Experimental characterizations of three-point bending fatigue behavior of four-step three-dimensional braided composite T-beam

This paper reports the three-point bending fatigue behaviors of four-step three-dimensional braided composite T-beam. The fatigue deformation and damage of three-dimensional braided composite T-beam at different stress levels and fatigue cycles have been obtained to explain the fatigue behaviors. The influence of stress levels on fatigue life is analyzed based on experimental S–N curves performed with the stress ratio (R) value of 0.1 at room temperature. Furthermore, the energy absorptions were analyzed by comparing the integral areas among different stress levels to indicate energy absorption mechanisms. In addition, the fatigue damage location distribution is found according to the damage morphologies of three-dimensional braided composite T-beam. The history of the overall stiffness degradation is found to exhibit three stages of fatigue failure: initial stage, steady stage, and final failure crack stages. The results of this investigation provide an insight into fatigue damage behavior and fatigue life of three-dimensional braided composite T-beam, and it shows that the three-dimensional braided composite T-beam is able to be used as connector.