Primary and secondary structures that comprise modern aircraft are typically combinations of metals and lightweight carbon fiber- or glass fiber-reinforced polymer composites joined using high-performance adhesives. Historically, the adhesive bonding process required joined substrates to be cured in an autoclave to minimize voids and ensure reliable, high-quality parts. This procedure was time consuming as well as capital intensive. Aircraft OEMs are now seeking more cost-effective technologies, such as out-of-autoclave (OOA) curing that can produce parts more inexpensively than those fabricated via conventional autoclave processing.
In response to this trend, a new structural paste has been developed—designated Epibond® 100-A/B epoxy adhesive—that is formulated for OOA curing. The toughened epoxy exhibits outstanding mechanical properties at temperatures from sub-ambient to 149°C (300°F) and retains its high glass-transition temperature (Tg) values even after long-term exposure to hot/wet conditions. The advanced material also accommodates the needs of aircraft OEM and repair facilities for adhesives that can be stored at room temperature, are easy handle and apply, and oven cure in 1-5 hours. As a result, the new OOA paste adhesive can decrease labor time and production costs.