確率的ＳＣＧモデルとエネルギー解放率を用いたトランスバースクラックに関する疲労破壊クライテリオン

Abstract

New fatigue fracture criteria for the transverse crack evolution in a composite laminate subjected to cyclic loading were proposed using the probabilistic model and energy release rate. First, a time-dependent fracture model that combines slow crack growth (SCG) with stochastic failure was established for a general brittle material. The fracture probability was obtained as a function of the number of cycles and maximum stress on the basis of the Paris law and Weibull distribution. Next, the above probabilistic SCG model was applied to the fatigue transverse cracking behavior to establish a stress intensity factor criterion. Thirdly, an energy criterion for predicting fatigue transverse crack density was shown through the combination of the energy release rate on the basis of a variational approach by Nairn with the SCG model. The predicted transverse crack density under the static tensile and fatigue loading was compared with the experiment result to verify the reasonability of the above fracture criteria. In addition, the transverse crack density rate versus the number of cycles predicted using the two fracture criteria and the Paris's equation proposed by Nairn was compared with the experimental results. The transverse crack initiation life was also derived from the energy criterion.