Response of Thoraco-Abdominal Tissue in High-Rate Compression

Abstract

Body armor protects the human from penetrating injuries. However, in the process of defeating a projectile, the back face of the armor can deform into the wearer at extremely high rates. This deformation can cause a variety of soft and hard tissue injuries. Finite element modeling represents one of the best tools to predict injuries from this high-rate compression mechanism. However, the validity of a model is reliant on accurate material properties for biological tissues. In this study, we measured the stress-strain response of thoraco-abdominal tissue during high-rate compression (1000 and 1900 s-1) using a split Hopkinson pressure bar. Using this method, high-rate material properties of porcine adipose, heart, spleen, and stomach tissue were characterized. At a strain rate of 1000 s-1, adipose (E=4.7MPa) was the most compliant, followed by spleen (E=9.6MPa), and then heart (E=13.6MPa) tissue. At a strain rate of 1900 s-1, adipose (E=7.3MPa) was most compliant, followed by spleen (E=10.7MPa), heart (E=14.1MPa), and stomach (E=32.6MPa) tissue. Only adipose tissue demonstrated a consistent rate dependence across these rates, with a stiffer response at 1900 s-1. However, comparison of these tissues to previously published quasi-static and intermediate dynamic experiments revealed a strong rate dependence with increasing stress response from quasi-static to dynamic to high strain rates. Together, these findings can be used to develop finite element models for high-rate compression injuries.