Effect of variation in frequencies on the viscoelastic properties of coir and coconut husk powder reinforced polymer composites

This study describes an investigation into the physical, mechanical and dynamic mechanical properties of coir (coconut fiber) and coconut husk particulates reinforced polymer composites which were prepared by the hot press method. The impact of coir loading on the physical and mechanical properties of the composites was examined in more detail. It was observed that the values of rigidity, flexural strength and hardness were raised up to 7.1 MN/m², 17.0 MPa and 92.5 MN/m², with increase in coir length. Impact energy reduced proportionately with increment in fiber length (from 0.78 J at no fiber inclusions to 0.42 J at 30 mm fiber length). With the increment of fiber length from zero to 10 mm, a reduction in density and increment in water absorption properties was observed. These properties (density and water absorption) remained with increase in fiber length for a given structure of matrix/filler. The surface morphology of composite with longest fiber length (30 mm) was investigated. Fiber pullout and little voids on composite surfaces were seen. Fundamentally, these regions can encourage the matrix impregnation onto the fiber. At the highest fiber loading and at highest frequency (10 Hz) used during the dynamic mechanical examination, the tan δ peak gets widened, underlining the enhanced fiber/matrix grip. Also, extra and noticeable peaks were seen at higher frequency conditions in the tan δ curves, because of the interlayer phenomenon.