高弾性ピッチ系炭素繊維による一方向ＣＦＲＰの曲げ疲労挙動 ３点曲げ負荷による

Abstract

Flexural fatigue tests were performed on three high modulus pitch-based carbon fiber (400, 500, 600GPa) unidirectional composites and a high modulus PAN-based carbon fiber one in order to investigate the effect of strong nonlinear elasticity on the compressive stress-strain relation of the pitch-based ones. In the test, the three-point flexural method was adopted with two stress ratios: R=0.05 and R=-1.0 (perfectly alternated loading). The test results showed that for both stress ratios the high modulus pitch-based carbon fiber unidirectional composites possessed as much fatigue durability as that of the high modulus PAN-based carbon fiber composites, though the pitch-based ones had stronger compressive nonlinearity than that of PAN-based ones. If the compressive nonlinearity were associated with fiber damage, the fatigue durability should be affected by the degree of nonlinearity. However, since this was not the case, it is considered that this nonlinearity in the high modulus pitch-based carbon fiber composites is not associated with fiber damage but is of an elastic nature.