Closed form solution for strain energy release rate distribution in debonded one-edge free postbuckled composite flanged joints

A closed form model predicting debond growth in composite flanged joints is presented. This model calculates the non-uniform distribution of strain energy release rate (G) across the crack front. Such a model is useful for assessing the effects of partial debonds in adhesively-bonded joints that are subjected to compressive loads. The model’s accuracy is gauged by comparison of the G profile prediction with finite element analysis (FEA) based virtual crack closure technique (VCCT) calculations. For the woven glass/epoxy joints analyzed, it was found that the closed form model predicted the peak values of G to within 20% of the FEA calculated values when the applied far-field strain εo was greater than 1.3 times the strain at which the flange first buckles, i.e., the critical buckling strain εcr. At moderate loads (εo < 1.3εcr), peak values of G were greatly under-predicted due to the nonlinear FEA predictions of εcr being lower than the analytical values. Since the amount of strain applied beyond buckling (εo − εcr) drives postbuckling deformation, the FEA predictions for G tend to exceed the closed form values. Physical insight into which material and geometric parameters strongly affect this problem is gained due to the analytical model being presented in closed form. Such expressions are useful in conducting trade-off studies for damage tolerant designs and for making decisions related to maintenance and repair.