Lessons Learned from PABST

The adhesive selection and surface treatment investigations for the Primary Adhesively Bonded Structures Technology (PABST) Program, Air Force contract F33615-75-C-3016, include several tests for environmental resistance and durability. During the performance of these tests, several lessons were learned about the characteristics of behavior of the adhesives, surface treatments, and the resultant bonded structure. The surface treatments proved to be fragile and easily damaged and contaminated when not protected by an adhesive primer system. Not all surface treatment systems provide an optimum environment resistance when processed in a normal production facility. The type of carrier used in the adhesive affects the durability of the system. Constant and cycled-stressed testing of adhesive-bonded specimens in an environment can define adhesive characteristics and bond line properties better than static unstressed exposure. Tests include wedge crack, lap shear, and double cantilever beam. Lap shear tests included stressed, cycle stressed, and nonstressed. The environments include 140°F and 100 percent relative humidity (RH), hydraulic oil, JP-4, water, salt spray, and beach atmosphere exposure.