R Venkatesh/Ceramics International 28 (2002)565-573 Results and discussion Weibull plots of as-received and Sno, coated fibres are shown in Fig. 3(a)and(b). The straight line plots PRD-166 fibres. The rough cobblestone surface of the and SnO2 coated follow Weibull distribution. Tabe,& Fig 2(a)and(b) shows the microstructure of alumina indicate that the tensile strength data for the as-rece alumina fibres is shown in Fig. 2(a). The zirconia parti- shows the tensile strength, Weibull modulus(m), scale cles are dispersed throughout the fibres but primarily along grain boundaries [Fig. 2(b)]. The dispersion of 20 wt% zirconia in PRD-166 fibre inhibits grain growth Table 7 and thereby improves strength and ughness of these Bend strength, WOF and fracture toughness of AG and ASG com- fibres [36]. The grain size of alumina, as determined by posites the lineal intercept method, was about 0.5 um and that r(%) Work of of zirconia particles was 0.33 um. XRD showed the zir fracture conia particles to be primarily in tetragonal form (MPa) /m-2) (MPa m/) 110 Table 6 AG Roughness strain A ed with thermal mismatch strain of PRD-166/SnO, and nO, interphase 0.026 0.0013 ASG 0602466 215 770 2.6 120 3.3 190 10 Fig. 6.(a, b and c) Fracture surface of PRD-166 alumina fibre/SnO2/glass matrix composites showing partial debonding and fibre pullout. Note the extremely rough PRD-166 fibreResults and discussion Fig. 2 (a) and (b) shows the microstructure of alumina PRD-166 fibres. The rough cobblestone surface of the alumina fibres is shown in Fig. 2(a). The zirconia particles are dispersed throughout the fibres but primarily along grain boundaries [Fig. 2(b)]. The dispersion of 20 wt.% zirconia in PRD-166 fibre inhibits grain growth and thereby improves strength and toughness of these fibres [36]. The grain size of alumina, as determined by the lineal intercept method, was about 0.5 mm and that of zirconia particles was 0.33 mm. XRD showed the zirconia particles to be primarily in tetragonal form. Weibull plots of as-received and SnO2 coated fibres are shown in Fig. 3(a) and (b). The straight line plots indicate that the tensile strength data for the as-received and SnO2 coated follow Weibull distribution. Table 2 shows the tensile strength, Weibull modulus (m), scale Table 6 Roughness strain A/r compared with thermal mismatch strain of PRD-166/SnO2 and Saphikon/SnO2 interphase A/r T PRD-166/SnO2 0.026 0.0013 Saphikon/SnO2 0.003 0.001 Fig. 6. (a, b and c) Fracture surface of PRD-166 alumina fibre/SnO2/glass matrix composites showing partial debonding and fibre pullout. Note the extremely rough PRD-166 fibre. Table 7 Bend strength, WOF and fracture toughness of AG and ASG composites Vf (%) Bend strength (MPa) Work of fracture (J/m2 ) Fracture toughness (MPa m1/2) 12 110 220 2.0 AG 20 140 – – 26 205 420 2.3 30 215 – – 42 230 770 2.6 24 120 580 2.8 ASG 36 150 900 3.3 46 190 – – R. Venkatesh / Ceramics International 28 (2002) 565–573 569