Light-Weight Design Application: Design of a composite vehicle roof and analysis in the frontal crash

Nowadays, light-weight design has absorbed attentions in automotive industry due to its beneficial impacts such as reducing fuel consumption and CO2 emission and, at the same time, maintain or even improve structural efficiency and performance. Beside other materials, such as aluminum, which can be used in light-weight design, composites play an important role due to their high strength, low weight and more durability. In this paper efforts have been made to investigate the design of a roof panel with different composite material solutions paying particular attention to its response in the car frontal crash. The roof panel modeling is carried out in the explicit finite element code LS-DYNA, which is suitable for crashworthiness analysis, with three material solutions of steel (that being the normal production solution will be the reference), aluminum and composite. MAT 24 ”Piecewise Linear Plasticity” is applied to model the steel and aluminum roof panels which is an elasto-plastic material model that can analyze failure based on plastic strain. MAT 54 “Enhanced Composite Damage” along with the Chang-Chang failure criterion is utilized to model the composite roof. This material model is quite common to model composite material because it reduces the number of experimental input parameters compared to damage mechanics-based material models and it can develop the progressive failure and material degradation during the crash. Roof sections are defined near the car body pillars to obtain the results in a wide range and ease to compare set of data. Results including section forces, section displacements and roof absorbed energy are computed and compared for different materials. Results reveal that the composite roof has almost similar response with aluminum and steel panels in frontal crash but is giving larger contribution to vehicle stiffness.