Penetration Resistance of Semi-infinite UHPFRC Targets with various Fiber Volume Fractions against Projectile Impact

Penetration resistance of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) was investigated within the framework of this study. Fiber volume fraction was set as the main test variable and two types of projectiles have been used. Deformable and non-deformable projectile had a full metal jacket with soft lead core and full metal jacket with mild steel core, respectively. Both projectiles were 7.92 mm in diameter and weighed 8.04 grams. Semi-infinite targets made of UHPFRC have been constructed with five different fiber volume fractions with gradual increments ranging from 0.125% to 2%. For the means of comparison, additional plain mixture specimens were casted. Semi-infinite targets have been introduced by using UHPFRC cubes of 200 mm in size. Projectile impact was simulated by using semi-automatic rifle calibre 7.62 × 39 mm at the shooting distance of 20 m. Muzzle velocities for both type of projectiles were around 710 m/s and only front crater with the tunnelling section occurred at the proximal face of the specimen. Depth of penetration, crater diameter and crater volume have been investigated based on various fiber volume fractions and various projectiles. The results from UHPFRC targets were compared with theirs plain mixture counterparts and among different fiber volume fractions. It has been experimentally verified that using steel fibers in the ultra-high performance concrete matrix results in lower damage in terms of depth of penetration, crater area and crater volume, while the latter two are far more affected by the increase of the fiber volume content than the former. Using short steel fibres as disperse micro-reinforcement provides enhanced performance of semi-infinite UHPFRC targets and is therefore essential for construction of protective structures in order to reduce the damage of the impacted elements and to increase the safety of the personnel.