Effect of cyclic moisture absorption/desorption on the strength of epoxy adhesive joints and moisture diffusion coefficient

ABSTRACT The effect of cyclic moisture-absorption/desorption on adhesive strength was investigated using water at 23°C. Bulk plates and open face lap joints were prepared using epoxy adhesive, and their weight transition and shear strength were measured. The diffusion coefficient of the absorption process increased with the number of cycles and reached a constant value. In contrast, the diffusion coefficient of the desorption process was not affected by the number of cycles. As a part of the calcium carbonate disappeared from the surface, the weight of the bulk plates was reduced, and this weight reduction was irreversible. However, the strength of the lap joint was not significantly damaged by moisture absorption at 23°C.