New model for interlaced yarns in the ballistic impact of flexible body armors

In this work, numerical implementations of a new biaxial fabric of interlaced yarns model for ballistic impact into flexible body armor are presented. First the model is applied to a single-layer panel of polyethylene Dyneemaå fibers in a matrix and impacted by various projectile geometries. We obtain the model results from a mass-spring, finite-difference model by modifying the code first developed at DSM. The results of the model are compared with experimental results and our previous biaxial model from firing 9 mm and FSP projectiles into Dyneemaå panels. For both models, parametric studies are presented using 2-D and 3-D graphics. The new biaxial interlaced yarns model extends our previous biaxial and axisymmetric membrane model by addressing biaxial influences on material inflow to the impact cone. The new model is much more complete and produces velocity, strain and deformation histories for the full system up to perforation or projectile halting. It can also treat cases of mixing different fabric types, which can result in interference effects depending on the layer stacking order, and can treat multiple layers with air gaps in between, where we will show that such gaps can seriously degrade performance.