BS in Materials Engineering
Materials Engineering Department
Cold cure two-part epoxy adhesives were tested in aluminum joints to investigate their viability for use in an ultralight aircraft. The joints consisted of Alclad 2024-T3 aluminum sheets adhesively bonded to extruded 6061-T6511 aluminum, and are part of low-load-bearing members required to carry a minimum load of 175 lbs./ft. or 14.58 lbs./in. The Alclad 2024-T3 and 6061-T6511 aluminum were prepared by sanding with 80 grit abrasive paper, the surface was cleaned with acetone to remove surface contaminants, rinsed with distilled water, and dried using paper towels. Once the surface was prepared, the test coupons were assembled using one of the three selected adhesives (Loctite E-05 MR, Loctite E-20 HP, and 3M 420DP) which were applied using a hand operated applicator gun with mixing nozzle. The samples were then placed on a jig to hold them securely while the adhesives cured. The samples were allowed to cure for several days. The samples were then loaded in tension to failure using an Instron tensile tester. The Loctite E-20HP adhesive achieved the average highest strengths of 1378.53 ± 360.25 lbs./in. The scatter is believed to be due to excessive adhesive buildup around the edges of the joint and due to variations in the machined parts. Due to its high strength, the Loctite E-20HP was used in testing 30 additional samples, with a revised joint design, to try and minimize scatter. The revised joints achieved average strengths of 1206.44 ± 584.96 lbs./in which still meets the required strength goals.