C. Kaya et al. Journal of the European Ceramic Society 29(2009)1631-1639 shows the manufacturing steps of the fibre-reinforced compos- Matrix suspension ites and Fig. 4 shows the final sintered composite plate and its microstructure Fiber 2.5. Mechanical testing Tensile and flexural strength test bars (50 mm x 15 mm x 3 mm and 100mmx x3 mm in dimensions for flexu ral and tensile test bars, respectively) were cut from sintered composite panels using an Accutom 5 high-speed, precision dia Filter Paper mond saw, and then both surfaces were ground to parallel using Top hot plate a 40 um diamond resin bonded disc. All sharp edges were bev- elled using 6 and 3 um diamond pastes on soft cloths in order to Spacer minimise possible flaw sources. The tensile surfaces were then Bottom hot plate polished to a 0. 25 um finish using diamond paste. A typical ten- sile test specimen is shown in Fig 5a. To enable samples to be Aluminium Foil assembled accurately, a jig was designed and manufactured as EPD coated fiber shown in Fig 5b. It is important that the samples be fixed and aligned correctly as the load must be applied along the centre- Schematic representation of (a) impregnation process and (b)wa line, otherwise shear forces will distort the results(see Fig 5c) g for consolidation of the multilayer composite plates The jig uses two steel pins to align the plates, with a small macralon block to centre the sample. Spacers are also required to keep the steel plates apart the correct distance. Room-and high-temperature four-point bend tests(test bars with dimen- sions 50 mm x 15 mm x 3 mm) were performed on an Instron Testing machine fitted with a furnace which had tungsten mesh Colloidal Y203 elements, which enabled the tests to be carried out at temper a-AlyO3 powder Liquid binder atures up to 1500C. The pushrods and fixtures are all made from a tungsten-zirconium-molybdenum alloy Specimens to I Distilled water be tested at 1300C were held at the test temperature for at least I h prior to the testing to allow the system to equilibrate and to ensure that the specimen was at this temperature. Tensile ultrasonic agitation Desizing the fibers tests were performed at room temperature. For flexural and ten- sile tests, a constant cross-head speed of 0.5 mm/min. was used The interlaminar shear strength of the coated and impregnate yers was also determined using the test specimen geome- Matrix me Coating of individual high solids-loading try shown in Fig. 6. In order to measure the bonding strength fiber mat by EPD between fibre mats, individually coated and impregnated mats were sintered together using exactly the same cycle used for the composite itself and a tensile test specimen, as shown in Fig. 6, was prepared. The Perspex plates used for alignment were strongly glued(Epoxy adhesive, Good Fellow, UK) to the fibre and the aluminium tap surfaces using adhesives that provide coated and impregnated fibres a very strong adhesion so that only the bonding strength could measured during the tensile test. For all mechanical prop- Formation of erty results reported, seven samples were used multilayer green value by eliminating the highest and the lowest values(to obtain CMC plates more reliable data and eliminate big variations and taking the fiv Pressureless sIntering 2.6. Acoustic emission monitorIng The location of sensors and the experimental design for Composite plate acoustic emission monitoring are shown in Fig. 7. Acoustic (AE)is Fig3. Flow chart showing the manufacturing of woven mullite fibre-reinforced on elastic waves generated by the rapid release of localised alumina matrix composites. sources like transient relaxation of stress and strain fields plas-C. Kaya et al. / Journal of the European Ceramic Society 29 (2009) 1631–1639 1633 Fig. 2. Schematic representation of (a) impregnation process and (b) warm pressing for consolidation of the multilayer composite plates. Fig. 3. Flow chart showing the manufacturing of woven mullite fibre-reinforced alumina matrix composites. shows the manufacturing steps of the fibre-reinforced compos￾ites and Fig. 4 shows the final sintered composite plate and its microstructure. 2.5. Mechanical testing Tensile and flexural strength test bars (50 mm × 15 mm × 3 mm and 100 mm × 10 mm × 3 mm in dimensions for flexu￾ral and tensile test bars, respectively) were cut from sintered composite panels using an Accutom 5 high-speed, precision dia￾mond saw, and then both surfaces were ground to parallel using a 40m diamond resin bonded disc. All sharp edges were bev￾elled using 6 and 3m diamond pastes on soft cloths in order to minimise possible flaw sources. The tensile surfaces were then polished to a 0.25 m finish using diamond paste. A typical ten￾sile test specimen is shown in Fig. 5a. To enable samples to be assembled accurately, a jig was designed and manufactured as shown in Fig. 5b. It is important that the samples be fixed and aligned correctly as the load must be applied along the centre￾line, otherwise shear forces will distort the results (see Fig. 5c). The jig uses two steel pins to align the plates, with a small macralon block to centre the sample. Spacers are also required to keep the steel plates apart the correct distance. Room- and high-temperature four-point bend tests (test bars with dimen￾sions 50 mm × 15 mm × 3 mm) were performed on an Instron Testing machine fitted with a furnace which had tungsten mesh elements, which enabled the tests to be carried out at temper￾atures up to 1500 ◦C. The pushrods and fixtures are all made from a tungsten–zirconium–molybdenum alloy. Specimens to be tested at 1300 ◦C were held at the test temperature for at least 1 h prior to the testing to allow the system to equilibrate and to ensure that the specimen was at this temperature. Tensile tests were performed at room temperature. For flexural and ten￾sile tests, a constant cross-head speed of 0.5 mm/min. was used. The interlaminar shear strength of the coated and impregnated layers was also determined using the test specimen geome￾try shown in Fig. 6. In order to measure the bonding strength between fibre mats, individually coated and impregnated mats were sintered together using exactly the same cycle used for the composite itself and a tensile test specimen, as shown in Fig. 6, was prepared. The Perspex plates used for alignment were strongly glued (Epoxy adhesive, Good Fellow, UK) to the fibre and the aluminium tap surfaces using adhesives that provide a very strong adhesion so that only the bonding strength could be measured during the tensile test. For all mechanical prop￾erty results reported, seven samples were used for each reported value by eliminating the highest and the lowest values (to obtain more reliable data and eliminate big variations) and taking the average value of the remaining five values. 2.6. Acoustic emission monitoring The location of sensors and the experimental design for acoustic emission monitoring are shown in Fig. 7. Acoustic emission (AE) is a non-destructive technique (NDT) based on elastic waves generated by the rapid release of localised sources like transient relaxation of stress and strain fields. Plas-