Effects of environmental exposure on fiber/epoxy interfacial shear strength

Abstract The TRI microbond technique for direct determination of fiber/resin interfacial shear strength in composites has been used for investigation the influence of environmental conditions on adhesive bonding in certain systems. The small dimensions involved in the method facilitate uniform exposure and short exposure times. We have observed significant changes in both average shear strength and in shear strength distributions on exposing aramid/epoxy and glass/epoxy microbond assemblies to steam or hot water. Shear strength dropped to a plateau value in both cases, the reduction being more drastic with the glass fiber. Vacuum drying restored shear strength completely in aramid/epoxy microassemblies, even when the surface of the aramid fiber had been chemically modified, but there was only partial regeneration of bond strength with the glass/epoxy system.