An Optimum Design for Composite Cylindrical Pressure Vessels

Composite materials have found wide applications in different engineering fields; mechanical, aeronautical, civil and chemical. This is due to the attractive properties which these materials possess as the high strength, high modules, low density, high corrosion resistance and well-tailored as needed through fabrication. One of these mechanical applications is composite pressure vessels of different shapes; cylindrical, spherical, toroidal and elliptical. In this paper, cylindrical pressure vessels fabricated from an inside liner (aluminum or polymeric material) reinforced with different composite overwrapped; glass, carbon and Kevlar mixed with epoxy resin have been considered. Generally, the composite pressure vessels contain the inside liner to prevent the leakage of the inside fluid, where the composite fibers cannot prevent that leakage due to the presence of voids and gaps between the fibers. The fibrous materials are used to give a reinforcement to the liner for sustaining the resulting hoop and longitudinal stresses in the vessel wall. A design optimization has been performed to get the optimal parameters (outer radius, fiber volume fraction and fiber orientation angle) governing the design objective which is minimizing the vessel weight. After formulation of the optimization problem, as objective and constraints functions, Kuhn-Tucker method has been used to declare the main conditions of optimum design. This technique is used since the problem is nonlinear with inequality constraints. Then, the optimum solution is obtained using MATLAB program and checked with Kuhn Tucker conditions.