400 Fig. 4. Stress-displacement curve for a uncoated and coated alumina/ of ASG composites was greater than AG composites due to contributions from modulus mismatch. crack 20p deflection, fiber bridging and some fiber pullout. Frac ture surface of SSG composites(Fig. 7a, b )showed neat Fig 3. As processed composites (a) Alumina fiber/glass.(b) Alumina fiber debonding and fiber pullout at the fiber/ Sno interface. Energy dispersive analysis on the pulled out Saphikon fiber surface showed only Al and no Sn [22] oughening mechanisms in ASG composites are crack Transverse strength of AG and AsG composites in deflection, fiber bridging, partial fiber debonding and direction Ti and T2 is shown in Table 3. The strengths pullout because of the relatively weak fiber/coating of these composites in the direction Ti and T2 are about interface [19-21 half those in the longitudinal direction. Aligned fiber The work of fracture evaluated from the area under composites are very weak when stressed perpendicular the load-displacement curve for both coated and un to the fiber axis because the fibers do not contribute to coated composites is shown in Table 4. Work of frac- strength. Table 3 shows that the composites behave ture increased with volume fraction of fibers in both uncoated and coated fiber composites. Work of fracture Table 3 Bend strength of AG and ASG composites in L, T and T> directions r(% Bend strength(MPa) TI T, 060 ASG Fig. 5. Fracture surface of PRD-166 fiber/glass composite showing50 R. Venkatesh Venkatesh / Materials Science and Engineering A Materials Science and Engineering A268 (1999) 47–54 268 (1999) 47–54 Fig. 3. As processed composites. (a) Alumina fiber/glass. (b) Alumina fiber/SnO2/glass. Fig. 4. Stress-displacement curve for a uncoated and coated alumina/ glass composite during longitudinal bend test. of ASG composites was greater than AG composites due to contributions from modulus mismatch, crack deflection, fiber bridging and some fiber pullout. Frac￾ture surface of SSG composites (Fig. 7a,b) showed neat fiber debonding and fiber pullout at the fiber/SnO2 interface. Energy dispersive analysis on the pulled out Saphikon fiber surface showed only Al and no Sn [22]. Transverse strength of AG and ASG composites in direction T1 and T2 is shown in Table 3. The strengths of these composites in the direction T1 and T2 are about half those in the longitudinal direction. Aligned fiber composites are very weak when stressed perpendicular to the fiber axis because the fibers do not contribute to strength. Table 3 shows that the composites behave toughening mechanisms in ASG composites are crack deflection, fiber bridging, partial fiber debonding and pullout because of the relatively weak fiber/coating interface [19–21]. The work of fracture evaluated from the area under the load-displacement curve for both coated and un￾coated composites is shown in Table 4. Work of frac￾ture increased with volume fraction of fibers in both uncoated and coated fiber composites. Work of fracture Fig. 5. Fracture surface of PRD-166 fiber/glass composite showing planar brittle failure. Table 3 Bend strength of AG and ASG composites in L, T1 and T2 directions V Bend strength (MPa) f (%) L T1 T2 AG 12 65 110 60 20 140 – – 26 100 205 75 30 – – 215 42 80 230 70 ASG 24 60 65 120 36 150 75 75 46 – – 190