Experimental and numerical investigation of the ballistic limit and critical thickness of jute/epoxy laminates under 9 mm projectile impact

This study investigates the ballistic response of multilayer jute/epoxy laminates subjected to 9 mm projectile impact through a combined experimental and numerical approach. Experimental results show that, at an impact velocity of 356 m/s, the projectile penetrates only 7-8 layers of a 39-layer laminate and rebounds without back-face deformation. A finite element model is developed and validated against experimental observations, showing good agreement in terms of penetration depth and damage mechanisms. A parametric analysis is conducted by varying the laminate thickness (number of layers) to determine the ballistic limit and the minimum thickness required for projectile arrest. The results identify a transition region between 23 and 26 layers, where the response changes from complete perforation to full projectile arrest, highlighting the strong influence of laminate thickness on ballistic performance.