Delamination is a very frequent damage mechanism that affects the integrity of laminated composites. In this study, the effect of ply orientation on crack growth resistance was analyzed for three different anti-symmetric interfaces ($\pm 30°,\pm 45°$ and $\pm 60°$) and compared to a unidirectional baseline under remote mode II loading. Fracture toughness at initiation was the same regardless of the ply orientation, nevertheless, the energy dissipated during crack propagation increased with ply angle. The fracture process exhibited by the anti-symmetric laminates showed repetitive zig-zag patterns featuring simultaneous crack migration and delamination. A first set of numerical analyses based on the virtual crack closure technique (VCCT) revealed that the anti-symmetric local fracture modes, i.e. longitudinal shear vs. transverse shear, are responsible for delamination and crack migration, respectively. The main damage mechanisms and their evolution, as observed experimentally, were well reproduced by an appropriate cohesive zone model, which takes into account the ply orientation during delamination.

分层是一种非常常见的损坏机制，会影响层压复合材料的完整性。在这项研究中，针对三种不同的非对称界面分析了层取向对抗裂纹扩展性的影响（$\pm 30°，\pm 45°$ 和 $\pm 60°$），并与远程模式II加载下的单向基线进行比较。不管层方向如何，开始时的断裂韧性都是相同的，但是，裂纹扩展过程中耗散的能量随层角度的增加而增加。反对称层压板表现出的断裂过程显示出重复的之字形图案，同时出现裂纹迁移和分层。基于虚拟裂纹闭合技术（VCCT）的第一组数值分析表明，反对称的局部断裂模式，即纵向剪切与横向剪切，分别负责分层和裂纹迁移。如实验观察到的那样，主要的损伤机理及其演变已通过适当的内聚区模型得到了很好的再现，该模型考虑了分层过程中的层定向。