Numerical investigation of the impact behaviour of bioinspired nacre-like aluminium composite plates

Abstract

Inspired by the hierarchical structure of nacre, an aluminium alloy (AA) 7075 based composite featuring layer waviness and cohesive interface is studied as a low weight impact resistant material. To investigate the mechanical response and the ballistic performance of this laminated structure, a numerical study of the proposed nacre-like composite plates made of 1.1-mm thick AA 7075 tablets bonded with toughened epoxy resin was performed using Abaqus/Explicit. Target thicknesses of 5.4-mm, 7.5-mm and 9.6-mm impacted by a rigid hemi-spherical projectile were simulated. The epoxy material was modelled using a user-defined interface cohesive element with compressive strength enhancement. A significant performance improvement was recorded for the 5.4-mm nacre-like plate (compared to the same thickness bulk plate), which was explained by the hierarchical structure facilitating both localized energy absorption (by deformation of the tablet) and more globalized energy absorption (by inter-layered delamination and friction). For a given projectile, however, the performance improvement of using the proposed composite decreased with increasing laminate thickness, which was attributed to the increased likelihood of ductile failure occurring prior to perforation in thicker bulk plates. For 5.4-mm thick plates impacted at high velocity, the nacre-like plate had a better ballistic performance than that of the plates made of continuous (flat and wavy) layers, which was attributed to the larger area of plastic deformation (observed in the nacrelike plate after impact) due to the tablets arrangement.

The effect of interface adhesion on buckling and cracking of hard thin films

“…A value of λ 0.14 was used in the simulations based on the range of reported values (0.05-0.25). 17,27 We assumed 0.02 0.07 , 17 10 , 17 and 2 , 28 with and being the normal and shear stiffness of the interface, respectively, and the experimentally reported residual stress. 4 To trigger the buckling, the film is perturbed in the out-of-plane direction with a small imperfection.…”

A numerical study of bioinspired nacre-like composite plates under blast loading

“…Their numerical model took into account layer waviness in both in-plane directions and used a triangular wave function [17]. Our recent numerical investigation has also showed that the impact response of aluminium alloy layered plates can be improved by using a nacre-like design, which took into account layer waviness in both inplane directions using a sinusoidal function [18]. We demonstrated that the nacre-like design induced a more diffused and globalised damage when compared to monolithic plates.…”

“…For the cohesive interface between layers, a user-defined cohesive element with compression-enhanced traction separation law [23] was used. Since these material models have been fully described in previous publications [18,[23][24][25], we therefore refer the reader to these papers for full details.…”

“…stiffness, strength, and fracture energies) [20] and were obtained from Wang et al [29]. There are also additional parameters in Table 2 used in the user-defined cohesive element, explained in detail in our previous papers [18,23]. They are elastic modulii E and G, tensile strength t n and shear strength t s , and fracture energies G Ic and G IIc .…”

“…The behaviour and mechanical properties of nacre have been extensively studied [11,13,16]; however, the performance of nacre-like engineering composites at the macroscale (millimetre-size) has only been scarcely explored [9,12,14,17,18]. Some recent work have shown the strong potential of nacre-like structures with respect to performance in sustaining blast and impact loading when compared to traditional laminated composite plates or bulk plates.…”