Armour Structures for Ballistic Impact

传统上，装甲由整体式高硬度钢制成。然而，最近对轻质装甲的需求很高，以改善各种应用中的机动性，包括个人防弹衣、车载装甲和飞机。这导致了非金属材料的使用，包括陶瓷和复合材料。陶瓷以其低密度、高硬度、高硬度、高强度等优点得到了广泛的应用。然而，陶瓷材料强度低，拉伸断裂韧性低。由于冲击引起的整体弯曲，或者由于压缩应力波从自由表面反射(将其转变为张力波)，可能会引入拉应力。这导致了复合装甲的发展，其中陶瓷面板由金属或聚合物复合材料等延性材料支撑，以抵抗拉应力。在弹道撞击过程中，弹丸首先被硬质陶瓷打碎或钝化，在更大的面积上耗散能量；背板弯曲以吸收剩余动能，延迟陶瓷的拉伸破坏，并允许更多的弹丸侵蚀。这是现在公认的轻型装甲设计。然而，多层复合装甲在弹道冲击中的性能还没有完全了解，因此多层结构的设计在物理学上没有很好的基础；关于设计参数，如应力波管理的层厚比，以及什么是有利的材料响应特性，特别是在将层连接在一起的界面上，存在着悬而未决的问题。

Traditionally, armours of been made of monolithic high hardness steel. Recently, however, there is high demand for lightweight armour for improved mobility in various applications, including personal body armour, vehicular armour, and on aircraft. This has led to the use of non-metallic materials, including ceramics and composites. Ceramics have become widely used due to their low density, high hardness, high rigidity and high strength. However, ceramics also have low strength low fracture toughness in tension. Tensile stress can be introduced due to global bending due to impact, or due to reflection of a compressive stress wave off a free surface (which changes it into a tensile wave). This has led to the development of composite armours where a ceramic faceplate is backed by a ductile material such as metal or polymeric composite to resist the tensile stresses. During ballistic impact, the projectile is first shattered or blunted by the hard ceramic, dissipating the energy over a larger area; and the backing plate bends to absorb the remaining kinetic energy, delaying tensile failure in the ceramic, and allowing more projectile erosion. This is now the accepted design for lightweight armours. However, the performance of multi-layered composite armours in ballistic impact is yet to be fully understood, and so the design of multi-layered configurations is not well founded in physics; and there are open questions around design parameters like layer thickness ratios for stress wave management, and what are favourable material response characteristics, particularly at the interface which bonds layers together.