Structural performance and failure analysis of aluminium foams

The thesis is about the characterization of the microstructure of several aluminium foams and its relation to the failure behavior of these materials under monotonic tension and fatigue. Due to the production processes brittle inclusions are present in the microstructure of the foams investigated. Because damage is introduced before the peak strain, which is the strain at the ultimate tensile strength (UTS), the peak strain and the UTS depend on the particular damage evolution before the peak strain. To monitor the damage evolution the electrical resistance and acoustic emission was measured during tensile tests. Brittle fracture increases the rate of damage accumulation and therefore decreases the peak strain and UTS. For decreasing relative densities below 5.5%, more bending and less stretching of struts decreases the damage accumulation and therefore increases the peak strain and UTS of Duocel open cell aluminium 6101 foam. Above 5.5% relative density annealing the foam samples or orienting the long axis of the elliptical cells transverse to the loading direction, in stead of longitudinal, has the same effect. For Replicated open cell aluminium 6101 foam densities below 5.5%, the increase in bending of struts results in the ability to shift deformation from a highly strained and damaged band to another band, thereby increasing the peak strain and UTS.