vibration correlation technique

Due to unique properties, grid-stiffened composite plates are used extensively in aviation, marine and automotive industry. In recent decades, several studies are done to predict the critical buckling load of grid-stiffened composite plates without breakdown or failure. One of the most important non-destructive methods, is Vibration Correlation Technique (VCT). The aim of this research is the prediction of the critical buckling load of grid-stiffened composite plates using VCT. For this purpose, nonlinear vibration analysis of grid-stiffened composite plates are firstly performed in different compressive loads using finite element software ABAQUS. In the next step, critical buckling load of grid stiffened composite cylinder shells is predicted using VCT. To validate the results of VCT, three grid-stiffened composite plates are fabricated using filament winding and hand lay-up method with same conditions and was placed under axial compression test. Finally, the critical buckling load is measured experimentally. The results show that the difference between the critical buckling load of VCT with experimental buckling load is less than 5%. This subject implies that VCT is suitable for prediction of critical buckling load of grid-stiffened composite plates with very high accuracy.

Due to unique properties, grid stiffened composite cylinder shells are used extensively in aviation, marine and automotive industry. In recent decades, several studies are done to predict the critical buckling load of grid stiffened composite cylinder shells without breakdown or failure. Vibration Correlation Technique (VCT) is one of the most important non-destructive methods that based on nonlinear vibration analysis. The aim of this research is the prediction of the critical buckling load of stiffened composite cylinder shells with lozenge grid by using VCT. For this purpose, linear and nonlinear vibration analysis of composite cylindrical shells were performed in different compressive loads by using finite element software ABAQUS, firstly. In the next step, linear buckling critical load was determined by using numerical methods. Then, non-linear critical buckling load of grid stiffened composite cylinder shells was predicted by using VCT. To validate the results of VCT, five composite cylindrical shells were fabricated by using filament winding method with same conditions and was placed under axial compression test. Finally, the critical buckling load was measured experimentally. The results show that the difference between the critical buckling load of VCT with experimental buckling load is less than 3%. This subject implies that VCT is suitable for prediction of critical buckling load of stiffened composite cylinder shells with lozenge grid with very high accuracy.