A computational investigation of impact into multi-plies of plain-woven fabric

To overcome the high computational cost associated with explicit representation of the fabric-yarn weaving structure/architecture in fabric-based flexible personnel protection, a meso-scale unit-cell based material model is first developed for a prototypical plain-woven Kevlar® 129 single-ply fabric. The model is next implemented into a "user-defined material" subroutine and coupled with the ABAQUS/Explicit commercial finite-element program. Within the user defined material subroutine, an effective "smeared" material response is computed which includes not only the in-plane phenomena (e.g. yarn tension, buckling, inter-yarn friction, and yarn slip), but also the out-of-plane effects (e.g. contact forces at the yarn crossovers, and fabric bending and twisting). The material model is next validated by caring out a series of transient non-linear dynamics finite-element analyses of impact of a single-layer fabric by a high-speed spherical steel projectile and by comparing the results with their counterparts obtained in the corresponding computational analyses in which yarns and their weaving is represented explicitly. Finally, the model is used in an investigation of the ability of a multi-ply soft-body armor vest to protect the wearer from impact by a 9mm round nose projectile. The effects of inter-ply friction, projectile/yarn friction and the far-field boundary conditions are revealed and the results explained using simple wave mechanics principles, high-deformation rate material behavior and the role of various energy absorbing mechanisms in the fabric-based armor systems.