Design of Lightweight Structures by Reinforcing Thin-Walled Cylinders

Abstract There is an enduring need for structures that are strong, stiff, and lightweight. In this work, we explore a rational approach to the design of such structures by building on the work of Wegst and Ashby [1]. Wegst and Ashby proposed partitioning the design space of thin-walled cylinders subject to pure bending loads based on the dominant failure mode to guide the selection of circular cross section shapes that maximize strength per unit mass. We extend this work by using the same framework to guide the selection of discrete internal reinforcements for these tubes. The partitioned design space, referred to as the Failure Mode Space (FMS), is generated for a given base tube using finite element analysis. Each branch of the failure envelope in the FMS is associated with a unique failure mode. We investigate three different reinforcement strategies: a) structural foam lining, b) a longitudinal rib and c) a ring stiffener to improve the mass-specific strength of a given base tube. Mass equivalence between the reinforced and un-reinforced tubes is used to project the reinforced tubes onto the FMS generated for the un-reinforced tubes. FE analysis of the reinforced tubes reveals that different reinforcement strategies behave differently in different partitions of the FMS based on the associated failure modes. The approach demonstrated in this preliminary study can be extended to more complex structures under generalized loading conditions.