MgO-Al2O3-SiO2 (MAS) and LiO2-Al2O3-SiO2 (LAS) glass ceramic systems is a material which is reported to have very good mechanical properties and thermal stability. These properties are suitable not only for replacing the conventional materials but also embark new fields which can satisfy the technical demands especially in aerospace applications. However, this work is primarily focusing on the fabrication of glass ceramic matrix composites. Since these glass ceramics are reported to have good thermo-mechanical properties, the study embarked upon the fundamentals of processing of MAS and LAS glass ceramic fibres, in order to open a new avenue for advanced glass fibre composites in high temperature applications. The present work aims to develop fundamental information for fabrication of MAS and LAS glass ceramic fibres and development of the glass ceramic fibre reinforced polymer (GCFRP) composite. The thesis gradually evolves in the direction of this goal by developing suitable bulk glass ceramics, glass ceramic fibres and glass ceramic fibre reinforced polymer composites. In the first part, the bulk MAS and LAS glass ceramics were prepared using melting and casting process. This was followed by controlled heat treatments at different temperatures. The crystallisation behavior of both glass ceramics showed that the temperature increase enhanced the rigidity of the glass structure, thereby superior and reliable properties such as density, nanohardness and reduced Young's modulus were successfully derived in the MAS and LAS system prepared at different annealing and subsequent heat-treatment regimes. The thermo-mechanical properties were correlated to the crystalline phases present in the system. SEM analysis showed that there was a significant variation in morphology of the crystalline phases with the changes in the heat treatment temperatures. In the second part, the mechanical properties of magnesium aluminium silicate (MAS) and lithium aluminium silicate (LAS) single fibres were investigated. The fibres were prepared using different methods namely melt drawing (MAS) and continuous drawing (LAS) respectively. The glass ceramic fibres were subjected to the optimised thermal treatments and the physical appearance observed indicated an absence of distortion before being tested using single fibre test (SFT). Relations between the properties of glass ceramic fibres and heat treatment conditions were clearly demonstrated by changes in density and Young's modulus. The latter was obtained with an acoustic approach which was successfully used in both systems. The glass and glass ceramic fibre selected were tested using the SFT and showed that different methods in fibre manufacturing process and different gauge lengths in the single fibre tests generate significantly different values in the mechanical properties of glass and glass ceramic fibres. The fibre strength distributions were strongly correlated with the diameter values of the tested fibres, and variation of the Weibull parameters depended on the gauge lengths. Moreover, scanning electron microscopy (SEM) examination of the fracture surfaces revealed the presence of fracture-inducing flaws located at the surface or in the interior of the fibre. Finally, an analysis of the fibrous glass ceramic MAS and LAS system was further developed towards the application in advanced composite materials. The manufacturing of single ply unidirectional glass ceramic fibre reinforced polymer composites was cautiously prepared at the fibre volume fraction of 30% by hand lay up technique due to the limited and fragile nature of the fibres. Both glass ceramic fibre composites were tested using dynamic mechanical thermal analysis (DMTA). The results showed distinctive differences in the storage modulus, E’ and tan δ between composites reinforced with MAS and LAS fibres. This indicates that the epoxy resin was strongly influenced by the presence of fibres of an appreciable fibres alignment. In addition, the quality of the laminate depended on the fibre volume fraction and void content. The investigation of surface fracture through fractography indicated a correlation between the properties of composites with the crystallinity of their structures. SEM photomicrographs displayed visibly good interfaces for all uncoated glass ceramic fibre systems in which MAS and LAS glass ceramic fibres were well bonded with the epoxy, compared to LAS and MAS uncoated glass fibre composites which revealed a weaker interface due to poor interfacial adhesion. Finally, their excellent dynamic thermo-mechanical properties conclude the scientific development carried out in this thesis, with the prospect of the continuing work into development of high-temperature applications in the aerospace industry.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:577434 |
| Date | January 2013 |
| Creators | Shamsudin, Zurina |
| Contributors | Hodzic, Alma |
| Publisher | University of Sheffield |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.whiterose.ac.uk/4281/ |
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