TUNING STRESS CONCENTRATIONS THROUGH EMBEDDED FUNCTIONALLY GRADED SHELLS

In this work, we explore the possibility of tuning stress concentrations in materials by judiciously designing embedded functionally graded shells. Specifically, we choose thick-walled cylinders to illustrate our central idea. We specifically consider the boundary value problem of a radially varying graded shell bonded to a thick-walled cylinder. We obtain closed-form solutions and our parametric numerical studies suggest that a graded soft shell can effectively drive the stress concentration from the inner surface of the shell to the shell-cylinder interface. For any boundary loading, an optimal inhomogeneity index that balances the stress concentrations along the inner surface and the interface can be identified. Using the solution to a completely homogeneous cylinder as a benchmark, the stress concentration factor can be reduced by more than 40%. The results of this work suggest the significant potential of functionally graded materials for tailoring the stress concentrations of engineering structures by bonding a properly designed inhomogeneous layer to the perimeter of geometric defects.