Shear deformation theory for compressive delamination buckling and growth

The elastic buckling and postbuckling analyses of an axially loaded beamplate with an across-the-width delamination symmetrically located at an arbitrary depth are studied. A variational-principle-consistent shear deformation theory coupled with a Griffith-type fracture criterion is developed to formulate the problem. The results for various length ratios and thickness ratios of delamination vs plate are calculated and compared with those without the transverse shear effect. It is indicated that the effect of shear deformation always lowers the critical buckling load and the ultimate load of the delaminated plate. The extent of this reduction depends on the ratio of inplane axial Young's modulus to transverse shear modulus and the length ratio and thickness ratio of delamination to plate. The energy release rate at the crack tip can be expressed in an analytic form. The results of the analysis show that, for the same applied load, the energy release rate is larger with transverse shear effect included. Therefore, the initiation of delamination growth will occur at a lower applied load than that evaluated with the classical lamination theory.