Dynamic Failure of Composite Panels Subjected to Underwater Impulsive Loads
Horacio Espinosa (Northwestern University), Xiaoding Wei ()
Eringen Medal Symposium in honor of G. Ravichandran
Wed 9:00 - 10:30
Salomon 001
Designing lightweight high-performance materials that can sustain high-pressure impulsive loading is of great interest for marine applications. In this study, a finite element fluid-structure interaction model is developed to understand the deformation and failure mechanisms of both monolithic and sandwich composite panels. A new failure criterion that includes strain-rate effects was formulated and implemented to simulate different damage modes in unidirectional glass fiber/matrix composites. The laminate model uses Hashin’s fiber failure criterion and a modified Tsai-Wu matrix failure criterion. The composite moduli are degraded using five damage variables, which are updated in the post-failure regime by means of a linear softening law governed by an energy release criterion. A key feature in the formulation is the distinction between fiber rupture and pull-out by introducing a modified fracture toughness, which varies from a fiber tensile toughness to a matrix tensile toughness as a function of the ratio of longitudinal normal stress to effective shear stress. The delamination between laminas is modeled by a strain-rate sensitive cohesive law. In the case of sandwich panels, core compaction is modeled by a crushable foam plasticity model with volumetric hardening and strain-rate sensitivity. These constitutive descriptions were used to predict deformation histories, fiber/matrix damage patterns, and inter-lamina delamination, for both monolithic and sandwich composite panels subjected to underwater blast. The numerical predictions were compared with experimental observations. We demonstrate that the new rate dependent composite damage model captures the spatial distribution and magnitude of damage significantly more accurately than previously developed models. The model also reveals that the foam plays an important role in improving panel performance by mitigating the transmitted impulse on the back-sheet while maintaining overall bending stiffness.