一方向炭素繊維強化複合材料の切欠材における層内疲労き裂の発生および進展挙動

概要

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The initiation and growth of intralaminar fatigue cracks in notched unidirectional carbon/epoxy laminates, Toray T800H/#3631, were investigated under tension-tension cyclic loading with constant stress amplitudes. The initiation of fatigue cracks at the notch root was caused by shear stress concentration. The fatigue life for crack initiation was a unique function of the maximum shear stress divided by the critical value of the maximum shear stress for static tensile fracture. Fatigue cracks propagated under mixed mode, mode I and mode II. When the crack length was short, the crack propagation rate was determined by the mode I stress intensity range, ΔK_I. As the crack length increased, the mode II stress intensity range, ΔK_II, became a dominant crack-driving force. Although the ΔK_I value increased with crack length, the propagation rate monotonically decreased and the crack finally stopped. Such deceleration and non propagation of cracks were caused by the increase of interlocking and friction between fracture surfaces. The condition of the non propagation of fatigue cracks was determined by a constant value of ΔK_I for short cracks in the ΔK_I-dominant region. 0n the other hand, for long cracks in the ΔK_II-dominant region, the threshold value of ΔK_II increased with increasing crack length.
一般社団法人日本機械学会の論文
1994-04-25