Chapter 10 - Sandwich structures

Abstract

Sandwich panels offer high stiffness at low weight. Their cores have the drawbacks that they cannot be used much above room temperature, and that their properties are moisture-dependent. The deficiencies can be overcome by using metal foams as cores. This chapter discusses the potential of the metal-foam-cored sandwich structures. Met foam-cored sandwiches are isotropic, can be shaped to doubly curved surfaces, and can be less expensive than attachment-stiffened structures. Syntactic foams—foams with an integrally shaped skin—offer additional advantages, allowing cheap, light structures to be molded in a single operation. The syntactic polymer foams command a large market. Technologies are emerging for creating syntactic met foam structures. Strength and stiffness, both are important while designing a sandwich beam. To exploit sandwich structures to the full, they must be optimized, usually by seeking to minimize mass for a given bending stiffness and strength. The benchmarks for comparison between optimized sandwich structures and rib-stiffened structures are stringer or waffle-stiffened panels or shells and honeycomb cored sandwich panels. Weight-efficient designs of panels, shells, and tubes subject to bending or compression are determined by structural indices based on load, weight, and stiffness. Weight is minimized subject to allowable stresses, stiffnesses, and displacements, depending on the application.