Energetic-statistical size effect in fracture of bimaterial hybrid structures

• This paper investigates the effect of stress singularities on the scaling of fracture of hybrid structures.
• The scaling mechanism transits from energetic to statistical as the stress singularities get weaker.
• The energetic-statistical scaling relation agrees well with the numerical simulations by a stochastic cohesive crack model.

This paper investigates the size effect on the strength of bimaterial hybrid structures, which consist of a weak bimaterial interface. A general scaling relation was recently derived by combining the energetic scaling of fracture of the bimaterial notch and the finite weakest link model. This scaling relation is now studied through a stochastic cohesive crack model, which is able to capture the fracture process at the bimaterial notch tip as well as the random fracture properties of the bimaterial interface. The numerical example includes a series of metal-composite hybrid beams with a centered V-notch under three-point bending. A wide range of notch angles is considered, which represents various orders of stress singularities. The simulation shows that, as the stress singularities get weaker, there exists a transition from the energetic scaling to the statistical scaling. Within this transition range, the size effect on the structural strength can be explained by a combined energetic-statistical mechanism.