| Bi-material interface is often observed in many advanced materials and structures. Measurement of the interface bonding strength is more challenging than the measurement of pure tensile or shear strength of a homogeneous material because of the presence of the stress singularity at the interface corner, nonuniform stress distribution along the interface and the co-existence of normal and shear stress components. In this PhD research project, a new innovative test method including specimen design, test procedure and an iterative calculation algorithm, is developed for more accurate determination of the interface bonding strength.;Three different types of bi-material interface are considered in this study; interface between elastic and elastic materials, between elastic and viscoelastic materials, and between viscoelastic and viscoelastic materials. Analytical solutions are developed to determine the stress singularity and conditions for its elimination for all the above three types of interface. The analytical solution for the elastic/elastic bi-material interface is derived based on the axi-symmetric asymptotic analysis. For the elastic/viscoelastic and viscoelastic/viscoelastic bi-material interfaces, the analytical solutions are obtained from the solution of elastic/elastic interface through the elastic-viscoelastic correspondence principle. The developed analytical solutions are further verified by FEM numerical analyses.;Three different materials; Aluminum, Epoxy and Polyvinylchloride (PVC) are considered. The elastic material properties of the selected materials are determined by uni-axial tensile tests. To determine the viscoelastic properties, relaxation tests are carried out on the viscoelastic materials. It is found that the order of the stress singularity changes with time due to the viscoelasticity of materials. If any stress singularity exists at the interface corner, with time the order of singularity increases. For a non–singular stress case at the interface corner, the order of the stress singularity may increase or decrease with time, depends on the bonding angle (specimen geometry).;With the proposed design that can eliminate the stress singularity at the bi-material interface corner, the loading capacity of the specimen is also increased. For example, the tensile load carrying capacity of such designed aluminum/epoxy bonded joint is increased by 2.65 times than that of the ASTM (American Society for Testing and Materials) butt joint design. Finally, as a practical application of this research, the optimal ranges of bonding angles at the interface corners of porcelain fused to metal (PFM) dental crowns with precious or non-precious metal alloys are suggested. |
