J-Integral of Interfacial Crack in the Bonded Joints of Dissimilar Materials

Abstract

In this study J-integral of interfacial crack in the bonded joint which was composed of the materials with different mechanical properties was studied by finite element method. J-values of two types of bonded joints under the uniformly tensile stress and the three-point bending load were studied. One type was the bimaterials joint, in which the material B was bonded directly to the material A, and the other type was the trimaterials joint, in which the material B was bonded to the material A by using the insert material C.
The obtained results were as follows;
(1) It was clarified that the normalized J-values of bimaterials joint, J/J_A=B, were able to be determined only by the ratio of Young's modulus of both materials, E_A/E_B, and J-values were hardly affected by Poisson's ratio. J_A=B was the J-value of same material joint.
(2) J-values of trimaterials joint were affected by the thickness of insert materials, d, and the ratio of Young's modulus of each materials, E_A/E_B and E_C/E_B.
The equation for calculating J-values of trimaterials joint under any loading condition was derived as shown as the next equation.
(J/J_a) -1/(J_c/J_a) -1=(d/d₀)^0.5
where
J_a: J-integral value of bimaterial (material A and material B)
J_b: J-integral value of bimaterial (material C and material B)
d₀: Ligament length
d: Thickness of insert material