WrapToR composite truss joints: Concept introduction and coaxial joint analysis and demonstration

Abstract

This study focuses on the development of coaxial continuously wound joint structures for Wrapped Tow Reinforced (WrapToR) trusses, which are carbon fibre composite lattice beams fabricated through a unique winding process. WrapToR truss beams have shown very high levels of performance as beam-like structures, but their usefulness can be greatly extended by using them as members within hierarchical space frames, which can be made into more geometrically complex and generally useful structures. However, the key challenge lies in creating effective joint structures able to connect together multiple WrapToR beams of different sizes and orientations. This paper addresses this challenge by presenting a modified WrapToR winding process which enables three-dimensional winding of arbitrary space frame joints, with an initial focus here on a proof of concept coaxial joint. This includes the design and manufacturing of a coaxial joint demonstrator and the development of a finite element analysis tool to predict its mechanical performance. A cantilevered beam structure combining this joint with two different sizes of WrapToR truss is built and tested, showing high levels of bending rigidity and good agreement with numerical prediction. Following this, the analysis tool is used to explore the achievable design space for coaxial WrapToR joints.