MINIMUM-COST DESIGN OF HYBRID COMPOSITE CYLINDERS WITH TEMPERATURE-DEPENDENT PROPERTIES

Laminated composite cylinders are optimized with the objective of mini mizing the material costs by means of hybridization. They are modelled as thick cylinders working under internal and/or external pressures. The optimal designs are subject to a lower bound on the failure pressu re determined by the maximum stress criteria. The cylinders are constr ucted such that the stress patterns match the material properties by p lacing the stronger material in high stress areas and the weaker mater ial in low stress areas. The resulting structure is of hybrid construc tion and the cost minimization is achieved not only by using an inexpe nsive material but also by minimizing the amount of the expensive mate rial used in the design. The effect of temperature change on the stres ses and the material properties is included in the analysis. Numerical results are given for graphite/glass hybrid cylinders and the efficie ncies of the designs are shown to be substantial by comparing the cost s of hybrid and non-hybrid designs. It is also shown that neglecting t he effect of temperature on the stiffness and strength parameters of t he materials would lead to underdesign and premature failure. (C) 1997 Elsevier Science Ltd.