Modelling the fracture of advanced carbon and related materials

Kipling, Gary David

Engineering
November 2012

Thesis or dissertation


Rights
© 2012 Gary David Kipling. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
Abstract

This thesis outlines the development of a novel computational model which is used to simulate the mechanical response of nuclear graphites on a microstructural scale. Application of finite element analysis (FEA) to the simulated microstructure models allows for the determination of material properties and demonstrates the effect of porosity on these outputs. Further, a methodology for crack propagation through the model enables the simulation of load-displacement curves and fracture parameters.

A comprehensive microstructural characterisation programme was undertaken to ascertain pore data for use in computational models. Composite images were generated through optical microscopy in order to sample large areas (10 x 10 mm) of the graphite surface. Results for this work demonstrated the inherent variability of graphite and successfully quantified the pore size distribution.

Extensive mechanical testing was undertaken to determine the failure distribution of graphite and two additional brittle materials (glass and ligament material). Biaxial and three-point flexural experiments were employed in order to test a large number of samples. Data from these test programmes was determined to be consistent with a normal distribution and did not provide conclusive evidence for disparate flaw populations. Additional experimental tests were performed to provide data that could be used in the determination of suitable modelling input parameters.

Development and solution of the microstructure model allowed accurate representation of pore distributions in an FEA environment which in turn enabled computationally derived mechanical properties to be determined. These properties were comparable to values expected of graphite. Additionally, some simulated fracture parameters compared favourably with experimental results. However, not all properties were representative due to the significant geometric contrast between computational models and experimental samples.

Publisher
Department of Engineering, The University of Hull
Supervisor
Neighbour, Gareth B.
Qualification level
Doctoral
Qualification name
PhD
Language
English
Extent
Filesize: 22 MB
Identifier
hull:6843
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