Robustness of Empirical Vibration Correlation Techniques for Predicting the Instability of Unstiffened Cylindrical Composite Shells in Axial Compression

Abstract

Thin-walled carbon fiber reinforced plastic (CFRP) shells are increasingly used in aerospace industry. Such shells are prone to the loss of stability under compressive loads. Furthermore, the instability onset of monocoque shells exhibits a pronounced imperfection sensitivity. The vibration correlation technique (VCT) is being developed as a nondestructive test method for evaluation of the buckling load of the shells. In this study, accuracy and robustness of an existing and a modified VCT method are evaluated. With this aim, more than 20 thin-walled unstiffened CFRP shells have been produced and tested. The results obtained suggest that the vibration response under loads exceeding 0.25 of the linear buckling load needs to be characterized for a successful application of the VCT. Then the largest unconservative discrepancy of prediction by the modified VCT method amounted to ca. 22% of the critical load. Applying loads exceeding 0.9 of the buckling load reduced the average relative discrepancy to 6.4%.

Vibration Correlation Technique for Cylindrical Structural Safety Assessment

“…In 2020, Skukis et al (Skukis, 2020) modified the work done by Arbelo et al (Arbelo, 2014) proposing a novel VCT based on the characteristic chart between the parametric forms (1 -p) 2 and 1 -f. The authors empirically verified a second-order relationship as illustrated in Fig. 2.17, which reproduces the results from (Skukis, 2020) for a schematic view.…”