Evaluation of high-temperature structural adhesives for extended service

Candidate high-temperature stable resin formulations were evaluated for adhesive properties when bonded to titanium treated with various surface preparations. The adhesive formulations included LARC-13, NR150 A2, NR150 B2, NR056X, FM-34, HR-602, and polyphenylquinoxaline. Eight titanium surface preparations were compared for resulting bond strength with the candidate adhesives. After initial evaluation, three adhesive systems (comprised of adhesive, primer, and titanium surface preparation) were selected for further screening. The screening (still in progress) includes cure-cycle optimization and bond properties from 219 K (-65 F) to 505 K (450 F), after isothermal aging at 505 K (450 F) up to 15,000 hours, and after humidity aging at 322 K 9120 F)/ 95 percent R. H. for up to 2000 hours. Larger-area bond capability of the three adhesive system can be demonstrated by fabrication of 30.5 cm (12 in) square titanium honeycomb sandwich and metal-to-metal bonded panels.