Ballistic impact response of laminated composite panels

Laminated ballistic composite panels are an important part of hard-plate protective body armour and may be subjected to a wide variety of impact conditions depending on the projectile, impact velocity and armour construction, to name a few.The ballistic response of laminated composite panels has been investigated through direct impacts of two non-deforming projectiles (7.5 mm diameter hardened steel 120° cylindrical–conical, and 9 mm hemispherical nosed) selected to enhance different failure mechanisms including penetration and delamination.Experimental and numerical studies were carried out to determine the ballistic response of laminated Kevlar® 29 and 129 composite panels, commonly used in protective body armour. These panels were impacted at velocities between 130 and 250 m/s, which were below the penetration limit of the panels.A numerical parametric study was initially undertaken to determine those material properties which reduce back face signature (BFS; maximum dynamic displacement), one of the important performance indicators for assessing personal protection. Experimental material characterization then allowed mechanical property data to be determined for numerical simulations, which showed good agreement with the experimental data, particularly for the conical projectile impacts on both types of Kevlar® panels.Numerical simulations of the impact tests accurately predicted the BFS and dynamic response for the conical projectile impacts, while the BFS for the hemispherical projectiles was slightly low. This can be attributed to the dominant delamination failure mechanisms, which may not be completely captured by the numerical model. Importantly, the numerical analysis accurately predicted the initial velocity of the panel back face for the hemispherical projectiles and the time to reach maximum BFS for the conical projectiles.