Modern aircraft employ the use of lightweight engineering materials such as sandwich composites to increase the flexural rigidity of their structural components. These sandwich composites are limited by their low interfacial strength between the outer facesheets and internal core, which can result in facesheet-core debonding at relatively low out-of-plane loads. In this study, sandwich composites that are reinforced with through-the-thickness stitching are considered. Stitched sandwich composite specimens, fabricated from 110 kg/m³ perforated foam core with cross-ply carbon/epoxy facesheets, were manufactured with different combinations of stitch densities (0.0016–0.01 stitches/mm²) and linear thread densities (400–1200 Denier) of through-the-thickness reinforcement. Single cantilevered beam (SCB) tests were performed to characterize the facesheet-core debonding within the stitched sandwich composites. Unique fracture morphologies were observed that exhibit dependency on stitch processing parameters. A discrete cohesive zone modeling approach is used to simulate the separation of the facesheet from the core. Three-dimensional finite element analysis reveals crack curvature near the stitching. Good agreement between predicted and experimental measurements were obtained.

现代飞机采用轻质工程材料，如夹层复合材料，以增加其结构部件的抗弯刚度。这些夹层复合材料受到外面板和内芯之间的低界面强度的限制，这可能导致面板-芯在相对较低的面外载荷下脱粘。在这项研究中，考虑了通过全厚度缝合增强的夹层复合材料。缝合夹层复合材料试样由 110 kg/m ³穿孔泡沫芯和交叉层碳/环氧树脂面板制成，采用不同缝合密度组合（0.0016–0.01 针/mm ²) 和全厚度钢筋的线密度 (400–1200 Denier)。进行单悬臂梁 (SCB) 测试以表征缝合夹层复合材料内的面板-芯部脱粘。观察到独特的断裂形态，表现出对针迹加工参数的依赖性。离散内聚区建模方法用于模拟面板与核心的分离。三维有限元分析揭示了缝线附近的裂纹曲率。获得了预测测量值和实验测量值之间的良好一致性。