The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.

There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence.

装甲系统的弹道性能和行为受两组主要变量控制，即几何和材料。其中，性能的一致性，尤其是针对小武器弹药的性能，将取决于组成材料特性的一致性。例如，在防弹衣系统中，纤维直径、机织织物的面密度和陶瓷的堆积密度是关键参数的示例，监控这些参数将构成相关质量控制程序的支柱。经常被忽视的，因为它可能落入用户的领域，是各种产品之间存在的接口；载体、软装甲插入物 (SAI) 和一块或两块硬装甲板（HAP1 和 HAP2）。如果各种产品来自不同的供应商，则尤其如此。

一个典型的防弹衣系统中有 30 到 150 个单独的层，每一层之间的每个界面都会以某种方式影响系统的弹道性能。例如，考虑以下界面/夹层：(i) 软装甲包内以及包和载体之间的摩擦、滑动、层间表面，(ii) 软装甲包内可能产生的气隙装甲包，(iii) 软装甲包和硬装甲板之间的互连空间，(iv) 多层背衬层压板的相邻层之间的界面性质，即使在高度压缩的超高分子量聚乙烯 (UHMWPE) 中变体，(v) 陶瓷与其基底之间的夹层，在 HAP 内，(vi) 堆叠式防弹衣系统内两块硬装甲板之间的几何配合。本文将对所有此类界面进行用户友好的概述，并就其重要性和影响力提供独特的指导。