Effects of aging factors on thoracic injury risk under blunt impact loading

Thoracic injury from blunt loading is the principle causative factor of death in automotive crashes, which has been shown to be particularly significant for the elderly. The purpose of this study is to characterize the effect of aging factors, such as morphological changes in the rib cage and material property changes in the biological structures, on the injury level under a blunt loading condition. To achieve this objective, a detailed finite element model of the thorax, including the internal organs for the adult (base) model (Model I), was developed. Age-related morphological changes in the rib cage (Model II) and material property changes in the biological structure (Models III and IV) were also developed. The developed rib and adult thorax models were validated using previously reported experimental test data. The simulation results showed that the age-related morphological changes in the rib cage decreased the thoracic injury tolerance in the case of a frontal impact, but a reverse effect was produced in the case of lateral impact loading. However, material property changes in the biological structure decreased the thoracic injury tolerance irrespective of the impact direction. The possible aorta injury site also matched well with previous observations; however, the peak maximum principal stress in the aorta was generated at different sites according to the impact direction.