Secondary penetration behavior in UHPC targets after penetration-explosion events

Deeply buried and ultrahigh-strength protective structures often require multiple sequential penetration-explosion cycles to be effectively neutralized. This study focuses on the secondary penetration behavior of ultrahigh-performance concrete (UHPC) targets after an initial penetration and explosion sequence, a subject that has received limited systematic attention. First, a series of penetration-explosion-penetration tests was performed on UHPC targets, with systematically varying secondary impact locations to examine their effect on penetration depth and local failure characteristics. Experimental results reveal that secondary penetration performance varied significantly with impact position, showing distinct differences in both the increase in penetration depth and the degree of projectile redirection across tested locations. In addition, a computational model incorporating the restart method was developed and rigorously validated through comparisons with experimental data. Furthermore, a systematic parametric study was conducted to examine the influence of impact location, velocity, and accumulated material damage on secondary penetration behavior, accompanied by a discussion of the underlying physical mechanisms.