Multiscale Numerical Simulation of Myocardium Subjected to Blunt Trauma

This study developed a macroscopic finite element model of the human body wearing NIJ III body armor target against blunt impacts of DBP10 type 5.8 mm rifle bullets and a microscopic representative volume element (RVE) finite element model of myocardial tissue to conduct multiscale numerical simulations of myocardium under blunt impact effects. Experimental tests on the bullet penetration of ballistic panels were compared with numerical simulations to validate the effectiveness of the macroscopic finite element model. Uniaxial quasi-static compression tests on sheep hearts were carried out, and the constitutive parameters of cardiac muscle fibers and connective tissues in the microscopic RVE model of myocardial tissue were fitted using the inverse finite element method. The numerical simulation results indicate that in the macroscopic behind armor blunt trauma (BABT) numerical simulation, the maximum stress in the heart reached 373 kPa, with a maximum nominal strain of  0.19. The calculated injury score for the heart was 0, indicating no damage. In the microscopic RVE model of myocardial tissue, stress was mainly concentrated in the connective tissue, with cardiac muscle fibers generally exhibiting higher strains than the connective tissues. Localized areas of high pressure were observed in the connective tissue, which could compress capillaries in the connective tissue, potentially leading to minor bleeding as indicated by blood pressure values.