Composites are increasingly used in aerospace applications where performance is the
foremost priority of industry. Research on carbon nanotube (CNT)-reinforced polymers
conducted in the past decade showed promising results for the improvement of mechanical,
thermal and electrical properties of composites. This thesis was undertaken in the context of
a larger project, the main goal of which is to develop a complete solution for the
manufacturing of carbon fibre-epoxy composites using CNT-reinforced epoxies, referred to
as multi-scale composites. This thesis focuses on the thermal aspect of this project under
three topics: 1) thermal conductivity of dry carbon fibre fabrics for understanding heat
diffusion in composites and similar fabric materials 2) thermal conductivity of CNTreinforced
polymers and composites for determining the effect of parameters including CNT
addition, and 3) modelling of heat transfer during composite manufacturing for ensuring that
their temperature distribution remains controlled.
In-plane k rip and through-thickness k rtt thermal conductivity data were measured for
two dry carbon fibre fabrics as a function of fibre volume fraction Vf . Results showed that
k rip varies linearly with Vf whilst k rtt varies in an exponential recovery trend with Vf . An
existing analytical model was used successfully for predicting k rip and simulations developed
for predicting k rtt values demonstrated that k rtt depends on the evolution of heat conduction
paths in the through-thickness direction as a result of improvements in the fibre contact
network.
A procedure was developed for manufacturing composites using the RFI process.
Thirty-two composites and multi-scale composite plates were manufactured and
characterised for investigating the effects of eleven material and manufacturing parameters
on fibre volume fraction, porosity, k rip and k rtt . Results showed that the effect of using
multi-walled CNT-reinforced epoxy on thermal conductivity of composites is negligible at
0.3% CNT loading. However, this reduced the porosity of the composites significantly.
Results also showed that using fabrics with higher surface densities led to a slight increase in
k cip .
A heat transfer model coupled with cure kinetics was developed for predicting
temperature profiles of the laminate during RFI manufacturing. The model was validated
experimentally and eleven simulation cases were run for investigating the effects of five
material and manufacturing parameters on temperature profiles in the laminate. Results
showed that the epoxy resins used in this project combined with the cure cycle recommended
by the manufacturer are well-suited for manufacturing laminates with a typical thickness of
approximately 5 mm as well as thick laminates of 15 mm to 20 mm.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/30252 |
| Date | January 2013 |
| Creators | Yang, Yue |
| Contributors | Robitaille, Francois |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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