Time：3:00pm, 5/15/2014

Place：A306, 1 West Building

Speaker：Prof. Yong NI, University of  Science and Technology, China

Title：Phase field modeling of combined buckling, delamination and cracking of layered materials

Abstract of Talk：

The structure of a thin film with internal stress on an elastic substrate has been widely used in thin film technology. The compressed film often leads to buckling instability with formation of wrinkle, buckle-delamination blister, ridge cracking or their combinations. Understanding the film morphology driven by the buckling instability is important in various applications, i.e., functional coating, flexible microelectronics, graphene nanotechnology, thin film metrology, mechanics-based nanofabrication. In this talk, I will discuss the phase field modeling of combined cracking, delamination and buckling in film-substrate systems. The model couples substrate elasticity, nonlinear film deformation and interface adhesion by integrating Green function method, Föppl-von Kármán plate theory and cohesive zone model. The buckling, cracking and delamination processes are formulated using the time-dependent Ginzburg-Landau kinetic equations, driven by minimizing the film-substrate total free energy. This model is able to capture formation of various buckling morphologies including wrinkling, buckle-delamination as well as combined buckling and cracking. The mechanism and conditions for their formations are identified, and good agreements with the experimental observations are obtained. The model may provide a computational tool for exploring the effects of pre-strain, substrate compliance and adhesion on the formation of complex nonlinear buckling and cracking patterns in layered materials.

Invited by：Yunzhi Wang, CMS