Molecular dynamics simulations of interfacial crack nucleation and propagation

Molecular dynamics (MD) simulations are carried out to studythe critical conditions for crack nucleation at the interface edges andfor crack propagation along the interface, and theirrelations. MD method is employed to examine the fracturebehaviors near the apexes of the interface edges and near the tip of theinterface crack, with the outer boundaries of the simulation cellsbeingconstrained by the elastic finite element displacement fields. Thesimulation results show that, at the instant of fracture initiation, themaximum stresses along the interfaces reach the ideal strength of theinterface; also their interface energies can just overcome the intrinsiccohesive energy of the interface material. Therefore, thefracture conditions for crack nucleation at the interface edges and forcrack propagation along the interface could be correlated through either theideal strength or the cohesive energy of the interface. Further, a unifiedcriterion for interface fracture initiation is proposed based on thesimulation results.