Influence of Different Factors on the Most Vulnerable Position of Steel - Aluminum Composite Target Plate under Constant Surface Density

In the previous research about the penetration resistance of steel-aluminum composite target plates, we found that when a few steel-aluminum composite targets with the same surface density and different thickness ratios were penetrated with the same incidence velocity, the residual velocity had a maximum value and the target plate had a minimum penetration resistance ( this point was called the inflection point (IP)). By means of numerical simulation and experimental verification, the influence of different factors on the location of the IP was studied. These targets with single material such as steel or aluminum were penetrated with velocity ranges from 820 m/s to 930 m/s. The simulation results showed that the position of IP is always near 0.188 even the incidence velocity, the penetration angle and the surface density of target plate are changed. When variform fragments with the same mass (4.6 g) were used for penetration, there is no IP in the spherical fragment but the IPs of the cube and cylinder were different from that of the rifle bullet, and its position is stable around 0.305. Therefore, the shape of the projectile affects the presence and location of the IP. Finally, the theoretical derivation of the optimal thickness ratio of the combined structure is carried out. For the composite target plate with the surface density of 5 g /cm 2 and 10 g/cm 2 , the optimal thickness ratio is 0.216 and 0.300, respectively.