Bragg Bands Generation in Beams and Plates for Mass Reduction and Vibroacoustic Performance

Résumé

Most of the existing approaches for designing locally resonant metamaterials involve addition or inclusion of elements such as tuned mass dampers or masses following a periodic pattern. The primary focus of this study is on the generation of Bragg bands in aluminum cantilever beams and plates following a subtraction-based approach. Periodic cells are created by using a simple machining operation, that is periodically removing material in the thickness direction. The goal is to design structures that are lighter than their homogeneous versions, but that can nevertheless exhibit similar or improved vibroacoustic behavior. Numerical simulations are first considered. Regarding beams, the effects of the number of periodic cells along length and the thickness removal are studied for a fixed beam length. For plates, the global vibration behavior as well as the sound transmission loss are evaluated for two plates with periodic diagonal material removal. Contact less vibration measurements using a multi-point laser vibrometer and an automatic impact hammer are then performed for beams and plates. Sound transmission loss measurements are also conducted for an homogenous aluminum plate, and two machined plates with two different diagonal periodicities for material removal. The obtained results generally indicate that simple machining operations can be a simple but efficient way for the generation of band gaps in beam-like and plate-like lightened structures.