THE EFFECT OF TEMPERATURE ON THE STRENGTH OF ADHESIVELY-BONDED COMPOSITE-ALUMINUM JOINTS

Different materials have different coefficients of thermal expansion, which is a measure of the change in length for a given change in temperature. When different materials are combined structurally, as in a bonded joint, a temperature change leads to stresses being set up. These stresses are present even in an unloaded joint which has been cured at say 150-degrees-C and cooled to room temperature. Further stresses result from operations at even lower temperatures. In addition to temperature-induced stresses, account also has to be taken of changes in adhesive properties. Low temperatures cause the adhesive to become more brittle (reduced strain to failure), while high temperatures cause the adhesive to become more ductile, but make it less strong and more liable to creep. Theoretical predictions are made of the strength of a series of aluminium/CFRP joints using three different adhesives at 20-degrees-C and - 55-degrees-C. Various failure criteria are used to show good correlation with experimental results.