ATERIALS GENGE S ENGIEERING ELSEVIER Materials Science and Engineering A268(1999)47-54 Mechanical properties of alumina fiber/glass matrix composites with and without a tin dioxide interface Ramanan venkatesh School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia (KCP), Tronoh, 31750, Perak, Malaysia Received 15 November 1998: received in revised form 15 February 1999 Abstract Alumina+ zirconia(PRD-166)and Saphikon fibers reinforced glass matrix composites with and without a SnO, interphase were prepared by slurry infiltration and their mechanical characteristics were evaluated. Longitudinal bend strength increased with volume fraction of fibers in both PRD-166/glass and PRD-166/SnO,/glass matrix composites. PRD-166/glass matrix composites failed in a brittle manner whereas PRD-166/SnO, glass matrix composites exhibited non-planar failure with crack deflection and fiber bridging as major toughening mechanisms. Saphikon /SnO2/glass matrix composites failed in a tough manner with extensive fiber pullout. The difference in the failure mode between PRD-166/Sno /glass and Saphikon/SnO,glass matrix composites w lue to fiber roughness. The toughness of PRD-166/ SnO /glass matrix composites was due to crack deflection, fiber bridging, partial fiber debonding and some fiber pullout. Major toughening mechanisms in Saphikon /SnO glass matrix composites were iber debonding and fiber pullout with minor contributions due to crack deflection and fiber bridging o 1999 Elsevier Science S.A. All rights reserved Keywords: Glass matrix composites; Tin dioxide interface: Saphikon matrix microcracking, matrix prestressing, fiber debonding, crack deflection and fiber pullout [1-5]. For Ceramics have strong ionic/covalent bonds and very a tough CMC, the interface between the fiber and the few slip systems compared to metals. This makes ce- matrix should be strong enough for load transfer but ramic materials strong but brittle. The high thermal weak enough to allow crack deflection. The interface stability of these materials coupled with their low den- bonding can be controlled either by selecting fiber and sity and high elastic moduli make them very attractive matrix materials which are thermodynamically stable at for high temperature applications [1] structural the processing and service temperatures or by applying materials, monolithic ceramics suffer from two impor- coatings that act as diffusion barriers, thereby prevent tant reliability issues, namely high sensitivity to process- ing a strong bond between the fiber and the matrix [6 ing and service generated flaws, and the inability to Different coatings that have been tried include C, Bn, tolerate stress levels. To increase the work of fracture SiC, TiC, ZrO2, SnO2, Monazite, magnetoplumbite, etc or the toughness of monolithic ceramics, numerous [6-10 ughening methods have been employed. These Alumina type oxide fibers appear to have consider- clude toughening by dispersion of second phase parti ble potential in reinforcing ceramic and glass matrix cles, i.e. transformation toughening and toughening by composites due to its oxidative stability and moderately incorporation of whiskers, ductile fibers or ceramic high strength and stiffness. Glass matrix composites fibers. Fiber reinforcement offers a great potential for offer a great commercial potential regarding tempera- improving strength and toughness of ceramic materials ture and environmental stability due to their ease of Increase in strength and toughness of CMCs can be fabrication, tailoring of properties achieved through a multitude of mechanisms namel processing. and glass react to form a strong che E-mail address: ramSnan @tm net. my(R. Venkatesh) bond at the interface thereby resulting in a brittle 0921-5093/99/S- see front matter c 1999 Elsevier Science S.A. All rights reserved. PI:s0921-5093099)00115-XMaterials Science and Engineering A268 (1999) 47–54 Mechanical properties of alumina fiber/glass matrix composites with and without a tin dioxide interface Ramanan Venkatesh School of Materials and Mineral Resources Engineering, Uni6ersiti Sains Malaysia (KCP), Tronoh, 31750, Perak, Malaysia Received 15 November 1998; received in revised form 15 February 1999 Abstract Alumina+zirconia (PRD-166) and Saphikon fibers reinforced glass matrix composites with and without a SnO2 interphase were prepared by slurry infiltration and their mechanical characteristics were evaluated. Longitudinal bend strength increased with volume fraction of fibers in both PRD-166/glass and PRD-166/SnO2/glass matrix composites. PRD-166/glass matrix composites failed in a brittle manner whereas PRD-166/SnO2/glass matrix composites exhibited non-planar failure with crack deflection and fiber bridging as major toughening mechanisms. Saphikon/SnO2/glass matrix composites failed in a tough manner with extensive fiber pullout. The difference in the failure mode between PRD-166/SnO2/glass and Saphikon/SnO2/glass matrix composites was due to fiber roughness. The toughness of PRD-166/SnO2/glass matrix composites was due to crack deflection, fiber bridging, partial fiber debonding and some fiber pullout. Major toughening mechanisms in Saphikon/SnO2/glass matrix composites were fiber debonding and fiber pullout with minor contributions due to crack deflection and fiber bridging. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Glass matrix composites; Tin dioxide interface; Saphikon 1. Introduction Ceramics have strong ionic/covalent bonds and very few slip systems compared to metals. This makes ce￾ramic materials strong but brittle. The high thermal stability of these materials coupled with their low den￾sity and high elastic moduli make them very attractive for high temperature applications [1]. As structural materials, monolithic ceramics suffer from two impor￾tant reliability issues, namely high sensitivity to process￾ing and service generated flaws, and the inability to tolerate stress levels. To increase the work of fracture or the toughness of monolithic ceramics, numerous toughening methods have been employed. These in￾clude toughening by dispersion of second phase parti￾cles, i.e. transformation toughening and toughening by incorporation of whiskers, ductile fibers or ceramic fibers. Fiber reinforcement offers a great potential for improving strength and toughness of ceramic materials. Increase in strength and toughness of CMCs can be achieved through a multitude of mechanisms namely matrix microcracking, matrix prestressing, fiber debonding, crack deflection and fiber pullout [1–5]. For a tough CMC, the interface between the fiber and the matrix should be strong enough for load transfer but weak enough to allow crack deflection. The interface bonding can be controlled either by selecting fiber and matrix materials which are thermodynamically stable at the processing and service temperatures or by applying coatings that act as diffusion barriers, thereby prevent￾ing a strong bond between the fiber and the matrix [6]. Different coatings that have been tried include C, BN, SiC, TiC, ZrO2, SnO2, Monazite, magnetoplumbite, etc. [6–10]. Alumina type oxide fibers appear to have consider￾able potential in reinforcing ceramic and glass matrix composites due to its oxidative stability and moderately high strength and stiffness. Glass matrix composites offer a great commercial potential regarding tempera￾ture and environmental stability due to their ease of fabrication, tailoring of properties and low cost of processing. Alumina and glass react to form a strong chemical E-mail address: ram5nan@tm.net.my (R. Venkatesh) bond at the interface thereby resulting in a brittle 0921-5093/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S0921-5093(99)00115-X