Due to the widespread use of polymer composite materials in industry, it is very important to carefully study the properties of these materials in various loading conditions, including high-speed impact. In this study, we investigate the numerical simulation of the effect of underwater explosion on a ship structure with a composite reinforced sheet. In this study, a reinforced composite panel with dimensions of 2 by 3 meters below the water surface is subjected to an explosive charge. This panel is reinforced by three longitudinal and two transverse reinforcements. The material of the reinforced panel is two types of composite polymer-based composites, Carbon-Epoxy and Glass-Epoxy, with five layers with a thickness
of 10 mm. The placement angle of the layers is 0.90/0/90/0. These materials are subjected to underwater explosion loading with two simple and fully trapped boundary conditions and in two cases with and without cracks. The results were extracted from Abacus software and compared with each other to determine the effect of each of these Check the parameters on the sheet behavior.