Moisture absorption in low level porosity, thermoplastic toughened epoxy composites
Moisture absorption in low level porosity, thermoplastic toughened epoxy composites
In this report, a new polyethersulphone toughened epoxy resin system, developed by ICI Materials Research Centre, is studied. The moisture absorption characteristics are determined over a range of test temperatures for nine varieties of the blend - each containing a different amount of thermoplastic. Results reveal that the addition of thermoplastic causes a decrease in saturation level, an increase in diffusivity and a decrease in activation energy. Equations are developed to fully describe the relationship between the absorption characteristics and thermoplastic content - enabling values to be extrapolated for any thermoplastic content blend at any temperature below glass transition temperature. The changes in absorption characteristics are attributed to a decrease in polarity on copolymerisation of the constituents, in addition to an initial increase in free volume. The absorption is shown to be initially Fickian in all blends, with non-Fickian anomalies occurring at the latter stages of testing in both neat resin and composite samples.
The existing equation for edge diffusion in three-dimensional samples was found to be inaccurate at low aspect ratios. A new equation is developed for use with all sample geometries, which gives results accurate to ± 4%. Modification of the diffusion equations for uni-directional composites has been made (including a new for anisotropic edge effects). When fitted to our data the model shows no enhanced diffusion at the fibre matrix interface, but supports the theory that differences in diffusion parallel and perpendicular fibre can be attributed to geometrical blocking effects alone. Diffusion coefficients and saturation levels are shown to be sensitive to void contents even below 1% volume fraction. This correlation between absorption properties and sample quality is shown even more closely when using ultrasonic attenuation rather than void content analysis.
University of Southampton
Fellows, Linda Mary Patricia
1999
Fellows, Linda Mary Patricia
Fellows, Linda Mary Patricia
(1999)
Moisture absorption in low level porosity, thermoplastic toughened epoxy composites.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In this report, a new polyethersulphone toughened epoxy resin system, developed by ICI Materials Research Centre, is studied. The moisture absorption characteristics are determined over a range of test temperatures for nine varieties of the blend - each containing a different amount of thermoplastic. Results reveal that the addition of thermoplastic causes a decrease in saturation level, an increase in diffusivity and a decrease in activation energy. Equations are developed to fully describe the relationship between the absorption characteristics and thermoplastic content - enabling values to be extrapolated for any thermoplastic content blend at any temperature below glass transition temperature. The changes in absorption characteristics are attributed to a decrease in polarity on copolymerisation of the constituents, in addition to an initial increase in free volume. The absorption is shown to be initially Fickian in all blends, with non-Fickian anomalies occurring at the latter stages of testing in both neat resin and composite samples.
The existing equation for edge diffusion in three-dimensional samples was found to be inaccurate at low aspect ratios. A new equation is developed for use with all sample geometries, which gives results accurate to ± 4%. Modification of the diffusion equations for uni-directional composites has been made (including a new for anisotropic edge effects). When fitted to our data the model shows no enhanced diffusion at the fibre matrix interface, but supports the theory that differences in diffusion parallel and perpendicular fibre can be attributed to geometrical blocking effects alone. Diffusion coefficients and saturation levels are shown to be sensitive to void contents even below 1% volume fraction. This correlation between absorption properties and sample quality is shown even more closely when using ultrasonic attenuation rather than void content analysis.
This record has no associated files available for download.
More information
Published date: 1999
Identifiers
Local EPrints ID: 463683
URI: http://eprints.soton.ac.uk/id/eprint/463683
PURE UUID: 2ead91f0-0fdd-475f-9f03-c0b894dc8634
Catalogue record
Date deposited: 04 Jul 2022 20:55
Last modified: 04 Jul 2022 20:55
Export record
Contributors
Author:
Linda Mary Patricia Fellows
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics