Effect of stress ratio on fatigue characteristics in the out-of-plane direction of thick CFRP laminates with toughened interlaminar layers

The effect of the stress ratio on fatigue characteristics in the out-of-plane direction of thick carbon fiber reinforced plastic (CFRP) laminates with toughened interlaminar layers was evaluated. The spool shaped specimens cut out the unidirectional thick CFRP laminates, which pile up 88 plies of the prepreg with toughened interlaminar layer, T800S/3900-2B, were used. The fatigue tests were conducted under the stress ratios of R = 0.1 and -1 to evaluate the effect of the stress ratio. As the results of the fatigue tests, the fatigue life of the specimens at R = -1 was shorter than that at R = 0.1. It was found that the fatigue properties of the CFRP laminates in the out-of-plane direction are affected by the stress amplitude from the experimental results. In addition, the fatigue life under the different stress ratio can be evaluated equivalently using the Walker model which can consider the mean stress effect.