Abstract
The influence of the matrix material on the deformation and failure mechanisms in metal matrix syntactic foams was investigated in this study. Samples with commercially pure Al (Al) and Al-12 wt % Si (AlSi12) eutectic aluminum matrix, reinforced by hollow ceramic spheres, were compressed at room temperature. Concurrently, the acoustic emission response and the strain field development on the surface were monitored in-situ. The results indicate that the plastic deformation of the cell walls is the governing mechanism in the early stage of straining for both types of foams. At large stresses, deformation bands form both in the Al and AlSi12 foam. In Al foam, cell walls collapse in a large volume. In contrast, the AlSi12 foam is more brittle; therefore, the fracture of precipitates and the crushing of the matrix take place within a distinctive deformation band, along with an occurrence of a significant stress drop. The onset stress of ceramic sphere failure was shown to be not influenced by the matrix material. The in-situ methods provided complementary data which further support these results.
Highlights
In the past decades, man-made materials with a relatively high volume fraction of void space, inspired by lightweight cellular structures found in nature, have drawn attention and many researchers have focused on their manufacture and characterization [1,2].Porous materials can advantageously combine the properties of the material they are made of with their structural properties to produce materials for certain applications, such as energy absorption, lightweight structures, mechanical damping, and filtering [2,3]
The Acoustic emission (AE) response up to approximately 5% strain is contrast, in Al foam the AE activity is still high at peak stress
The results of this study show that the Adaptive sequential k-means clustering (ASK) analysis of AE data, combined with SEM, video, and Digital image correlation (DIC) analyses, is useful in monitoring of the dynamics of deformation video, and DIC analyses, is useful in monitoring of the dynamics of deformation behavior behavior
Summary
Man-made materials with a relatively high volume fraction of void space (i.e., a low relative density), inspired by lightweight cellular structures found in nature, have drawn attention and many researchers have focused on their manufacture and characterization [1,2].Porous materials can advantageously combine the properties of the material they are made of with their structural properties to produce materials for certain applications, such as energy absorption, lightweight structures, mechanical damping, and filtering [2,3]. Metal matrix syntactic foams (MMS foams) are a relatively new class of materials which comprise of enclosed porosity inside stiff spheres (or “microballoons”) incorporated in the metallic matrix. Owing to these spheres, MMS foams can typically withstand higher stresses compared with conventional metal foams containing gas porosity [6]. MMS foams can typically withstand higher stresses compared with conventional metal foams containing gas porosity [6] They are, recognized for their potential as energy absorbers in the transport industry or impact protection [5].
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