Effects of joining and testing parameters on the adhesive strength of epoxy-bonded aluminum and beryllium

Hollow spherical targets are frequently fabricated by the joining of two ad hesively bonded hemispheres. Other materials used for Intertial Confinement Fusion (ICF) experiments, including aluminum, stainless steel, sapphire, a nd various plastics, are also bonded using adhesives. This paper presents the mechanical testing results cg Dexter-Hysol EA9330. The base metals were either an aluminum 6061-T6 or beryllium S200D. The uni axial tensile (from room to liquid helium temperatures), lap shear, and cre ep properties of the adhesive under consideration were evaluated. We found that the highest lap shear strength was obtained when the test panel was as sembled with fresh adhesive (time = 0 min.) and degraded to about 77% of th at value in 120 minutes. Butt tensile strength increased from about 8 ksi ( 1 ksi = 1000 lbs/in(2) = 6.90 MPa) at room temperature to about 19 ksi at - 269 degrees C for both the aluminum and beryllium base metals. The lap shea r strength decreased from about 5 ksi at room temperature to about 3 ksi at cryogenic temperatures. Creep tests in both butt tensile and lap shear con figurations demonstrated a very narrow stress level for which the time to f ailure decreased from over 720 hours to less than 20. Finally, we found that the surface treatment is critical to achieving the h ighest strength adhesive bonds. Some inconclusive but interesting test data is presented opening the way for further investigation.