Effects of Longtime Environmental Exposure on Mechanical Properties of Sheet Materials for a Supersonic Transport.

Abstract : Studies of the effects of longtime environmental exposure on mechanical properties of supersonic transport sheet materials have been conducted. These materials include titanium alloys, stainless steels, aluminum alloys, and a composite. Titanium alloys and stainless steels have been investigated since 1961, and results have shown that exposures of 30,000 hours at 550 F (561 K) have had little effect on the strength characteristics. Hot salt stress corrosion occurs in titanium alloys under certain combinations of stress, temperature, and time but does not appear to be a problem at the operating conditions of a Mach 2.7 supersonic transport. Aluminum alloys were investigated to provide materials information for the Mach 2 speed range and have been found to be temperature limited by longtime creep strength. Properties of the polyimide resin glass fiber composite have been determined after 4000 hours exposure. This material appears to be suitable for extended use in a Mach 2.7 supersonic transport.