The responses of stitched ultra-high-molecular-weight polyethylene woven fabrics upon ballistic impact

This paper investigates the influence of thread stitching on the ballistic performance of plain weaves made of ultra-high-molecular-weight polyethylene multi-filament yarns. The inter-yarn friction is increased due to the constraint imparted by the sewing thread. The yarn pull-out test shows that the peak-load force of the sample with one stitching line is almost 10 times greater than that of the unstitched plain weave, and the maximum pull-out force increases with the loading rate. Ball-bearing impact tests are performed to characterize the ballistic performance of the stitched and the unstitched samples, and finite element simulation is used to study the underlying mechanisms of energy absorption. The ballistic penetration tests show that the stitched fabrics outperform the plain weave in terms of energy absorption. The most significant improvement in ballistic performance is observed in stitched panels where sample SL2T (a triple-ply plain fabric system stitched on every two yarns) exhibits a specific energy absorption over two times greater than that of multi-ply systems consisting of plain weaves. It is also found from the high-speed photography that thread stitching constrains the yarn displacement and therefore eliminates the possibility of yarn pull-out, enabling the primary yarns to be well-engaged with the projectile at low impact velocities and to be stretched to fail at high impact velocities. Numerical predictions show that thread stitching enlarges the area of stress distribution and widens the transverse deflection, making the stitched systems absorb more energy than the unstitched system shortly after impact.