Moisture absorption effect on adhesive filled bonded joints

Abstract The effect of filler type and content on the performance and durability of adhesive bonded joints upon exposure to damp heat (water immersion) has been investigated using concurrently step lap shear and thermo mechanical analysis (TMA) experiments. A TMA based approach is developed in order to predict the strength of the bonded constructions. Two types of fillers were used in order to achieve the objectives: glass beads (GB) and alumina ceramic powder (ACP). It is shown that ACP filled adhesives have higher strength retention than GB filled ones. It is also demonstrated that valuable information can be extracted from TMA measurements. Generally, the increase of the coefficient of thermal expansion (CTE) of the bonded joints is found to be in agreement with the decrease of the step lap joint strengths after exposure. The increase of the CTE of the bonded joints resulting from exposure to hot water seems to increase the stresses, which in turn affect the overall strength. Similarly, bulk adhesive results show that GB filled systems are more susceptible to water than ACP filled ones, which confirms the decrease in strength of GB filled bonded constructions.