Smooth topological design of lightweight vibro-acoustic sandwich structures by maximizing sound transmission loss

The vibro-acoustic coupling mechanism and its optimization design of lightweight sandwich structures are globally hot research topics. The traditional parameter adjustment approach highly relies on the experience of designers, which makes it difficult to achieve lightweight design while regulating the acoustic insulation performance of sandwich structures at a limited cost. This paper proposes a new dynamic three-field floating projection topology optimization (FPTO) method to conduct vibro-acoustic coupling topological design for lightweight insulated sandwich structures, to achieve superior sound insulation performance by maximizing sound transmission loss with a volume constraint. The effectiveness and accuracy of the proposed method were verified on representative 2D and 3D numerical examples and also validated with impedance tube tests. The results show that novel optimized structures with a smooth boundary for practical applications and superior acoustic insulation performance than conventional designs can be obtained based on the proposed method. For instance, at an optimization target frequency of 1200 Hz, the total sound transmission loss, corresponding to the optimized target sound insulation performance of the 3D sandwich case, showed an improvement from 56.68 dB to 70.8 dB, compared to the common closed honeycomb structures in engineering practice under the equal mass conditions. Moreover, the numerical simulation and experimental results showed good agreement. The study suggests that the dynamic three-field FPTO method is promising for optimizing acoustic and vibration performance in lightweight vibro-acoustic sandwich structures.