LARC-13 polyimide adhesive bonding

The development of an addition-curing polyimide adhesive suitable for low pressure bonding without the generation of volatiles during cure is reported. LARC-13 is designed for bonding of polyimide matrix composites and of titanium to be used above 500 F, and is based on an oligomeric bis-nadimide which allows its processing at 50 psi or less, making it suitable for the bonding of fragile honeycomb sandwich structures. Few volatiles are evolved during its cure allowing large enclosed structures to be bonded, and it has high room and elevated temperature strengths and good strength retention after short terms up to 1100 F. LARC-13 was successfully used to bond the outer and inner skins of a polyimide/graphite wing shear panel for 500 F use, and for a short-term exposure up to 1100 F. Preparation of the adhesive, bonding, aging, and testing of lap shear and honeycomb samples are discussed.