For bonded dissimilar materials, the free-edge stress singularity usually prevails near the intersection of the free-surface and the interface. When two materials are bonded by using an adhesive, an interlayer develops between the two bonded materials. When a ceramic and a metal are bonded, the residual stress develops because of difference in the coefficient of thermal expansion. An interlayer may be inserted between the two materials to defuse the residual stress. Stress field near the intersection of the interface and free-surface in the presence of the interlayer is then very important for evaluating the strength of bonded dissimilar materials.In this study, stress distributions on the interface of bonded dissimilar materials with an interlayer were calculated by using the boundary element method to investigate the effect of the interlayer on the stress distribution. The relation between the free-edge singular stress fields of bonded dissimilar materials with and without an interlayer was investigated numerically. It was found that the influence of the interlayer on the stress distributions was confined within a small area of the order of interlayer thickness around the intersection of the interface and the free-surface when the interlayer was very thin. The stress distribution near the intersection of the interface and the free-surface was controlled by the free-edge stress singularity of the bonded dissimilar materials without the interlayer. In this case, the interlayer can be called free-edge singularity-controlled interlayer. If a stress distribution on the interface is known for one thickness of an interlayer h, stress distributions on the interface for other values of h can be estimated.

No abstract

The electric potential CT (computed tomography) method proposed by the present authors was applied to the identification of delamination defect in layered carbon fiber reinforced plastics (CFRP) composites, which have strong anisotropy in electric conductivity. The electric potential readings on the top surface of the layered composite materials was used for the identification. The anisotropy of the electric conductivity of each layer was taken into account in the boundary element calculations of electric potential distribution. Numerical simulations were made on the identification of elliptical delaminations on the interface of layers. It was found that the method was applicable for the estimation of the location and size of delamination even in the presence of considerable measurement noise.

Free-edge stress singularity usually develops near the edge of interface of bonded dissimilar materials. Because of the difference of the coefficient of the thermal expansion of the materials, the residual stress may develop when two materials are bonded. To defuse the residual stress, an interlayer may be inserted between the two materials. Stress distribution near the edge of the interface in the presence of the interlayer is very important to evaluate the strength of the bonded dissimilar materials. In this study, stress distribution on the interfaces of the bonded dissimilar materials with an interlayer under thermal stress loading was calculated by using the boundary element method. An effect of an interlayer on the stress distributions on the interface was examined numerically. It was found that the influence of the interlayer on the stress distribution was limited within a region where distance from interface edge is smaller than the interlayer thickness. Stress distribution around the edge of the interface of the bonded dissimilar materials with an interlayer can be normalized by the parameters of the singularity and the thermoelastic constant stress term of the bonded dissimilar materials without an interlayer.

No abstract