Numerical investigation of the bodywork effect (K-effect)

Abstract
Add-on armour kits composed of high-hardness steel plates are often used to improve the protection of light personnel carriers and logistic vehicles against the ballistic impact of small caliber ammunition, such as the 5,56×45 mm and the 7,62×51 mm NATO Ball projectiles. The protective kits are integrated inside the existing vehicle bodywork. There are indications, however, that the overall ballistic protection can also become less efficient by using the add-on armour, especially for the 5,56×45 mm threat. This phenomenon is referred to as the bodywork effect: the ballistic protection offered by the bodywork plate in combination with the additional armour plate is lower than the protection offered by the armour plate alone. This paper investigates the origin of the bodywork effect through a series of numerical simulations. For validation purposes, a limited number of firings have been performed. Split Hopkinson pressure bars tests were used for the characterization of the dynamic behaviour of the integrated armour plate material.