Mechanical Properties of Micro-sized Walnut Shell Particulate-Filled Polyester Composites

This study focuses on the development of a polymer composite using bio-based particulate fillers. In this case, polyester serves as the matrix material, while micro-sized walnut shell particulates (WSP) are used as the filler. Composites were fabricated with varying filler content, ranging from 5 wt. % to 20 wt. %, and the impact of filler loading on the mechanical properties—such as tensile strength, flexural strength, compressive strength, and hardness—was thoroughly investigated. The experimental results reveal that incorporating micro-sized walnut shell particulates enhances the mechanical properties of the composite. Notably, the tensile strength of the composite increased by 16.6%, while the flexural strength improved by 21.6% at a 20 wt. % filler loading compared to the neat polyester. Both tensile modulus and flexural modulus showed a linear increase with filler content, reaching maximum values of 2322 MPa and 2523 MPa, respectively, at 20 wt. % filler loading. Additionally, the compressive strength of the neat polyester was found to be 86.5 MPa, which increased by 19.4% to a higher value when 20 wt. % of walnut shell particulates were added. The hardness of the composite also exhibited a significant rise, attaining a value of 0.832 GPa at 20 wt. % WSP content—an improvement of 59.4% over the neat polyester.