Application of the Wave Propagation Approach to Sandwich Structures: Vibro-Acoustic Properties of Aluminum Honeycomb Materials

Abstract

Featured Application: Acoustic design and characterization of sandwich panels.Abstract: Sandwich structures are manufactured using multiple combinations of materials for core and laminates. The real performances are influenced by variability in the composing layers and even by the uncertainties introduced while bonding them together. Therefore, experimental tests are usually the preferred way to assess the most important parameters required to develop and to characterize the product, the main downsides lying in their cost and time consumption. This work explores a practical application of the wave propagation approach by means of a case study, in which some significant properties of an aluminum honeycomb panel are obtained starting from simple vibro-acoustic tests carried out on beam specimens. After determining the frequency-dependent bending stiffness function, the sound transmission loss is predicted and compared with the experimental results obtained in sound transmission suites. The same vibro-acoustic tests are used to estimate the core shear modulus. Finally, a parametric study is proposed to show how this technique can be effectively used in the early design stage, when producing physical samples is often impossible due to time and money constraints. The method proved to be a reliable and powerful tool in all the tested applications, providing good results with limited computational effort.

The stiff plate location into the shoe influences the running biomechanics

“…This induces different lever arms to the MTP joint centre of rotation that may influence the forefoot bending and affect all the lower limb kinematic and kinetic behaviour. From a mechanical point of view, bending an object causes tensile stresses and lengthening on one side, compressive stresses and shortening on the other, and no tensile or compressive stresses on the neutral axis of the cross-section (Piana, Petrogalli, Paderno, & Carlsson, 2018;Turner & Burr, 1993). A similar stress distribution may occur in the midsole during the forefoot bending in running.…”

Sound Characterization through Intensity of Acoustic Radiation Measurement: A Study of Persian Musical Instruments

“…Giordano used the parameter p/v, where p represents the sound pressure captured in the near field and v represents the velocity of the soundboard (1998). It is worthwhile considering that a similar method has been recently developed for the acoustic situation of sound insulation [17], far from musical instruments. Unfortunately, all these studies have one prevalent outcome: the frequencies of resonance have not coincided with those of acoustic emission, and they often have an adverse correlation.…”

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

“…In the present paper, the wave propagation approach, as presented in the work by Nilsson and Nilsson [25] is used as a theoretical background for defining a test method to obtain the mechanical and dynamic properties of a sandwich material. The symmetry of the structure is assumed in obtaining the equations governing its transverse displacement ( Figure 2), whose derivation is summarized in [26]. with the nominal data of the materials constituting the layers, so to highlight the effects of the manufacturing process on the sound insulation properties of the final product.…”

“…The flexibility of the method lies in the combination of an analytical model, which, although simplified, is valid in many practical circumstances, and of relatively simple experimental tests, which allow to encompass the actual vibrational behavior of the material through its apparent bending stiffness. A particularly promising application is the design of new products with specific sound insulation properties, as shown by Piana et al [26], where the same approach is used to model the vibro-acoustic properties of aluminum honeycomb sandwich panels and to identify the most sensitive parameters in the development of new configurations. In this case, A, B, and C coefficients are calculated directly from the properties of the constituent layers, which can, in principle, be used to design new structures at an early stage, trying to optimize their acoustic behavior whilst keeping an eye on production constraints.…”