Dynamic response and failure of carbon/epoxy composite sandwich subjected to underwater impulsive loading

In this work, the dynamic response and failure modes of carbon/epoxy sandwich structures with PVC foam cores subjected to underwater impulsive loading are experimentally investigated. The 3D digital image correlation technique with high speed photography is used to capture the dynamic response of the structures. The effects of loading intensity, core density, fluid-structure interaction and ply orientation of face sheets on the deformation and damage of the clamped sandwich structures are assessed. The results showed that the compression of PVC foam can effectively reduce the deformation and damage of the sandwich structures. The maximum deflection of rear face sheets increases with PVC core density increasing. The total deflection of sandwich plates including front sheets, cores and rear sheets increases with the decreasing of core density and fluid-structure interaction parameters. Additionally, the influence of ply orientation of carbon/epoxy face sheets on the blast resistance of the sandwich structures can be ignored in the range of normalized impulse intensity (0.08-0.29) used in the tests. With the loading intensity increasing, the failure modes of the sandwich plates present permanent deflection, fiber breakage at boundary and matrix crack of carbon/epoxy at front face-sheets, core compression and debonding between cores and face sheets including front and rear sheets. The results obtained from those tests can provide valuable reference to design the lightweight protective structures.