Experimental and numerical study of non-penetrating FMJ ballistic impacts on coupled soft and bone tissue surrogates

This study evaluates the biomechanical response of biofidelic human tissue surrogates, including embedded bone simulants, under non-penetrating ballistic impacts to bridge the gap between current armor certification standards and thoracic injury biomechanics. A combined experimental and numerical approach was implemented, consisting of 14 ballistic impact tests using real ammunition at velocities ranging 209 and 439 m/s. The experimental setup utilized ballistic gelatin with an embedded thoracic cage surrogate to simulate the human thorax, protected by advanced soft body armor. Parallel finite element analyses were performed, employing a validated visco-hyperelastic constitutive model for the gelatin and a damage-based composite model for the ballistic panel. The results demonstrated high fidelity in reproducing the early-stage non-linear dynamics (0-4 ms), quantifying the correlation between projectile kinetic energy, transient cavity depth and morphology, and the peak pressure waves within the soft tissue surrogate. The study further characterizes the transition from elastic deformation to structural failure of the embedded thoracic cage surrogate, identifying critical velocity thresholds for multiple rib fractures. The numerical model not only reproduced the experimental response but also captured the complex energy dissipation mechanisms of the ballistic panel and the subsequent inertial and stress-wave response of the soft tissue. These findings validate the reliability of integrating biofidelic surrogates with advanced finite element modeling to predict transient cavity development, pressure transmission and complex fracture patterns behind armor. Compared with traditional clay-based assessment methods, the proposed framework provides improved insight into both soft tissue deformation and bone fracture risk, offering a reliable basis for the design and optimization of personal protective systems. Ultimately, this study establishes a fundamental precursor for the analysis of increasingly complex anatomical geometries and intricate impact scenarios.