Multidisciplinary optimization of a lightweight torpedo structure subjected to an underwater explosion

Undersea weapons, including torpedoes need to be designed to survive extreme loading conditions such as underwater explosions (UNDEX). In this work, a multidisciplinary optimization problem is solved for a lightweight torpedo model subjected to UNDEX. A torpedo configuration with least possible weight for a given level of safety from an explosion at a critical distance is obtained. The torpedo is modeled using both metallic and composite material models. The similitude relations are used to model the pressure wave resulting from an explosive, which is assumed as a spherical wave. The response of the composite flat plate is obtained prior to the torpedo for validating the analysis routine and determining the stress levels in each of the layers. The response of a composite lightweight torpedo model is also obtained and structural optimization is performed to achieve the minimum weight subject to the required safety levels. Similar analysis and optimization was performed for a stiffened metallic torpedo. The optimal designs for both models are compared and it is observed that the composite torpedo model is stronger and lighter than the metallic design when subjected to an UNDEX at a given standoff distance.