Ballistic Resistance of UHPFRC Panels Subjected to Armor-Piercing Projectiles

In this study, thin armor panels were designed and constructed using ultra-high-performance fiber-reinforced concrete (UHPFRC), and their ballistic resistance to armor-piercing small arms fire was assessed. The fiber dosages selected for the panels were 3% and 4% by volume, with average UHPFRC compressive strengths at 28 days of 144 MPa ($\pm 4.5$) and 141 MPa ($\pm 12.1$), respectively. The panels’ front and rear surfaces were $350\times 350\mathrm{mm}$, and the thicknesses were 40, 50, and 60 mm. Ballistic performances of the panels were assessed at two bullet velocities representing different operational distances. The two distances were based on a threat associated with urban operations (approximately 10 m) and field operations (approximately 300 m). A $7.62\mathrm{mm}\times 51$ armor-piercing round was used for testing. The testing demonstrated that at close range the panels could absorb a high level of energy, up to 3,089 J, and at this range, all panels were perforated. The results of the 60-mm panels impacted by a 300-m equivalent range shot, absorbed energy of up to 2,066 J, and slowed down the projectile to a very low velocity or a complete stop. Basic and advanced predictive models were used to estimate the resistant energy of the panels according to material characteristics such as fiber content, thickness, and mechanical properties. A numerical model was also developed. An ANSYS version R18.2 smooth particle hydrodynamics Autodyn model provided good predictions of the crater dimensions. It also demonstrated an impact behavior similar to that of the UHPFRC panel compared to real tests; however, further work is needed to represent the bullet core and jacket more accurately.