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

The interfacial shearing and "peeling: stresses in an elongated bi-material assembly, adhesively bonded at the ends and subjected to the change in temperature, are predicted, based on an approximate structural analysis (strength-of-materials) model. The stresses in the bonded joints due to the thermal expansion (contraction) mismatch of the adherends materials within the bonded areas ("local" mismatch stresses), as well as the stresses in these joints, caused by the thermal mismatch of the adherends materials within the unbonded midportion of the assembly ("global" mismatch stresses), are considered, and the interaction of the "local" and the "global" stresses is evaluated and analyzed. It has been shown that if the bonded joints are made long enough, the maximum stresses in the assembly 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 evaluations and mechanical ("physical") design of bi-material assemblies in electronic and photonic packaging.