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Aerospace Materials: Chapter 5. High Performance Polymers And Advanced Composites For Space Application

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  • 1. Chapter 5 High performance polymers and advanced composites for space application Rikio Yokota Introduction The AIAA reported on the state of space technology in SPACE 2000–2020. New and more advanced polymer composites having lighter, stronger, more dimensionally stable, and stiffer properties were predicted as being needed to develop space platforms to exploit the solar system [1]. Although international space station programmes have been delayed due to worldwide economic problems, there have been many technically notable successes, such as on board satellite repair technology, planetary exploration using space vehicles such as the US Mars pathfinder, deployment of large space structures, and the development of application satellites. During this period, graphite/epoxy carbon fibre reinforced polymer composite (CFRP), which is an advanced polymer composite, has been developed actively and used in spacecraft primary structures. It is still almost the only suitable material for these primary structures. High temperature matrix resins such as addition-type polyimides and high temperature thermoplastic resins are under development (see chapters 13 and 15), but are not yet familiar in space [2]. Aromatic polyimides are well known to have excellent thermal, mechan- ical, and electrical stability based on their hetero-aromatic structures, and various high performance polyimide films have been developed and nomi- nated as suitable materials for the membranes of flexible large structures, such as extendable solar arrays [3]. This chapter discusses the technological development of high performance polymers and advanced polymeric composites for space applications in Japan, covering the following topics: 1. advanced composites for spacecraft primary structures; 2. advanced composites for the newly developed three-stage M-V rocket;Copyright © 2001 IOP Publishing Ltd
  • 2. 3. high performance polymeric materials and composites for flexible and/or rigid extendable structures; and 4. heat resistant matrix resins. Advanced composites for spacecraft primary structures In Japan, space activities that are conducted in various government minis- tries and agencies are coordinated by the Space Activities Commission. The Institute of Space and Astronautical Science (ISAS) is the central institute for scientific research in space, and the National Space Development Agency (NASDA) is in charge of the development of application satellites and their launchers. ISAS was founded in 1981 by reorganization of the Institute of Space and Astronautical Science, University of Tokyo. The present ISAS is a national research institute conducting inter-university research in cooperation with researchers from universities in Japan and other countries. Table 5.1. Summary of ISAS scientific satellites Date Name Weight (kg) Application 1970.2 OHSUMI 24 test satellite 1971.9 SHINSEI 66 cosmic ray et al 1972.8 DENPA 75 plasma et al 1974.2 TANSEI-2 56 test satellite 1975.2 TAIYO 86 solar x-rays et al 1977.2 TANSEI-3 129 test satellite 1978.2 KYOKKO 126 auroral image et al 1978.9 JIKIKEN 90 plasma et al 1979.2 HAKUCHO 96 x-ray stars et al 1980.2 TANSEI-4 185 test satellite 1981.2 HINOTORI 188 solar flares et al 1982.2 TENMA 216 x-ray galaxies et al 1984.2 OHZORA 216 upper atmosphere 1985.1 SAKIGAKE 138 test spacecraft 1985.8 SUISEI 140 Halley’s comet 1987.2 GINGA 420 x-ray sources et al 1989.2 AKEBONO 295 auroral and plasma 1990.1 HITEN 140 lunar swingby 1991.8 YOHKOH 420 solar flares 1992.7 GEOTAIL 1008 ISAS and NASA 1993.2 ASCA 420 x-ray sources et al 1995.3 S.F.U. 4000 space experiments 1997.2 HALCA 830 space VLBI antenna 1998.7 NOZOMI 540 Mars explorationCopyright © 2001 IOP Publishing Ltd
  • 3. ISAS succeeded in launching the first Japanese satellite OHSUMI into orbit in 1970. Since then, 24 scientific and test satellites have been launched, including SUISEI and SAKIGAKE to explore Halley’s comet in 1986. To improve performance and increase payload capability, launchers and satellites require the development of primary and secondary structures that are much lighter than those produced from conventional metals. Since the main structural configuration of SUISEI was made of carbon fibre reinforced epoxy, ISAS used advanced composites for the primary structures of all the satellites. Table 5.l shows the list of all the satellites and spacecraft launched by ISAS. ASCA, launched in 1993, is a structurally advanced spacecraft to investigate solar sources. Because the focal length of ASCA’s ray mirror is so long, a high-precision Extendable Optical Bench (EOB) construction, made from carbon fibre reinforced polymer, was developed for the primary structure as shown in figure 5.l [4]. All the tubes of the EOB are made of carbon fibre composite, using high modulus type fibres. The tubes are laminated so that the longitudinal thermal expansion coefficient of the Figure 5.1. Extendable optical bench (EOB) structure of x-ray telescope satellite ASCA.Copyright © 2001 IOP Publishing Ltd
  • 4. Figure 5.2. Outline of M-V rocket and M-34 filament wound carbon fibre reinforced polymer motor casing.Copyright © 2001 IOP Publishing Ltd
  • 5. tubes can be made zero or even negative. The lamination configuration is designed such that the negative expansion of the tubes compensates the positive expansion of the metal top plates. Advanced composites for the M-V rocket M-V is the new generation satellite launcher of ISAS [5]. The first flight of M- V-1 was successfully completed in February 1997. M-V is a 30 m long, 2.5 m diameter, 130 ton, three-stage solid propellant rocket, with a 2 ton launch capability to low earth orbit (LEO). As shown in figure 5.2, the third stage M-34 rocket motor casing is made of filament wound carbon fibre reinforced epoxy. A filament wound motor casing was selected not only because of its potential high performance but also because of its cost advantage over a tita- nium alloy casing. To accommodate more than 10 tons of M-34 rocket motor solid propellant, the interior volume of the casing is 6.0 m3 . The maximum operating pressure is more than 6.0 MPa. The large nose faring is made of an aluminium honeycomb sandwich shell with carbon fibre composite face sheets. The M-34 nozzle introduced a deployment system of tapered double reverse helical spring extensors, made of glass fibre reinforced compo- sites (GFRP). High performance composites for flexible structures A flexible solar array is an attractive example of applying a flexible and extendable advanced composite with aromatic polyimide film. Japan’s space- craft SFU retrieved by the Space Shuttle in January 1995, deployed two large flexible solar arrays in low earth orbit. Because of a high glass transition temperature Tg and outstanding mechanical properties even at very low temperatures, aromatic polyimide is the most successful, widely used poly- meric material in space [6]. Until ten years ago, spacecraft were equipped with rigid power generators of the solar paddle type. As spacecraft became larger they required much more electric power, and flexible solar arrays are the most attractive way for power generation. Figure 5.3 illustrates the SFU spacecraft and the solar array configuration with extendable mast. The deployed wing is 2.4 m wide and 9.7 m long. The solar array is composed of two boards and the mast canister. The extendable/retractable mast is continually coilable, consisting of three glass fibre reinforced polymer spring rods (longerons) and radial spacers. The main source of the spring force is generated by the bending strain energy of the glass fibre reinforced polymer longerons. The radial spacers were made of moulded UPILEX-R. No mechanical backlash exists, because there are no pin-joint hinges, result- ing in high dimensional stability. Each array blanket consists of 48 hingedCopyright © 2001 IOP Publishing Ltd
  • 6. Figure 5.3. Illustrated SFU spacecraft and deployed configuration of its solar array with the extendable mast. polyimide panels (films), 202 mm wide and 2400 mm long. About 27 000 solar cells are mounted on the two array blankets and generate 3.0 kW power. The silicon cells are 100 mm thick with 100 mm cover glass bonded by S-691-RTV silicon type adhesive on to the polyimide panels [3]. Development of a large deployable antenna in Muses-B is another advanced technology in space [7]. Figure 5.4 illustrates the Muses-B antenna launched in 1997 to be used aboard the satellite for Space-VLBI (Very Long Baseline Interferometry). A 10 m diameter parabolic antenna with mesh surface was successfully deployed with steps extending the six extendable masts in low earth orbit. Figure 5.5 shows a deployment test of the MUSES-B flight model antenna. This incredibly complicated system consists of 6000 fine cables of high modulus Kevlar 149 aramid covered by a CONEX aramid net. Because of the requirement for high surface accuracy, each cable must keep precisely its length without creep under tension in space. It is known that a high strength KevlarCopyright © 2001 IOP Publishing Ltd
  • 7. Figure 5.4. Configuration of MUSES-B antenna: (1) stowed in the nose faring, (2) deployed.Copyright © 2001 IOP Publishing Ltd
  • 8. (a) (b) (c) (d) Figure 5.5. Sequential deployment test of MUSES-B flight antenna: (a) stowed; (d) after deployment.Copyright © 2001 IOP Publishing Ltd
  • 9. 149 cable exhibits very little elongation as stressed and has negative expansion over a wide range of temperatures. The tension of each cable and each extend- able mast was controlled strictly, using tensioners on the top of each mast. This is the first application of high performance organic fibres for a large deployable parabolic antenna surface in space. Heat resistant matrix resins Aromatic polyimides are used widely in industry, because they possess high thermal stability, good mechanical properties, excellent electrical properties and excellent environmental stability [8]. Figure 5.6 shows the chemical struc- tures of commercially available, space application, polyimide films. Metal- lized polyimide films, called flexible multi-layer thermal insulations (MLI), are now indispensable for passive thermal control systems of spacecraft as well as for flexible solar arrays. However, polyimides with these outstanding properties often give poor processability even in the addition-type oligoimide such as BMI and PMR-15. Because of their intermolecular ordered structure, aromatic polyimides have poor molecular mobility beyond the glass Figure 5.6. Chemical structures of commercially available, space application polyimide films.Copyright © 2001 IOP Publishing Ltd
  • 10. Figure 5.7. Temperature dependence of storage and loss moduli for isomeric biphenyl-type polyimide films. transition temperature Tg , resulting in extremely severe processing condi- tions for structural applications [9]. Figure 5.7 shows the temperature depen- dence of storage and loss moduli for isomeric biphenyl polyimide films. The asymmetric biphenyl polyimide, a-BPDA/PDA has a very inflected chain structure compared with the semi-rod s-BPDA/PDA polyimide, as shown in figure 5.7. The a-BPDA/PDA annealed at 4008C shows a higher Tg than the s-BPDA/PDA treated under the same conditions [10]. The difference in the extent of the storage modulus decrease at Tg for the two polyimides in figure 5.7 is attributed to the difference in the intensity of intermolecular interactions, suggesting an improvement in the processability of a-BPDA derived polyimide resins. Figure 5.8 shows thermogravimetric results under nitrogen for the novel poly{(phenylsilylene) ethynylene1,3-phenyleneethynylene} (MSP-1), polyimide PI(BPDA/PDA), and their 1/1 blended films. Inorganic/organicCopyright © 2001 IOP Publishing Ltd
  • 11. Figure 5.8. Thermogravimetric data in N2 flow of the novel poly {(phenylsilylene) ethyny- lene-1,3-phenyleneethynylene} (MSP-1), PI(BPDA/PDA), and their 1/1 blend films. polymer blends of this type can be expected to form a class of new thermally stable, toughened matrix resins [11]. Summary Advanced polymer matrix composites are important in a range of space applications, notably in primary satellite structures, rocket casings, flex- ible/extendable structures such as antennae and as thermal insulators. References [1] Brodsky R F and Morais B G 1982 Aeronautics & Astronautics May pp 54–65 [2] Yokota R 1995 Proceedings of 1st China–Japan Seminar on Advanced Engineering of Plastics, Polymer Alloys and Composites (Society of Polymer Science, Japan) p 100 [3] Shibayama Y et al 1991 Proceedings of the European Space Power Conference, Florence, Italy p 735 [4] Onoda J et al 1994 IAF-94-1.1.174, Israel [5] Onoda J et al 1994 ISTS-94-b-19, JapanCopyright © 2001 IOP Publishing Ltd
  • 12. [6] Yokota R et al 1997 Proceedings of 7th Symposium on Materials in a Space Environ- ment, Toulouse, France (ESA/ONERA) [7] Takano T et al 1996 ISTS-96-e-18, Japan [8] Yokota R 1996 Structure and Design of Photosensitive Polyimides ed K Hone and T Yamashita (TECHNOMIC) chapter 3 [9] Serafini T T 1984 Polyimides: Synthesis, Characterization and Applications ed K L Mittal (New York: Plenum) vol 2 p 957 [10] Hasegawa M, Yokota R, Sensui N and Shindo Y Macromolecules in press [11] Yokota R, Ikeda A and Itho M 1998 Polymer Prep. Japan 47 643Copyright © 2001 IOP Publishing Ltd

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