Shear stress and normal stress act on adhesive layer of double lap joint ・It is known that the shears tressd istribution becomes flat and joint strength in creases as adherend thickness increases.Inthisstudy, compression and tensiontests of double lap joint were carried out in order toclarify the effect of adherend thicknesson joint strength・ Shear stress distribution acting on theadhesive layer under tensile force and that under compressive force are the same. On the other hand, compression test and tension test differ from each other in direction of normal stress actingon the adhesive layer. From comparison of the joint strength under compression test with that under tension test, it was observed that large deterioration of the joint strength occurred as adherend thicknessbecomes large due to the normal stress which was provided in the adhesive layer when the doublelap joint was subjected to tensile force. The strength deterioration increases in proportion to an increase in adherend thickness.

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The destruction load of the micro resist pattern is measured quantitatively by means of applying load with an atomic force microscope (AFM) tip. By the fatigue effect, the dot-shaped pattern of 160 nm in diameter, to which the constant load is applied repeatedly with the AFM tip. is destructed. The destruction load without fatigue effect is approximately 90nN, However, withfatigue effect, the pattern destruction occurs even at lower load, 1.3 and 53.1 nN. The results indicate the pronounced fatigue effect by increasing the applying load until 105nN. This methodcan be useful for the quantitative analysis of fatigue effect in micro scale.

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The estimation method of the shear adhesive strength was studied using the biaxial testing machine and cruciform adhesive joints. An epoxy resin was used as the adhesive. Material constants of adhesive were measured using adhesive bulk specimens to harden adhesive simple substance. Combined stresses were loaded by bulk specimens. From this result, the von mises yield criterion can be used for this adhesive. A elastic-plastic analysis was done by the finite element method (FEM) using the von mises yield criterion. Stress distributions of the adhesive layer of the cruciform joint were evaluated by FEM. Regardless of the load ratio, distributions of three normal stresses on the adhesive layer agreed approximately. Therefore, shear stresses control the von Misese quivalent stress. If the stress condition of the adhesive layer can be evaluated with the equivalent stress, cruciform joints fracture mainly by the shear stress. And the resultant shear stress in fracturing becomes constant regardless of the loading rate. Thus, Biaxial loading tests were done. The experiment result agreed with the analysis result. The strength of the cruciform joint, the torsional strength of the bulk specimen and that of the cylindrical butt joint was compared. These strength agreed approximately. From above-mentioned result, in case of the adhesive which can use von mises yield criterion, it is possible to evaluate a shear strength by this evaluating method.

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