R. Jones et al./Composites: Part A 30(1999)569-575 i.e. filament winding, traditional lay-up and autoclaving and 6. Summa most recently resin transfer molding. Fig. 8 shows an exam- ple of a 20.3 cm diameter prototype combustor liner fabri Nicalon fiber reinforced CMC fabricated with a polymer cated by filament winding using a CG Nicalon fiber tow impregnation and pyrolysis process are strong, tough mate- This liner has a(0+ 66) wound architecture. This liner is a rials useful in structural applications. The data presented example of where the CMC can be used in a land based here illustrates that Cg nicalon fiber reinforced CMC can turbine application. The ation uses temperatures be used effectively at temperatures up to 1100"C for long which are greater than 1100C periods of time. Above 1100C the creep of CG Nicalon Fig 9 duct component that was fabricated using a becomes a significant factor such that HI-Nicalon silicon esin tra olding process and a three-dimensional carbide fiber is the preferred reinforcement. Composites of CG Nicalon fiber. In this case. this reinforced with HI-Nicalon were tested at 1200C with resulted in a near-net shaped component that required good results, further work is required to find the upper very little machining at the attachment flange temperature limit of these materials. A number of different Fig. 10 shows CMC exhaust flaps fabricated for testing on CG Nicalon reinforced composite parts were fabricated and a general electric F-110 turbine engine. These flaps were have successfully been tested in simulated and in real appli- fabricated using traditional lay-up and autoclaving methods cation environments with CG Nicalon fabric prepreg. These components were successfully ground tested by ge aircraft engines to 70% of the required design life. Overall CMC performance was References excellent, the testing is being continued [12] [1] Yajima S, Omori M, Hayashi J, Okamura K, Matsuzawa T, Liaw C. 5. Future direction for PIP CMCs 2] Verbeeck W, US Patent No. 3 853 567, 10 December, 1974 3]Petrak DR Polymer-derived ceramics. Engineered Materials Hand- There are a number of improvements that were identified book1991:4:223-226 that will significantly improve the PIP processing and [4] Cannady JP. US Patent No. 4 535 007, 13 August, 1985 performance of CMCs. These include the elimination of 5] Rugg KL, Tressler R E. Comparison of the creep behavior of silicon arbide fibers. Ceram. Trans., Adv. Ceram.-Matrix Composites Ill solvents used for impregnation of polysilazane resin into porous CMC, The elimination of this solvent will result in 6] Hurst J, Yun H-M, Gorican D. A comparison of the mechanical prop- a more environmentally friendly process. Also, the use of a erties of three polymer-derived small diameter SiC fibers. Ceram neat, low viscosity resin will pr for faster processing of Trans., Adv. Ceram.- Matrix Composites Ill 1996: 74: 3-15 the CMC, considerably improving the economics. It should [7 DiCarlo JA, Yun H-M and Goldsby JC. Creep and rupture behavior f advanced SiC fibers. In Proc. Int. Conf Compos Mater. 10th, Vol also result in the elimination of porosity that can be 6. ed. Poursartip, Anoush, Street, Ken. Tenth International Confer- produced during autoclaving because of removal of low ence on Composite Materials Society, Vancouver, Canada, 1995, pp boiling point species. This should result in nearly pore- free materials that will give improved interlaminar shear mechanical behavior at high temperature of the oxygen-free Hi-Nica- properties in the CMC lon fiber. Ceram. Trans., High-Temp. Ceram. -Matrix Composites Il The development of improved and more stable interface 1995;58:299-304 chemistries is another key improvement needed. This wil 9] Yun HM, Goldsby JC, DiCarlo JA. Tensile creep and stress-rupture result in a more environmentally stable and durable CMc at avior of polymer derived SiC fibers. Ceram. Trans. 1994: 46: 17. elevated temperatures and in extreme environments, such as air, combustion atmospheres and moisture [10] Jia N. Effects of microstructural instability on the creep behavior of Si-C-O(Nicalon) fibers in argon. Diss. Abstr. Int 1994; B Another key development for Dow Cornings CMC is the 54(7):370 demonstration of significantly improved mechanical proper- [11] Boisvert RP, Lara-Curzio E CFCC News, August 1997, No. 9,pp ties and durability through the incorporation of a more 13-15 stable, higher temperature fiber. This includes the fabrica- [12] Staehler JM, Zawada LP. The residual tensile properties of four cera- tion and evaluation of CMcs fabricated with dow Corning's sylramict Sic fiber Jan. 12-16, Cocoa Beach, FL, 1997i.e. filament winding, traditional lay-up and autoclaving and most recently resin transfer molding. Fig. 8 shows an exam￾ple of a 20.3 cm diameter prototype combustor liner fabri￾cated by filament winding using a CG Nicalon fiber tow. This liner has a (0 ^ 66) wound architecture. This liner is an example of where the CMC can be used in a land based gas turbine application. The application uses temperatures which are greater than 11008C. Fig. 9 shows a duct component that was fabricated using a resin transfer molding process and a three-dimensional woven preform of CG Nicalon fiber. In this case, this resulted in a near-net shaped component that required very little machining at the attachment flange. Fig. 10 shows CMC exhaust flaps fabricated for testing on a general electric F-110 turbine engine. These flaps were fabricated using traditional lay-up and autoclaving methods with CG Nicalon fabric prepreg. These components were successfully ground tested by GE aircraft engines to 70% of the required design life. Overall CMC performance was excellent, the testing is being continued [12]. 5. Future direction for PIP CMCS There are a number of improvements that were identified that will significantly improve the PIP processing and performance of CMCs. These include the elimination of solvents used for impregnation of polysilazane resin into porous CMC. The elimination of this solvent will result in a more environmentally friendly process. Also, the use of a neat, low viscosity resin will provide for faster processing of the CMC, considerably improving the economics. It should also result in the elimination of porosity that can be produced during autoclaving because of removal of low boiling point species. This should result in nearly pore￾free materials that will give improved interlaminar shear properties in the CMC. The development of improved and more stable interface chemistries is another key improvement needed. This will result in a more environmentally stable and durable CMC at elevated temperatures and in extreme environments, such as air, combustion atmospheres and moisture. Another key development for Dow Corning’s CMC is the demonstration of significantly improved mechanical proper￾ties and durability through the incorporation of a more stable, higher temperature fiber. This includes the fabrica￾tion and evaluation of CMCs fabricated with Dow Corning’s SYLRAMICe SiC fiber. 6. Summary Nicalon fiber reinforced CMC fabricated with a polymer impregnation and pyrolysis process are strong, tough mate￾rials useful in structural applications. The data presented here illustrates that CG Nicalon fiber reinforced CMC can be used effectively at temperatures up to 11008C for long periods of time. Above 11008C the creep of CG Nicalon becomes a significant factor such that HI-Nicalon silicon carbide fiber is the preferred reinforcement. Composites reinforced with HI-Nicalon were tested at 12008C with good results, further work is required to find the upper temperature limit of these materials. A number of different CG Nicalon reinforced composite parts were fabricated and have successfully been tested in simulated and in real appli￾cation environments. References [1] Yajima S, Omori M, Hayashi J, Okamura K, Matsuzawa T, Liaw C. Chem. Lett. 1976;551. [2] Verbeeck W, US Patent No. 3 853 567, 10 December, 1974. [3] Petrak DR. Polymer-derived ceramics. Engineered Materials Hand￾book 1991;4:223–226. [4] Cannady JP. US Patent No. 4 535 007, 13 August, 1985. [5] Rugg KL, Tressler R E. Comparison of the creep behavior of silicon carbide fibers. Ceram. Trans., Adv. Ceram.-Matrix Composites III 1996;74:27–36. [6] Hurst J, Yun H-M, Gorican D. A comparison of the mechanical prop￾erties of three polymer-derived small diameter SiC fibers. Ceram. Trans., Adv. Ceram.-Matrix Composites III 1996;74:3–15. [7] DiCarlo JA, Yun H -M. and Goldsby JC. Creep and rupture behavior of advanced SiC fibers. In Proc. Int. Conf. Compos. Mater. 10th, Vol. 6. ed. Poursartip, Anoush, Street, Ken. Tenth International Confer￾ence on Composite Materials Society, Vancouver, Canada, 1995, pp. 315–322. [8] Chollon G, Railler R, Nasalain R. Structure, composition and mechanical behavior at high temperature of the oxygen-free Hi-Nica￾lon fiber. Ceram. Trans., High-Temp. Ceram.-Matrix Composites II 1995;58:299–304. [9] Yun HM, Goldsby JC, DiCarlo JA. Tensile creep and stress-rupture behavior of polymer derived SiC fibers. Ceram. Trans. 1994;46:17– 28. [10] Jia N. Effects of microstructural instability on the creep behavior of Si–C–O (Nicalon) fibers in argon. Diss. Abstr. Int. 1994;B 54(7):3701. [11] Boisvert RP, Lara-Curzio E. CFCC News, August 1997, No. 9, pp. 13–15. [12] Staehler JM, Zawada LP. The residual tensile properties of four cera￾mic matrix composites following F110 engine testing. Presented at the Engineering Ceramics Meeting of the American Ceramic Society, Jan. 12-16, Cocoa Beach, FL, 1997. R. Jones et al. / Composites: Part A 30 (1999) 569–575 575