Fish scale-inspired stab-resistant body armour

While commercially available lightweight "stab-proof" apparel exists, these offer little resistance to true stabbing as they are 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 the course of 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 unknown. Nature showcases a plethora of puncture-resisting materials and structures. At the macroscale, 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. We use additive manufacturing methods to manufacture biomimetic armour made of nylon, a common protective artificial material used in slash-proofing textiles. Stab-testing the HOSBD body armour standard 2017, we find that biomimetic scales made of nylon offer greater protection against direct stabbing, than continuum nylon material sheets do. This can be attributed to (a) heightened flexibility in an interlocked fish scale structure that does not exist in a continuum sheet of the same material and (b) the effect of the fish scales overlapping, resulting in a greater penetration depth requirement before the structure undergoes perforation.