Characterization and performance analysis of natural fibres as reinforcement in polymer composite

Abstract

A systematic study has been carried out in the current study to investigate the mechanical (tensile strength, Young’s modulus and strain to failure) and physical properties (SEM, FTIR and TGA) of jute, bamboo and coir (brown and white) single fibres. Subsequently, unidirectional as well as woven fabric composites were manufactured and tensile, flexure (longitudinal and transversal both directions were conducted for unidirectional [UD] composites) and impact properties of the composites were determined. Void free composite have been made by using vacuum technique in case of unidirectional composites. On the other hand, Hot press and Resin Transfer Molding (RTM) processes were conducted to fabricate woven jute fabric composites. Water absorption tests were also carried out in this study for woven jute fabrics composites using various fibre volume fractions and polymers. The tensile properties (tensile strength, Young’s modulus and strain to failure) were determined by varying span length in case of single fibres. Tensile properties were carried out for woven jute fabric composites before and after water absorption test. Scanning Electron Micrograph (SEM), Fourier Transformation Infra Red (FT-IR) and Thermo Gravimetric Analysis (TGA) were also carried out to determine the physical properties of fibres in order to correlate with their strength; Young’s modulus and strain to failure and physical properties were observed in terms of composites. The study has revealed that with increasing test span length of single fibres, Young’s modulus increases and tensile strength as well as strain to failure decreases. This is because no extensometer could be used in this test set-up and machine displacement (denoted by α) is used for the modulus determination. It is also attributed that larger span length helps to minimize the machine displacement compared to smaller ones. At longer span lengths, the relative effect of slippage in the clamps is smaller. The Young’s modulus and strain to failure were corrected by using newly developed equations. Among all fibres, bamboo fibres had the highest Young’s modulus values. Jute fibre had smoother surface and good thermal properties (burnt at ≈ 2560C) compared to other three examined fibres. In case of UD composites, analytical results showed good agreement with theoretical values. In comparison between jute and bamboo fibre UD composites, it is observed that bamboo fibre showed better results in terms of tensile strength and jute fibre showed better values in terms of Young’s modulus. Bamboo fibre showed superior flexure strength with longitudinal distribution while jute fibre composite showed the good results in strength with transverse fibre distribution. Fibre distribution was not aligned uniformly for both bamboo and jute fibre in UD composites and in case of jute fibre composites some fibre have broken during processing. Composite containing higher percentages of fibre showed good tensile and impact behaviour. 4 ply shows better flexural properties for both polyester and polyvinylchloride (PVC) composite. Both tensile and flexural properties decreased after water absorption. It is observed from the SEM image that fibre at first debonded during loading tensile force and then fibre pulled out from the composite. Jute/Polyester composites showed better flexural properties. Tendency of resistance to water absorption of polyvinylchloride composite was higher than that of polyester composites because of its interfacial bonding. SEM images suggested that there is a good interlocking between jute and polyester composite compare to jute-PVC composite interlocking.