Blast Absorption Capacity of Brittle Mineral Foam: an Experimental Evaluation

Cellular materials, such as aluminum foam, have proven to be effective energy absorbents. They can be used as the crushable core for blast mitigation sacrificial cladding. In this paper insights into the blast response of a brittle mineral foam-based sacrificial cladding are presented. The experimental set-up used consists of a rigid steel frame (1000 mm × 1000 mm × 15 mm) with a square cavity of 300 mm x 300 mm in the center. An aluminum plate, representing the structure, with a total surface of 400 mm × 400 mm and a thickness of 2 mm is clamped into the steel frame. Two synchronized high-speed cameras in a stereoscopic configuration are used to capture the dynamic response of the aluminum plate at a frame rate of 20000 frames per second. The transient deformation fields are computed using a three-dimensional digital image correlation technique. The blast load is obtained by detonating 20 g of C4 placed at a distance of 250 mm from the center of the tested aluminum plate. The absorption capacity of the brittle mineral foam is assessed by comparing the out-of-plane displacement, the velocity, the acceleration and the major principal strain of the thin aluminum plate with and without the protective mineral foam. Two foam configurations with different thicknesses are considered: 60 mm and 120 mm. It is shown that adding the brittle mineral foam reduces the out-of-plane displacement together with the displacement velocity and acceleration of the aluminum plate at least by a factor of two. Post-mortem analysis of the foams shows that mitigation of the blast load in the present set-up and under the considered loading is partially obtained by crushing of the cell walls but mostly though the growth of cracks in the specimen.