Damage Of 3-D Braided Composite Under Ballistic Penetration--Refined Quasi-Microstructure Model And Finite Element Calculation

Compared with the laminated composites, the three-dimensional braided composites have the higher inter-laminated shear strength and fracture toughness which lead to the higher impact damage tolerance. Because of the complexity of the microstructure, the research and the application of such kind of composites in the anti-ballistic protection field is still in the primary state. It is very important to investigate the penetration process and the damage mechanism of this kind of the composite under the ballistic impact for optimization of bullet-proof composites.In this paper, the "fiber inclination model" for the description of 3-D textile structural reinforced composite is employed to decompose the 3-D composite at quasi-microstructure hierarchy based on the real composites structure. From this decomposition scheme, the 3-D braided composite is equivalent to four inclined laminae and the crossover of the four laminae is neglected. Then the lamina model considering the microstructure and having the same fiber volume content with the 3-D braided composite is established. The finite element method (FEM) code with explicit algorithm is used to simulate the ballistic penetration of the rigid projectile into the lamina target. The residual velocity of the projectile and the deformation of the lamina target are obtained. The comparison between the numerical results and the experimental results proves that the decomposition scheme of the 3-D composite at the microstructure hierarchy in this paper is valid and reasonable. In addition, the damage pattern and the damage mechanism of the composite is also discussed.The main conclusions are as follows: (1) the refined quasi- microstructure is established based on the real structure of the 3-D braided composite. The structure of the calculation model is equivalent to the real structure of the composite. (2) The comparison between the residual velocity of the projectile, the deformation of the lamina target and the residual penetration hole on the target according to the model calculation and the experimental results proves that the decomposition scheme of the 3-D composite at the microstructure hierarchy in this paper is valid and reasonable. (3)the deformation of the target, the projectile acceleration, the projectile velocity and kinematic energy decrement as functions of the time was used to describe the whole process of penetration. The damage pattern and the damage mechanism of the composite is also disused. (4) From the comparison between the model based on the continuum assumption of the composite and the model based on the real structure of the composite, it proves that the latter is more reasonable and accurate, and they also can be applied to numerical simulation of the ballistic impact process of other 3-D braided reinforced composites.