Predicting buckling-driven delamination propagation in composite laminates: An analytical modelling approach

Robust and efficient predictions of buckling-driven delamination propagation, enabled by a novel analytical modelling approach, are presented. The model considers full mechanical coupling (extension-shear, extension-bend, extension-twist/shear-bend and bend-twist), contact and mode-mixity and thus significantly enhances the capabilities of current analytical approaches. A problem description in cylindrical coordinates enables the evaluation of the energy release rate along the delamination boundary. The model uses an energy formalism to determine the post-buckling deformation and a crack-tip element analysis employing force and moment resultants acting on the delamination boundary to determine the energy release rate. Composite panels with circular thin-film delaminations and various multi-directional stacking sequences are investigated for in-plane compressive loading. Predictions of applied strains causing delamination growth, i.e. threshold strain, show good agreement with published experimental data and 3D finite element analysis. A parametric study varying the ratio of delamination size to depth is performed. Based on the findings obtained, governing deformation characteristics of buckling-driven delamination growth are identified and insight into damage tolerant design of composite laminates is obtained, which is of particular interest for compression after impact (CAI) strength of composite structures.

Automated summary

This study introduces a novel analytical modelling approach for robust and efficient predictions of buckling-driven delamination propagation. The model considers various mechanical couplings and contact modes, significantly enhancing the capabilities of current analytical approaches. The findings help identify governing deformation characteristics of buckling-driven delamination growth and provide insights into damage tolerant design and the improvement of compression after impact (CAI) strength in composite structures.