Predicted thermal stresses in a bimaterial assembly adhesively bonded at the ends

The interfacial shearing and "peeling" stresses in an elongated bimaterial assembly, adhesively bonded at the ends and subjected to the change in temp erature, are predicted, based on an approximate structural analysis (streng th-of-materials) model. The stresses in the bonded joints due to the therma l expansion (contraction) mismatch of the adherend materials within the bon ded areas ("local" mismatch), as well as the stresses, caused by the therma l mismatch of the adherend materials within the unbonded midportion of the assembly ("global" mismatch), are considered. The interaction of the "local " and the "global" stresses is evaluated and analyzed. It is shown that if the bonded joints are made long enough, the maximum stresses in the assembl y will not be different from the stresses in an assembly with a continuous adhesive layer, no matter how long the unbonded midportion of the assembly might be. The obtained results can be helpful in the stress-strain evaluati ons and physical (mechanical) design of bimaterial assemblies in electronic and photonic packaging. (C) 2001 American Institute of Physics.