparable to the yarn diameter. Only the contribution of the displacement due to flexion is shown to be sensitive to the distribution of the forces on the contact surface. A good agreement between the model predictions and tensile measurements of the response of plain weave fabric has been obtained.

Metal matrix composites (MMCs) possess excellent physical and mechanical properties. The filler reinforcement into the metallic matrix improves the stiffness, specific strength, wear, creep and fatigue properties compared to the conventional engineering materials. The present work is a study of the effect of reinforcement of different types of fillers in metal matrix and their merits and demerits. Effect of different dispersion on the mechanical properties like tensile strength, strain, hardness, wear and fatigue of MMCs and its different applications are also highlighted in the paper. MMCs (Metal matrix composites) uses metal matrix dispersed with other metal, ceramic or organic compounds. Reinforcements are usually done to improve the various properties of the base metal.  The  particle  distribution  plays  a  very  important  role  in  the properties of MMCs. Copper, Magnesium and Aluminium has attracted most attention as base metal in metal matrix composites [1]. These MMCs are widely used in aircraft, aerospace, automobiles, defence and various other fields [2]. The most commonly used reinforcements are Silicon Carbide (SiC), TiO2,  Aluminium  Oxide  (Al2O3),  B4C,  Y2O3,  Si3N4,  AlN  [3-7].  Al2O3  reinforcement  shows good compressive strength and wear resistance. Boron Carbide is one of hardest known elements. It has high fracture toughness and  elastic  modulus.  The  addition  of  Boron  Carbide  (B4C)  in  MMCs increases their hardness, but does not improve the wear resistance significantly [4].

The objective of the present work is to improve physical and mechanical properties of
local gypsum reinforced with Resole resin. The water-gypsum ratio was kept at 45% throughout all these experiments. The prepared composites show a clear improvement in impact, compression strength and modulus of elasticity while, the bending strength is reduced when the Resole resin proportion in gypsum was increased from 2.5 to 10%. The other objective of this study was to evaluate the water absorption of Resole-gypsum composite. From the experimental results it may be concluded that swelling % was reduced when the Resole percentage in gypsum-Resole composite was increased.

The aim of this work is to provide some economic value to the agricultural residues by using them as reinforcements in polymer composites. Sugarcane bagasse and coconut shell powder are termed as reinforcements along with unsaturated polyester matrix. Sugarcane fibers are surface treated with sodium hydroxide and hydrochloric acid for better surface adhesion. Effect of water absorption of untreated and surface treated sugarcane fiber polyester composites filled with coconut shell filler were evaluated on tensile specimens. It was observed that untreated sugarcane fiber composites absorb less percentage of water when compared to NaOH treated and HCl treated sugarcane fiber composites. Tensile properties of sugarcane fiber composites are decreased with increase in water absorption. Morphological study through scanning electron microscope reveals that interfacial bonding between fiber and matrix was found excellent NaOH treated sugarcane fiber compared to untreated and HCl treated sugarcane fiber.

In this work, hybrid composites were fabricated by hand layup method to hybridize treated Pineapple leaf fibre (PALF) and kenaf fibre (KF) in order to achieve superior mechanical properties on untreated hybrid composites. Silane treated PALF/KF phenolic hybrid composites were prepared on various fibre fraction to investigate mechanical properties and compared with untreated PALF/KF phenolic hybrid composites. The effects of silane treatment on hybrid composites were investigated by fourier transform infrared spectroscopy (FTIR) and found very effective peaks. Effects of treated hybrid composites were morphologically investigated by using scanning electron microscopy images and analysed the tensile results. Treated PALF/KF phenolic hybrid composites enhanced the flexural strength, modulus, impact strength and energy absorption while tensile strength and modulus decreased. The overall performances of 70 % PALF 30 % Kenaf hybrid composites were improved after silane treatment. Silane treatment of fibres improved the mechanical performance of hybrid composites and it can be utilized to produce components for building structure, materials and automobile applications.

The main issue of this research to improve and develop the mechanical properties of the socket composite material for below-knee (BK) prosthesis; several composite materials were proposed, consisting of perlon, Kevlar and carbon fibers, and natural fibers were added as a new idea for the research. Making the theory calculations were for several layers of materials, by using mathematical model, to obtain the best lamination with and without kenaf by calculating the best modulus of elasticity and the best E /ρ ratio. So the experimental tests were carried out on the lamination with a total of 12 layers for thickness (4 mm) each of them, (Group G/withot kenaf) and (Group D/ with kenaf). The experimental part included examining the samples by tensile test, bending test, impact test. The results of the tensile test results were for the first lamination and the second lamination for the ultimate tensile strength (134.47 MPa) and (187.39MPa) respectively. As for the elasticity modulus, it was as follows (16.78 GPa) without kenaf and (17.49 GPa) for kenaf lamination. Through the theoretical and experimental results, it was found that the use of natural kenaf fibers led to the improvement of the maximum tensile strength 39.35% and modulus of elasticity 4.23%. The impact resistance was improved by using kenaf by 8.8% due to its durability higher than perlon fiber.

Plate and shell analysis using classical plate theory (CPT) has a lack of accuracy in predicting the influence of transverse deformation, because of its assumption that the line normal to the surface remains straight and normal to the midplane before and after deformation. The next revision by constant shear deformation theory or famous as first order shear deformation theory (CSDT/FOSDT) still suffers a disadvantage that has a constant value in the shear term that is called shear locking phenomenon. This matter has been corrected by higher order shear deformation theory (HOSDT) using a refined assumption that the line normal to the surface should be in a parabolic function and not normal to the midplane, but normal to the surfaces so that it fulfills the zero strain in the surface. The analysis of the bending part of laminated composite flat shell element is applied by higher order lamination theory (HOLT) that is adopted from HOSDT. This model is accurate for thicknesses variation and complex materials. HOLT model is implemented into finite element procedure to find deflection, stresses and internal forces. It can be concluded that the displacement and stresses in HOLT model are higher than FOLT the ones (first order lamination theory) in small ratio of a/h dan its result almost the same value for a/h ratio more than 10. In a square plate case, the displacement gets smaller if the fiber arranged into cross-ply sequence. Interlaminar stresses along the thickness is not distributed continuously, but they have certain modes that depend on the depth of point position, the lamina or layer number, fiber orthotropic angle of each layer and a/h ratio.

Purpose: The aim of this study was to investigate the possibility of improving the tribological properties and thermal conductivity of composites with structural modification of polyamides by the additions of copper and graphite.
Design/methodology/approach: The study involved testing polyamide composites containing metallic powder. As the matrix was used polyamide 6 Tarnamid 27 Natural produced by Azoty Tarnów, which strengthened copper, graphite or molybdenum disulfide with varying participation in the composite. Taken tensile test, Brinell hardness, thermal conductivity and the tribological wear resistance. Analyzed the influence of the type of dopant and the participation of the studied property.
Findings: The study showed the desirability of the use of graphite and copper as fillers polyamide. The resulting composites are characterized by satisfactory mechanical properties and thermal conductivity. Applied fillers also showed a positive effect on the value of the coefficient of friction wear him down much.
Research limitations/implications: No synergistic effect of fillers on the properties of a ternary mixture polyamide-graphite-copper property in all test. Tribological wear for this material was significantly higher than for the binary mixtures of polyamide-graphite and polyamide-copper. According to the literature, composite reinforced with graphite and copper should have a best tribological properties, far in excess of other subjects. Low wear resistance of this material disqualify applications on the nodes friction.
Practical implications: The results obtained newly developed composites, combined with the relatively low price of graphite and copper as compared with the price of molybdenum sulfide II may be reasons to use them as analogues of commercial mixtures of PA with MoS2.
Originality/value: The results are original and valuable cognitive nature. They bring a new and expanded information about the effects of fillers on mechanical and physical properties. Unique data on tribological wear resistance depends on the type and amount of filler.

Fibre-reinforced composites are susceptible to damage resulting from impacts. This damage may lead to a reduction of composite strength and load-bearing abilities, both in static loading as well as during subsequent impact events. Composites with improved tolerance to ballistic impact using inexpensive, common materials i.e. E-glass fibre and unsaturated polyester resin, have been manufactured by means of modern, yet popular moulding technology. Composite materials were reinforced with an E-type glass fibre in the form of a continuous filament mat and woven roving. The fibre content in the composites was varied to evaluate the effect of the reinforcement fraction on impact tolerance. The composites were manufactured using the Resin Transfer Moulding (RTM) method. The extent of damage in glass fibre/polyester composites after non-penetrating ballistic impact has been evaluated. Samples of the manufactured laminates were subjected to impact using a compressed-air gun test assembly. The impactor was a free-flying 3-gram hardened steel sphere, and the impact velocities were up to 125 m/s. After the impact and damage evaluation, the samples were photographed in transmitted light, and the obtained images were digitally processed by software to measure the area of delamination. It was found that the damaged area is directly proportional to the impact energy. Moreover, reinforcement in the form of a continuous-filament mat compares favourably to loose woven roving; such reinforced composites have a much smaller area of delamination after impact of a given energy. The impacted samples were sectioned and imaged microscopically in low magnification. The damage in continuous-filament mat-reinforced composites is visibly less severe than in composites with fabric reinforcement.
Keywords: polymer composites, laminates, unsaturated polyester resin, glass fibre, ballistic impact, damage

Precise control in dispersing nanostructured materials in a polymer blend structure is a key requirement in designing materials with tailor-made properties. In this study, the dispersion of a conducting additive (multiwalled carbon nanotubes, MWNTs) in a co-continuous polymer blend structure was controlled by introducing surface-active groups, which react in situ and localize in the thermodynamically nonpreferred phase. In addition, by modifying the MWNTs with a macromolecule, which is mutually miscible with the entities, the nanoscopic particles can be localized at the interface. This way, different MWNTs can be positioned in different phases under macroscopic processing conditions. Herein, we report that this unique strategy has led to simultaneous enhancement in both mechanical strength and electrical conductivity of the blend nanocomposites. In addition, intriguingly, the microwave shielding efficiency can also be tuned by this ordered arrangement of MWNTs in the blend structure in striking contrast to when the MWNTs are in the thermodynamically favored phase. An outstanding twofold enhancement in the Young's modulus, as compared to control blends, and an impressive bulk electrical conductivity of 1 Sm À1 was noted for a particular blend structure wherein different MWNTs were positioned in different phases. In addition , the best blend structure designed here also exhibited a minimum reflection loss (R L) of approximately À61 dB and a shielding effectiveness of > 30 dB at 18 GHz. These data uncover the importance of polymer blends in designing lightweight electromagnetic interference (EMI) shielding materials .

"Las propiedades elásticas de la familia de los minerales isoestructurales Cu3VSe4, Cu3NbSe4 y Cu3TaSe4 han sido calculadas por primera vez usando el estado del arte en cálculos atomísticos de primeros-principios, utilizando la Teoría de los Funcionales de la Densidad y la Aproximación del Gradiente Generalizado para el funcional de la energía de intercambio-correlación. Las propiedades elásticas calculadas son el módulo volumétrico (B), las constantes elásticas (c11, c12 y c44), el factor de anisotropía de Zener (A), el módulo de cizalladura isotrópico (G), el módulo de Young (Y), y la razón de Poisson(ν). A través de estas cantidades también hemos calculado otras propiedades termodinámicas tales como la velocidad promedio del sonido transversal (st) y longitudinal (sl) y la temperatura de Debye (ΘD). Los valores calculados de B, c11, c12 y c44, G, Y , y ν nos llevan a la conclusión que estos compuestos son compresibles, frágiles y quebradizos"

Thermal Barrier Coatings (TBCs), routinely prepared from Ceramic based compositions (typically 8%Y 2 O 3-ZrO 2 or 8YSZ) are being engineered to protect the metallic components from degradation in applications like gas turbines, jet and automotive engines. With a goal of finding improved TBC materials a wide variety of ceramics are being researched worldwide. Before physically preparing the TBCs of uncommon compositions in the laboratory, their suitability to perform can be predicted. Limited accessibility to detailed and realistic information on the influence of newer compositions (other than 8YSZ) on TBCs warrants methods to obtain this information. In this paper, 8YSZ TBCs coated onto aluminium substratesare studied for thermal fatigue, thermal barrier and materials characteristics to determine the reliability of the coating configuration to withstand the harshness of test conditions under the framework of experiments. Thereafter, the results have been used to corroboratethe developed simulation model. Results obtained via thermal tests confirm the suitability of the model and we can predict the thermal barrier effects of TBCs when prepared from materials other than YSZ. KEYWORDS Y 2 O 3-stabilized Zirconia plasma sprayed TBCs, Structural phase analysis, TBC metrology, simulation model of TBCs on aluminium substrate.

Polymer blends have the potential to be developed into new resins for specific applications with balanced performance properties and economic advantages. In this paper, polypropylene (PP) and linear low-density polyeth-ylene (LLDPE) blends were investigated at specific composition of PP/LLDPE (60/40) blends (PL40) using a Twin Screw Extruder (TSE). The nano-calcium carbonate (CaCO 3) content was varied (between 0-40 wt %), and the composites were investigated using slit die rheometers. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques, revealed the existence of favorable interaction between the surface of CaCO 3 nanoparticles and PL40 matrices after surface modification of aminopropyltriethoxy silane (AMPTES) coupling agent. Rheological properties reveal that both the apparent viscosity and the pseudo-plasticity of the PL40 nanocomposites increases with increasing nano-CaCO 3 contents and decreases slightly by treated nano-CaCO 3 with 2% AMPTES. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus (G′) and glass transition temperature (T g) are enhanced upon treated nano-CaCO 3 with a coupling agent. The results from the mechanical properties exhibited that the impact strength was optimum at 20% nano-CaCO 3 content, but tensile strength slightly decreased for untreated PL40 nanocomposites. However, treatment with amino coupling agent improved tensile strength. This attribute to the enhancement of dispersion of the nano-CaCO 3 particles in PL40 matrix, leading to improved interfacial adhesion. Treatment of nano-CaCO 3 significantly improved the Young's modulus and flexural modulus compared to the untreated PL40 composites. The crystallization behavior of the composites supported the strong interfaces formed on addition of the amino coupling agent. Furthermore, scanning electron microscopic (SEM) showed evidence of improvement in the dispersion of treated CaCO 3 in the PL-40 matrix.

Bu patent PVA, PEG, PPG gibi polimer malzemeyi ve tercihan borik asit vb bir bor bileşiği belirli oranlarda karıştırıp reaksiyon ürünü hibrit polimeri 400-700 oC kalsinasyon ve 1000-1600 oC sinterleme işlemine tabi tutarak bor karbür üretim yöntemi ile ilgilidir. Bu yöntemin en büyük özelliği ısıl işlem sırasında isteğe bağlı olarak mikro dalga fırın kullanarak enerjiden ve zamandan büyük tasarruf edilmesini sağlamasıdır. Ayrıca bu yöntemle kalsinasyon sonrası öğütme işleminden sonra pelet aşamasında sinterlenecek malzemeye elementel bor yada borik asit katarak bor karbürün borca daha zengin olması veya aluminyum yada mağnezyum katarak değişik bor karbür alaşımlarının hazırlanması mümkün olabilmektedir.

Fibre-reinforced plastics (FRP) are susceptible to damage resulting from impacts, even non-penetrating ones. This damage, even without outright destruction, may lead to reduction of fibre-reinforced plastics strength and static load-bearing abilities. This paper presents the results of three-point flexural tests on glass fibre/polyester composites after non-penetrating ballistic impact, where the word “ballistic” refers to a high-speed free-flying impactor (projectile). This is a continuation of previous studies, during which the extent of damage in glass/polyester composites after non-penetrating ballistic impact was evaluated. Materials used in the study were laminated composites produced via the Resin Transfer Moulding (RTM) technology. This laminates were produced using Polimal 1094 AWTP-1 unsaturated polyester resin and E-glass reinforcement in the form of multiple perpendicular layers of chopped-strand mats, continuous-filament mats, twisted-yarn fabrics and woven rovings. Com...

The economic exploitation of rubber tree (Hevea brasiliensis) usage is primarily directed toward latex extraction. After the productive life of the rubber tree forest, the managed area is harvested for planting reformulation. The harvested wood is most often used for energy generation purposes. The aim of this work was to study the feasibility of using rubberwood waste and castor oil-based polyurethane resin in the production of particleboards. Homogeneous and heterogeneous panels were made with nominal dimensions of 500 x 500 mm and thicknesses of 10 mm using particles from GT1 and RRIM600 clones of the rubber tree and 12% castor oil-based polyurethane adhesive. The panels were pressed at 140 °C for 12 min with 40 kgf/cm 2 specific pressure. Density, moisture content, thickness swelling, water absorption for 2 and 24 h, static bending, and internal bonding determinations were performed according to the Brazilian Standard (NBR) 14810-3 (2006) for the physicalmechanical panel characterization. The results show that using Hevea brasiliensis in particleboard production is viable. However, multilayer boards exhibited better results.

The article presents synthesis, characterization, mechanical properties and fracture behavior of the epoxy polymers reinforced with either pristine or epoxy functionalized silica nanoparticles. The nanoscale silica is prepared and functionalized in situ via acidic hydrolysis and pre-organization of different alkoxysilane precursors into the epoxy monomers. It is demonstrated that epoxide functionalization of silica nanoparticles not only improves their distribution in the epoxy polymer, but simultaneously enhances the strength [>60%], Young's modulus [>85%] and tensile toughness [>56%] of the resulting hybrids, without adversely affecting their ductility [<7%], even at 15 phr silica loading. The atomic force micrographs of the 'stress fractured' hybrid surfaces reveal that stronger interfacial interactions lead to the effective dispersal of stress and offer efficient resistance to crack propagation. Furthermore, different types of fracture mechanisms are investigated and it is evidenced that crack deflection is the most likely mechanism contributing to the improved mechanical performance of these hybrid epoxy/silica polymers.

In the course of their “life”, fibre-reinforced plastics (FRP) are subjected to impacts which can cause damage. This damage may lead to a reduction of FRP strength and static load-bearing abilities. In this contribution, new results of three-point flexural tests on glass fibre/polyester composites after non-penetrating ballistic impact are presented. Composite materials were reinforced using a continuous filament mat and a woven roving, and the fibre content varied in the range of 42÷61% wt. The materials were produced using the Resin Transfer Moulding (RTM) method. The impactor was a free-flying 3 g steel ball, and the impact velocities approached 130 m/s. After the impact and evaluation of the extent of damage, the samples were subjected to three-point bending tests under fixed conditions. Reduction in the critical load value was noticed. A novel approach to the evaluation of residual strength has been presented. This approach allows estimation of the actual load-bearing ability of damaged material without removing the undamaged parts of the sample. The said approach involves testing samples including a damaged area as well as undamaged samples. It was considered what effect complete elimination of the damaged field would have on the load-bearing ability of the sample. The load transmitted through the undamaged area surrounding the area of delamination was then subtracted. This allowed for evaluation of the percentage of residual properties in the damaged area. It was found that reinforcement in the form of a continuous-filament mat compares favourably to loose woven roving. Higher-reinforced composites after the impact test seem to lose their properties to a higher extent.

Keywords: polymer composites, laminates, unsaturated polyester resin, glass fibre, ballistic impact, residual properties

Titanate nanosheets (TiNS), titanate nanotubes (TiNT), and scrolled titanate nanosheets (STiNS) were used to synthesise polymer nanocomposites by solution processing. The hardness was found to increase by 90% on addition of 2% TiNS while the modulus (Er) increased by 103% compared to the pure polymer. Small angle X-ray scattering (SAXS) measurements of composite films were used to study alignment of nanostructures within the polymer. The obtained data on mechanical properties of composites have been tested against theoretical values and it was established that both nanostructures alignment as well as their mechanical properties affect the hardness and modulus of the polymer composites. At a low content of TiNS, the reinforcement behaviour matched well with Halpin-Tsai theory which assumes the filler has unidirectional orientation. After addition of 2 wt% TiNT, the hardness and modulus of the polyamic acid salt composites increased by 91% and 165%, respectively, and were higher than theoretical predictions, indicating that both TiNT and STiNS, prepared by hydrothermal synthesis, may have higher mechanical properties than bulk TiO 2. At a high filler loading (>2 wt%), the mechanical properties of composites do not fit established theories due to agglomeration of titanate nanostructures.

 Composites are superior to conventional materials due to their high strength to weight ratio. Of late, because of environmental concerns, natural fibres are finding their places in composites. However, their hygroscopic nature affects the mechanical properties of the composites adversely. Applications of composites for decking, flooring and outdoor facilities have made it necessary to evaluate the water uptake characteristics of natural fibre composites. The objective of this paper is to review the water absorption behavior, its effect on mechanical properties and the efforts to reduce the absorption of various natural fibre reinforced composites. Keywords–Natural fibres, Water absorption, Hydrophilic, Mechanical properties

The economic exploitation of rubber tree (Hevea brasiliensis) usage is primarily directed toward latex extraction. After the productive life of the rubber tree forest, the managed area is harvested for planting reformulation. The harvested wood is most often used for energy generation purposes. The aim of this work was to study the feasibility of using rubberwood waste and castor oil-based polyurethane resin in the production of particleboards. Homogeneous and heterogeneous panels were made with nominal dimensions of 500 x 500 mm and thicknesses of 10 mm using particles from GT1 and RRIM600 clones of the rubber tree and 12% castor oil-based polyurethane adhesive. The panels were pressed at 140 °C for 12 min with 40 kgf/cm2 specific pressure. Density, moisture content, thickness swelling, water absorption for 2 and 24 h, static bending, and internal bonding determinations were performed according to the Brazilian Standard (NBR) 14810-3 (2006) for the physical-mechanical panel charact...

Purpose: The aim of this study was to investigate the possibility of improving the tribological properties and thermal conductivity of composites with structural modification of polyamides by the additions of copper and graphite. Design/methodology/approach: The study involved testing polyamide composites containing metallic powder. As the matrix was used polyamide 6 Tarnamid 27 Natural produced by Azoty Tarnow, which strengthened copper, graphite or molybdenum disulfide with varying participation in the composite. Taken tensile test, Brinell hardness, thermal conductivity and the tribological wear resistance. Analyzed the influence of the type of dopant and the participation of the studied property. Findings: The study showed the desirability of the use of graphite and copper as fillers polyamide. The resulting composites are characterized by satisfactory mechanical properties and thermal conductivity. Applied fillers also showed a positive effect on the value of the coefficient of...

The economic exploitation of rubber tree (Hevea brasiliensis) usage is primarily directed toward latex extraction. After the productive life of the rubber tree forest, the managed area is harvested for planting reformulation. The harvested wood is most often used for energy generation purposes. The aim of this work was to study the feasibility of using rubberwood waste and castor oil-based polyurethane resin in the production of particleboards. Homogeneous and heterogeneous panels were made with nominal dimensions of 500 x 500 mm and thicknesses of 10 mm using particles from GT1 and RRIM600 clones of the rubber tree and 12% castor oil-based polyurethane adhesive. The panels were pressed at 140 °C for 12 min with 40 kgf/cm 2 specific pressure. Density, moisture content, thickness swelling, water absorption for 2 and 24 h, static bending, and internal bonding determinations were performed according to the Brazilian Standard (NBR) 14810-3 (2006) for the physicalmechanical panel characterization. The results show that using Hevea brasiliensis in particleboard production is viable. However, multilayer boards exhibited better results.

Nanocomposites fabricated using epoxy resin systems modifed with nanofibers are likely to play an important role in various automotive, aerospace, marine and other applications where poymeric resins are widely used. Polymer nanofibers and glass nanofibers are of, considerable interest in many applications as secondary reinforcement in structural composites. In the present study, epoxy resin was modified with chopped electrospun glass nanofibers. The electrospinning technique is an effective method of producing uniform diameter nanofibers with both random and oriented fiber mats. Tetraethyl Orthosilicate (TEOS) sol-gel was used to produce uniform thickness of nonwoven nanofiber mat. This paper presents fabrication and testing of two phase nanocomposites. Paper presents comparison of mechanical properties of EPON 862/W resin system with and without TEOS electropsun nanofibers (ENFs). Two different types of nanoreinforcements were investigated, the first one used chopped nanofiners with weight percentages ranging from 0.08% to 0.4 % of resin weight in nanocomposites. The second type of nanocomposites were fabricated using nanofiber mats rather than chopped nano fibers. All nanocomposite panels were fabricated with uniform thickness and were tested using ASTM standards. The present study indicated that chopped nanofibers disperesed in epoxy resinunder tensile loading have better mechanical properties as compared to the properties of nanocomposites fabricated using TEOS elecrospun nanofiber mats and neat resin.

New epoxidized, p-cresol novolac resin (PCN) and p-ethyl phenol novolac resin (PEPN) where synthesized from the reaction of p-cresol or p-ethyl phenol with formaldehyde in molar ratio 1:0:0:8 in the presence of oxalic acid as a catalyst. Subsequently, the obtained products wee reacted with substantial amount of epichlorohydrin at 90°C in basic medium affording EPCN and EPEPN, respectively. Two different crosslink agents, ethylenediamine (EDA) and hexamethylenetetamine (HMTA) were used as crosslink agent for curing of the epoxy novolac resins EPNC and EPEPN. The structure of PCN and PEPN were characterized by FTIR and 1HNMR spectroscopies. The thermal properties of cured EPCN and EPEPN were investigated using thermal gravimetric analyzer (TGA). The cured products showed better thermal stability when HMTA used as a crosslink agent. The adhesive strength of the new epoxy novolacs were measured on wood-wood bonding joints by means of compression-, tensile-, strain-, bending-, shear stre...

The synthesis of methylcellulose (MC) from chemically purified cellulose extracted from sugarcane bagasse was carried out with dimethyl sulfate (DMS) in the presence of sodium hydroxide and acetone as solvent under heterogeneous conditions and the degree of substitution (DS) was determined as 1.44. 3D porous composite of methylcellulose/polyvinyl alcohol (MC/PVA) was prepared by freeze drying process. The synthesized products were characterized by FE-SEM, FTIR, 1H NMR and XRD. Porosity was calculated as 86% and the binary image, histogram of pores distribution of MC/PVA porous composite were investigated by ImageJ processing technique which shows the roughness of the topographical structure. Synthesized methylcellulose enhances the value to this abundant agro-industrial residue and may extend its range of biomedical applications.► Extraction of cellulose from agro-waste sugarcane bagasse. ► Synthesis of methylcellulose from cellulose with 1.44 degree of substitution. ► Porous composite of methylcellulose/poly(vinyl alcohol) blend by freeze drying process. ► 86% porosity of porous composite was calculated using gravimetric measurement. ► Topographical pore distribution of porous composite by image analysis using ImageJ software.