Micro-CT characterization of structural features and deformation behavior of fly ash/aluminum syntactic foam

The structure of a fly ash/aluminum syntactic foam was characterized using X-ray microcomputed tomography. Microstructural features, such as size, morphology and distribution of fly ash microballoons, were quantitatively related to the deformation behavior using interrupted compression tests. The syntactic foam was found to exhibit four distinct stages of deformation: (i) elastic; (ii) dispersed collapse of the fly ash microballoons; (iii) unification of the dispersed collapse region forming a band of densification, usually normal to the loading axis, via localized plasticity; and (iv) final densification. The tomographic observations show that deformation is initially controlled by the fragmentation and collapse of dispersed individual fly ash particles. After significant strain, sufficient microballoons have collapsed, localizing the stress and hence damage, and forming densification bands through severe plastic deformation of the aluminum matrix. A peak stress of 73 MPa and an energy absorption capacity of 27 MJ m−3 at 47% strain were obtained.