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Abstract:The integrated near-net-shape structure of 3D braided composites provides excellent impact resistant properties over laminated composites. At the same time, the load distribution and damage mechanisms throughout the structures become more complicated. In this paper, a finite element model based on three unit-cells is established to simulate the penetration process of 3D braided composites under high velocity impact. A 3D rate-dependent constitutive model is developed to determine the constituent behavior in the three unit-cells.Tsai-Wu criterion with Mises criterion and an instantaneous degradation scheme are coded by a user material subroutine VUMAT developed in Abaqus/Explicit. The whole process of ballistic damage evolution of 3D braided composites is simulated, and the impact resistance and damage mechanisms are revealed in detail in the simulation process. The effects of striking velocity on the ballistic properties and energy absorption characteristics of the composite structures are also discussed.

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In the current study, a finite element model was established to simulate the penetration process of composite laminates under high-velocity impact. A 3D ratedependent damage constitutive model was developed to simulate the ballistic response of unidirectional fiber-reinforced composite laminate. Numerical models were built based on a damage model where cohesive contact method was involved. The user-developed FORTRAN subroutine (VUMAT) was written and implemented in ABAQUS/ Explicit 6.11 version. The ballistic resistance and damage characteristics of composite laminate were discussed, and the damage model was validated. The results of the FEM were observed to agree well with experimental observation. According to the results, the ply angle of the laminate had great influence on the damage distribution; thus, when the ply angle increases, the ballistic resistance and damage areas on both front and rear side of the laminate decrease. Again, the result shows that increasing the thickness of the laminate was advantageous to the ballistic resistance and damage characteristics of the composite laminates. The prediction of the model was proved to have good accuracy and efficiency.