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

Abstract

Thin-walled shells like cylinders are primary structures in launch-vehicle systems. When subjected to axial loading these shells are prone to buckling. The corresponding critical load heavily depends on deviations from the ideal shell shape. In general, these deviations are defined as geometric imperfections and although imperfections exhibit comparatively low amplitudes, they can significantly reduce the critical load. Considering the influence of geometric imperfections adequately into the design process of thin-walled shells poses major challenges for structural design. An alternative to robust design of thin-walled shell by accurate consideration of geometric imperfections is the development of a robust or imperfection-insensitive shell architecture. In this article a special hybrid cylinder is presented and analyzed. The composite shell design is based on an interstage structure of the Ariane 6 by MT Aerospace and has special CFRP belts which are intended to reduce the imperfection sensitivity of the shell. The shell was tested at the German Aerospace Center in Braunschweig and the corresponding results are presented and described. The hybrid cylinder was analyzed with the Southwell-method and geometrically nonlinear finite element analyzes. The results show that the Southwell-method delivers conservative buckling load estimations and that the CFRP belts reduce the imperfection sensitivity significantly.

Imperfection-insensitive continuous tow-sheared cylinders

“…This paper explores the design space of a CTS cylinder, derived from an interstage structure for the Ariane 6 [41]. Section 2 discusses the numerical model used, the designs explored and the types of analyses employed.…”

On the development of shell buckling knockdown factors for imperfection sensitive conical shells under pure bending

“…By reducing the complete membrane stiffness of a shell, a lower-bound with respect to imperfections can be determined [35]. Improved lower-bound methods were proposed by Hühne et al [36], Hao et al [37], Meurer et al [38], Tian et al [39], Wang et al [40], [41], Wagner et al [42], [43], [44], [45], [46]. However, most of the lower-bound methods were only be applied to cylindrical shells [47], [48] or cylindrical shells [49], [50] under axial compression.…”

Buckling of Rectangular Composite Pipes under Torsion

“…Thin structures usually fail not for lack of material strength or delamination but through buckling load because the buckling load of thin structure lower than material failure load. The buckling load can be increased by careful design of the layup sequence of the composite layers; however, no available simple design equation or chart were found in spite of there being many studies on composite structures [3][4][5][6][7][8][9][10]. The buckling load under shear force has been studied; however, those studies were not for composite rectangular tubes, but rather for long anisotropic plates [11,12].…”