Responses of 3D biaxial spacer weft-knitted composite circular plate under impact loading. Part II: Impact tests and FEM calculation

The responses of 3D biaxial spacer weft-knitted composite circular plate under impact loading had been investigated both in experimental and finite-element analysis (FEA). The impact tests were carried out with a modified split Hopkinson pressure bar (SHPB) apparatus and copared with the results from the quasi-static indentation tests. The load-displacement curves of the composite circular plate under impact were obtained to analyze the energy absorption and dynamic responses. It is found that the failure loads, energy absorptions, and impact deformation increase with the increase of impact velocity. The damage along the course direction is more severe than that along the wale direction. The main damage mechanism includes matrix spallation in the rear side under impact, while the fiber extension and pullout in quasi-static test. Incorporated with the unit-cell model developed in Part 1 of this paper (B. Sun, H. Hu, & B. Gu, The Journal of the Textile Institute, 101, 28-34) a user-defined subroutine VUMAT (FORTRAN Vectorized User Material) was developed to connect with commercially available finite-element code ABAQUS/Explicit. The interaction between the subroutine and ABAQUS/Explicit was analyzed. The impact responses of the knitted composite can be calculated with the subroutine and ABAQUS/Explicit. The good agreement between the experimental and finite-element method calculation indicates the feasibility of extending the unit-cell model to engineering structures made of the 3D knitted composite.