Experimental and Theoretical Study on Biaxial Normal-Shear Bonding Strength at Interface between Elastic/Elastic, Elastic/Viscoelastic and Viscoelastic/Viscoelastic Materials

• Author / Creator

  Chowdhuri, Mohammad A

• 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, non-uniform 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, elastic and viscoelastic materials, and 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 verified by FEM numerical analyses.
  The elastic properties of materials are determined through uni-axial tensile tests and the viscoelastic properties are by relaxation tests. 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 case, the stress singularity may increase or decrease with time, depends on the specimen geometry.
  With the developed design that can eliminate the stress singularity at the 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.

• Subjects / Keywords

  • Analytical solution, Dental crown, Mechanical testing
  • Interface bonding strength, Stress singularity, Viscoelasticity

• Graduation date

  Fall 2012

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32P8D

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.