A numerical study of a nacre-inspired ballistic armour system

  • Jacob T Best

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

There is growing interest in the application of biological systems to solve engineering problems. Of particular interest in this research is the biological material nacre, found in the inner layer of Haliotis rufescens (red abalone). This material exhibits a fracture toughness three orders of magnitude greater than its constituent components. Designing a tiled armour system predicated on the functional architecture of nacre could enhance multi-hit performance without compromising ballistic performance or momentum dissipation of the armour against a single impact. The specific features of interest are topological interlocking between tiled platelets and the inclusion of a ductile interlayer cohesive matrix. These features may allow for ceramics such as alumina (Al2O3) to retain the high hardness and yield stress that make them suitable as ballistic protection while adding the potential for multi-hit capability and increased durability. This research focuses on the development of a tiled alumina ceramic armour system to protect against a 7.62 mm AP M2 round impacting at 875 m s-1 with the potential for multi-hit capability.
Using the explicit dynamic solver, LS-DYNA, the geometric design space of a tiled ceramic armour system is explored to determine optimal thickness, edge length and spatial arrangement of tiled systems as well as investigating the change in damage mechanisms that occur when transitioning from a monolithic design. This showed that, for a single shot, a monolithic plate is the optimal armour system for ballistic performance and the introduction of any through-thickness interfaces greatly inhibits ballistic properties. Therefore, any tiled armour design must focus on mitigating this reduction in performance while optimising secondary performance criteria such as multi-hit capability.
A novel tile geometry is proposed featuring nacre-inspired topologically interlocking surfaces. A parametric study is conducted for each characteristic surface profile for a range of tile sizes in order to optimise ballistic performance against a single impact and to minimise the armour sensitivity to impact location. Further, a cohesive matrix is introduced in the inter-layers of the tiled system to mirror the ductile organic polymers of nacre. Finally, the proposed armour designs are tested against multiple impacts.
Date of Award1 Oct 2019
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorStephen R Hallett (Supervisor)

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