Abstract
It is necessary to evaluate the mechanical properties of foam materials at wide range of strain rates, since these materials have the strain rate dependence of strength. In this study, we evaluated the dynamic compressive behaviour of the closed-cell foam materials using the load-measuring apparatus with opposite load-cells, which is applying the drop-weight testing machine. In order to measure large deformation at dynamic strain rate range, universal rate range load-cell, which can reduce the influence of the reflected stress wave, was used. In addition, load equilibrium can evaluate using opposite load-cells which consist of movable (drop-weight) and stationary load-cells. In this study, the commercially available ALPORAS closed-cell aluminum foam was used. From the results of quasi-static tests, three deformation processes of elastic response, plateau deformation and densification were confirmed in stress-strain relation. Within the set of experiments, the closed-cell aluminum foam was locally deformed from cells with low strength and the stress variation occurred during plateau deformation, regardless of the strain rate. In addition, it was clarified that the stress equilibrium was not achieved at the dynamic strain rate. This is thought to be a phenomenon caused by local deformation of cell structure.
Highlights
The foam structure has various characteristics such as lightweight, impact absorption, sound absorption, and waterproof characteristics [1]
In this study, we evaluated the compressive behaviour of the closed-cell foam materials at the dynamic strain rate using the load-measuring apparatus with opposite load-cells, which is applying the drop-weight testing machine
The stress variation due to the collapse of cells occurred in the plateau deformation region
Summary
The foam structure has various characteristics such as lightweight, impact absorption, sound absorption, and waterproof characteristics [1]. In order to know the impact absorption characteristics of the foamed aluminum, it is necessary to acquire an accurate stress-strain relation of the foamed structure. The quasi-static properties (10-1 s-1 or less) using a universal testing machine and the impact properties (102−103 s-1)using a split Hopkinson pressure bar (SHPB) method [5, 6] have been evaluated in the foamed aluminum [7, 8]. Since the dynamic strain rate (100−101 s-1) is difficult to measure with the universal testing machine or SHPB method, the research paper are very few, regardless of the foam structure. In this study, we evaluated the compressive behaviour of the closed-cell foam materials at the dynamic strain rate using the load-measuring apparatus with opposite load-cells, which is applying the drop-weight testing machine
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