Investigation of delamination in laminated composites under quasi-static and fatigue loading conditions by acoustic emission

Despite the fact that fiber reinforced plastic composites have excellent mechanical properties, various failure mechanisms can be occurred in these materials. Delamination is the most common failure mode in laminated composites that can be occurred under quasi-static and fatigue loading conditions. The present study is concerned with the investigation of mechanical and Acoustic Emission (AE) behavior of delamination in glass/epoxy composites under mode I quasi-static and fatigue loading conditions. First, the unidirectional and woven specimens were subjected to mode I quasi-static loading. The behavior of the delamination in the specimens was investigated and interlaminar fracture toughness of the specimens was calculated. Then, according to the information that obtained from quasi-static loading, the similar specimens were subjected to the fatigue loading. The mechanical and AE behavior of the delamination under fatigue loading was investigated. A linear relationship was established between cumulative AE energy and fatigue crack growth and fatigue crack growth curve was predicted using the AE method. Then, energy release rate variations curve and fatigue crack growth rate diagram were predicted using AE method. The predicted results by AE have a good compatibility with the visually based data that recommended by standard. The results indicate that, the AE method has good applicability for health monitoring of composite structures that subjected to quasi-static and fatigue loading conditions.