Interlaminar Defect Identification by Vibration Correlation Technique in Filament Winding Cylinder Under Axial Loading

Composite shells are widely used in various industries due to their low weight and high strength. Designing these structures involves various engineering analyses, and one of the most important studies is the investigation of the buckling of shells under axial load. The aim of this research is to investigate the vibrational correlation method on composite cylinders with delamination defects. Delamination defects can occur in structures under different conditions and have a significant impact on the strength of the cylinder. Therefore, in this study, different dimensions and quantities of delamination defects in various specimens were examined using the vibrational correlation method. Carbon fibers of type T300 were used as the reinforcement material, and the epoxy resin LY556 was used as the matrix. The hardener and accelerator combined with the resin in this research are HY917 and DY70, respectively. The layer stacking in the specimens was done with angles [55 90 90 55] using the filament winding method, and artificial delamination defects were created between layers 2 and 3 using Teflon sheets. The manufactured specimens were subjected to modal testing under various compressive forces, and then the critical buckling load of the specimens was obtained using the modal testing method. Using numerical modeling software, critical buckling loads and natural frequencies were calculated for various axial compressive loads through linear and nonlinear analysis. These numerical results were compared with experimental results. The vibrational correlation method accurately predicted the critical buckling load in defect-free specimens with a 3% error, but its accuracy was significantly