JOURNAL OF SOUND AND VIBRATION Journal of Sound and Vibration 301 (2007) 93–105 Structural-acoustic optimization of sandwich structures with cellular cores for minimum sound radiation H. Denli, J.Q. Sun à Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA Received 8 February 2006; received in revised form 31 May 2006; accepted 11 September 2006 Available online 14 November 2006 Abstract An optimization study of sandwich structures with cellular cores for minimum noise radiation in a wide frequency band, subject to the constraints on the fundamental frequency and weight is presented. Sensitivity functions of the radiated acoustic power are used to improve the computational time and accuracy in near optimization. Numerical examples indicate that significant reduction of narrowband and broadband sound radiation can be achieved. r 2006 Elsevier Ltd. All rights reserved. 1. Introduction Since sandwich structures in aerospace industry are often stiff and light, and have low damping, they can experience resonant motions and radiate sound. Advanced sandwiches structures must meet not only stiffness to weight ratio demands, but also have improved acoustic performance. An optimization study of the cellular core of sandwich structures to minimize the radiated sound power in a wide frequency band, subject to the constraints on the fundamental frequency and weight is presented. Sandwich structures consist of three layers. Two thin and stiff skins are bonded to a low density core on both sides. The skins usually carry the in-plane loads and bending moments, while the core, which has lower stiffness compared to the skins, resists the transverse shear loads. The advantage of composite sandwich structures lies in that they possess large bending or torsional rigidity with very low-specific weights; they also provide an excellent platform for optimization of structures to meet various objectives. Minimum weight sandwiches have been studied extensively [1,2]. Optimization of sandwich structure for sound reduction is more challenging, and has been studied by a few researchers [3–5]. The present study is focused on sandwich structures with a cellular, frame-like core. The multifunctional properties of cellular solids have generated a great deal of interest for their application in the aerospace industry. The topological design of periodic multifunctional core structures has been explored, and the relationship between topology and performance has been established by Evans, Hutchinson, Fleck, Ashby and Wadley [6]. Vibration of sandwich beams with a honeycomb truss core is analyzed in Ref. [7]. A unit cell analysis to investigate the effect of its resonance is also presented in this reference. It has ARTICLE IN PRESS www.elsevier.com/locate/jsvi 0022-460X/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jsv.2006.09.025 à Corresponding author. Tel.: +1 302 831 8686; fax: +1 302 831 3619. E-mail address: jqsun@udel.edu (J.Q. Sun).