A New Approach for Protection against Ejection Trajectory of Scabbed Materials of Ultrahigh-Performance Concrete under Projectile Impact

Scabbing on the rear face of concrete under impact produces fragments that act as additional projectiles causing fatality or severe damage to the occupants or systems. Ultrahigh-performance concrete (UHPC) has outstanding properties and has proven efficacy in the impact-resistant design of structures. However, the potential damage due to the impact of fragments of scabbed pieces still prevails. This study developed a new approach for preventing ejection of scabbed materials of UHPC under single and repeated bullet impact (using a single-stage gas gun facility). The ejection of scabbed materials was controlled using woven carbon-epoxy and glass-epoxy laminated composite sheets attached to the rear face of UHPC samples. The ejection of scabbed pieces was controlled in UHPC targets with composite backing in the case of both single and repeated impact under similar conditions. Furthermore, a numerical simulation based on nonlinear finite-element code was performed for repeated impact on a UHPC target with a carbon-epoxy laminated composite. The results of the numerical simulation had a good agreement with the experimental data. Thus, the synergistic effects of steel fiber-reinforced UHPC with composite backing can be used to enhance the impact performance of UHPC.