Study on energy absorption mechanisms of Chinese fir under tangential dynamic compression

Owing to its porous hierarchical structure, wood is widely used in impact-protection applications such as packaging, vehicle crash protection, and cushioning structures, and its dynamic mechanical behavior strongly depends on grain orientation. While the energy-absorption mechanism of softwood under radial dynamic compression has been systematically investigated, that under tangential compression remains poorly understood owing to the fundamentally different load-bearing configuration. To address this gap, tangential compression tests were conducted on Chinese fir ( Cunninghamia lanceolata ) across strain rates from 9.52 × 10⁻⁴ to 229 s⁻¹ , combined with multi-scale in-situ characterization using digital image correlation (DIC), computed tomography (CT), and scanning electron microscopy (SEM). A finite element model incorporating strain rate effects was established based on a modified WoodST constitutive model. The results show that Chinese fir exhibits pronounced strain rate sensitivity under tangential compression: the yield stress increases by 15.1%–62.7% with increasing strain rate, although the dynamic enhancement is markedly lower than that under radial compression (43.0%–84.2%). In contrast to the plateau-stress hardening under radial loading, the tangential plateau stress shows a softening response accompanied by distinct stress oscillations. The tangential failure mechanism changes markedly with strain rate, shifting from progressive earlywood collapse with geometric deflection of latewood under quasi-static loading to a rapid instability mode dominated by inertia-induced latewood buckling and earlywood–latewood cooperative shear under dynamic loading. The rate-dependent WoodST model effectively predicts the tangential dynamic response, with prediction deviations for yield stress and plateau stress within 15% and 5%, respectively. These findings reveal that the tangential and radial directions correspond to two complementary transverse energy-absorption mechanisms, establishing grain orientation as a designable parameter for specific impact scenarios; together with the developed rate-dependent constitutive model, they provide theoretical and methodological support for the directional optimization design of wood-based energy-absorbing structures.