The interface stress distributions in scarf adhesive joints with dissimilar adherends under statictensile loadings are analyzed using two-dimensional and three-dimensional finite element calculations for the two cases where the adhesive length is held constant and where the width of the adherends is held constant. The effects of Young's modulus ratio Ef/E2 between the dissimilar adherends, adhesive Young's modulus, the scarf angle θand the adhesive thickness on the interface stress distributions are examined.In addition, the joint strength is predicted based on the maximum principal stress theory. It is found that when the scarf angle is around θ=60°, the singular stress at the edges of the interfaces is minimal in the 3-D FEM calculations, while the singular stresses vanish for θ=52° in the 2-D FEM calculations. It is noticed that the strength of the joints with dissimilar adherends is smaller than that of the joints with similar adherends.In addition, it is found that the jointstrength decreases as Young's modulus ratio E1/E2 increases. For verification of the FEM calculations,the strains in the adherends and the joint strengths were measured in the experiments. The measuredstrains are infairly good agreement with those obtained from 3-D FEM calculations. Also, themeasured joint strength is fairly consistent with the 3-D FEM results. The difference in the normalized maximum principal stress is small between the two cases while the joint strength is a little bitlarger in the case where the width is held constant.

In UV-curing adhesives, sufficient adhesive strength with relatively high elastic modulus at roomtemperature and high Tg cannot be obtained by the stress concentration at the interface between the adhesive and adherend. To verify the effect of surface morphology on adhesive strength, flat and sawtooth surface structures were studied. Changing surface morphology from flat to sawtooth structures,fracture mode was found to be changed from interfacial failure to the mixed mode with cohesive failure and the initial adhesive strength could be grea tly improved. On the otherhand, under 60℃ 90%RH storage, it was found that the sawtooth structure shows the fracture mode transition to the interfacial fracture only over storage time and dhesive strength is reduced with the accelerated rate of deterioration. The cause of this reduction in adhesive reliability is considered as follows. The adhesive absorbs moisture first to swell. Then, the total swelling force affects the local peeling on the highest surface points of sawtooth surface structure. For high reliability, it is important to further improve the stress tolerance and the reduction of the swelling rate by lowering the moisture absorption of the adhesive.

weight compound having carbonyl group and hydroxyl group as compatibilizer in PMMA/PVA blend was investigated. As a result, single loss modulus peak appeared. It was found that the using of compatibilizer is effective to develop the dispersibility of components.