Minimum cost design of hybrid cross-ply cylinders with uncertain material properties subject to external pressure

Minimum cost design of hybrid cross-ply cylinders is presented which employ high-stiffness and expensive materials in the surface layers and the low-stiffness and inexpensive layers in the middle layers to combine the advantages of the two materials. Hybrid construction takes advantage of the sandwich effect whereby most of the load is carried by the surface layers. The cylinder is subject to external pressure with the material properties displaying uncertain-but-bounded variations around their nominal Values. For a given external pressure, the material cost is minimized by minimizing the thickness of the surface layers. Analysis to determine the worst-case combination of material uncertainties makes use of convex modeling to compute the least favorable solution defined here as the minimum buckling pressure. The minimum cost designs are investigated for various problem parameters such as the wall thickness and the level of uncertainty. The relative sensitivities of the buckling pressure to material properties are also studied by defining sensitivity indices. (c) 2014 Elsevier Ltd. All rights reserved.