An experimental vibration-buckling investigation on classical and variable angle tow composite shells under axial compression

Two laminated composite shells, one with a conventional straight fiber laminate denoted the classical laminated shell and the second one with a variable angle tow reinforced composite, had been excited and their natural frequencies and mode shapes had been measured and monitored as a function of the axial compression load. Then, the in-situ buckling loads of the two tested specimens were predicted using the Vibration Correlation Technique (VCT) and compared with actual experimental buckling loads and Finite Element buckling predictions, yielding matching, consistent and repeatable results. It was shown that the VCT predicts the actual in-situ buckling loads of laminated composite thin walled cylindrical shells with a high accuracy, yielding 96% and 98.6% of the experimental buckling load, for the classical and variable angle tow composite shells, respectively. These results, although based on only two specimens, join the relatively small data base published in the literature, proving the nondestructive nature of the VCT approach, making it an adequate method for application on thin-walled structures, like shells. In addition, some testing recommendations are presented, to effectively enable the successful application of the VCT for in-situ buckling prediction of the buckling sensitive structures, like composite cylindrical shells.