K.L. Choy et al./ Materials Science and Engineering 4278 (2000)187-194 bide 'Nicalon'and'Tyranno' fibres were used to rein Properties of fibres [1] force glass and glass-ceramic matrices. The properties Fibre Tensile strength of these fibres are given in table 1 (GPa (GPa Carbon‘HM Silicon carbide 000 2. 2. Composites Silicon carbide glass-ceramic matrix composites were investigated for their mechanical roperties. These composites along with fibre/matrix compositions, fibre diameters, lamina thickness, Hot pressed glass and glass-ceramic composites are overall stacking sequenced and plate geometries are he highest strength ceramic matrix composites(CMCs) summarised in Table 2. The glass matrix composites available. The properties of a CMc depend on vari- both had a matrix of borosilicate glass though the ables that include, fibre/matrix strength and moduli, embedded fibres were carbon and silicon carbide in a fibre/matrix bond strength, fibre volume fraction and cross-ply and unidirectional lay-up respectively. The fibre diameter. The thermal coefficient of expansion two glass composites both had a BMAS matrix with between the fibre and matrix can affect the composite silicon carbide fibres in a cross-ply stacking sequence strength, as well as the porosity within the matrix For these two later composites only the volume Accurate mechanical data is essential for designers con- fraction of fibres varied. Samples C and d were templating the use of such ceramic composites in struc- termed "fibre-rich' and 'fibre-poor'respectively. These tural applicatio materials represented deviations from the usual fibre This paper reports on an investigation conducted to distribution produced in such composites determine the mechanical properties of a range of glass and glass-ceramic matrix composites. The tensile prop- erties. stress-strain behaviour. interlaminar shear and 23. Fabrication flexural properties have been investigated; the results of which are considered in the light of the microstructures all the composites were prepared by slurry present. Thus far, failure mechanisms evaluated by impregnation and hot pressing technique. The process other researchers have mainly considered axial proper- for mposite starts by y winding ng slurry ties of a unidirectional long fibre composite, which are impregnated tow onto the mandrel to form stacked in a cross-ply arrangement(0/90). Furthermore, monolayer tapes. The slurry consists of water, a resin his paper will also briefly examine some of the off-axis binder(Pva with 40% PC)[4] and glass powder properties of the composites. The anisotropic nature of These tapes are cut up to make plies which are then these composites with respect to interlaminar/transverse stacked and densified to form the final composite in a strengths is also discussed hot pressing operation. For the borosilicate glass matrix, the composite was hot-pressed at temperature of about 1000oC. In the case of the 2. Experimenta glass-ceramic matrices, to achieve 100% barium osumilite, the composites were ' ceramed or matrices 2.1. Fibres crystallised at temperatures of 1200-13000C. This process prevented the formation of undesirable celsian Carbon'Hercules Magnamite'(HM) and silicon car- and hexcelsian phases in the matrix [4] Table 2 Composites provided for mechanical testing Sample Fibre Matrix Fibre diameter Lamina thickness Stacking Plate geometry Carbon Hercules Borosilicate 275 100×100×2.2 Magnamite Silicon carbide "Nicalon Borosilicate 100×100×6.3 C· fibre Silicon carbide arium osumilite l50×150×2.4 Tyranno D'fbre.rich Silicon carbide 210×210×1.9 (BMAS)188 K.-L. Choy et al. / Materials Science and Engineering A278 (2000) 187–194 Table 1 Properties of fibres [1] Fibre Young’s modulus Tensile strength (GPa) (GPa) Carbon ‘HM’ 2.7 350 Silicon carbide 2.4 190 ‘Nicalon’ Silicon carbide 200 2.7 ‘Tyranno’ bide ‘Nicalon’ and ‘Tyranno’ fibres were used to rein￾force glass and glass–ceramic matrices. The properties of these fibres are given in Table 1. 2.2. Composites Two glass and two glass–ceramic matrix composites were investigated for their mechanical properties. These composites along with fibre/matrix compositions, fibre diameters, lamina thickness, overall stacking sequenced and plate geometries are summarised in Table 2. The glass matrix composites both had a matrix of borosilicate glass though the embedded fibres were carbon and silicon carbide in a cross-ply and unidirectional lay-up respectively. The two glass composites both had a BMAS matrix with silicon carbide fibres in a cross-ply stacking sequence. For these two later composites only the volume fraction of fibres varied. Samples C and D were termed ‘fibre-rich’ and ‘fibre-poor’ respectively. These materials represented deviations from the usual fibre distribution produced in such composites. 2.3. Fabrication All the composites were prepared by slurry impregnation and hot pressing technique. The process for making the composite starts by winding slurry impregnated tow onto the mandrel to form monolayer tapes. The slurry consists of water, a resin binder (PVA with 40% PC) [4] and glass powder. These tapes are cut up to make plies which are then stacked and densified to form the final composite in a hot pressing operation. For the borosilicate glass matrix, the composite was hot-pressed at a temperature of about 1000°C. In the case of the glass–ceramic matrices, to achieve 100% barium osumilite, the composites were ‘ceramed’ or matrices crystallised at temperatures of 1200–1300°C. This process prevented the formation of undesirable celsian and hexcelsian phases in the matrix [4]. Hot pressed glass and glass–ceramic composites are the highest strength ceramic matrix composites (CMCs) available. The properties of a CMC depend on vari￾ables that include, fibre/matrix strength and moduli, fibre/matrix bond strength, fibre volume fraction and fibre diameter. The thermal coefficient of expansion between the fibre and matrix can affect the composite strength, as well as the porosity within the matrix. Accurate mechanical data is essential for designers con￾templating the use of such ceramic composites in struc￾tural applications. This paper reports on an investigation conducted to determine the mechanical properties of a range of glass and glass–ceramic matrix composites. The tensile prop￾erties, stress–strain behaviour, interlaminar shear and flexural properties have been investigated; the results of which are considered in the light of the microstructures present. Thus far, failure mechanisms evaluated by other researchers have mainly considered axial proper￾ties of a unidirectional long fibre composite, which are stacked in a cross-ply arrangement (0/90). Furthermore, this paper will also briefly examine some of the off-axis properties of the composites. The anisotropic nature of these composites with respect to interlaminar/transverse strengths is also discussed. 2. Experimental 2.1. Fibres Carbon ‘Hercules Magnamite’ (HM) and silicon car￾Table 2 Composites provided for mechanical testing Sample Fibre Matrix Fibre diameter Plate geometry Lamina thickness Stacking (mm) (mm) sequence (mm) A 7 100 Carbon ‘Hercules Borosilicate 275 (0/90)2s ×100×2.2 Magnamite’ B Silicon carbide ‘Nicalon’ Borosilicate 7–10 – (0) 100×100×6.3 Silicon carbide 8 300 (0/90) C ‘fibre-poor’ Barium osumilite 2s 150×150×2.4 ‘Tyranno’ (BMAS) D ‘fibre-rich’ Silicon carbide Barium osumilite 210 8 160 (0/90)3s ×210×1.9 ‘Tyranno’ (BMAS)