An effect of compressive loads on the out-of-plane fatigue properties of thick CFRP laminates with the toughened interlaminar layers was investigated. The unidirectional [O_<88>] and quasi-isotropic [45/0/-45/90]_<11s> laminates were fabricated using T800S/3900-2B prepreg. This prepreg is constituted of a fiber layer and an interlaminar toughened layer in which polyamide particles are dispersed uniformly. The spool shaped specimens which were machined from the thick laminates were loaded in the out-of-plane direction of the specimen. The fatigue tests were performed at three types of stress ratios of R= 0.1, -1 and -3. As the results of the fatigue tests, it was conformed that the fatigue life was reduced with the compressive load under same maximum stress. In addition, the effect of the stress ratio on the fatigue life was dependent on the laminate configuration. When the cyclic loading at R= -3 were applied in the unidirectional specimen, the shear fracture mode was observed in the high-cycle region.
