In situ microtensile testing and X-ray microtomography-based finite element modelling of open-cell metal foam struts and sandwich panels

Abstract

Microtensile testing was used to determine the mechanical properties of individual aluminium alloy foam struts. Finite element modelling of as-tested struts was carried out using X-ray microtomography scans of the undeformed struts to define the geometry. Strut deformation was described by continuum viscoplastic damage constitutive equations calibrated by microtensile test data of the aluminium alloy in its optimally aged condition. The as-tested strut finite element model was used to develop a procedure that compensates for the effect of grip slippage inherent in the microtensile testing of metal foam struts, which results in a considerable reduction in observed elastic stiffness compared to the typical value of 70 GPa for aluminium alloys. The calibrated constitutive equations were then implemented in finite element models of sandwich panels with the aluminium metal foam as its core material. The finite element models were used in simulations of cases of low energy impact to represent tool drop conditions in order to investigate the suitability of new wing skin designs using metal foam core sandwich panels. An optimal strut aspect ratio was identified through simulation that provides the greatest energy absorption per unit mass while ensuring core damage is accurately reflected by facesheet deformation, which is necessary for detection and repair.