Response of Cylindrical Composite Structures to Underwater Impulsive Loading

The response of cylindrical composite structures subjected to underwater impulsive loads is analyzed. The analysis focuses on the effect of varying structural attributes and material properties on load-carrying capacity, deflection, energy dissipation and damage. The structural designs studied are monolithic composite structures, and sandwich structures with foam cores of different relative densities and different radii. Underwater impulsive loads are generated using a novel experimental setup, and deflection and core compression are characterized using high-speed digital imaging. The experiments are supported by fully dynamic 3D numerical calculations which account for fluid-structure interactions and damage and failure mechanisms in the materials. For the same applied impulse, the monolithic cylindrical sections experience significant warping, delamination and cracking, while sandwich structures experience significantly lower damage. In sandwich structures, as the core density increases, the transmitted impulse and overall damage also increase. Deflection and warping in the impulsively loaded region are influenced by the radius of curvature and material orientation. Results show that cylindrical sandwich structures have superior blast-resistance than cylindrical monolithic structures of equal mass with only relatively minor increases in wall thickness. The experiments, computations and structure-performance relations offer approaches for improving the blast mitigation capabilities of cylindrical composite sections in critical parts of a ship structure like the keel, hull and pipes.