1 9m m 10y250 FIGURE 6-1 ( a) Scanning electron photomicrograph of sintered Tio2 fiber. ( D. French and R.b.caSs,DEvelopingiNnovativeCeramicFibers,www.ceramicbulletin.orgMay1998,pp.61-65) (b)SEM photomicrograph of an individua/ PZT filament of 25 um diameter. ( D. French and R.b.cAss,DevelopinginnovativeCeramicFibers,www.ceramicbulletin.orgMay1998,pp.61-65) (c) PZT fiber weave for a smart structure composite French and R. B. Cass, Developing InnovativeCeramicFibers,www.ceramicbulletin.orgMay1998,pp.61-65).(d)single-crystalSic platelets(nominal size, 150 um) Fibers Long, continuous fibers with a large aspect ratio (i.e, length-to-diameter ratio)of metals, ceram- ics, glasses and polymers are used to reinforce various types of matrices. A hard and strong naterial such as a ceramic in a fibrous form will have fewer strength-limiting flaws than the same material in a bulk form. As preexisting cracks lower the fracture strength of brittle ceramics, reducing the size and/or probability of occurrence of cracks will diminish the extent of streng loss in the ceramic, thus allowing the actual strength to approach the theoretical fracture strength in the absence of cracks, which is 0.1 E. where e is the elastic modulus If the fiber diameter scales with the grain size of the material, then the fracture strength will be high. In other words 398 MATERIALS PROCESSING AND MANUFACTURING SCIENCE(a) (c) (b) (d) FIGURE 6-1 (a) Scanning electron photomicrograph of sintered -1702 fiber. (J. D. French and R. B. Cass, Developing Innovative Ceramic Fibers, www.ceramicbulletin.org, May 1998, pp. 61-65). (b) SEM photomicrograph of an individual PZT filament of 25 i.tm diameter. (J. D. French and R. B. Cass, Developing Innovative Ceramic Fibers, www.ceramicbulletin.org, May 1998, pp. 61-65). (c) PZT fiber weave for a smart structure composite. (J. D. French and R. B. Cass, Developing Innovative Ceramic Fibers, www.ceramicbulletin.org, May 1998, pp. 61-65). (d) Single-crystal SiC platelets (nominal size, 150 pm). Fibers Long, continuous fibers with a large aspect ratio (i.e., length-to-diameter ratio) of metals, ceram￾ics, glasses and polymers are used to reinforce various types of matrices. A hard and strong material such as a ceramic in a fibrous form will have fewer strength-limiting flaws than the same material in a bulk form. As preexisting cracks lower the fracture strength of brittle ceramics, reducing the size and/or probability of occurrence of cracks will diminish the extent of strength loss in the ceramic, thus allowing the actual strength to approach the theoretical fracture strength in the absence of cracks, which is ~0.1 E, where E is the elastic modulus. If the fiber diameter scales with the grain size of the material, then the fracture strength will be high. In other words, 398 MATERIALS PROCESSING AND MANUFACTURING SCIENCE