Quasi-static three-point bending and fatigue behavior of 3-D orthogonal woven composites

3-D orthogonal woven composites (3DOWC) have attracted great attention in the industrial and civil fields, due to their excellent mechanical properties. However, due to the mutual perpendicular yarns in three directions, its mechanical properties especially for fatigue behavior are very unique but critical for structural design in the practical applications. An experimental study was carried out for the quasi-static three-point bending and fatigue behavior of 3-D orthogonal woven composite (3DOWC). The 3-D orthogonal woven fabric (3DOWF) was reinforced with epoxy resin with the technique of Vacuum Assisted Resin Transfer Molding (VARTM). The damage process of specimens in quasi-static three-point bending tests was detected by acoustic emission (AE) detector. Simultaneously, the critical load levels i.e. the stress levels used in the bending fatigue experiments were also obtained according to AE results. The bending fatigue tests were performed at different stress levels, and the SN curves, stress-strain curves, stiffness degradation curves and residual strength of the composite specimens were also obtained. For the three-point bending fatigue loading condition, the characterizations of the three-stage failure process and crack propagation behavior were observed and illustrated. This study is the first time to systemically illustrate the fatigue stress level of 3-D orthogonal glass woven composites by acoustic emission (AE) detector and the detailed failure process are very important to guide the parameter and structural of the 3DOWC in real applications.