SIMPLIFIED METHODOLOGY FOR PREDICTION OF CRITICAL BUCKLING PRESSURE FOR SMOOTH-BORE COMPOSITE CYLINDRICAL-SHELLS

The critical buckling pressure of composite cylindrical shells can be predicted using linear eigensolutions or geometrically nonlinear insta bility calculations. Classical linear eigensolutions generally overpre dict the critical collapse pressure by a significant margin. Nonlinear instability calculations tend to provide more accurate results but at a greater cost. A simple accurate method for predicting critical buck ling pressures is needed to reduce the time and cost associated with g enerating preliminary structural designs for composite pressure hulls. In this article, simple closed form equations for the critical buckli ng pressure of smooth-bore composite cylinders were developed and vali dated. The equations are valid for both solid and sandwich shell confi gurations. These equations are a modification of the classical Von Mis es eigensolution for isotropic cylindrical shells with length to diame ter ratio's varying between 0.5 and 8. The modified equations take int o account reductions in the buckling pressure due to material anisotro py, shear deformation, nonuniform stress distribution through the thic kness, and effective shell thickness (sandwich shells only). The buckl ing equations were validated using hydrostatic pressure test data for two solid shell configurations and three sandwich shell configurations . The predicted values of critical buckling pressure were within 15% o f the experimental values for the solid shells and within 5% of the ex perimental values for the sandwich shells. These results demonstrate t he viability of using these simple equations for preliminary design of composite pressure hulls.