| Abstract: | A hot-melt processable copolyimide designated 422 previously synthesized and characterized as an adhesive at NASA Langley Research Center for bonding Ti-6A1-4V has been used to bond Celion 6000/LARC-160 composite. Comparisons are made for the two adherend systems. A bonding cycle was determined for the composite bonding and lap shear specimens were prepared which were thermally exposed in a forced-air oven for up to 5000 h at 204°C. Lap shear strengths (LSSs) were determined at room temperature, 177°C, and 204°C. After thermal exposure to 5000 h at 204°C, room temperature and 177°C LSSs decreased significantly; however, a slight increase was noted for the 204°C test. Initially the LSS values were higher for the bonded Ti-6AI-4V than for the bonded composite; however, the LSS decreased dramatically between 5000 and 10 000 h of 204°C thermal exposure. Longer periods of thermal exposure up to 20 000 h resulted in further decreases in LSSs. Although the bonded composite retained useful strengths ( > 11.1 MPa) for exposures up to 5000 h, based on the poor results of the bonded Ti-6A1-4V beyond 5000 h, the 422 adhesive bonded composites would most likely also produce poor strengths beyond 5000 h exposure. Adhesive bonded composite lap shear specimens exposed to boiling water for 72 h exhibited greatly reduced strengths at all test temperatures. The percent retained after water boil for each test temperature was essentially the same for both systems. |
