(1) Field of the Invention
The present invention relates to spring members made of a carbon fibers/carbon composite material (hereinafter referred to briefly as "C/C composite material") which have not formerly existed, and also to processes for the production of the same.
(2) Related Art Statement
The spring members such as spiral springs have been used as mechanical elements in a variety of machines, equipment, mechanics, etc. Therefore, the spring members are indispensable and important parts in the fields of daily domestic products, industrial products, etc.
The spring members have been conventionally and generally made of metallic materials. Further, production of spring members made of ceramic materials having thermal resistance, wear resistance and corrosion resistance has been recently investigated and some such ceramic spring members have begun to be used.
Meanwhile, it has been attempted to reduce, the weight of automobile vehicles and aircraft in order to principally enhance fuel consumption efficiency. As one countermeasure therefor, reduction in weight of the spring members has been demanded. Further, in various industrial machines, light weight spring members have been demanded for various purposes.
However, since the spring members made of metallic materials have poor heat resistance, they cannot exhibit sufficient spring performance under high temperature use conditions. Therefore, the metallic spring members cannot be used per se or cannot be used for an extended time period at such high temperature use conditions. As for metallic springs, stainless steel, low-alloy steel, tool steel and the like are principally used. However, these materials, which are called heat resistive alloys, undergo conspicuous reduction in strength and conspicuous deformation at temperatures over 400.degree. C. so that the materials are rapidly permanently set. Accordingly, the metallic spring members cannot be used under the above environmental conditions. Furthermore, even super heat resistive alloys such as Inconey or Hastalloy suffer conspicuous reduction in strength and conspicuous deformation at temperatures over 700.degree. C. so that they undergo permanent set. Therefore, these super heat resistive materials cannot be used for spring members under such environmental conditions.
Further, some metallic spring members are generally likely to corrode, and their abrasion resistance is poor. Further, if a magnetic field acts upon the spring member, it is likely to be magnetized, so that a limitation is posed upon use of the spring members under an environment in which the spring members may be influenced by magnetic fields.
On the other hand, when spring members made of ceramics such as silicon nitride or zirconia are used repeatedly at high temperatures, there is a high possibility that they may be broken. Therefore, such spring members have low heat impact resistance, and when the temperature exceeds a certain temperature in a range of 500.degree.-1000.degree. C., their strength rapidly decreases, and they are deformed or broken. Further, since the ceramics have no toughness, the ceramic spring member is likely to be broken so that it is extremely troublesome or difficult to handle such spring members so as not to break them.