In this paper, residual strength of poly-p-phenylene benzobisoxazole (PBO) fiber with kinking damage under ultraviolet irradiation was investigated in monofilament tests. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 5, 2.5, 1.25 and 0.65 mm. Kink damage density was defined to evaluate occurrence of kinking damage. UV irradiation time was 1 and 10 h, the irradiation intensity was 8 W/m^2. It was found that the residual strength of fiber with kink damage decreased with increasing kink damage density. When the PBO fiber with kink damage was subjected to ultraviolet light, the residual strength is greatly reduced due to the auto-oxidation generated in the kink damaged region.
