缝合复合材料层板低速冲击损伤数值模拟

建立了缝合复合材料层板在低速冲击载荷下的渐进损伤分析模型。模型中采用空间杆单元模拟缝线的作用；采用三维实体单元模拟缝合层板，通过基于应变描述的Hashin准则，结合相应的材料性能退化方案模拟层板的损伤和演化；采用界面单元模拟层间界面，结合传统的应力失效判据和断裂力学中的应变能释放率准则判断分层的起始和扩展规律。通过对碳800环氧树脂复合材料（T800/5228）层板的数值仿真结果和试验结果相比较，验证了模型的正确性，同时讨论了不同冲击能量下缝合层板的损伤规律。研究结果表明：缝线能够有效地抑制层板的分层损伤扩展；相同冲击能量下缝合与未缝合层板的基体损伤和纤维损伤在厚度分布上相似，缝合层板的损伤都要小于未缝合层板。

Numerical simulation of low-velocity impact damage on stitched composite laminates

A progressive damage finite element model was established for the analysis of stitched composite laminate under low velocity impact. The stitching threads were described as spatial truss elements in the model, and three-dimensional solid elements were used to simulate the stitched laminates. Strain-based Hashin failure criteria coupled with corresponding stiffness degradation technologies was used to predict the type and evolution of intralaminar damage modes. Cohesive elements were adopted in interlaminar zones to simulate the initiation and evolution of delamination through stress-based failure criteria and facture-mechanics-based criterion of strain energy release rate. The reasonability of the model was validated by the comparison between numerical simulation results and experimental data on T800 carbon fiber reinforced epoxy resin composites (T800/5228) laminate. Finally the damage law of the stitched laminates at different impact energies was discussed in detail. The results show that the evolution of delamination is restrained effectively by the stitching threads, and the distribution of fiber and matrix damage on the thickness of the stitched laminates is similar to the unstitched laminates at the same impact energy, in which the damage area of stitched laminates is less than that of the unstitched laminates.