Debonding of the interface between a thin film and an orthotropic substrate

• Interface debonding in an orthotropic bilayer is investigated.
• Three crack patterns are considered.
• The energy release rate and mode mixity are derived.
• The effect of material constants is investigated.
• Stable or unstable plane strain delamination and crack channeling are discussed.

Interface debonding in an orthotropic bilayer consisting of a thin film and a half-plane substrate is investigated. Three crack patterns including a plane–strain interface crack, a delamination channeling crack, and a channeling crack with film cracking and interface debonding are considered. Based on the modified Stroh formalism and the orthotropic rescaling technique, the energy release rate for the three cracks and mode mixity for the plane–strain interface crack are derived in the closed form for each numerically determined dimensionless function. Special attention is paid to the effect of orthotropic material constants on the energy release rate and mode mixity. Stable or unstable plane strain delamination and crack channeling are discussed according to fracture criteria based on the energy release rate.