Reliability evaluation of critical local buckling load on the thin walled cylindrical shell made of composite material

The goal of this research is to evaluate the variability of the buckling load in thin orthotropic cylindrical shells due to the deviation with respect to the nominal values, for both the geometrical and material properties. In this research also the fiber orientation i.e the alignment with respect to the cylinder axis was considered. The research is developed by comparing the results obtained through analytical formulas and numerical results (f.e.m.) for isotropic and orthotropic materials. The coefficient of variation for critical buckling load (for symmetrical and non-symmetrical deformation), assumed for comparing the standard deviation values, is linear with the variation of material and geometrical parameters. The standard deviation on critical buckling load considering both the material and geometrical variations and fiber orientation can be very well described by a surface. From these surfaces it is important to underline that to quantify the dispersion values on the critical buckling load, the material properties assume the fundamental role with respect to the fiber orientation. The main implications of these results are correlated to the fact that, for example, during the manufacturing process, the geometrical and material variability is more important than the fiber orientation in order to have a reliability component.