Experimental study on the dynamic responses of foam sandwich panels with different facesheets and core gradients subjected to blast impulse

Sandwich panels with an energy-absorbing core material have exhibited great potential in lightweight structures for blast protection. In this study, the deformation/failure modes of sandwich panels against blast impulse were investigated experimentally. The blast tests were conducted on the aluminum foam-core sandwich panels with different facesheet materials, namely aluminum alloy, steel, and carbon fiber reinforced plastics (CFRP); and the cores involve uniform foam and graded foam. The deformation modes of the whole sandwich panels as well as the front facesheet, foam core, and back facesheet were analyzed systematically. It is shown that the deformation patterns are fairly sensitive to the impulse intensity, facesheet material, and foam core gradient. Based upon the measurements, the back facesheet deflection increases linearly with the impulse, apart from the petal-tearing failure of front facesheet. When considering the specific impulse and the same metallic back facesheets, the blast resistance of the sandwich specimen with CFRP front facesheet is superior to these of the metallic front facesheet specimens. Interestingly, the sandwich panels with the aluminum front and steel back facesheet perform better in blast resistance than those with the steel front and aluminum back facesheet. The blast resistance of sandwich panels with a positive gradient of core density (i.e. core density linearly decreased along the blast direction) is superior to those with a negative gradient of core density; and the performance increases with increasing density difference. Compared with the uniform core, the positively-graded foam core with a larger density difference exhibits a stronger blast resistance, while those with a smaller density difference present a weaker blast resistance, The study is expected to provide some fundamental data and design guide for a more efficient sandwich structure with lighter weight and higher capacity of blast protection.