Characterisation of Manufacturing Induced Defects in Curved Carbon Fibre Reinforced Polymer Composites and their Effects on Compressive Behaviour

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dc.contributor.advisor Battley, M en
dc.contributor.advisor Allen, T en Ramesh, Abhiram en 2020-04-24T03:10:32Z en 2020 en
dc.identifier.uri en
dc.description.abstract Curved Carbon Fibre Reinforced Polymer (CFRP) components with large thicknesses often have significant variability in quality due to an increased amount of porosity, discrete voids, corner thickening, and wrinkles. To improve the reliability and reduce the cost of CFRP products, it is necessary to characterise typical defects and understand their effects on damage behaviour. Image processing techniques have been developed to characterise the morphology of voids and wrinkles in curved CFRP parts using micro-CT scan data and micrographs. Algorithms were developed to automate the extraction of 3D void morphology, and to determine the average ply orientation of specimens. Software tools were developed to extract characteristics of ply wrinkles from lowmagnification reflective optical micrographs. The effect of real defects on compressive strength was investigated using two approaches; standardised compression tests with acoustic emission monitoring and high-speed imaging, and a novel compression test methodology developed to conduct in-situ X-ray micro-CT scans of specimens under load. Parametric numerical models incorporating varying severities of voids and wrinkles were developed and used to determine the role of defect severities on the stress concentrations and distributions. Results obtained have demonstrated that thick curved CFRP laminates can have complex void and wrinkle morphologies. Humidity during lay-up, de-bulk frequencies, and part geometry, caused a variation in part quality. Wrinkle were most severe between 50%-65% of thickness from the mould surface. Corner regions had up to 25% increase in thickness compared to the nominal geometry. Local void volume fractions of up to 8% were found in curved CFRP parts. Large voids were over 20 mm in length and up to 8.2 mm, and 1.35 mm in width and thickness, respectively. The effect of defects on the resulting laminate compressive strength is more dependent on individual defect parameters than the average defect characteristics. An increase in lengths and widths of voids causes local stress increases in the associated lamina and a reduction in the final failure strength. An increase in the volume of the largest void resulted in a reduction in compressive strength. Large voids can lead to localised instability of smaller laminate sections, leading to sublaminate buckling causing delamination and failure. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri en
dc.rights.uri en
dc.title Characterisation of Manufacturing Induced Defects in Curved Carbon Fibre Reinforced Polymer Composites and their Effects on Compressive Behaviour en
dc.type Thesis en Engineering en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en
dc.rights.accessrights en
pubs.elements-id 799111 en Engineering en Engineering Science en
pubs.record-created-at-source-date 2020-04-24 en

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