一方向炭素繊維強化複合材料の非主軸疲労強度に与える応力比の影響

概要

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Influences of stress ratio on the off-axis fatigue strength of a unidirectional fiber-reinforced composite T800H/2500 have been studied. Tension-tension and tension-compression fatigue tests on plain coupon specimens with fiber orientation angles θ = 0, 10, 15, 30, 45 and 90° were performed for stress ratios R = 0.5, 0.1, -0.3 (θ= 0°) and R = 0.5, 0.1, -1.0 (0°< θ ⪇ 90°), respectively. Also, a fatigue damage mechanics model that considers the effect of stress ratio was formulated. Fatigue strength of the unidirectional T800H/2500 decreased as the stress ratio decreased, irrespective of off-axis angle. The S-N relationships were almost linear in the range of fatigue loading up to 10^6 cycles, regardless of off-axis angle and stress ratio. The non-dimensional effective stress based on the classical static failure theory succeeded in a unified description of the directional characteristic of the off-axis fatigue strength for all stress ratios. The proposed fatigue damage mechanics model can predict the stress-ratio dependent off-axis fatigue behavior of the unidirectional system employed.
2003-07-25