Sound Absorption and Mechanical Characterization of Neem Gum and Coconut Dust-Based Hybrid Epoxy Composites

Abstract

This study focuses on the development and characterization of lightweight hybrid epoxy composites reinforced with neem gum (NG) and coconut dust (CD), targeting sustainable structural applications. Composites were fabricated with a constant 70% epoxy resin and varying NG and CD contents (5NG25CD, 10NG20CD, 15NG15CD, 20NG10CD, and 25NG5CD). Among these, the 15NG15CD composition demonstrated optimal performance, achieving a tensile strength of 42.1 MPa, flexural strength of 83.2 MPa, impact strength of 6.12 J, and Shore D hardness of 82. Water absorption tests showed significantly reduced moisture uptake (25.6%), indicating enhanced dimensional stability. Sound absorption tests revealed a peak sound absorption coefficient of 0.35 for the 20NG10CD composite, followed by 0.33 for 15NG15CD, indicating effective acoustic damping characteristics across all variants (ranging from 0.24 to 0.35). Scanning electron microscopy (SEM) revealed strong interfacial adhesion and uniform particle dispersion within the epoxy matrix, contributing to superior mechanical properties. These eco-friendly, lightweight composites exhibited excellent strength, moisture resistance, and versatility, making them suitable for lightweight structural components, automotive interiors, and sustainable packaging solutions.