A design approach for super-efficient Wrapped Tow Reinforced Hierarchical Space Frames

Abstract

This manuscript delineates the inception and development of a novel holistic paradigm in the design and manufacture of hybrid-composite structures: the Wrapped Tow Reinforced Hierarchical Space Frames (WrapToR-HSF). By promoting an innovative approach towards enhancing structural efficiency in space frames, the WrapToR-HSF methodology proposes to use a smaller number of longer, truss based members in the macrostructure of space frame structures in a manner which provides significant potential for mass reduction. In transforming the theoretical underpinnings of WrapToR-HSF into a pragmatic technological entity, this work takes a multi-disciplinary approach to evolve in parallel novel hardware and software. These developments, in turn, expedite the production rates of truss members and enable the all-encompassing design of WrapToR-HSF structures.
The innovation in truss beam manufacturing developed here is a unique truss winding process and associated machinery known as "Trusstrusion". This purpose-built setup, conceived from scratch, employs a seamless process to wrap trusses via a contra-rotating multi-tow winding system in series with a chord member advancement mechanism. A prototype Trusstruder was designed and built, and mechanical testing of WrapToR truss specimens made with it show excellent performance, and also provide validation of numerical models derived from a custom-developed finite element code, affirming the validity of the approach.
The remarkable concordance between the experimental outcomes and the numerical models underscores the reliability of the code. This code is then used to elucidate the mechanical superiority of WrapToR truss members vis-à-vis standard unidirectional (UD) fibre-reinforced plastic (FRP) tubular struts. This investigation unravels the intricate physics integral to lattice modelling, especially with regards to capturing complex potential failure modes, and leads to clear, simple conclusions around the relative performance under compression of tubes versus trusses, with trusses proving superior for all but the most heavily loaded of structures. As a further necesary step toward widespread adoption of WrapToR-HSF technology, this work culminates in the development of a bespoke optimisation strategy for hierarchical space frames to minimise mass, which can then be combined with the automated design process tools developed to rapidly produce super efficient hierarchical space frames combining WrapToR truss beams with 3D printed junctions. While much remains to be done before these structures can become commonplace and useful in our society, this work has directly addressed several key underlying gaps in our knowledge and developed a robust suite of tools on which future work can be built.

Date of Award	5 Dec 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Ben K S Woods (Supervisor), Terence Macquart (Supervisor), Mark Schenk (Supervisor) & Alberto Pirrera (Supervisor)