Dealing with Imperfection Sensitivity of Composite Structures Prone to Buckling

Buckling analysis of an imperfection-insensitive hybrid composite cylinder under axial compression – numerical simulation, destructive and non-destructive experimental testing

“…A similar project started 2012 in Europe, the DESICOS project [32] (new robust DESign guideline for Imperfection sensitive COmposite launcher Structures) to develop and validate new deterministic [33], probabilistic [34] as well as experimental [35], [36] design approaches for composite shells [37], [38], [39], [40]. A comprehensive overview regarding this project is for example given in [2].…”

Buckling prediction of panels using the vibration correlation technique

“…Since the early seventies an extensive work has been performed at the Laboratory of Aeronautical Structures, Faculty of Aerospace Structures, the Technion, I.I.T., Haifa, Israel, to better define the in situ actual boundary conditions of stringer stiffened aluminum cylindrical shells, and thus better predicting their experimental buckling loads [7]. The direct prediction of the buckling loads of compressively loaded shells using the VCT yielded, in most of the cases, loads higher than the experimental ones, and it was shown that, in the vicinity of the buckling load, the curve of frequency squared vs. the compressive load ceases to be linear and performs a sharp bend towards the actual buckling load (zero frequency) due to the initial geometric imperfections of the specimens [8][9][10][11][12][13][14][15]. Recently, new studies (see for example [6][7][8][9][10][11][12][13][14][15][16][17][18]) have shown again that the use of the VCT for direct predictions of buckling loads in composite shells is not yet mature enough to be applied in industrial applications, like space launchers.…”

“…The direct prediction of the buckling loads of compressively loaded shells using the VCT yielded, in most of the cases, loads higher than the experimental ones, and it was shown that, in the vicinity of the buckling load, the curve of frequency squared vs. the compressive load ceases to be linear and performs a sharp bend towards the actual buckling load (zero frequency) due to the initial geometric imperfections of the specimens [8][9][10][11][12][13][14][15]. Recently, new studies (see for example [6][7][8][9][10][11][12][13][14][15][16][17][18]) have shown again that the use of the VCT for direct predictions of buckling loads in composite shells is not yet mature enough to be applied in industrial applications, like space launchers. To overcome the above described shortcomings of the method, when applied to structures like shells, presenting non-stable behavior in the post-buckling region, a new relationship between the natural frequency and the applied compressive load was proposed by Souza et al [9][10][11][12][13][14][15][16][17][18][19][20][21], yielding the following equation: …”

Probabilistic and deterministic lower-bound design benchmarks for cylindrical shells under axial compression

“…An alternative approach to assess the imperfection sensitivity of complex shell structures is the application of perturbation or lower-bound methods [57]. Deterministic lower-bound methods are applied in order to quantify the influence of so called "worst" imperfections and were extensively studied within the DESICOS project [58] (new robust DESign guideline for Imperfection sensitive COmposite launcher Structures) in order to develops and validates new deterministic [59], [60], [61] probabilistic [30] as well as experimental [62], [63] design approaches for composite shells [64], [65]. A comprehensive overview regarding this project is for example given in [66].…”