Illustrating hybrid effect and damage evolution of carbon/aramid braided composite under low-velocity impact

This study illustrates the hybrid effect and damage evolution of carbon/aramid braided composites under low-velocity impact, using a finite element model (FEM) of a complete braided structure. The model was established based on a real three dimensional (3D), five directional (5d) braided structure by taking the interior, surface, corner braided and axial yarns into consideration. Constitutive material modeling and failure criteria were introduced into the model. The degree of damage was determined by comparing the volumes of units removed on failure. Three hybrid structure types were adopted to investigate the relationships between stress distribution and damage evolution. The results showed that the impact response and failure morphology were significantly dependent on hybrid effects under different low-velocity impacts. The impact response curves of hybrid structures showed obvious toughness characteristics. The addition of aramid fiber as an axial yarn could prolong the overall impact response time and reduce failures. Moreover, the hybrid effect strongly influenced the stress distribution and damage evolution in different circumstances. Hybrid structures led to a large stress distribution area and a low stress level, which could reduce the material failure caused by stress concentration. This work provides a sound method for designing hybrid structures and expanding the application potential of 3D braided composites.