Delamination is a critical mode of failure that occurs between plies in a composite laminate. The cohesive element, developed based on the cohesive zone model, is widely used for modeling delamination. However, standard cohesive elements suffer from a well-known limit on the mesh density-the element size must be much smaller than the cohesive zone size. This work develops a new set of elements for modelling composite plies and their interfaces in 3D. A triangular Kirchhoff-Love shell element is developed for orthotropic materials to model the plies. A structural cohesive element, conforming to the shell elements of the plies, is developed to model the interface delamination. The proposed method is verified and validated on the classical benchmark problems of Mode I, Mode II, and mixed-mode delamination of unidirectional laminates, as well as on the single-leg bending problem of a multi-directional laminate. All the results show that the element size in the proposed models can be ten times larger than that in the standard cohesive element models, with more than 90% reduction in CPU time, while retaining prediction accuracy. This would then allow more effective and efficient modeling of delamination in composites without worrying about the cohesive zone limit on the mesh density.

翻译：分层是复合材料层合板层间发生的一种关键失效模式。基于内聚区模型发展的内聚单元被广泛用于分层建模。然而，标准内聚单元存在一个众所周知的网格密度限制——单元尺寸必须远小于内聚区尺寸。本研究开发了一套用于三维建模复合材料铺层及其界面的新单元。针对正交各向异性材料，开发了一种三角形Kirchhoff-Love壳单元用于模拟铺层。同时，开发了一种与铺层壳单元相匹配的结构内聚单元，用于模拟界面分层。所提出的方法在单向层合板的I型、II型和混合型分层经典基准问题，以及多向层合板的单腿弯曲问题上得到了验证。所有结果表明，所提模型的单元尺寸可比标准内聚单元模型大十倍，CPU时间减少90%以上，同时保持了预测精度。这将使得复合材料的层间分层建模更加高效，而无需担忧内聚区对网格密度的限制。