Experimental characterizations of bending fatigue of a four-step 3-D braided rectangular composite under different stress levels

This article reports the bending fatigue behavior of a four-step 3-D rectangular braided composite at different stress levels. The S–N curve and the stress vs. deflection history were recorded to investigate the bending fatigue behaviors of the braided composite. Specifically, the area of the stress hysteresis loop in each loading cycle and the accumulated area of the whole loading cycles were calculated from the stress vs. deflection history curves. All the integral areas were compared at different stress levels for analyzing the energy absorption. Then, the energy absorptions during the bending fatigue were compared to analyze the energy dissipation mechanisms taking place during the fatigue process. The stiffness degradation was also calculated to show the fatigue damage. The damage morphologies of the 3-D braided composite specimens were photographed to compare the failure modes under different stress levels.