Physico-mechanical, thermal and dynamic mechanical behaviour of natural-synthetic fiber reinforced vinylester based homogenous and functionally graded composites

In the present work, hybrid natural-synthetic fiber (bagasse and Kevlar) reinforced vinylester resin based homogeneous and functionally graded composites have been fabricated. The physical, mechanical, thermal and dynamic mechanical properties of the fabricated composites have been studied. The physical properties like, density and void content of the investigated composites was remains in the range of 1.136-1.157 g cm−3 and 1.21%-1.78% respectively and found to increase with increase in fiber content. The functionally graded composites exhibited highest hardness, flexural strength and impact energy up to 70 HRL, 46.16 MPa and 0.463 J, respectively. Comparatively to the homogeneous composites, an increase of 4% in hardness, 6% in flexural strength and 17% in impact energy recorded for the graded composites. The composites have been characterized for their thermal stability behaviour through thermo-gravimetric analysis (TGA). In general, it has been found that fiber reinforced composites exhibit a relatively higher magnitude of thermal stability as compared to pure vinylester resin. With increased temperature, the degradation rate accelerates leading to reduction in thermal stability behaviour. Finally, the composites have been subjected to dynamic mechanical analysis (DMA) to determine loss modulus, storage modulus and loss-tangent as a function of temperature. Results indicated that storage and loss modulus of the homogeneous and graded composites exhibit an improvement as compared with pure vinylester resin. The glass transition temperature of the neat vinylester resin, corresponding to the damping peak, was 96 °C, whereas for fiber reinforced composites it increased by nearly 2 °C-6 °C and remains in the range of 98 °C-102 °C.