Numerical fracture analysis and model validation for disbonded honeycomb core sandwich composites

Disbond damage propagation in honeycomb core sandwich structures is investigated numerically and experimentally. A fully parametric two-dimensional finite element model of a disbonded honeycomb core sandwich specimen is presented. Energy release rate and mode-mixity were numerically determined using the Crack Surface Displacement Extrapolation (CSDE) method. An advanced method was adopted to obtain the homogenized mechanical properties of the honeycomb core based on the geometry of a single honeycomb cell and the material properties of the cell wall paper. The numerical model was benchmarked against CFRP/Nomex (R) Single Cantilever Beam (SCB) specimen tests and a closed-form semi-analytical model. The results show a close agreement between analytical, numerical and experimental energy release rate, as well as analytical and numerical mode-mixity. An extensive sensitivity analysis was also carried out and the effects of the geometry and the material properties of the SCB specimen on the energy release rate and mode-mixity have been investigated.