On the analysis and optimization of a pressurized mid-plane asymmetric sandwich non-circular cylindrical shell.

摘要

Sandwich constructions have been used increasingly since World War II. However, according to Noor, Burton and Bert, the concept of sandwich construction was originated by Fairborn in 1849.; Today, composite and sandwich shell structures can be of use in a variety of structures. So it is important and valuable to study the behavior of both sandwich and shell structures to fully utilize sandwich constructions for these applications.; However, in almost all cases of sandwich constructions to date, the construction is mid-plane symmetric. This simplest construction limits the usage of sandwich constructions. There are many needs for sandwich constructions using different faces. On the other hand, considering that many advanced composite materials have different strengths and elastic moduli in tension and compression, even if the two faces are made of same material, different face thickness can provide a superior structure.; For shells, a circular cross section results in a state of membrane stress when the shell is subjected to a uniform internal pressure, but it may limit the structure's efficient usage. An axially asymmetric shell is desirable for some uses.; Because the non-circular cylindrical shell being considered is subjected to an internal pressure, a state of plane strain in the axial direction can be assumed, for the shell away from bending boundary layers at each end of the fuselage shell. Therefore, both exact and energy solutions are developed for ring sections composed of isotropic and anisotropic materials used in sandwich constructions. The governing equations are obtained by applying the Theorem of Minimum Potential Energy. The energy solutions are compared to the exact solution and validate the approximate method.; The energy solutions developed are for a slice of a non-circular cross section (a box-like structure) shell subjected to a constant internal pressure, and involve a mid-plane asymmetric sandwich construction. The structure and material systems are then optimized using a factor of merit.; Then, solutions are derived for a non-circular shell subjected to a constant internal pressure. Solutions obtained through piece-wise matching of plate and shell sections are verified with membrane solutions. An optimization is then performed using those solutions.