Abstract
Shock absorption often needs stiff but lightweight materials that exhibit a large kinetic energy absorption capability. Open-cell metal foams are artificial structures, which due to their plateau stress, including a strong hysteresis, can in principle absorb large amounts of energy. However, their plateau stress is too low for many applications. In this study, we use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nickel is deposited by electrodeposition as coating on the strut surface. The mechanical behaviour of cellular materials, including their behaviour under higher strain-rates, is governed by their microstructure due to the properties of the strut material, pore/strut geometry and mass distribution over the struts. Micro-inertia effects are strongly related to the microstructure. For a conclusive model, the exact real microstructure is needed. In this study a micro-focus computer tomography (μCT) system has been used for the analysis of the microstructure of the foam samples and for the development of a microstructural Finite Element (micro-FE) mesh. The microstructural FE models have been used to model the mechanical behaviour of the Ni/Al hybrid foams under dynamic loading conditions. The simulations are validated by quasi-static compression tests and dynamic split Hopkinson pressure bar tests.
Highlights
Cellular materials like metal foams are a very interesting class of bionic lightweight materials
We use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nickel is deposited by electrodeposition as coating on the strut surface
The microstructural FE models have been used to model the mechanical behaviour of the Ni/Al hybrid foams under dynamic loading conditions
Summary
Cellular materials like metal foams are a very interesting class of bionic lightweight materials. Open-cell foams mimic the construction elements of human femur bones or the star fish skeletons. Nature uses these cellular structures as advanced, evolution-optimised lightweight materials. Based on their special microstructure, consisting of a network of interconnected pores, metal foams are able to undergo large deformations at a nearly constant stress, forming a stress plateau [1, 2]. The stress plateau evolves by the successive collapse of single pore layers. Due to the stress plateau, the foams are able to absorb considerable amounts of kinetic energy by plastic dissipation, whereas metal foams can be used as crash absorbers
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