The use of fibre reinforced polymers is rapidly increasing in a range of applications, from aviation to sporting goods. While the outstanding material properties offered by modern composites make them widely applicable they often suffer from brittle, catastrophic failure. Their inherent brittleness limits their application for safety critical applications without large safety margins. This thesis sets out to introduce design principles that introduce a degree of 'pseudo- ductile' failure behaviour to advanced fibre composites. Much of the inspiration for the work comes from looking at the failure processes of natural hierarchical materials. Many of these materials are able to sustain large amounts of damage at different length scales without catastrophic failure, with many of them being essentially ceramics. Nacre, a relatively simple discontinuous laminated material, served as a major inspiration. Three main strategies were employed to reduce the effects of brittle fracture. Ply terminations were used to selectively weaken a laminate allowing one large fracture to be replaced with a number of smaller ones. Thereby giving indication of the laminates failure and significantly increasing the strain to failure over a traditional laminate. Ply perforations, where portions of a ply are cut, were used to weaken a laminate allowing the location of the fracture to be controlled. The third method tailored interlaminar fracture toughness allowing for steady crack propagation where traditional laminates would suffer unstable crack growth. The work introduces three distinct and highly expandable methodologies capable of reducing the limitations of modern composites.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:557974 |
| Date | January 2011 |
| Creators | Malkin, Robert Edward |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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