Experimental validation of the origin of the bodywork effect (k-effect) in the up-armouring of civil and military vehicles

This study served to obtain qualitative and quantitative knowledge about the so-called bodywork effect or K-effect (from its German designation "Karroserie-effekt"). This phenomenon is mostly encountered in applications where an existing vehicle is armoured by integrating a ballistic kit inside the existing body work. It manifests itself as a lowering of the ballistic limit (V50) of the armour configuration when a thin metallic plate is placed at a small distance in front of the armour. In this study the 5.56 x 45 NATO Ball (SS109, M855) was used as the threat to the armour (high hardness steel plate). Measurements of the ballistic limit for different configurations were made. By the use of several techniques, different possible origins for the body work effect were investigated. Flattening of the projectile nose was identified as the main origin of the K-effect. This origin was validated by firing adapted 5.56 ammunition (truncated nose), which led to a considerable lowering of the V50. The result of this work could have great repercussions for all people working in the field of uparmouring existing civil and military vehicles, or working in the field of testing, evalution and validation of vehicle armour systems. There could also be an interest for people working in the field of ammunition development, although only for very specific applications.