Studies of Impefection Sensitive Conical Composite Structures

Abstract

The stability of shell structures has been an object of studies for more than a century. Thin walled cylindrical and conical structures are widely used in aerospace, offshore, marine, civil and other industries. Nowadays, with the growing application of composite materials a deep understanding of the influence of their properties and the laminate stacking sequence on the mechanical behaviour of shell structures is increasingly more important. As it is already known, one of the most significant sources of discrepancy between theoretical predictions and experimental results for the buckling load is the presence of geometric imperfections. Currently, imperfection sensitive shell structures are generally designed, at the preliminary design phase, according to the guideline NASA SP-8007 for cylinders and NASA SP-8019 for truncated cones using the conservative lower bound curve, which does not consider composite material characteristics. Hühne developed the Single Perturbation Load Approach (SPLA), a robust design method that stimulates a single buckle, which is assumed as a “worst-case” geometrical imperfection [1]. There have been carried out considerably more numerical, analytical and experimental studies on cylindrical shells than on conical shells. Currently typical composite launcher structures are investigated by 12 partners in the European project DESICOS [4]. The aim of this paper is to study the SPLA on a conical shell structure and compare it with the NASA design approach.