Fatigue Strength of High-modulus Type PBO Fiber with Kinking Damage

Abstract

In this study, fatigue strength of high-modulus type PBO (Poly-p-Phenylene Benzobisoxazole) fiber with kinking damage was investigated in monofilament fatigue tests. PBO fiber is high polymer material and has the highest tensile strength and tensile modulus of elasticity in any polymeric fiber. Kinking damages was created on surface of virgin fiber by winding bundle fibers to steel rod. Diameter of steel rod was set to 0.625 mm. Average value of compressive strain on surface of fiber determined based on the diameter of steel rod was -1.71 %. 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 of PBO fiber with kinking damage was lower than that of PBO fiber without kinking damage. Fatigue strength decrease of PBO fiber with kinking damage in a low cycle area was larger than that in a high cycle area.