Hypervelocity penetration of concrete

Experiments have been conducted with 6.25 mm diameter tungsten rods striking concrete at 2.2 km/s. Three concretes were used—one was 2.35 g/cm3 and the other two were 2.27 g/cm3. The erosion rates were measured to be T/ΔL = 2.4–3.1 depending on the density of the concrete. This is greater than the hydrodynamic value, which shows that the strength of the penetrator is affecting the penetration. The cratering efficiency was computed (which included surface spall) and was found to be commensurate with the strength of the concrete, 28–34 MPa. CTH calculations were conducted using the brittle fracture kinetics (BFK) and Holmquist–Johnson–Cook (HJC) material models for concrete. Density in the calculations was 2.25 g/cm3. It was not possible to match erosion rates at 2.2 km/s, which were too high in the calculations. Also, computed crater volumes were much too small, mainly due to spall in the experiments that was not shown in the computations. Another significant inaccuracy of the calculations was the damage extent, which became unrealistically widespread as time increased in the BFK model.