負の応力比のもとでのCFRP積層板のモードII層間疲労き裂の進展挙動

概要

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The effect of the stress ratio on growth behavior of mode II interlaminar fatigue cracks was studied with unidirectional carbon/epoxy laminates, Toray T800H/#3631. The end loaded split (ELS) specimens were used for tests under negative stress ratios. For each stress ratio, the crack propagation rate was given by a power function of the stress intensity range, ΔK_<II>, or the maximum stress intensity factor, K_<IImax>, in the region of rates above 10^<-9> m/cycle. Below this power law region, there exists a threshold value of the stress intensity range, ΔK_<IIth>, for the fatigue crack propagation. The value of ΔK_<IIth> was constant for the stress ratio between -1.0 and 0.6. In the power law region, both ΔK_<II> and K_<IImax> affect tht crack propagation rate. The effect of K_<IImax> decreases as the crack propagation rate decreases. In the near-threshold region, the crack propagation rate is controlled only by the ΔK_<II> value ; the value of K_<IImax> has no effect on the crack propagation. A simple equation was proposed for predicting the propagation rate of mode II fatigue cracks under various stress ratios. Predictions agreed well with the experimental results for both positive and negative values of the stress ratio. The effect of the stress ratio on propagation mechanisms of fatigue cracks was discussed on the basis of fractographic observation.
一般社団法人日本機械学会の論文
1995-05-25