Performance enhancement of armour steel against blunt projectiles using pre-layers

Damage containment is one of the key factors for optimising operational readiness of warships after an internal warhead detonation. Ship designers currently have no other option than to rely on state of the art solutions applied in vehicle and personal protection; mainly ballistic composites. These solutions are prone to being traded off during the design process due to cost of the bulk material. Areas to protect are in the order of magnitude of hundreds of square meters. This called for development of a cost efficient, but lightweight protection against fragments. TNO has teamed up with industrial partners to develop understanding of the physical phenomena involved in pre-layers on armour steels [1], in order to optimise protective solutions. Goal of the project was to assess the potential of using polymer coated armour steels in combination with blast bulkheads. The project consisted of three iterations of testing and analysis. The first test programme was aimed at understanding the physics explaining why armour steels perform significantly better against blunt projectiles when covered with an additional thin layer of a relatively soft material. Knowledge from the preliminary tests was applied to protective concepts for blast bulkheads. The pre-layer on the armour steel allows it to dissipate the energy over a wider area of the steel. In the experiments extreme stretching of the armour plate occurred and about twice the amount of energy is dissipated in the armour steel compared to the uncoated situation. The work resulted in protective concepts that fulfilled the mass requirements and are based on affordable materials. The project team considers this technology to be promising for future application in warships. Solutions from this project will be engineered further into a prototype concept. There is spin-off possible to other platforms like vehicles and offshore rigs, where mass and cost are equally important.