Optimal Design of a Multifunctional Sandwich Panel With Foam Core: Lightweight Design for Flexural Stiffness and Acoustical Transmission Loss
Résumé
Nowadays there is a trend for developing multifunctional structures involving mechanical specifications with other requirements such as acoustical and thermal management.
For that purpose, hybrid materials have been developed during the past decades showing their high efficiency for multifunctional applications.[1 – 4] Hybrid materials take advantage from the combination of materials and from the use of an additional design scale which is the geometry. Architectured materials such as foams, honeycombs, and truss structures have been widely studied regarding both the influence of the materials and the geometrical parameters.[5 – 7] Among these, foams are the most studied, the less expensive and the most used of hybrid materials, and therefore could be considered as the most representative hybrid materials. It is used for very demanding applications such as for aeronautical industry [8] but also in building trades or in packaging.[9] When integrated in a sandwich panel, the performances achievable with foams can be tremendous. Its porosity network ensures a good thermal resistance due to the presence of air, while its low density is bene fi cial for mechanical applications. The mechanical behavior of such sandwich panels has been studied by several authors leading to series of books [10,11] and articles.[12 – 14] The structure of a sandwich panel has also been investigated to develop efficient acoustical panels with an increased acoustical transmission loss. A prior work from Lang and Dym [15] showed that sandwich panels with a soft core could be designed in order to favor the development of unsymmetrical vibration modes which enables to obtain an improved transmission loss. Based on this work, several authors developed acoustical models dedicated to the prediction of the acoustical transmission loss of sandwich panels.[16-18] The main issue addressed in this paper is that a high stiffness-to-mass design of a sandwich panel usually ends to a poor acoustical transmission loss. Then the design of a panel for both mechanical and acoustical properties becomes sensitive. Wang et al. [19] investigated the optimal design of a sandwich panel by setting constraints on the acoustical and mechanical behavior and by looking for the minimum weight design. For that purpose the previous authors used a genetic algorithm and found a competitive solution compared to usual mechanical structures.
Generic design methods have been developed in the late 1990s, particularly the performance index method. [20] However, a more re fi ned procedure is needed to deal with multiple criteria in the design process.
In this paper, the design of a classical sandwich panel with a foam core is considered. A Pareto set optimization using a genetic algorithm is used to assess the interactions between a set of performances composed of mass, fl exural stiffness and acoustical transmission loss. Trade-off surfaces will be calculated in order to evaluate the in fl uence of material and geometrical parameters. The design process developed here involves both materials selection and geometrical design and is part of a toolbox for a “ materials by design ” approach.