Moisture absorption effect on adhesive filled bonded joints

The effect of filler type and content on the performance and durability of adhesive bonded joints upon exposure to damp heat (water immersion ) has be en investigated using concurrently step lap shear and thermo mechanical ana lysis (TMA) experiments. A TMA based approach is developed in order to pred ict the strength of the bonded constructions. Two types of fillers were use d in order to achieve the objectives: glass beads (GB) and alumina ceramic powder (ACP). It is shown that ACP filled adhesives have higher strength re tention than GB filled ones. It is also demonstrated that valuable informat ion 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 exposu re. 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 decreas e in strength of GB filled bonded constructions.