New method for interfacial evaluation of carbon fiber/thermosetting composites by wetting and electrical resistance measurements

Abstract

Interfacial properties were evaluated for carbon fiber (CF) with different thermosetting polymeric matrices in composites. CF tow was wet by phenolic or epoxies, and the interfacial adhesion evaluated by electrical resistance changes. The interfaces between two types of CF tows with phenolic resin and three types of epoxies were investigated. The change in electrical resistance was found to depend on the wettability of CF by the polymer resins, with the more obvious resistance changes being associated with better wettability. The electrical resistance changes were measured 20 min after the polymer resin was dropped on the CF tow. To confirm the relationship between changes in resistance and interfacial properties, both interfacial shear stress (IFSS) and interlaminar shear stress (ILSS) were also measured. The results of these mechanical measurements were generally consistent with the electrical resistance measurements in that the materials with high electrical resistance also exhibited high IFSS and ILSS.