Development and Characterisation of Transparent Glass Matrix Composites

Bo Pang*, David McPhail, Doni J. Daniel, & Aldo R. Boccaccini
Imperial College London

The reinforcement of glass with ceramic fibres or particles is a common approach to improve the thermo-mechanical and functional properties of this material. Usually carbon or SiC fibres are used as reinforcing elements. However, during the manufacturing process the optical transparency of glass is lost because of the opaque carbon or SiC fibres used or due to the different optical properties of the composite constituents. Current research efforts are therefore focused on the development of transparent or translucent glass matrix composites containing oxide fibres as reinforcement, which should exhibit suitable optical and thermo-mechanical properties, the so-called ‘optomechanical composites’. In this investigation, alumina fibre reinforced borosilicate glass or soda-lime silicate glass matrix composites were fabricated and characterised. Fibres in different orientations were sandwiched between glass slides and the composite specimens were heat treated at temperatures up to 1000 °C, which is higher than the glass softening point, to induce consolidation of the structure by viscous flow. The transparency of the composites was achieved by introducing optical windows, which are the matrix regions formed by the fibres aligned perpendicularly to each other in the glass matrix. The composites light transmittance was calculated in dependence of fibre spacing using a new equation derived from previous models available in the literature [1]. Theoretical values of light transmittance were verified by experimental data measured on different composites using a Shimadzu UV-3600 spectrophotometer. In addition, in separate experiments, ZrO2 coated fibres were introduced as reinforcement with the aim to improve the mechanical properties of the composites. It was anticipated that the zirconia coating would introduce optimal fibre/matrix interfaces leading to improved fracture behaviour. The zirconia coating was obtained by a newly developed sol-gel process. The microstructure and chemistry of the interfaces between the matrix and fibres were investigated using a range of techniques, including SEM and SIMS. Overall, the new composites represent attractive transparent materials for possible applications in impact resistant windows for blast, ballistic and thermal shock protection. Further characterisation of fracture strength, toughness and interpretation of failure mechanisms is required in future experiments. [1] A.F. Dericioglu, S. Zhu and Y. Kagawa, Cer. Eng. Sci. Proc. 23[3] (2002) 485-492. .