Multi-scale Modelling of Fracture in Open-Cell Metal Foams

Metal foams possess attractive mechanical properties like high stiffness to weight ratio.When used to build light-weight structures they require a good combination of strength and ductility. They are ductile under compression but rather brittle in tension with a few percent of overall strain to fracture. Second-phase particles, grain boundary precipitates and inclusions are often associated with the knock-down of the ductility. Through a heat treatment the microstructure can be changed, however, this also changes the associated yield stress and hardening behaviour of the strut material. How this will affect the overall behaviour depends sensitively on the foam’s cellular architecture, e.g. the cell size and shape distribution, the cross-sectional geometry of the strut, and its relative density. The goal of this work is to study these dependencies using a multi-scale modelling framework that takes all these ingredients into account. In this paper, we present the combined effect of the solid material strain hardening and the relative density on the initiation and accumulation of damage and overall strength of the structure

The Effect of Cellular Architecture on the Ductility and Strength of Metal Foams

A multiscale finite element model has been developed to study the fracture behaviour of two-dimensional random Voronoi structures. The influence of materials parameters and cellular architecture on the damage initiation and accumulation has been analyzed. The effect of the solid material's strain hardening, relative density and architectural randomness on the ductility and fracture strength of the cellular solid are investigated. The results suggest materials-design directions in which the heat treatment, the solid material properties, its microstructure and the cellular architecture can be tuned for an optimized performance of cellular materials.</p

Fracture of open-cell foams:A discrete modelling approach

A discrete model based on two-dimensional Voronoi tessellation has been used to study damage and fracture in open-cell metal foams. The present study focuses on elastic-fracture behaviour of the foam. A competition mechanism among various damaging struts leading to damage localization and formation of a fracture band has been observed. The effect of relative density is presented in terms of scaling relationships for the peak stress and peak strain are presented here. Finally the detrimental effect of the effect of the presence of the precipitates will be studied as well, showing a severe knock-down in the strength and ductility.</p

Fracture of open-cell foams: A discrete modelling approach

A discrete model based on two-dimensional Voronoi tessellation has been used to study damage and fracture in open-cell metal foams. The present study focuses on elastic-fracture behaviour of the foam. A competition mechanism among various damaging struts leading to damage localization and formation of a fracture band has been observed. The effect of relative density is presented in terms of scaling relationships for the peak stress and peak strain are presented here. Finally the detrimental effect of the effect of the presence of the precipitates will be studied as well, showing a severe knock-down in the strength and ductility

Multi-scale Modelling of Fracture in Open-Cell Metal Foams

Metal foams possess attractive mechanical properties like high stiffness to weight ratio.When used to build light-weight structures they require a good combination of strength and ductility. They are ductile under compression but rather brittle in tension with a few percent of overall strain to fracture. Second-phase particles, grain boundary precipitates and inclusions are often associated with the knock-down of the ductility. Through a heat treatment the microstructure can be changed, however, this also changes the associated yield stress and hardening behaviour of the strut material. How this will affect the overall behaviour depends sensitively on the foam’s cellular architecture, e.g. the cell size and shape distribution, the cross-sectional geometry of the strut, and its relative density. The goal of this work is to study these dependencies using a multi-scale modelling framework that takes all these ingredients into account. In this paper, we present the combined effect of the solid material strain hardening and the relative density on the initiation and accumulation of damage and overall strength of the structure