Development and multi-response optimization of sustainable hemp fibre/cassia gum reinforced polyester hybrid composites for structural and insulation applications

Abstract The growing demand for lightweight and sustainable materials has prompted the development of natural fibre-reinforced polymer composites with multi-functional properties. In this study, hemp fiber/Cassia gum reinforced polyester hybrid composites (HC0–HC5) were prepared by hand lay-up and then compression molding. The effect of Cassia gum loading on mechanical, thermo-mechanical, thermal, dielectric, morphological, and water absorption properties was systematically investigated. Tensile, flexural, impact, dynamic mechanical, dielectric strength, water absorption, SEM, FTIR, DSC, TGA, and DTG analyzes were carried out. Overall differences among the HC0-HC5 formulations were evaluated by one-way analysis of variance (ANOVA) and equal-weight multi-response optimization. The overall performance enhanced with increasing Cassia gum loading up to HC3. The HC3 formulation showed the best overall performance among the investigated formulations, with tensile strength of 46.5 MPa, flexural strength of 69.3 MPa, impact strength of 5.70 kJ/m 2 , storage modulus of 4250 MPa, dielectric strength of 16.3 kV/mm, and Tmax of 411 °C. The water absorption increased with Cassia gum loading, but HC3 showed the best overall performance index of 91.4%. ANOVA showed significant differences in formulations overall ( p < 0.05). These results provide a base for further research on sustainable hemp fibre/Cassia gum reinforced polyester composites for multifunctional engineering applications.