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.