Impact of fibre surface treatment on the mechanical properties of waste mulberry silk/epoxy composites

Abstract

Natural fibre-reinforced composites are increasingly investigated as sustainable alternatives to synthetic materials; however, their hydrophilic nature and weak fibre–matrix adhesion often limit structural performance. This study explores the reinforcement potential of waste mulberry silk fabric, sourced from discarded textiles, in epoxy composites, with emphasis on the role of silane surface treatment. Raw and γ-aminopropyltriethoxysilane (APTES)-treated silk fabrics were incorporated into epoxy resin through a hand lay-up process at varying fibre weight fractions (11.13–33.38 wt%). Mechanical tests, including tensile, flexural, interlaminar shear strength (ILSS), impact strength, and hardness, were conducted in accordance with ASTM standards. Silane-treated composites consistently outperformed untreated counterparts, exhibiting nearly twofold improvements in tensile strength and modulus, ~20% higher flexural strength, ~35–45% higher ILSS, and substantially enhanced impact resistance. Hardness values and dimensional stability under moisture exposure were also superior in treated composites. SEM analysis confirmed that silane modification introduced surface roughness and improved interfacial bonding, leading to reduced fibre pull-out and enhanced stress transfer. The findings demonstrate that silane-treated waste mulberry silk fabrics are effective reinforcements for epoxy, enabling lightweight, high-strength, and moisture-resistant composites suitable for engineering and structural applications.