The crack growth driving force and the resistance to cleavage cracking associated with crack front transmission across a high-angle grain boundary in a Si thin film were analyzed, and a closed-form solution of grain boundary toughness was obtained. It was noticed that the fracture resistance of the grain boundary was a function of the film thickness. This size effect was attributed to the non-uniform nature of cleavage front advance.

Energy Equilibrium of Cleavage Front Transmission across a High-Angle Grain Boundary in a Free-Standing Silicon Thin Film. Y.Qiao, J.Chen, X.Kong, S.S.Chakravarthula: Engineering Fracture Mechanics, 2008, 75[8], 2444-52