Force Isolation by Locally Resonant Metamaterials to Reduce NVH 2018-01-1544
The combination of lightweight design and performant Noise, Vibrations Harshness (NVH) solutions has gained a lot of importance over the past decades. Lightweight design complies with the ever more stringent environmental requirements, however conflicts with NVH performance, as low noise and vibration levels often require heavy and bulky systems, especially at low frequencies. To face this challenge, locally resonant metamaterials come to the fore as low mass, compact volume NVH solutions, beating the mass law in some tunable frequency zones, referred to as stopbands. Metamaterials are artificial materials made from assemblies of unit cells of non-homogeneous material composition and/or topology. The local interaction between unit cells leads to superior performance in terms of noise and vibration reduction with respect to the conventional NVH treatments. Previously the authors showed how wave propagation along one-dimensional structures can be reduced by metamaterial additions. In this paper the authors apply the concept of metamaterials to reduce vibration in a complex 2D structure, excited at one specific input location. Numerical and experimental results are shown for a simplified set-up representing part of a body of a vehicle excited by a shock absorber. By adding metamaterials on a limited portion of the structure, an average of 6.8 dB with a minimum of 3 dB vibration reduction is achieved in a 50 Hz frequency band centered around the target frequency of 300 Hz, by only adding 2.4 percent of mass to the structure. The frequency band, the attenuation and the added mass are all tunable by design.