Mechanical, morphological and interfacial characterization of peanut shell powder modified milkweed–Aristida hystrix hybrid fiber reinforced epoxy composites

Abstract

The present study investigates the effect of fiber hybridization and peanut shell powder filler incorporation on the mechanical and interfacial performance of milkweed and Aristida hystrix fiber reinforced epoxy composites. A series of hybrid composites were fabricated by maintaining a constant epoxy content (60 wt%) and peanut shell powder filler content (10 wt%), while systematically varying the weight fractions of milkweed and Aristida hystrix fibers. Mechanical characterization was carried out through tensile, flexural, impact, hardness, interlaminar shear strength (ILSS), tensile modulus, and flexural modulus tests. The results indicate a pronounced improvement in mechanical properties with increasing hybridization, achieving optimum performance at an equal fiber distribution (H3: 15 wt% milkweed + 15 wt% Aristida hystrix). The H3 composite exhibited the highest tensile strength (61 MPa), flexural strength (86 MPa), impact strength (10.2 J), hardness (83 Shore D), ILSS (12.1 MPa), tensile modulus (3.5 GPa), and flexural modulus (4.1 GPa). Scanning electron microscopy (SEM) analysis of fractured surfaces revealed improved fiber–matrix interfacial adhesion, reduced fiber pull-out, and uniform filler dispersion in the optimized hybrid composites, corroborating the enhanced mechanical performance. In contrast, the unfilled composite exhibited interfacial debonding and void formation, leading to inferior properties. The combined use of fiber hybridization and bio-based peanut shell powder filler is thus demonstrated as an effective approach for developing sustainable, high-performance epoxy composites suitable for lightweight structural applications.