Green composites were obtained by incorporation of short jute fibres in natural rubber matrix using a laboratory two-roll mill. The influence of untreated fibre content (1, 2.5, 5, 7.5 and 10 phr) on the mechanical properties, dynamic mechanical properties, swelling properties was examined. The behaviour of prepared green composites under cyclic compression was also investigated. Fibre dispersion in rubber matrix was studied by scanning electron microscopy. The highest tensile strength (21.1 MPa) and highest tear strength (39.9 N/mm) were found for composites containing 2.5 and 5 phr of short jute fibres, respectively. The results also suggested that increasing fibrous filler content resulted in increasing of tensile moduli 100, 200 and 300 % of elongation and hardness, and decreasing of rebound resilience and abrasion resistance of prepared jute/natural rubber composites. The cyclic compression test showed that increasing the amount of short jute fibres in the rubber matrix is related to increase of the energy dissipated in the composite. The incorporation of short jute fibres into the rubber matrix improves the stiffness of the composites, and it is related to the interaction between fibre surface and rubber matrix. The application of short fibres in higher amounts leads to formation of fibre agglomerates reducing the mobility of the rubber polymer chains. The mentioned agglomerates act as defects in rubber matrix, which caused decreasing of some properties, e.g. relative elongation at break. 相似文献
Because of their properties, flax fibres can be used as reinforcing material in composites, e. g. as substitute for glass fibres in composites with polypropylene. A major drawback of this application is the high water adsorption of the natural fibre and its low adhesion to the hydrophobic polymer. Therefore, improvement of adhesion to the polypropylene matrix by application of bifunctional silanes was investigated. While silanes with alkyl groups did not significantly improve the fibre-matrix adhesion, it was found that silanes which carry functional groups capable of reacting by formation of free radicals under processing conditions lead to a remarkable improvement. For silanes with vinylic and methacrylic groups, the dependence of adhesion on the nature of hydrolysis catalyst, on the compound which initiates the free-radical reaction, and on the degree of fibre silylation was investigated. The degree of silylation was varied under optimum concentration conditions. 相似文献
Epoxy resins and their fibre or particulate composites are widely used in various industries, including building, naval, aircraft, automotive and aerospace. Modern polymer science and technology focus on the development of green polymers and composites. There are two major areas of interest in the case of epoxy resins: the development of bio-based resins and the production of composites with natural fibres. One of the most interesting challenges is developing fully bio-based composites: that is, epoxy resins based on renewable resources and natural fibres. This paper presents a review of literature on epoxy resins and hardeners based on renewable resources (especially vegetable oils) and epoxy composites with natural fibres. We also describe some of the effective methods of improving the mechanical properties of epoxy–natural fibres composites, including chemical modification of the fibre surface and the application of hybrid reinforcements. 相似文献
AbstractThe deformation behaviour of the new high performance polymer fibres, poly(p-phenylene benzobisoxazole) (PBO) and polypyridobisimidazole (PIPD) and their adhesion to an epoxy composite matrix have been investigated. Both fibres give well defined Raman spectra, and the deformation micromechanics of PBO and PIPD single fibres and composites were studied from stress induced Raman band shifts. Single fibre stress-strain curves were determined in both tension and compression, thus providing an estimate of the compressive strength of these fibres. It was found that the PIPD fibre has a higher compressive strength (~1 GPa) than PBO (~0·3 GPa) and other high performance polymer fibres, because hydrogen bond formation is possible between PIPD molecules. It has been shown that when PBO and PIPD fibres are incorporated into an epoxy resin matrix, the resulting composites show very different interfacial failure mechanisms. The fibre strain distribution in the PBO-epoxy composites follows that predicted by the full bonding, shear lag model at low matrix strains, but deviations occur at higher matrix strains due to debonding at the fibre/matrix interface. For PIPD-epoxy composites, however, no debonding was observed before fibre fragmentation, indicating better adhesion than for PBO as a result of reactive groups on the PIPD fibre surface. 相似文献
The compatibility of matrix and fibre properties is one of the key parameters in the successful design of fibre reinforced cementitious composites. In order to achieve the desired performance, the properties of each constituent of composite should be properly configured. The aim of this study was to investigate the performance of two polymer based micro-fibres (polypropylene and polyvinyl alcohol) in different matrices (high strength and comparatively low strength with fly ash incorporation) which were designed to contain considerably high amounts of fibres (1% by volume) while maintaining their self-compactability. The fresh state thixotropic behaviour of fibre reinforced matrices was minimised by proper adjustment of water/cementitious material ratio and admixture dosage. The mechanical properties (first crack strength and displacement, flexural strength and relative toughness) of prismatic composite samples were compared by three point flexural loading test. The typical behaviours of selected composites and collapse mechanisms of PP and PVA fibres in these matrices were characterised by microstructural studies. It was concluded that, a high strength matrix with a high strength fibre give the best performance from the view point of flexural strength and toughness performance. However, incorporation of fly ash did not cause a significant reduction in composite performance possibly due to its enhancing effect on matrix–fibre interface adhesion. The possibilities and suggestions to further improve the performance of the composites were also discussed. 相似文献
This study reports the synthesis and mechanical properties of new inorganic polymer (geopolymer) composites unidirectionally reinforced with 4–10 vol.% natural cellulose-based fibres (NZ flax, phormium tenax). The geopolymer matrix was derived from dehydroxylated kaolinite-type clay. The mechanical properties of the fibre-reinforced composites improve with increasing fibre content, achieving ultimate flexural strengths of about 70 MPa at 10 vol.% fibre content. This represents a significant improvement on the flexural strength of the unreinforced geopolymer matrix (about 5.8 MPa), and all the composites show graceful failure, unlike the brittle failure of the matrix. Scanning electron microscopy was used to study the morphology of the fibre-matrix regions and a combination of thermogravimetric analysis (TGA) and thermal shrinkage measurements of these composites suggests that despite the formation of microcracks due to water loss from the geopolymer matrix, the fibres are thermally protected by the matrix up to 400 °C. The flax fibres do not appear to be compromised by the alkaline environment of the matrix, suggesting new possible applications for these low-cost simply prepared construction materials. 相似文献
Mechanical properties of natural rubber/allyl acrylate and allyl methacrylate grafted cellulose fibre composites are presented. Stress/strain measurements and dynamic mechanical measurements indicate that the adhesion between grafted fibres and matrix is better than that in samples containing untreated cellulose fibres. This makes it possible to vary the composite properties by varying the fibre type and/or fibre amount. 相似文献
Preparation and properties of poly(propylene)‐poly(propylene) composites have been investigated. Poly(propylene) fibres of varying diameter have been incorporated in a random ethylene co‐poly(propylene). The composites prepared from the same semi‐crystalline polymer in the matrix and reinforcement have lead to inherently strong interfacial bonding between the two phases of the same polymer. The composites demonstrated enhanced stiffness, which increased with fibre diameter. The structure, thermal, static and mechanical properties of poly(propylene) long fibre reinforced random co‐poly(propylene) composites have been studied with reference to the fibre diameter. The matrix and fibre components retained their separate melting temperatures. After melting, the two phases remained separate and showed their individual crystallization temperatures on cooling, and melting temperatures on a second heating. The melting temperature of the poly(propylene) fibres increased after formation of the composites. The compression molding of the composites at a temperature below the melting temperature of the fibres caused annealing of the fibre crystals. By incorporation of long poly(propylene) fibre into random co‐poly(propylene), the glass transition, storage and static modulus have been found to be increasing and composite with the largest fibre diameter shows better properties. Transcrystallization of the matrix poly(propylene) was observed.
Optical microscopy of composites with fibre diameter 68 μm. 相似文献
The axial mechanical, electrical and thermal properties of carbon nanotubes (CNTs) can be exploited macroscopically by assembling them parallel to each other into a fibre during their synthesis by chemical vapour deposition. Multifunctional composites with high volume fraction of CNT fibres are then made by direct polymer infiltration of an array of aligned fibres. The fibres have a very high surface area, causing the polymer to infiltrate them and resulting in a hierarchical composite structure. The electrical and thermal conductivities of CNT/epoxy composites are shown to be superior to those of equivalent specimens with T300 carbon fibre (CF) which is widely used in industry. From measurements of longitudinal coefficient of thermal expansion (CTE) of the composites we show that the CTE of CNT fibres is approximately ?1.6 × 10?6 K?1, similar to in-plane graphite. The combination of electrical, thermal and mechanical properties of CNT fibre composites demonstrates their potential for multifunctionality. 相似文献
Tensile tests were performed on two different natural fibre composites (same constituent material, similar fibre fraction and thickness but different weave structure) to determine changes in mechanical properties caused by various aqueous chemical treatments and whether any permanent changes remain on drying. Scanning electronic microscopic examinations suggested that flax fibres and the flax/polypropylene interface were affected by the treatments resulting in tensile property variations. The ductility of natural fibre composites was improved significantly under wet condition and mechanical properties (elongation-to-failure, stiffness and strength) can almost retain back to pre-treated levels when dried from wet condition. Preheating is usually required to improve the formability of material in rapid forming, and the chemical treatments performed in this study were far more effective than preheating. The major breakthrough in improving the formability of natural fibre composites can aid in rapid forming of this class of material system. 相似文献
The structural performance of polymer composites reinforced with plant fibres when exposed to fire was experimentally evaluated and compared against an E‐glass fibre laminate. Fire testing under combined one‐sided radiant heating and static tensile loading revealed that flax, jute, or hemp fibre composites experience more rapid thermal softening and fail within much shorter times than the fibreglass laminate, which is indicative of vastly inferior structural performance in fire. The plant fibre composites soften and fail before the onset of thermal decomposition of the plant fibres and polymer matrix, whereas the E‐glass fibres provide the composite with superior tensile properties to higher temperatures and higher applied tensile stresses. The tensile performance of the three types of plant fibre composites in fire was not identical. When exposed to the same radiant heat flux, the flax fibre composite could withstand higher tensile stresses for longer times than the hemp and jute laminates, which showed similar performance. 相似文献
AbstractThis paper presents an overview of the research performed to date by a Swedish interdisciplinary team of scientists striving to develop multifunctional composite materials for storage of electric energy in mechanical load paths. To realise structural batteries from polymer composites, research pursued on carbon fibres for use as negative electrode in the battery as well as on polymer electrolytes for use as polymer matrix in the composite is reported. The work on carbon fibres comprises characterisation of the electrochemical capacity of commercial carbon fibre grades and how this is affected by mechanical load. Co-polymers are studied for their multifunctional performance with respect to lithium ion conductivity and stiffness. Also, rational processing of these polymer electrolytes and the effect of processing on their properties are addressed. 相似文献
A new approach to manufacture short-fibre-reinforced ceramic matrix composites (CMC) by mixing carbon fibres, ceramic fillers and a viscous ceramic precursor by means of a plastic forming technique is introduced. To transform the composite from the polymer into a nitride ceramic state, a two-step process consisting of pyrolysis and nitridation is applied. Transformations of the polymer-modified RBSN (PMRBSN) during this process are examined in terms of dimensional changes, porosity and phase composition. The role of the precursor during the processing and nitridation sequence, aspects concerning fibre shortening and packing and the effects on the material properties as Young's modulus, strength, hardness, porosity, crack deflection and fibre pullout are discussed. 相似文献
AbstractIn order to enhance the bonding force of sisal fibres (SF) and polymer matrix, different surface modifiers (alkali, coupling agent and borax) were used to treat the fibres. The SF/phenol formaldehyde (PF) resin composites were prepared through compression moulding. Thermal properties of the treated SFs and fibre composites were studied by thermogravimetric analysis and thermal expansion analysis. The effect of SF modification on the friction and wear properties of composites was investigated using wear tester under dry condition. The treated fibre surface and the worn surfaces of SF/PF composites were observed by SEM. The results showed that the surface of SF became rough after borax treatment, and the initial decomposition temperature increased by 13·6°C, compared to untreated SF. Thermal stability and wear properties of the PF composites with treated fibre were obviously increased due to the fibre modification. For example, wear volume of the composites with sisal treated by borax decreased by 73·3%. Scanning electron microscopy photos showed that the wear mechanism changed from fatigue wear to slight plough wear. 相似文献
Silicon-based preceramic polymers are attractive candidates for the manufacture of high temperature and corrosion resistant ceramics, particularly in regard to the formation of a ceramic matrix in long fibre reinforced ceramic matrix composites (CMCs). The manufacture of CMCs constitutes of the infiltration of fibre preforms followed by a subsequent crosslinking and pyrolysis of the Si-precursor, yielding an amorphous ceramic matrix. However, due to the inherent shrinkage of ceramic precursors, a high number of polymer impregnation and pyrolysis (PIP) cycles is required to obtain dense composites. Nevertheless, their microstructure is characterized by large interbundle pores which show a negative impact on the mechanical properties.In order to improve the performance of the long fibre reinforced CMCs as well as to accelerate the manufacturing process, a novel approach was investigated. Thereby, micro-sized powders of Al and Ti are used as active fillers. The powders were strewed between the fabric plies and infiltrated by the resin transfer moulding (RTM) technique. Since reactions with the polymer matrix are associated with a volume increase during pyrolysis, a more dense ceramic matrix is obtained.The processing of the CMCs employs the commercial polysilazanes CERASET SN and VL20 as preceramic precursors. The reinforcement constitutes of Tyranno SA fibres. To densify the composites, up to five PIP cycles were performed. CMC samples were aged in air to evaluate the impact of oxidation on microstructure and mechanical properties. Microstructural characterization was conducted using both optical and electron microscopy. The conversion of the filler particles was analysed by means of EDX and XRD. 相似文献
The advantage of basalt fibres in comparison to glass fibres was demonstrated. The process parameters for production of basalt
fibre are reported. The manufacturing processes in processing polypropylene composites with low combustibility and poly(ethylene
terephthalate) composites filled with basalt fibres in lines based on a cascade screw-disk extruder are examined. Technology
for obtaining polymer coatings using composites with basalt flakes and their properties are described.
Translated from Khimicheskie Volokna, No. 3, pp. 59–63, May–June, 2008. 相似文献