Advances in interface fracture mechanics

Many engineering applications involve the use of layered materials. Interface fracture, however, is a major concern. It is therefore essential to know the mechanics of interface fracture to reliably predict performance and lifetime, give confidence, demonstrate compliance, etc. It is also essential to be able to conduct and post-process experiments to determine interface strength material properties, to know the intrinsic resistance against interface fracture. This paper presents the latest advances in interface fracture mechanics, developed by the authors, which address these essential requirements in various applications. In particular, the coverage includes the latest developments of thin film and thermal barrier coating (TBC) blister mechanics; pockets of energy concentration (PECs), which are a newly discovered sub-critical blister mechanism; and the new theory of dynamic interfacial fracture. A reliable condition that must be satisfied for blisters to form is demonstrated and validated across an extensive review of experimental results in the literature. The derived blister mechanics theories can accurately determine blister morphology for a range of blister types, or by reversing the calculation, determine interface fracture toughness based on blister dimensions. The mechanism of PECs and their capability to drive subcritical nucleation and propagation has been demonstrated through finite-element method (FEM) simulation. And the delamination propagation speed-dependent energy release rate (ERR) of a fracture under high loading rates, including the effect of vibration, can be calculated, and used to determine the delamination initiation toughness (DIT) and the delamination arrest toughness (DAT), based on experimental measurements of delamination length.