Balsa wood, sandwich panels

It was the former, however, which, initially, proved to be of great interest to the aircraft industry. The essence of an idea of de Bruyne was worked on by Chance Vought, in the United States of America. They used Redux 775 Liquid and Powder adhesive to bond thin aluminium skins to end-grain balsa wood sheets in order to produce sandwich panels. These panels were called Metalite (Fig. 29). 

However, the majority of sandwich panels now utilise a honeycomb core rather than either balsa wood or plastic foam the adhesive can be based on either thermosetting or thermoplastic chemistries. The three basic components used in honeycomb sandwich construction are discussed below. 

The combination of core (aluminium, aramid, paper, carbon, glass or balsa), skins (aluminium, steel, titanium, FRP, melamine or wood) and adhesive (film or paste, epoxy, phenolic, PUR, PI, cyanate ester, acrylic or thermoplastic) gives a sandwich panel which is an integrally bonded, load-bearing structure. 

Bonded sandwich structures are vital in aircraft design as they enable significant weight reduction without the loss of stiffness and strength. A sandwich panel comprises metallic or synthetic surface skins integrally bonded to a central core. In some instances, this core is balsa wood or, because of objections to using natural products in structural components, a foamed plastic. Typical examples of the latter are foams of polyvinyl chloride, phenolic, and polyurethane (PUR). 

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