Experimental and theoretical studies of fiber-reinforced composite panels subjected to underwater blast loading

Fluid-structure interaction (FSI) experiments on monolithic and sandwich composite panels were performed to identify key failure mechanisms resulting from underwater blast loading. Panel performance was compared in terms of impulse deflection. Various failure mechanisms such as delamination between laminas, matrix damage and fiber rupture in laminas, and foam crushing were identified. A 3-D rate-dependent numerical model was developed to understand the experimentally observed failure mechanisms. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional composite plies. This rate-dependent numerical model predicted the responses of composite panels subjected to underwater blast loading with more correlated material damage patterns with the experimental observation than previously developed models. The model also revealed the important role of the soft foam core in sandwich composite panels for improving panel performance by mitigating the transmitted impulse to the back-side face sheet while maintaining overall bending stiffness.