Layup Optimisation and Response of Lightweight Composite Tubular Structures under Thermomechanical Loading Conditions using Particle Swarm Optimisation.

Composite tubular structures are increasingly being used in applications with thermomechanical loading conditions such as pressure vessels, rocket nozzles, gas piping and gun barrels. While significant weight reduction over existing monolithic materials is able to be achieved, notable challenges exist in lightweighting optimisation of their layup due to the complexity of the solution space. This paper aims to investigate the use of Particle Swarm Optimisation (PSO) for the layup optimisation of composite tubular structures under combined thermal and mechanical loading. Closed-form 3D elastic solutions are used to determine the stress state of a particular layup, with statistical-based convergence and failure criteria considered. Layup optimisation variables include ply thickness, ply angle, fibre-volume fraction and the number of plies. Several tube geometries and thermomechanical loading conditions are investigated to characterise their influence on optimisation convergence and lightweighting outcomes. The PSO approach is shown to successfully optimise lightweighting within a fixed confidence interval for the boundary conditions considered when compared to known results, achieving significant efficiency improvements over alternative algorithms. Additionally, the increased optimisation efficiency enables investigation into the influence of thermomechanical loading conditions on the layup design required to maximise lightweighting. The presence of thermal loading is found to enhance lightweighting over pure mechanical loading by enabling improved stress distribution across tube solutions. When considered without a monolithic liner material, thermal loading establishes a temperature threshold above which tubular composite composites are unable to be integrated without failure due to stress interactions. This study demonstrates the effectiveness of PSO as an approach to improving the efficiency and performance of lightweighting optimisation for composite tubular structures over traditional methods. In addition, several key interactions between the optimised layup and thermomechanical loading conditions are identified. These outcomes will improve the capability of lightweighting optimisation performance and enable better understanding of composite thermomechanical response. [ABSTRACT FROM AUTHOR]