Experimental validation of a topology optimized 2D sandwich panel for sound transmission minimization

In industry, an increasing pressure is perceived to obtain dynamical systems which are light-weight, load-carrying and achieve excellent noise and vibration properties. Sandwich panels with specifically designed structural-acoustic cores have shown potential to reconcile these conflicting requirements. Optimization techniques can be used to automate the design process while making a trade-off between the conflicting requirements. This work proposes a methodology to easily validate the sound transmission loss (STL) of 2D structures. The experimental validation considers a thin slice of the extruded 2D topology as an input and by a purely structural excitation and measurement, the STL is obtained. This enables a fast validation of novel sandwich core designs without the need to go to 3D simulations, fabrication and measurements. In this manuscript, the experimental validation is demonstrated for a sandwich core design coming out of a topology optimization framework which achieves a high STL by a mode-conversion effect. The methodology can equally well be applied to validate a 2D design obtained via other strategies. The near-2D finite sample is fabricated, tested and compared to two reference cases being the equivalent mass and double mass case. These two cases are selected to show the performance of the optimized design while still being lightweight. An excellent match is achieved between the numerically and experimentally obtained STL performance for the specific design considered, demonstrating the validity of the experimental validation technique and confirming the mode-conversion effect to achieve high STL.