K.L. Choy et al./ Materials Science and Engineering 4278 (2000)187-194 钟:计“家 espii Fig. 1 SEM micrographs for composite samples A, B, C, and D (Table 2). Magnification x 150 for all micrographs (a) Sample A,(b) Sample 2.7. Flexural properties 3.2. Tensile properties Flexural failure is expected to occur for a CMC Measurements of the strain width and thickness of beam, when 2S/d> cu/te Using previous values, a the specimen were taken at several points, and the suitable span was determined. Three point bending was minimum value of cross-sectional area was used in onducted using the same procedure as ILs testing on calculations. Stress values and Youngs moduli were samples A,C and D and by application of the equa- calculated using: o=P/bd, and E=(AP/An(/bd) ion, E=Sm/4bd, the results were obtained where m is the initial linear portion of the load deflection curve 3. Results and discussion Table 4 Summary of microstructural observation Fig. I shows the scanning electron micrographs of Sami Stacking Comments the composites: (a) Sample A and(b) Sample B(c) sequence Sample C and (d) Sample D. All micrographs shown are at magnification x 150. a summary of the mi- A (0/90) Uneven fibre distribution in plies/ ma- crostructural observations for the glass/glass-ceramic trix rich regions between plies with matrix composites is presented in Table 3. Table 4 Porosity on a fine and large scale ob- summarises the microstructural observations for the glass/glass-ceramic matrix composites. (0/90) Fibre-poor n fibre distribution in plies/matrix rich regions between 3. 1. Image analysis plies with significant porosity Fibre-rich, tightly packed fibres in plies with some bundles/no matrix The fibre volume fraction and porosity for com- posites are summarised in table 5.190 K.-L. Choy et al. / Materials Science and Engineering A278 (2000) 187–194 Fig. 1. SEM micrographs for composite samples A, B, C, and D (Table 2). Magnification ×150 for all micrographs. (a) Sample A, (b) Sample B, (c) Sample C, (d) Sample D. 2.7. Flexural properties Flexural failure is expected to occur for a CMC beam, when 2S/d\scu/tc. Using previous values, a suitable span was determined. Three point bending was conducted using the same procedure as ILS testing on samples A, C and D and by application of the equa￾tion, Ec=S3 m/4bd3 , the results were obtained where m is the initial linear portion of the load deflection curve. 3. Results and discussion Fig. 1 shows the scanning electron micrographs of the composites: (a) Sample A and (b) Sample B (c) Sample C and (d) Sample D. All micrographs shown are at magnification ×150. A summary of the mi￾crostructural observations for the glass/glass–ceramic matrix composites is presented in Table 3. Table 4 summarises the microstructural observations for the glass/glass–ceramic matrix composites. 3.1. Image analysis The fibre volume fraction and porosity for com￾posites are summarised in Table 5. 3.2. Tensile properties Measurements of the strain, width and thickness of the specimen were taken at several points, and the minimum value of cross-sectional area was used in calculations. Stress values and Young’s modulli were calculated using: s=P/bd, and E=(DP/Dl)(l/bd), Table 4 Summary of microstructural observation Sample Comments Stacking sequence A Uneven fibre distribution in plies (0/90) /ma- 2s trix rich regions between plies with significant porosity. B Porosity on a fine and large scale ob- (0) served. C ‘Fibre-poor’, uneven fibre distribution (0/90)2s in plies/matrix rich regions between plies with significant porosity. D ‘Fibre-rich’, tightly packed fibres in (0/90)3s plies with some bundles/no matrix rich regions