March 7 , 2008, 2:00 p.m., Holmes Hall 244

Near-interfacial and Interfacial Fracture Simulation
by the Extended Finite Element Method

Yuhai Yan

Design of composite structures in many important industrial applications requires good understanding of the fracture behavior around the material interfaces.  In this research, near-interfacial and interfacial fractures are modeled by the extended finite element method (XFEM), a numerical technique developed recently to model crack propagation.  In the XFEM, the crack, or the discontinuity in displacements, is represented by enriching the nodes around crack with additional degrees of freedom.  Among its advantages are that no remeshing is needed; crack path is independent of the finite element mesh; it is applicable to preexisting cracks as well as evolving cracks; and it is numerically robust although extra implementation efforts are needed.

The XFEM is first applied for the simulation of near-interfacial crack propagation in a metal-ceramic layered structure.  An experimental evidence indicates that, in a ceramic-metal-ceramic sandwich structure, a near-interfacial crack in the ceramic layer can be drawn to or deflect away from the metal layer depending on the difference in elastic properties across the interface. The crack propagation paths predicted by the XFEM simulation are found to be consistent with the experimental observation.  In the simulation of the interfacial fracture, a bi-material plate with a crack on the interface is modeled. In the proposed scheme, the nodes on the crack are enriched with only the Heaviside functions. The stress intensity factor analysis demonstrates that such an enrichment strategy can produce satisfactory results for interfacial fracture problems.