Effect of Kinking Damage on Fatigue Fracture Behavior of PBO Fiber

Abstract

In this study, effect of kinking damage on fatigue fracture behavior of PBO (Poly-p-Phenylene Benzobisoxazole) fiber was investigated in monofilament fatigue tests. Two types of the PBO fibers were used in the experiment. One was the conventional type. The other was high-modulus type with a higher crystal orientation than the conventional type. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod set to 0.625 mm. Load-controlled fatigue tests were carried out using a sinusoidal load with frequency 10 Hz and stress ratio of R = 0.5, and the load cell capacity was 10 N. It was found that fatigue strength with kinking damage was lower than that without kinking damage in neither AS fiber and HM fiber. Fatigue strength decrease of AS fiber and HM fiber with kinking damage in a low cycle area was larger than that in a high cycle area. The fatigue fracture of PBO fiber with kinking damage presented the different aspect at a high cycle area and a low cycle area in neither AS fiber and HM fiber.