Design and impact response analysis of a novel thoracic physical model

To systematically evaluate the thoracic safety of non-lethal kinetic projectiles (NLKP), a structurally adjustable and simulation-compatible three-rib physical chest model was designed and fabricated. The projectile representation was first validated through rigid-wall impacts at 29 m/s and 61 m/s on a controllable gas-launch platform. The measured force–time histories agreed well with the AEP-99 corridors, confirming the fidelity of the projectile model. Further chest-impact experiments were then conducted using the validated projectile model at 56 m/s and 86.5 m/s. The measured chest-wall displacements, together with the maximum value of the viscous criterion (VCmax), all fell within the validation corridors specified in the NATO Allied Engineering Publication-99 (AEP-99), demonstrating that the proposed model exhibits excellent dynamic-response consistency and predictive accuracy under medium- and low-velocity impacts at or below 90 m/s. The largest deviations between simulation and experiment were 16% and 21%, respectively. A projectile-hardness scan (Soft/Medium/Hard) showed that VCmax increased from 0.298 to 0.336 at 56 m/s and from 0.765 to 0.856 at 86.5 m/s, indicating a more pronounced risk amplification at higher energies. For rib-spacing levels of 0.8S₀/S₀/1.2S₀, peak displacement/force changed by about ±6% and VCmax shifted by 5.7%–6.2%, remaining within an engineering-acceptable band. Compared with the Surrogate Human Thorax for Impact Model (SHTIM), the proposed model adhered more closely to the corridor mid-line at 56/86.5 m/s and yielded VCmax values of 0.308/0.803 (both within the recommended ranges), whereas SHTIM slightly underestimated the high-energy case, confirming an advantage in response fidelity and criterion consistency. Based on the validated setup, systematic finite-element analyses were performed for four representative NLKP—NS, CONDOR, SIR-X, and RB1FS—over 60–90 m/s to elucidate how projectile structure and material govern injury risk. Additional high-velocity simulations (100–120 m/s) showed that the soft-tissue layer dominated energy absorption and dissipation, whereas the rib layer experienced rapidly increasing peak von Mises stress that exceeded the yield limit, revealing a severe fracture risk at elevated speeds. A thickness-sensitivity study demonstrated that the soft-tissue-layer thickness exerted the strongest regulation on total absorbed energy and deformation, while the rib-layer thickness was most effective for limiting peak deflection; the skin-layer thickness had only minor influence within the tested range. These results establish an integrated experiment–simulation framework for thoracic impact evaluation of NLKP, quantify velocity-dependent and layer-specific injury mechanisms, and identify key structural parameters—especially soft-tissue thickness—that control energy management and deformation, providing support for injury assessment and for optimizing protective equipment and testing protocols.