Load interaction effects in fatigue-driven delamination in fiber-reinforced polymer composites are neglected in state-of-the-art models although this assumption highly underestimates the delamination growth under variable amplitude (VA) loading. A new phenomenon called “transient delamination growth” has recently been observed in VA fatigue experiments by the authors. In the current work a new crack growth rate model with transient delamination growth capabilities is presented. The new model evaluates the crack growth rate by addition of a steady-state non-interaction term and a transient interaction term. The former term neglects load interaction effects and is characterized from constant amplitude loading tests, while the latter term includes load interaction effects and is characterized from two-level block loading tests. Fatigue tests are conducted on glass/epoxy DCB specimens by means of a new test fixture. The new crack growth rate model is able to accurately represent the crack growth rate at high-to-low load amplitude changes during multi-level block loading tests and reduces the error in delamination growth prediction by nearly 50% compared to non-interaction models.

在最先进的模型中，纤维增强聚合物复合材料中疲劳驱动的分层中的载荷相互作用效应被忽略，尽管这种假设大大低估了可变振幅 (VA) 载荷下的分层增长。作者最近在 VA 疲劳实验中观察到一种称为“瞬时分层生长”的新现象。在目前的工作中，提出了一种具有瞬态分层增长能力的新裂纹增长速率模型。新模型通过添加稳态非相互作用项和瞬态相互作用项来评估裂纹扩展速率。前项忽略载荷交互作用，以等幅加载试验为特征，后项包括载荷交互作用，以两级分块加载试验为特征。通过新的测试夹具对玻璃/环氧树脂 DCB 样本进行疲劳测试。新的裂纹扩展速率模型能够准确表示多级分块加载试验中从高到低载荷幅值变化时的裂纹扩展速率，与非交互模型相比，分层扩展预测误差降低了近50%。