Acoustic behavior of sandwich plates

Abstract

Sandwich structures of honeycomb cores and carbon laminate face sheets are ideal to meet low-weight and high-stiffness specifications. However, these structures are susceptible to noise problems. They tend to radiate structure-borne sound very efficiently or be transparent for air-borne sound. The problem's root is the coincidence frequency, at which the wavelengths of beam and air coincide. In the vicinity of the coincidence frequency, observing wave fields with slanted incidence, the air's trace wavelength can match the beam's wavelength. Unlike homogenous structures, where wave trace matching only occurs in a narrow frequency band, sandwich structures can display this effect in a more than two decade wide frequency region. This facilitates noise transmission in a wide frequency band. The first focus of this paper is how to avoid this problem in the first place by designing the sandwich adequately. To check the region of wave trace matching, dispersion curves are used. A simplified but sufficiently accurate dispersion curve is proposed. The second focus lies in the interpretation of the dispersion curve, i.e. what is physically happening in the beam structure. The third focus is placed on the experimental identification of the sandwich beam structure's shell parameters including its damping. Special attention is placed on which measures are necessary and which not in the experimental setup and experimental procedure to achieve sufficiently accurate results.

In-plane elastic wave propagation in aluminum honeycomb cores fabricated by bonding corrugated sheets

“…In general, Bloch wave theory allows for expressing the periodic behavior of a wave, including its dispersive and attenuative behaviors, across solid materials with spatially periodic heterogeneities. Thus, it is often used as a homogenization tool to describe the wave propagation characteristics in periodic and heterogeneous mediums [20,22–24], such as the periodic double-walled honeycomb considered in this study as well as sandwich structures comprising composite sheets and honeycomb cores [30].…”

Vibro-Acoustic Characterization of a Composite Structure Featuring an Innovative Phenolic Foam Core

“…Choosing A, B, and C as the values that minimize Q. The solution procedure described in detail in [36] uses three equations to determine the dynamic parameters of the beam along the entire frequency range, but other fitting approaches have been explored in the literature, such as writing frequency as an explicit function of the bending stiffness and minimizing the error in frequency [37]. As pointed out in Ege et al [38], at increasing frequencies the damping increases, resonances are less pronounced, the modes overlap and the frequency response tends to smooth out, thus, this modal identification method can normally be used in a limited frequency range depending on the material.…”

Multi-objective optimization approach on diffuse sound transmission through poroelastic composite sandwich structure

“…They [42] also considered generalized displacements of the Carrera Unified Formulation to analyze dynamic of the FG doubly curved shells. Nentwich and Fuchs [43] presented STL of the sandwich structures interlayered with honeycomb core. However, two cost functions including the weight and deflection of the structure were investigated by Khalkhali et al [44] to multi objective optimize of the sandwich structures.…”