Analysis of delamination crack tip fields for adhesive surface between skin and spar for helicopter blades

The blades of helicopters suffer from centrifugal forces, flap moments, lag moment s and torsion moments. Based on these loading characteristics, the displacement equations of skin and spar were derived through the nonlinear structural model for blades under generalized two dimensional deformation. Based on the Stroh formalism, the asymptotic solutions of stress fields and displacement fields for the delamination crack tip between skin and spar were obtained by applying the interfacial fracture mechanics to anisot ropic bimaterials. Combined with the special solutions, the st resses and stress intensity factors were computed for the delamination crack tip in the adhesive surface between skin and spar of the helicopter blade under centrifugal forces by applying the boundary collocation way, and the results are close to the values by the interface element way. The results show that the way in this paper is effective for analyzing the delamination failure between skin and spar, which could be used as the basis to research the delamination failure of composite blades.