Design of multi-wall composite shells

This paper investigates a problem of optimal design of a multi-walled cylindrical shell under axial compressive loads. The multi-walled shell consists of two load-carrying layers connected by a set of composite walls. The main structural element of the load-carrying layer is a monolayer comprising parallel-laid fibers that are interconnected by a polymer binder — a matrix. The wall represents a unidirectional composite made from the same material as the load-carrying layers.
Both strength and stability constraints are taken into account during mathematical modeling. The critical load corresponding to a general form of buckling is determined by a classical formula for an orthotropic shell with “reduced” stiffnesses. The critical load corresponding to a local form of buckling is calculated using the well-known formula for a smooth orthotropic plate. The target function is the mass of the structure.
The solution to the problem of optimal design of a multi-walled structure is proved to be unique. The conditions ensuring the existence of the problem solution are formulated. The example of evaluating the efficiency of reinforcing elements in a shell structure is given. The presented research results can find application in design problems for modern composite structures in rocket and space industry.