The bond shear strength in the wide temperature ranges and the dynamic viscoelasticity of one-component moisture curable polyurethane adhesive (PU) were measured. In addition, the relationship between the viscoelastic behavior and the bond performance after water absorption was also examined in detail. From the dynamic mechanical analysis, the storage modulus (E') decreased gradually in the temperature ranges from 0 to 170ºC, and the clear peak of glass transition temperature was never observed. The tendency of bond shear strength in the temperature ranges from 0 to 150ºC was similar to that of the aqueous polymer solution type isocyanate adhesive, and the bond shear strength was about 17% lower than that of the resorcinol formaldehyde adhesive over the room temperature. E' value of PU film after water dipping was slightly lower than that of dried PU film around the room temperature, however the value was about 1/3 around 80ºC. The bond shear strength of PU after cured for one week with high pressurized pressing or high frequency heating met the JAS standard. In the bond shear strength test after water absorption, the wood failure was hardly occurred because the PU adhesive layer well absorbed water.

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A novel tissue consisting of carboxymethylated chitosan (CM-Chitosan) with various degree of substitution of carboxymethylation/degree of deacethylation (DS/DD=COOH/NH2) was developed. In this adhesive, CAD works as a crosslinking reagent of amino groups of CM-Chitosan. The boding time of CAD/CM-Chitosan adhesive reached equilibrium within 5 min when DS/DD of CM-Chitosan was 0.27 and 0.76. While, the bonding time of the CM-Chitosan whose DS/DD was 0.52 rapidly increased within 5 min, however, it took 30 min to become constant level. The bonding strength decreased with increasing CAD concentration when DS/DD of CM-Chitosan was 0.27 and 0.76. On the other hand, bonding strength increased up to CAD concentration of 5 mM and then decreased when DS/DD of CM-Chitosan was 0.52. It was clarified that the resulting bonding strength of CM-Chitosan (DS/DD=0.52) was 4-fold higher than that of fibrin-based adhesive which is commonly used in clinical field.

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In the assembly lines of cars, long handling arms of aluminum alloy have been used for the forming of automotive bodys. We developed a new handling arm bonded CFRP plates adhesively on the side in order to reinforce the stiffness and reduce the vibration. In our last study, a new method to predict the fatigue life of the handling arms was proposed. In the method, the fatigue life of the actual arms was calculated based on those of smaller joint specimens (scale-downed specimens) bonded adhesively. The smaller specimens were loaded so that the stress value in the adhesive layer could be similar to those in the actual arms. The stress values of the arms and specimens were calculated by Finite Element Method. The other prediction methods based on material mechanics was also evaluated because it was easier the previous method based on FEM. It was, strangely, more precise rather than the previous analytical one in terms of predicting the fatigue lives. The reason may be unconscious of three dimensional effects such as crack propagation in the width direction of the adhesively bonded joints. Therefore, the effect had to be investigated more carefully in order to determine which method is more suitable. In this study, we investigated the validity of the prediction methods based on FEM and material mechanics for the various case of different thickness and width of the adherends. Additional fatigue tests were carried out using four types of the smaller specimens having the different thickness and width for the aluminum adherends. As the result, we found that the fatigue lives must be influenced mainly by the thickness of the aluminum alloy and we could predict them by means of precise stress analysis considering the adherend thickness.

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