Abstract:

To meet the dual demand of lightweight design and crash safety performance improvement in passenger vehicles， in this study the synergistic reinforcement mechanism of polyurea coating thickness （0-7 mm） and interface strength （6 - 14 MPa） on the impact resistance of a one-piece die-cast aluminum rail that directly carries longitudinal loads is investigated. Through material-level static and dynamic tensile tests on polyurea， interfacial double cantilever beam （DCB） tests， and component-level quasi-static and dynamic crush tests on the rails， combined with a three-dimensional finite element model built on the LS-DYNA platform， multi-dimensional validation and parametric analysis of the coating are conducted. The results show that polyurea exhibits significant strain rate hardening behavior. When the coating thickness is 6 mm， the impact peak load of the rail can be increased by 16.53%. However， parameter analysis reveals that a thickness of approximately 3 mm achieves optimal energy absorption efficiency. The interface strength of around 12 MPa provides the best energy transfer efficiency， while insufficient strength may lead to interfacial delamination. The comparison between simulation and experimental results shows that the error in peak impact force is controlled within 10%， with highly consistent failure modes observed. In conclusion， by appropriately matching the polyurea coating thickness and interface strength， the load-bearing capacity， energy absorption efficiency， and structural integrity （e.g.， reduced fragment scattering） of the rail can be effectively enhanced， while improving deformation behavior during impact and suppressing local brittle fracture and buckling instability， thereby providing both theoretical support and engineering guidance for the coordinated design of automotive lightweight and safety.

Key words: cast aluminum longitudinal beam, polyurea coatings, finite element analysis, impact property