On the Assessment of Design Tools for Thick-Walled, Thermoplastic Composite Pipe

  • Harry Barnard

Student thesis: Doctoral ThesisEngineering Doctorate (EngD)


This thesis documents an experimental study investigating the usage of continuous carbon fibre reinforced polyetheretherketone matrix composites in thick-walled, internally pressurised cylinders. In this context, "thick-walled" is defined by walls of a thickness greater than 1/20th of the internal diameter of the cylinder.

A controlled experimental study was performed in which five different angle-ply, thick-walled cylinders were produced and internally pressurised until failure. Predictions of stresses, strains, deflections and burst pressure were produced using an exact mathematical model implemented from the literature. Experimentally recorded axial and radial deflections were compared and contrasted with the aforementioned predictions to assess the efficacy of the model and the mechanical characterisation performed on ply and unidirectional sub-laminate specimens.

It was found that the model was capable of reasonably accurate predictions of the cylinders with fibres wound at an angle preferential to the direction of loading. However, it could not predict the non-linear load/displacement response of the cylinders with fibres wound at 45degree{} or more to the loading direction. Additionally, fibre failure was observed at stresses up to 42% lower than those recorded during material characterisations.

Geometric inconsistencies, material and manufacturing defects and volumetric size effects were identified as contributing factors to the failure stress reduction. The model was modified to account for volumetric size effects and produced realistic survival probability values, although it was found that laminate thickness contributed disproportionately to the observed size effect. However, further experimental work with different materials is required to confirm the relationship between fibre-direction strength variability and size effect magnitude.
Date of Award24 Mar 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorIvana Partridge (Supervisor) & Alberto Pirrera (Supervisor)

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