A study on acoustic characteristics of automotive magnesium composite dash panel

A dash panel is a plate that separates the engine compartment from the cabin and mainly serves to block engine noise. The effect of automotive lightweight design on sound insulation performance of the dash panel needs to be studied. In this paper, the study of acoustic characteristics of automotive magnesium composite dash panel was conducted in four steps. Firstly, the sound insulation performance of a basic magnesium alloy plate was investigated using finite element method/indirect boundary element method (FEM/IBEM) and was verified with corresponding sound insulation test. The result proved that the structural-acoustic coupling based FEM/IBEM was feasible for calculating the sound insulation. Secondly, finite element models of two bare (steel and magnesium alloy) dash panels were created and the FE model of the steel dash panel was verified with a constrained modal test. The sound insulation performance of the two bare dash panels of different materials was then predicted by developing their FEM/IBEM models, and the modal contribution was examined based on the partially-coupled modal assumption. It was found that although the weight was lightened the sound insulation performance did not deteriorate, and the performance was even better in some frequency bands after replacing steel with magnesium alloy. Thirdly, the sound insulation performance of composite dash panel applied with acoustic packages was studied. It was found that the sound insulation performance deteriorated in a low frequency band (0–1000 Hz) for certain acoustic packaging materials, and it was not always true that the thicker the acoustic package, the better the sound absorbing performance. Finally, the finite element-statistical energy analysis (FE-SEA) method was used to extend the sound insulation research of the composite dash panel to the full-frequency band. The results showed that acoustic packaging design of key areas could have significant acoustic optimization effects. Relevant discussions on the results were provided and conclusions were made.