Fracture mechanics investigation on crack propagation in the nano-multilayered materials

A set of new investigation method is proposed for the fracture mechanics experiments and analyses of nano-multilayered materials. The crack propagation behavior in a SiN/Cu nano-cantilever is investigated by fabricating a crack-like notch in the SiN layer. Two types of crack propagation behaviors are observed, including crack propagation in SiN layer and crossing-interface crack propagation through SiN/Cu interface. The interaction integral method combined with energy analyses is adopted for numerical simulation of the crack propagation behavior. The kinetic energy of the crack propagation is discussed. It is found that for the present brittle fracture process, the traditional Griffith criterion is not suitable and a new hypothesis based on the kinetic energy of the crack propagation is proposed that the crack will keep propagating until the accumulated kinetic energy is consumed totally to form new crack surface. Moreover, the hypothesis is consistent with the experimental results. It provides a significant thought for the analysis and prediction of nanoscale crack propagation behavior.