Size-driven transitions in ballistic limit velocity and energy absorption mechanisms for plain weave fabrics

Aramid plain weave fabrics are extensively utilized in flexible protective systems. In this study, ballistic tests were conducted using spherical projectiles of different diameters to impact aramid fabrics with varying yarn fineness. The effects of projectile and yarn dimensions on the ballistic performance of the fabric were analyzed. Combined with numerical simulations, the study elucidated the energy transformation and distribution mechanisms during the penetration process, revealed the transition mechanism of yarn failure modes, and identified the critical threshold of size effect. Furthermore, a predictive model for the ballistic limit velocity (V₅₀) of single-layer plain weave fabrics was established, incorporating both size effects and the shape of the projectile nose. The results indicate that, for the same type of fabric, as the projectile diameter increases, both V₅₀ and specific energy absorption (SEA) increase. Compared to fabrics with coarser yarns, those with finer yarns exhibit relatively higher SEA, although the former shows higher V₅₀. As the projectile diameter decreases and yarn fineness increases, the failure mode of the plain fabric gradually shifts from a thrusting mode to a windowing mode. A projectile-to-yarn width ratio of approximately 9 marks the transition point of the fabric failure mode and the critical threshold of the size effect. Compared to conventional models, the revised ballistic limit velocity model demonstrates significantly improved prediction accuracy, with a maximum error within 22 %.