Impact Simulation and Structural Optimization of a Vehicle CFRP Engine Hood in terms of Pedestrian Safety

With the rapidly developing automotive industry and stricter environmental protection laws and regulations, lightweight materials, advanced manufacturing processes and structural optimization methods are widely used in body design. Therefore, in order to evaluate and improve the pedestrian protection during a collision, this paper presents an impact simulation modeling and structural optimization method for a sport utility vehicle engine hood made of carbon fiber reinforced plastic (CFRP). Head injury criterion (HIC) was used to evaluate the performance of the hood in this regard. The inner panel and the outer panel of CFRP hood were discretized by shell elements in LS_DYNA. The Mat54-55 card was used to define the mechanical properties of the CFRP hood. In order to reduce the computational costs, just the parts contacted with the hood were modeled. The simulations were done in the prescribed 30 impact points. In order to validate the reduced finite element model, pedestrian impact tests were carried out. To further improve the performance in terms of pedestrian safety, CFRP layers were added to strengthen the outer panel. A parametric optimization was carried out. Surrogate model was constructed by three approximation approaches and the errors were compared. Four algorithms were utilized to solve the optimization problem. The best optimization is done through Kriging model approximation and the non-dominated sorting genetic algorithm-the third version (NSGA-III). The optimal design is relatively light and reduces the HIC value of the critical point from 2397 to 876. This method can be a useful tool for pedestrian protection and related works.