Hierarchical Experimental Characterization of the Human Rib Cage for Nonlethal Projectile Impact Applications

Kinetic energy nonlethal weapons are designed to induce target compliance without causing severe injury and death. Computational torso models are a powerful tool used to evaluate the safety of new projectile designs before they are fielded, but the utility of such biomechanical models relies on experimental data for validation. To address this need, biomechanical test data from three different types of postmortem human subject (PMHS) experiments are presented. In the first test series, rib peak velocities were evaluated in four PMHS torsos during impacts with a rubber projectile. In the second test series, flesh over the ribs of these same PMHS was removed, termed defleshed, to allow for direct impact to the ribs. By comparing the rib response between the first two test series, it was determined that the layer of flesh and muscle has a substantial effect on the rib response. The third test series evaluated the individual rib response by performing dynamic three-point bend tests on the nonfractured ribs from the previously tested PMHS. The general trends across the three test series demonstrate that the intermediate rib levels (ribs 6-8) are structurally stiffer than the upper and lower ribs. Additionally, anterior rib cage impact locations tend to be more compliant than lateral and posterior locations. Results provide valuable validation data for future computational torso models by characterizing the response of the fleshed rib cage, bare rib cage, and isolated rib in an application for kinetic energy nonlethal weapons.