WrapToR composite truss structures
: analysis, manufacturing, characterisation, and optimisation

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

The wrapped tow reinforced (WrapToR) truss combines the benefits of a truss geometry with the impressive material properties of composites to produce highly efficient structural members. While composite trusses are not a new concept, this work uses a novel manufacturing process to produce a unique wound truss configuration. Adapted from filament winding, the manufacturing process involves wrapping wetted fibre tow around rigid longitudinal members to form a truss geometry. This manufacturing method dramatically reduces labour demands compared with traditional trusses, which require assembling a large number of parts. The WrapToR truss concept therefore offers a low-cost method for producing structural members that could offer significant weight savings in a range of applications. To progress towards commercial application, the current work focuses on further developing and understanding the novel truss concept. The research is divided into two main themes: manufacturing and analysis.

The manufacturing work focused on developing and understanding the novel truss winding process. Prior to this work, WrapToR trusses were produced using a manual hand-winding process that is both inaccurate and labour-intensive. A key objective was to automate the process to improve consistency and throughput. This objective was achieved through the design and manufacture of a three-axis truss winding machine. Additional process development work found that twisting the shear member tow while winding significantly improved load-carrying capability.

The analysis work focused on developing tools that could predict truss behaviour under static loading scenarios. Models based on matrix structural analysis techniques were built and experimentally validated using a series of three-point bending tests. Initially, the models’ ability to predict pre-failure response was investigated. This preliminary investigation revealed the necessity of modelling behaviour at the truss joints to capture overall truss deformations. Failure analysis was later conducted in which the key truss failure mechanisms were identified and predicted. The mechanisms investigated were member material failure, joint failure, and local and global buckling. The critical loading of these mechanisms was predicted by implementing failure criterion within the developed truss model. Again, the predictive capabilities were validated via a series of three-point bend tests.

An efficient design method was later developed that maximised truss structural efficiency by embedding the analysis tools within an optimisation algorithm. Results of this optimisation study showed huge weight-saving potential of the truss technology. Compared to conventional carbon fibre tubes, one truss configuration displayed over 50% mass reduction while offering equivalent strength and stiffness performance.

Through development of the manufacturing process and exploration of modelling techniques, this work has significantly advanced understanding of the WrapToR truss technology. Combined with the demonstration of structural performance, the work lays the foundations for implementing the technology within commercial applications.
Date of Award23 Mar 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorMichael R Wisnom (Supervisor) & Ben K S Woods (Supervisor)

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