Stress intensity factors of double cantilever nanobeams via gradient elasticity theory

•Double cantilever nanobeam model via the gradient elasticity theory is presented.•Stress intensity factors are obtained and exhibit size effects.•Stress intensity factors are reduced if the size effect is considered.•Fracture toughness is enhanced for nanobeams compared to large scale beams. Growth of crack modeled as double cantilever beam at nanoscale is studied. Using the gradient elasticity theory, the energy of nanocantilevers is calculated. The energy release rate and stress intensity factor of double cantilever nanobeams are obtained. Results indicate that the energy release rates and stress intensity factors exhibit pronounced size effects if the thickness of the nanobeam falls in the same order of the characteristic length. The fracture toughness of the nanostructures is apparently enhanced. The energy release rates and stress intensity factors have little size-dependence if the thickness of the nanobeam is greater much than the characteristic length.