No description available.

One of the greatest limitations to the use of polymer composites is the high cost of the techniques traditionally employed in their manufacture. Therefore, less Labour intensive, lower cost manufacturing methods such as resin transfer moulding (RTM) have been developed. Such processes require a resin with low viscosity at the processing temperature. Resins that exhibit good high temperature performance tend to be viscous, and are usually brittle when cured. Conventional toughening agents, such as polyethersulfone, further increase the viscosity of the blend. This work focuses on the use of hyperbranched polymers as resin additives, as these low viscosity materials can have the potential to act as toughening agents. It was hypothesised that the thermal properties of the blend could be simultaneously enhanced by the incorporation of a thermally stable inorganic phase, and as such the synthesis of organic-inorganic hybrids was investigated. Organic-inorganic hybrids of a commercially available hyperbranched polyester, Boltorn E1, were synthesised using two hydrolytic sol-gel methods. In both methods the inorganic phase was silica; one process was carried out in solution, the other was an emulsion method. The sol-gel processes were carried out under comparatively mild conditions and so allowed the introduction of organic material that would be degraded by high temperature processing. Both methods yielded nano-scale hybrid products, as confirmed by electron microscopy and infrared spectroscopy studies. Particulate hybrids of Boltorn E1 and silica, of approximately 100 nm diameter, were successfully synthesised using the emulsion method. The use of hyperbranched polymers as additives to epoxy resins was investigated, both as the organic component of organic-inorganic hybrid additive, and as resin modifiers in their own right. The addition of Boltorn E1 failed to increase the fracture toughness of a variety of epoxy resins. The reasons for this were identified. The addition of hybrid particles did not enhance the thermal properties of a trifunctional epoxy resin, as the additive sterically inhibited resin cross-linking. It was hypothesised that reducing particle size and agglomeration would prevent this plasticising effect.

No description available.

Optimised design of textile composite structures based on computer simulation techniques requires an understanding of the deformation behaviour during forming of 3-dimensional double-curvature components. Purely predictive material models are highly desirable to facilitate an optimised design scheme and to significantly reduce time and cost at the design stage, such as experimental characterisation. In-plane shear and out-of-plane bending are usually thought to be the key forming mechanisms. Therefore, this thesis is concerned with studies of the shear and bending behaviour by experimental characterisation and theoretical modelling. Micromechanical interaction between fibre and matrix offers fundamental understanding of deformation mechanisms at the micro-scale level, leading to development of composite viscosity models, as input to shear and bending models. The composite viscosity models were developed based on rheological behaviour during movement of fibres, and validation was performed using experimental results collected from the literature. A novel characterisation method for measuring the bending behaviour, by means of a large-displacement buckling test, was attempted due to some significant advantages over other methods. Development of a bending model was also undertaken for unidirectional composites but experimental validation suggests further study may be required for woven composites. The shear behaviour was characterised using a picture frame test for viscous polymer composites. To obtain reliable experimental data, some efforts of improving the characterisation method were made. The experimental results were then used to validate a shear model, suggesting that further improvement is required, in terms of weave patterns, rate and temperature dependence.