Fracture Mechanics Investigation Of Nano-multilayered Cantilever With A Crack-like Notch

Many advanced micro-mechanical and electronic devices are made frommultilayers of different materials, and the size is even on the nanoscale. Theinvestigation of fracture behavior is very significant to the design and safety analysis ofnano-multilayered structures. However, the fracture mechanics experiments and therelated analysis of this type of materials are still very limited. This thesis focus on thefracture mechanics investigation of nano-multilayered cantilever with a crack-likenotch.In Chapter1, the background and significance of the thesis are introduced, and thereseach status of the investigation on the fracture mechanics of the nano-multilayeredmaterials is reviewed. Considering the shortages and limitation in this area, the maincontents of this thesis are determined.In Chapter2, some basic theories related to this thesis are introduced, and a set ofinteraction integral method combined with the extend finite element method which issuit for this project is derived.In Chapter3, a set of new investigation method is proposed for the fracturemechanics experiments and analyses of nano-multilayered materials. Three differenttypes of crack propagation behaviors, including crack propagation in SiN layer,debonding at the SiN/Cu interface and crossing-interface crack propagation bahaviorthrough SiN/Cu interface, are investigatied, respectively.In Chapter4, The interaction integral method combined with energy analyses isadopted for numerical simulation of the crack propagation behavior, and the stressintensity factors (SIFs) corresponding to the crack initiation at the crack tip are obtained,and the surface energy density of SiN layer, SiN/Cu interface and Cu layer are derived,respectively.In Chapter5, the kinetic energy of the crack propagation is discussed. For thepresent brittle fracture process, a new hypothesis based on the kinetic energy of crackpropagation is proposed that the crack will keep propagating until the accumulatedkinetic energy is consumed totally to form new crack surface. Moreover, the hypothesisis consistent with the experimental results. It provides a significant thought for theanalysis and prediction of nanoscale crack propagation behavior.