The Deformation of Expanded Clay Syntactic Foams during Compression Characterized by Acoustic Emission

Kádár, Csilla and Máthis, Kristián and Chmelík, František and Knapek, Michal and Orbulov, Imre Norbert (2020) The Deformation of Expanded Clay Syntactic Foams during Compression Characterized by Acoustic Emission. In: Proceedings of the 11th International Conference on Porous Metals and Metallic Foams (MetFoam 2019). The Minerals, Metals & Materials Series . Springer, Cham. ISBN 978-3-030-42797-9; online ISBN 978-3-030-42798-6

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Abstract

The deformation and failure mechanisms in syntactic foams with different metal matrices were investigated in this study. The syntactic foams were produced by the infiltration method using lightweight expanded clay particles (LECA) as a space holder and commercially pure Al or eutectic Al-12%Si alloy for the matrices. The samples were compressed at room temperature; simultaneously, the acoustic emission (AE) response and the surface deformation were monitored and collated with the deformation curves. In the case of the Al foam, ductile behavior with long plateau stress was observed. During this plateau regime, multiple active shear bands were detected. In contrast, the AlSi12 foam exhibited more brittle deformation behavior. At the end of the quasi-linear stage, the localization of the strain started within one large shear band, accompanied by a significant stress drop. The AE analysis revealed that the deformation was mostly governed by the fracture of LECA particles and the plastic deformation of the matrix material for both types of foams. After strain localization, in the case of the AlSi12 foam, the fracture of the matrix became significant, causing the deterioration of the sample. As for the Al foam, besides the fracture of the LECA particles, the plastic deformation of the matrix played an important role in preventing the foam from falling apart.

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