Asymptotic solution for interface crack between two materials governed by dipolar gradient elasticity: Amplitude factor evaluation

•The application of the asymptotic solution for interface crack between mismatched materials that obey the dipolar strain gradient elasticity under plane strain conditions.•The development of the procedure combining and generalizing the analytical and numerical methods applicable in the fracture problems of the strain gradient elasticity under plane strain conditions.•The assessment of the amplitude factors in the asymptotic solution for the interface crack between the materials obeying the isotropic gradient elasticity.•The concept of the Betti theorem extended to dipolar gradient elasticity is used to generalize the two state integral methods in fracture mechanics of materials obeying the isotropic gradient elasticity.•The implementation of mixed finite element formulation using the Lagrange multipliers.