Experimental Tests and Numerical Simulations on the Ballistic Impact Response of a Highly Inhomogeneous Aluminium Foam

Abstract

A sandwich structure is a composite material consisting of thin skins encapsulating a cellular core. Such structures have proven to be excellent energy absorbents and are frequently found in various types of protection. Even so, few studies exist in the open literature on the response of the core material itself under extreme loadings such as blast and impact. Since a blast load is usually accompanied by numerous fragments, it is important to understand and be able to predict the ballistic impact resistance of the often highly inhomogeneous cellular core materials in design. In this study, the ballistic impact response of an aluminium foam with a complex cell structure has been investigated both experimentally and numerically. First, an extensive material test program involving compression tests on cubic specimens loaded in the thickness direction of the foam was carried out to reveal the mechanical properties of the material. In addition, several of the specimens were scanned before testing using X-ray Micro Computed Tomography (XRMCT) to map the multi-scale topology and morphology of the material. These data were later analysed to extract density-variation plots in many different material orientations. Second, ballistic impact tests were conducted using a gas gun where rigid spheres were launched towards aluminium foam plates, and the ballistic limit velocity and curve of the foam material were established. Finally, numerical simulations of both the material tests and the ballistic impact tests were carried out using LS-DYNA and different modelling approaches based on the XRMCT data. It will be shown that, independent of the modelling strategy applied, good agreement between the experimental impact tests and the numerical predictions can be obtained. However, XRMCT data are important if the final goal is to numerically optimise and improve the behaviour of inhomogeneous foams with respect to energy absorption, thermal isolation, or similar properties.

On the Ballistic Perforation Resistance of a Sandwich Structure with Aluminium Skins and Aluminium Foam Core

“…An alternative is to use X-ray tomography to disclose information about the microstructure. Brekken et al [6] used X-ray micro computed tomography (XRMCT) to map the porous morphology and density variation of a highly inhomogeneous aluminium foam. The data was used to calibrate a crushable foam constitutive model intended for large scale impact simulations.…”

“…The data was used to calibrate a crushable foam constitutive model intended for large scale impact simulations. Here, the same aluminium foam as in [6] was used as core material in a sandwich panel. The panel was made by adding thin aluminium plates as skins on each side of the foam core.…”

Finite Element Analysis of Ceramic–Composite Structures for Ballistic Applications: Effect of Ceramic Thickness and Cell Structure

“…Importantly, this research highlights the crucial role of XRMCT data in optimizing and improving the behavior of inhomogeneous foams, especially in terms of their energy absorption and thermal insulation properties. [ 12 ]…”

“…This provides a valuable tool for designing and optimizing protective solutions that utilize sandwich structures. [ 14 ]…”

“…Importantly, this research highlights the crucial role of XRMCT data in optimizing and improving the behavior of inhomogeneous foams, especially in terms of their energy absorption and thermal insulation properties. [12] Other study provides valuable insights into enhancing the ballistic perforation resistance of both plain and reinforced concrete slabs, which has direct implications for the design of structures and infrastructure exposed to extreme loads. The research in this study validates a constitutive relationship that is suitable for large-scale numerical simulations of concrete structures when subjected to ballistic impact forces.…”