Epoxy comes to the rescue and conquers cryogenic wind tunnel
1 min read
A specially formulated aerospace epoxy has come to the rescue in a particularly tricky cryogenic wind-tunnel-model bonding application, which posed some interesting challenges for traditional engineering thermoplastics.
The application not only runs at very low temperatures and in vacuum conditions but also presents high levels of thermal, thermal cycling and mechanical shear stresses.
Cooled to 113K at a rate of 40K/hour and then reheated over a 4 hour cycle, the model's stainless, aluminium, neodyne magnet and fibre reinforced plastic substrates are all deforming at their individual CTEs, thus inducing further stress on the parts and adhesive joints. Certainly any metal adhesive would have a difficult time meeting any one of these challenging performance requirements, all the more so all of them at once.
As a NASA qualified low outgassing aerospace adhesive, multifunctional Master Bond EP21TCHT-1 was found to be ideal for the high vacuum testing application. Being a toughened, two part epoxy, the cryogenic adhesive was a good CTE match for the assembly of the difficult to bond substrates used in the wind tunnel model. Developing a high bond strength of 2,200 PSI in shear at ambient temperatures, it retains significant adhesive strength in cryogenic environments, down to 4K.
The adhesive bonds produced are resistant to thermal cycling and many chemicals. As an added bonus, the hardened epoxy adhesive exhibits high thermal conductivity useful in the model's overall temperature cycling performance.
