Delaminations buckling and growth phenomena in stiffened composite panels under compression. Part II: a numerical study

A numerical study has been carried out on stiffened composite panels under compression, focusing on the delamination-related phenomena. A robust numerical finite elements model has been introduced to simulate the compression behavior of the panel, including the delamination buckling and growth, and to provide reasonable predictions of the strain measurements in the delaminated area. The robustness of the novel approach, which adopts an improved (mesh and time step independent) virtual crack closure technique for the simulation of the delamination propagation, has been demonstrated by comparisons with standard commercial FEM (Finite Element Method) codes results and experimental data. Indeed, the numerical results, in terms of strains and delamination size as a function of the applied load, have been compared to experimental strain gauges readings, embedded optical fibers measurements, and thermography images of the delamination taken at different load steps. Actually, the performed numerical activity contributed to improve the knowledge on delamination-related phenomena in stiffened composite panels, focusing on delamination growth initiation and delamination growth stability, by providing reasonable justifications and interpretations of experimental strain measurements and thermography images.