Investigating the Thin-Film Versus Bulk Material Properties of Structural Adhesives; Final rept

摘要

A combined experimental and computational investigation was performed to determine whether the material properties of structural adhesives differ between their thin-film in situ and bulk forms. Both shear and tensile tests were performed using bulk adhesive specimens as well as in situ adhesive specimens. Three aerospace-grade adhesives were used: Loctite EA 9394, EA 9392, and EA 9360. For in situ adhesive tests, three bondline thicknesses of 0.25 mm (0.01 in.), 1.27 mm (0.05 in.), and 2.54 mm (0.10 in.) were investigated. Shear tests focused on the use of the V-notched Iosipescu shear specimen, featuring a 120DG notch angle for use with thin adhesive bondlines. Additionally, the thick adherend lap joint test configuration was evaluated for determining shear properties of adhesives. Tensile tests focused on adhesively bonded butt joint specimens as well as bulk adhesive bar specimens. The results from in situ and bulk adhesive shear tests suggest that the slight decrease in apparent shear strength with increasing bondline thickness was produced by slight changes in the adhesive stress state. Further, the shear strengths obtained from bulk adhesive tests were comparable to those from in situ tests.