Interfacial properties of glass fiber/brittle-ductile dual-matrix composites using micromechanical techniques and acoustic emission

The interfacial adhesion and microfailure modes of glass fiber-reinforced brittle unsaturated polyester/modified epoxy composites were investigated via micromechanical techniques and acoustic emission (AE). Various silane coupling agents caused different degrees of interfacial adhesion and subsequent microfailure modes. In the brittle matrix layer, the number of matrix fragments was significantly influenced by the type of silance coupling agents. The more cracks, the higher the interfacial adhesion under both dry and wet conditions. This is attributed to the chemical and hydrogen bondings in two interphases. The results obtained from microdroplet and fragmentation tests were correlated by associating with the AE technique. The sequential occurrence of mainly three groups of AE were as follows: the first group originated mainly from brittle matrix cracking. The second and the third groups resulted in fiber breakage and ductile matrix cracking and debonding. For dual-matrix specimens the micromechanical tests provide reliable information with regard to the interfacial adhesion and characterize the microfailure modes when combined with the AE technique.