Impact of sizing on fiber-matrix interface of basalt and glass fiber reinforced infusible acrylic thermoplastic and bio-epoxy thermoset composites
A.K. Sidharth, Maurice N. Collins, A.J. Comer
Abstract
• Interfacial properties studied via nanoindentation and single fiber push-out tests. • Tailored sizing needed for sustainable resin compatibility in composites. • Sizing improved basalt thermoset interface but hindered basalt thermoplastic. • Glass fiber sizing is not optimal for bio-epoxy and thermoplastic resin systems. • Interface analysis reveals distinct failure modes across fiber and matrix types. This study explores the impact of commercial fiber sizing on the interfacial properties of glass and basalt fiber-reinforced thermosetting (Infugreen©) and thermoplastic (Elium©) composites, manufactured via vacuum-assisted liquid resin infusion. Sized and desized fibers were evaluated to assess the effect of sizing on fiber–matrix interactions. Single fiber push-out tests were used to determine the Interfacial Shear Strength (IFSS), while nanoindentation was used to assess the interphase thickness. Results indicate that sizing significantly impacts basalt fibers differently in thermoplastic versus thermoset matrices. In thermoplastic composites, sizing led to a notable reduction in IFSS and interphase thickness, while in thermoset composites, IFSS was enhanced with a thicker interphase in sized samples. For glass fibers, the sizing marginally influenced IFSS in thermoplastic composites, resulting in an interfacial shear strength of ∼40 MPa, yet decreased IFSS in thermoset composites, suggesting suboptimal compatibility with the sustainable epoxy matrix used. Thermoplastic composites exhibited matrix cracking close to the interface, while the thermoset specimens exhibited clean interfacial debonding. These findings highlight the need for tailored sizing formulations to ensure compatibility with emerging resin systems, optimizing interfacial adhesion and mechanical performance in fiber-reinforced composites.