Research on the Bandgap Characteristics and Vibration Isolation and Sound Insulation Performance of Hollowed-Out Composite Panels

This study investigates the application of phononic crystal plates for automotive vibration and noise attenuation through a combined material–structure design approach. Four materials—aluminum, lead, epoxy resin, and plexiglass—were selected to construct a composite plate with a low-density matrix and high-density metallic inclusions. Finite element modeling in COMSOL Multiphysics identified organic glass–lead as the optimal configuration, balancing wide bandgap performance with low-frequency characteristics and lightweight requirements. Parametric analysis demonstrated that rectangular inclusions provide the widest bandgap under equal area conditions, and increasing their volume fraction shifts the bandgap to lower frequencies while broadening its width. The study verifies the reliability of the finite element method (FEM) and further explains the formation mechanism of the bandgap. This study proposes a phononic crystal plate structure with optimal performance: a rectangular phononic crystal plate with a length of A = 20 mm and a height of B = 10 mm serves as the matrix, and four identical rectangular inclusions each with an area of S = 16 mm2 are embedded in it. The matrix material is organic glass, while the material of the inclusions is lead. The resulting optimized structure exhibits a complete Lamb wave bandgap from 6.29 to 22.03 kHz, with strong elastic wave attenuation extending over 6.00–30.00 kHz. Acoustically, it achieves sound transmission loss (STL) exceeding 130 dB within 5.85–27.91 kHz, peaking at 143.99 dB. These results verify the structure’s dual functionality in simultaneous vibration isolation and sound attenuation within the same frequency range, demonstrating the potential of phononic crystal plates for targeted noise and vibration control in automotive engines and rotating machinery.