Aluminum expands about twice as much as steel and two to three times as much as window glass for the same temperature change, and plastics expand more still. When dissimilar materials are bonded over a large area, temperature swings shear and peel the bondline. Engineers handle CTE mismatch with flexible adhesives, thicker bondlines, shorter bond lengths or by curing at a temperature close to service conditions.
Glass to aluminum frame, two meters long, the CTE mismatch will shear a rigid epoxy, use the silicone.
Also heard as
- thermal mismatch
- differential expansion
Related terms
Adherend
Each of the parts in a bonded joint; the surface the adhesive has to grip.
Bondline
The layer of adhesive between two bonded parts, and in shop talk the thickness of that layer.
RTV
Room-temperature vulcanizing silicone, a rubbery adhesive-sealant that cures without heat, usually from air moisture.
Polyurethane adhesive
An adhesive based on isocyanate chemistry that cures into a tough, somewhat flexible bond.