Fish Scale-Inspired Stab-Resistant Body Armour

Abstract

While commercially available lightweight “stab-proof” apparel exists, it offers little resistance to true stabbing as it is primarily designed to withstand slash attacks. Yet, crimes involving the use of a knife or sharp instrument have consistently been rising in the UK over several decades. For the most part, the various proposed solutions to stab-proofing are based on speciality textiles and while these have shown success in slash-proofing, their utility for stab-proofing is still somewhat of a misnomer. Nature showcases a plethora of puncture-resisting materials and structures. At the macro-scale, these include carapaces, egg cases, toughened skin, and more. One of the most effective protective mechanisms known comes through surface scaling, present on animals such as reptiles and fish. Scaled protective armours present in extant fish species include overlapping elasmoid scales, interlocking ganoid scales, placoid scales, tessellating carapace scutes, and interlocking plates. Here, we research overlapping and interlocking scaled structures to ascertain the stab penetration resistance of biomimetic scaled structures against continuum material to obtain the force–time relationship of the impact event as well as ascertaining the penetration depth. We use additive manufacturing methods to manufacture biomimetic armour made of nylon, a common protective artificial material used in slash-proofing textiles. Stab testing to the closely replicated HOSDB body armour standard 2017, we find that biomimetic scales made of nylon offer greater protection against direct stabbing than continuum nylon material sheets. This can be attributed to (a) the heightened flexibility in an interlocked fish scale structure that does not exist in a continuum sheet of the same material; (b) the effect of overlapping of the fish scales, resulting in a greater penetration depth requirement before the structure undergoes perforation; and (c) segmentation into smaller armour plates (of the same thickness) rather than continuum sheets provides a lower span-to-depth ratio, therefore leading to a smaller deflection of the plate upon impact and a greater deceleration and, hence, a greater impact force.

Keywords

• AMBA
• fish scale
• armour
• stab
• biomimetic
• segmented