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 parti￾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 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 zir￾conia 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 com￾posites 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