Application of Digital Image Correlation Method to Water Swelling Measurement of Light Cure Composite Resin

A digital image correlation method was applied to study the swelling deformation of a light cure composite resin due to water absorption. Five specimens of stainless steel were fabricated by filling the resin into a cylindrical cavity prepared with a bonding agent. The specimens were irradiated using a visible-light curing unit and photographed with a CCD camera as reference images before deformation. The swelling deformation was analyzed using the reference image and evaluated by measuring the displacement fields on the free surface of the cavity as a function of soaking period into water, and the following results were obtained. The swelling deformation due to water absorption can be evaluated using the present method. The displacement distribution was continuous at the interface between the resin and substrate, and its absolute value exhibited the maximum in the resin close to the interface and the minimum near the center of the cavity. The deformation was increased largely in the early stage (about a week) of soaking period, then gradually increased in the middle stage (about 2-3 weeks), and tended to be saturated in the later stage (about 4 weeks) for the composite resin tested.