Effect of Silane Bonding State on Interfacial Strength in Glass Fiber-Epoxy Composites

Abstract

The effect of silane treatment on interfacial reinforcement in glass fiber epoxy composites was investigated. Single filament coupon test was employed to measure the interfacial strength between glass fiber and matrix. The interfacial strength was evaluated not from the critical fiber length, but from the coupon stress at the first fracture of embedded filament. A parameter named “Interfacial Transmissibility” was proposed to reveal the transmissibility of tensile force through silane interphase from matrix to glass fiber. Thus, the parameter gave adhesive property of silane interphase from mechanical. viewpoint. The interfacial transmissibility, t_I, was then calculated from the ratio of fiber strength to the tensile stress occurring on fiber at the first fracture. The value of t_I was affected by silane concentration and by removal of the silane physisorbed on glass fiber with methanol. As a result, optimum amounts giving maximum interfacial strength was present regardless of the existence of physisorbed silane. However, the removal of nonbonding silane made the maximum t_I higher and the optimum silane amount lower. Those results were interpreted in terms of two kind of silane bonding state; the chemisorbed and physisorbed siloxane networks.