Deng Huachao, Toda Keitaro, Sato Mio, Koyanagi Jun
Department of Materials Science and Technology, Tokyo University of Science, Tokyo 125-8585, Japan.
Japan Aerospace Exploration Agency, Osawa, Tokyo 181-0015, Japan.
Materials (Basel). 2023 Sep 7;16(18):6120. doi: 10.3390/ma16186120.
Fatigue failure of carbon fiber-reinforced plastics (CFRPs) under cyclic loadings has attracted the attention of researchers recently. In this study, the entropy-based failure criterion is proposed to investigate the fatigue lifetime of unidirectional CFRPs subjected to multiple-amplitude cyclic loadings. Due to the heterogeneity of CFRPs, a micro-finite element model considering matrix resin and fibers independently is developed, and the entropy-based damage criterion is implemented into a user-subroutine of Abaqus to model the progressive damage of matrix resin. The fatigue lifetime of CFRPs under typical loading sequences consisting of two stages, such as varying from low to high (L-H) or from high to low (H-L) loading sequence, is estimated with the proposed failure criterion. Numerical results show that the initial damage occurs near the area between two fibers, and a transverse crack propagates progressively under the cyclic loading. The difference in predicted lifetime to final failure in L-H and H-L stress levels is 6.3%. Thus, the effect of loading sequence on the fatigue lifetime can be revealed via the proposed entropy-based damage criterion. Comparisons with the conventional linear cumulative damage (LCD) and kinetic crack growth (KCG) theories are also conducted to demonstrate the validity of the proposed method. The entropy-based failure criterion is a promising method to predict the residual strength and fatigue lifetime of CFRP components.
碳纤维增强塑料（CFRP）在循环载荷作用下的疲劳失效近来已引起研究人员的关注。在本研究中，提出了基于熵的失效准则，以研究单向CFRP在多幅值循环载荷作用下的疲劳寿命。由于CFRP的非均质性，开发了一个独立考虑基体树脂和纤维的微观有限元模型，并将基于熵的损伤准则应用于Abaqus的用户子程序中，以模拟基体树脂的渐进损伤。利用所提出的失效准则估算了CFRP在由两个阶段组成的典型加载序列（如从低到高（L-H）或从高到低（H-L）加载序列）下的疲劳寿命。数值结果表明，初始损伤发生在两根纤维之间的区域附近，并且在循环载荷作用下横向裂纹逐渐扩展。L-H和H-L应力水平下预测的最终失效寿命差异为6.3%。因此，通过所提出的基于熵的损伤准则可以揭示加载序列对疲劳寿命的影响。还与传统的线性累积损伤（LCD）和动态裂纹扩展（KCG）理论进行了比较，以证明所提方法的有效性。基于熵的失效准则是预测CFRP构件剩余强度和疲劳寿命的一种很有前景的方法。
