Effect of grain size of coconut shell particles on the structural properties of coconut shell (CNS) powder and areca husk fly ash reinforced polymeric composites

Recent developments have focused on utilizing natural fibers, such as hemp and coconut shell, which are biodegradable, environmentally friendly, and readily available. When combined with polymers to enhance strength while minimizing composite weight, such green composites have attracted attention for applications in manufacturing, packaging, aerospace, sports, housing, and other sectors. This study determined the fabrication of epoxy-based composites reinforced with coconut shell powder (CSP) of varying grain sizes and areca husk fly ash as a novel matrix for improved green polymer composites. The mechanical properties, including tensile and flexural strengths, were evaluated. Results showed that CSP-reinforced composites with a grain size of 150 µm exhibited the highest tensile strength (19.48 MPa) and flexural strength (58.52 MPa), whereas composites with a 600 µm grain size showed the lowest values (11.79 MPa and 44.97 MPa for tensile and flexural strengths, respectively). Composites with 600 µm exhibited reductions of 39.48% in tensile strength and 33.91% in tensile modulus, and 23.15% in flexural strength and 21.38% in flexural modulus compared to CSP–areca husk fly ash composites with 150 µm grain size. SEM analysis indicated that smaller grain sizes provide a larger surface area for resin adhesion, enhancing the mechanical performance of the composites. These lightweight, natural fiber-reinforced composites show potential as sustainable alternatives to conventional materials in structural, locomotive, and household applications.