一方向強化CF/PEEK積層板のモードII層間はく離疲労き裂伝ぱの破壊機構(特集高分子系複合材料)

概要

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The effect of stress ratio on the near-threshold growth of delamination fatigue cracks was investigated with unidirectional CFRP laminates made from toughened thermoplastic matrix resin. Tests were carried out under mode II shear loading by using end notched flexure specimens with a special loading device. The crack growth behavior under different stress ratios indicated that the fatigue crack growth rate was well correlated to the stress intensity range near the threshold region. The fatigue crack growth resistance of CF/PEEK laminates was slightly higher than that of conventional CF/epoxy laminates. However, the increase of the fatigue crack growth resistance by toughening the matrix resin was smaller than that under mode I loading. The reason for this poor toughening effect was discussed based on fractographic observation. Comparison of the change of stress-ratio dependency and the relative fatigue threshold was made from brittle CF/epoxy laminates to toughened CF/PEEK laminates under both mode I and mode II loadings. The stress-ratio dependency and the relative threshold were expressed by unique functions of the fracture toughness of the same laminates under the same loading modes.
1997-04-15