Strain-rate dependence for Ni/Al hybrid foams

¹ Saarland University, Institute of Applied Mechanics, Campus A4.2, 66123 Saarbrcken, Germany
² European Commission, Joint Research Centre (JRC), Institute for the Protection and Security of the Citizen (IPSC), European Laboratory for Structural Assessment, via E. Fermi 2749, 21027 Ispra (VA), Italy
³ Academy of Sciences of the Czech Republic, v.v.i., Department of Biomechanics, Institute of Theoretical and Applied Mechanics, Prosecka 76, 190 00 Prague 9, Czech Republic

^a e-mail: anne.jung@mx.uni-saarland.de
^b e-mail: martin.larcher@jrc.ec.europa.eu
^c e-mail: jirousek@itam.cas.cz
^d e-mail: koudelkap@itam.cas.cz
^e e-mail: george.solomos@jrc.ec.europa.eu

Published online: 7 September 2015

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.