Experiments and Computational Modeling of a Sealed Open Cell Foam in an Underwater Shock Tube

Background

Open cell foams have recently been used as a simulant for lung parenchyma to model underwater blast injury and thus the foam’s mechanical response characteristics are of interest to the underwater blast community.

Objective

The compressive response of a soft, sealed open cell foam (FlexFoam-iT! VIII) subjected to underwater hydrostatic pressure and shock is investigated through an experimental and computational study.

Methods

Real-time deformation of the foam during loading is captured via high-speed cameras, and a 3D digital image correlation technique calculates the foam’s transient volumetric strain. Fully coupled fluid–structure interaction (FSI) models of the experiments are developed for the FSI code Dynamic System Mechanics Advanced Simulation (DYSMAS), where the Arruda-Boyce hyperelastic model calculates the foam constitutive behavior.

Results

Simulated foam volumetric strains exhibit excellent correlation to shock test data. Hydrostatic experiments show that deformation of the sealed foam under hydrostatic compression is similar to the behavior of compressed air, until reaching volumetric strain levels exceeding 50%. Quasistatic DYSMAS simulations at numerous applied hydrostatic pressures produce volumetric strains between those measured in hydrostatic experiments with sealed foam (lower bound of strain at a given pressure) and in confined compression experiments with unsealed foam (upper bound).

Conclusion

The FSI modeling approach in DYSMAS showed a strong correlation with experimental results. Given this foam's prior successful use in a physical lung simulant, this computational approach is a good candidate for future modeling of human lung tissue response to underwater shock.