Fabrication and characterisation of oxide fibre-reinforced glass matrix composites for optomechanical applications
Researcher: Dr Deborah Da Silva
Supervisor: Professor Bill Lee and Professor Aldo Boccaccini
Stiff and strong ceramic fibres have been incorporated into brittle glass matrices in order to increase their mechanical strength and fracture toughness. In the present work, a novel processing technique has been investigated, in which the reinforcing fibres are “sandwiched” unidirectionally between glass slides and heat-treated for consolidation into composites by viscous flow of the glass matrix, filling the gaps between the reinforcing fibres. Highly dense and transparent composites were produced combining alumina (NextelTM) or sapphire fibres with soda-lime silicate or borosilicate glasses. Their microstructural, optical and mechanical properties were investigated and compared to those of the unreinforced glass matrix processed under the same conditions. Moreover, a sol-gel technique was developed for coating the fibres with a ZrO2 interfacial layer.
As-received and ZrO2 coated NextelTM and sapphire fibre-reinforced composites were produced, with fibre contents of up to 1 vol. % and total light transmittance in the range of 70 to 93 % of the matrix transmittance. Sapphire fibre-reinforced borosilicate glass composites exhibited the highest measured flexural strength (73 MPa), followed by ZrO2 coated NextelTM fibre-reinforced soda-lime silicate composites (0.6 vol. %), which exhibited mean flexural strength of 64 MPa. The introduction of a ZrO2 interfacial layer effectively increased the flexural strength of the composites compared to the unreinforced matrix and the as-received fibre-reinforced composites. In addition, there was evidence of fibre pullout and crack deflection upon failure during flexural and fracture toughness tests, as well as a fail-safe behaviour upon flexure, which enabled the composites to retain their integrity. A robust processing methodology was thus demonstrated of producing high quality oxide fibre-reinforced glass matrix composites, with high optical transparency and favourable fracture properties. The composites produced are promising materials for a wide range of applications, notably in the construction industry, special machinery and architecture.