Relationship of interface fracture energy and interlaminar shear strength of carbon fiber reinforced composite under hydrothermal treatment

The mechanical and physical properties of composite materials are greatly influenced by the structure and properties of fiber/matrix interface. Short beam shear test is often performed to evaluate the laminar interface properties in real applications, especially for studying them after a given hydrothermal treatment. However, the results depend on the interface and the matrix properties, so the degradation mechanism of composite under hydrothermal condition is difficult to analyze only based on the short beam shear test. In this study, carbon fiber/epoxy resin interface properties, quantified by means of interface fracture energy, are tested in various hydrothermal conditions, such as hygroscopic treatments, re-drying treatment, temperature from 25°C to 130°C and 130°C after hygroscopic treatment. In addition, to analyze the relationship of interface properties measured by micro-mechanical and macro methods, short beam shear tests are simultaneously performed in the same treatments. The results show that interface fracture energy degrades obviously after hygroscopic treatments rather than under high temperature, while the degradation degree of interlaminar shear strength is more sensitive to temperature. Moreover, interlaminar shear strength for studied composite under various treatments largely depends on the mechanics property of matrix than interface property.