A novel hybrid composition of sisal fibrils and kenaf fibers has been introduced first time as reinforcement in composite preparation for the environmental friendly high strength electrical insulation applications. Hybrid reinforcement was increased from 10 to 40 wt% in unsaturated polyester resin. The sisal fibril used in this study was extracted from sisal fiber. Alkali treatment was employed and FTIR analysis was done to study its effect on sisal fibrils and kenaf fibers. A positive hybridization effect was observed for the composites. Hybrid composite showed 24 and 18% increase in tensile strength, 30 and 36.4% increase in flexural strength, and 196.3 and 196% increase in impact strength as compared to the composites having same loading of 40 wt% with sisal fibrils and kenaf fibers, respectively. Scanning electron microscopy of the fractured mechanical testing samples was carried out to understand the nature of fibril/fiber/matrix interface. Electrical characterization showed high electrical insulation capability of the hybrid composites. Thermal stability of hybrid composites was also found higher than sisal fibrils and kenaf fibers reinforced composites. A comparative study of properties of sisal fibril/kenaf fiber reinforced hybrid polyester composites with various single and hybrid fiber composites is done. It has been concluded that the developed novel hybrid composite has the potential to replace various existing natural and synthetic fiber composites. POLYM. COMPOS., 40:664–676, 2019. © 2017 Society of Plastics Engineers

Environment friendly high strength electrical insulating material was developed using fibrillated sisal and epoxy resin. Coarse sisal fibers were fibrillated into fibrils using mechanical disintegration. Fibrillated fibers provided a high strength, renewable, light weight dielectric variant reinforcement to epoxy resin. Different weight fractions (10–35%) of Agave sisalana fibrils were thoroughly mixed with epoxy resin system to develop composites. Chemical treatment was employed to improve the surface as well as chemical composition of sisal fibril to enhance mechanical strength and electrical insulating properties of composite. Chemical treatment of fibrils improved the tensile strength from 47.4 to 51.99 MPa at 35 wt% loading of sisal fibril in epoxy composite. A few important predictive models namely rule of mixture, Halpin–Tsai, Nielson Chen and Manera model were compared with the experimental values obtained in this present study. Nielson Chan model predicted the experimental data most accurately with an average relative error of 15.82%. Similarly the dissipation factor touched a level of 0.097, thereby indicating good insulation properties of composite. The tests were conducted at lower frequency range to higher frequency range 1–10 kHz and the composite material exhibited stability at high frequency range as compared to low frequency range. POLYM. COMPOS., 39:E2175–E2184, 2018. © 2017 Society of Plastics Engineers

This paper presents an experimental method for tensile testing of unidirectional carbon fibre composites. It uses a novel combination of a new specimen geometry, protective layer, and a robust data analysis method. The experiments were designed to test and analyze unprotected (with conventional end-tabs) and protected (with continuous end-tabs) carbon fibre composite specimens with three different specimen geometries (straight-sided, butterfly, and X-butterfly). Initial stiffness and strain to failure were determined from second-order polynomial fitted stress–strain curves. A good agreement between back-calculated and measured stress–strain curves is found, on both composite and fibre level. For unprotected carbon composites, the effect of changing specimen geometry from straight-sided to X-butterfly was an increase in strain to failure from 1.31 to 1.44%. The effect of protection on X-butterfly specimens was an increase in strain to failure from 1.44 to 1.53%. For protected X-butterfly specimens, the combined effect of geometry and protection led to a significant improvement in strain to failure of 17% compared to unprotected straight-sided specimens. The observed increasing trend in the measured strain to failure, by changing specimen geometry and protection, suggests that the actual strain to failure of unidirectional carbon composites is getting closer to be realized.

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