Enhanced acoustic insulation properties of composite metamaterials having embedded negative stiffness inclusions

Abstract

a b s t r a c tDespite the fact that the concept of incorporating Negative Stiffness (NS) elements within mechanical systems was formulated and validated more than 40 years ago, it has only recently received consistent attention. In this work, the design of a layered mechanical metamaterial having implemented NS inclusions is presented and its acoustic wave propagation properties are modelled. A dedicated twodimensional periodic structure theory scheme is developed in order to compute the frequency dependent damping loss factor of the metamaterial structure. The acoustic transmission properties through the modelled panel are computed within a Statistical Energy Analysis (SEA) scheme. It is demonstrated that the suggested layered metamaterial exhibits highly superior acoustic insulation performance close and above the acoustic coincidence range, thanks to the drastic increase of its structural damping properties implied by the NS elements. Additionally, the proposed configuration presents superior performance in a broadband frequency range when compared to a viscoelastic damping constraint layer of equivalent mass.

Platonic crystal with low-frequency locally-resonant spiral structures: wave trapping, transmission amplification, shielding and edge waves

“…This model generalizes the effect on a single frequency previously shown in [20]. It can be also considered as an alternative to the challenging problem of opening large stop bands at low frequency for vibration and acoustic isolation [32,36,37].…”

On spectral partitioning of signed graphs

“…Inclusions with negative stiffness can occur in mechanics if the inclusion is stored with energy [21], e.g., pre-stressed and constrained. We design inclusions with negative stiffness by pre-tensing the spring to be repulsive [4]. Allowing only the transversal movement of the masses, as in [5], gives the necessary constraints.…”

“…Dumbbell" graph Our final example is the "Dumbbell" graph, displayed in Figure 8, consisting of two complete sub-graphs of slightly unequal sizes, 6 and 7, to break the symmetry, attracted by two edges with positive weights, (3,9) and (4,10), and at the same time repelled by two other edges, (1,7) and (2,8), with negative weights, where all weights are unit by absolute value. Since the weights of the 4 edges between the two complete sub-graphs average to zero, intuition suggests cutting all these 4 edges, separating the two complete sub-graphs.…”

Quantification of Guided Wave Interaction Effects With Localised Structural Nonlinearities in Complex, Composite Structures

“…The vibration of a uniform waveguide through the WFE technique was investigated in [32,33]. The WFE method has recently found applications in predicting the vibroacoustic and dynamic performance of composite panels and shells [34,35,36,37,38,39,40] , with pressurized shells [41,42] and complex periodic structures [43,44,45,46] having been investigated. The variability of acoustic transmission through layered structures [47,48], as well as wave steering effects in anisotropic composites [49] have been modelled through the same methodology .…”