Local buckling prediction for laminate with delamination based on critical buckling load of the sub-laminate with the maximum flexural stiffness

A method was proposed for the global strain prediction of the composite laminate with special delaminations when the local buckling occurs. It was presented that the critical force of delamination buckling is determined by the maximum flexural stiffness of the sub-laminates in the delaminated region, so if two delaminations of same size have the same maximum sub-laminate flexural stiffness, their critical buckling force must be equal to each other. With the critical buckling force of a certain sub-laminate known, the loads on the debonded layer and intact layers were calculated using their axial stiffness. With the total load the global strain of the laminate was obtained when the local buckling occurs. Then, the three dimension finite element (FE) models of composite laminate with delamination of different area, depth and location were developed with ABAQUS, which are employed to simulate local buckling under quasi-static loading. The obtained delamination buckling loads compliance with above assumption. The proposed method was used to prediction global strain when the delamination buckling occurs, which agrees with those of FE well. Hence this method can be used to set up the samples for delamination depth detection.