Formable Sandwich Structures for Aerospace Applications
A process has been developed for the production of sandwich structures which can be formed to complex contours without detrimental effects to the bond juncture between the core and face sheets. The sandwich structures are produced by roll-bonding, a process which results in a reliable diffusion bond between the core and face sheets which has the properties of the base metal. To support the sandwich structure during rolling, the voids in the sandwich are filled with a material which can be preferentially removed after roll-bonding and forming have been completed. For titanium alloys, which are well-suited to this process, mild steel is used as the filler material. The steel is removed as a last step in the process by preferential leaching in a dilute nitric acid bath. After roll-bonding and with the steel filler still in place, samples of Ti-6A1-4V truss core sandwich have been bent to a radius of 2T without failure at the normal forming temperatures of 1400–1600°F for this alloy. Compound curvatures, such as dome sections, have been formed from this same material. A wide variety of core configurations can be bonded by this process. The chief limitation to the core design is that there must be continuity of the filler metal to permit its removal.
KeywordsSandwich Structure Sandwich Panel Face Sheet Aerospace Application Steel Matrix
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