Tow Scale Dry Fibre Architectures for High-Performance Ductile Composites

Abstract

High-performance fibre reinforced composites have excellent mechanical properties such as high specific strength and stiffness, excellent corrosion resistance and high fatigue life. Therefore, they have been in use for advanced lightweight application such as aero-structures, spacecraft, automobile, wind turbine blade and sports equipment. However, one key limitation of conventional composites is their brittleness and catastrophic failure under the tension, without sufficient warning or residual load-carrying ability. The lack of warning before failure leads to safety concerns which can limit their applications due to the unpredictable failure behaviour. Hence, it is necessary to fabricate a new generation of high-performance composite that overcomes the key limitations of composites and fail gradually with plastic deformations while still carrying the load. To attain such an ambitious outcome, development of new inherent ductile reinforced material with novel architectures is required. This research work aims to design and develop novel processes for dry fibre architecture for reinforced (preform) materials to improve the ductility or pseudo-ductility of high-performance composites. Two different processes have been investigated to prepare hybrid preform for ductile composites. The first process, commingled hybrid tow was prepared from carbon and glass fibre spread tow using air-assisted spreading and commingling technology where carbon and glass fibres were partially hybridised at the tow level. A comparative study of the tensile properties of the thin ply layer by layer hybrid and commingled hybrid composites with epoxy resin were carried out. It was found that both hybrid composites failed more gradual and exhibited improved tensile failure strain compared to carbon fibre spread tow composite. The second process, the hybridisation of two different dry fibres with dissimilar failure strain was done through the micro-wrapping process where low strain to failure fibres helically wrapped with high strain to failure fibres and produced core-shell type hybrid tow. Micro-wrapped hybrid tows were produced using two different types of wrapping arrangement, single helix and the double helix. In order to compare micro-wrapped hybridisation process to another kind of hybridisation, a side-by-side parallel placement hybridisation process was considered. Four different types of hybrid configurations (T700/E-G, T700/S-G, M55/S-G and M55/T700) tows have been prepared and studied their structural and tensile properties. A detailed study on the effect of micro-wrap hybrid architecture on the ductile or pseudo-ductile properties of the composite has been carried out and compared with side by side hybrid architecture. The investigations were carried out in three stages-mesoscale composites (single hybrid tow composite rod), UD composite laminates and UD woven composites laminates. Additionally, the influence of two epoxy resin systems (room temperature and high-temperature curing resin) on the composite mechanical properties was also studied. Tensile test results revealed that micro-wrapped hybrid composites (rods and laminates) demonstrated excellent pseudo-ductile behaviour with little stress drop after low strain fibre failure for all four hybrid configurations. On the other hand, a significant stress drop was observed in side by side hybrid composites after LS fibre failure. The matrix properties played a significant role in the composites ultimate failure strain. About 27% higher failure strain was attained with room temperature curing resin compared to high temperature curing resin composites. Double helix micro-wrapped hybrid tow composite also demonstrated similar results of single helix micro-wrapped hybrid composites. Therefore, the novel micro-wrapped hybrid architecture could be a suitable approach to produce low-cost textile preform for high performance ductile or pseudo-ductile composites.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Venkata Potluri (Supervisor) & Arthur Wilkinson (Supervisor)