Fragmentation of two-fiber hybrid microcomposites: stress concentration factors and interfacial adhesion

Stress concentration profiles resulting from the progressive fragmentation of a single fiber, and fiber/polymer interfacial adhesion, were assessed by testing a two-fiber hybrid microcomposite. The specimen consisted of a highly pre-stressed E-glass fiber and a lightly stressed Kevlar fiber, embedded in an epoxy film. The large pre-stress ensured saturation of the fragmentation process in the glass fiber. The interfacial adhesion was quantified by an energy balance approach as well as by a conventional stress balance (Kelly–Tyson) scheme. The stress concentration profiles induced in the Kevlar fiber by breaks in the nearby E-glass fiber were measured by micro-Raman spectroscopy, using several interfiber distances. The experimental results were compared with an extension of our earlier theoretical scheme for the stress concentration factor profile.