JP3218628B2 - Cryogenic fiber reinforced plastic composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced plastic composite used as various members in an extremely low temperature environment.

[0002]

2. Description of the Related Art In recent years, research and development using liquid helium in a cryogenic environment have been actively conducted in the field of superconductivity and the like, and materials for cryogenic use have been developed in stainless steel, titanium alloys, aluminum alloys and the like. Metal materials and non-metallic materials such as fiber reinforced plastics. Since the application fields of materials at such cryogenic temperatures are diverse,
There are many requirements for the required performance, and they differ for each field. For example, in the medical field applied to a skid magnetometer, MRI, or the like, a cryostat may have magnetic susceptibility, conductivity, vibration damping, liquid helium (hereinafter referred to as H).
e) Leakage and the like are important, and as the support material, dimensional stability and low thermal conductivity are important. On the other hand, in the transportation fields such as linear motor cars and aerospace, lightness will be an important required property, and in any field, mechanical properties, workability, etc. are required performance.

[0003] Conventionally, metal materials which have been widely used as cryogenic materials have excellent performance in mechanical properties, workability, and He leakage property, but because of their high thermal conductivity, the heat-insulating support materials are not suitable. Naturally, it cannot be used for a heat transfer section such as a cryostat or a dewar, and has a large coefficient of thermal expansion and poor dimensional stability, which makes it more difficult to apply to a support material. Also,
Since a metal material has high conductivity and magnetic susceptibility, when applied to a skid magnetometer, a high S / N ratio cannot be obtained, and MR
When used in a cryostat for AC equipment such as I, SMES, etc., the amount of He evaporation increases due to heat generated by eddy current, which has been a problem in terms of thermal efficiency and economy. Furthermore, in the state-of-the-art transportation fields such as linear motor cars,
There is a strong demand for weight reduction for the purpose of speeding up and energy saving, and even at present, even light alloys such as aluminum are too heavy.

In the field of cryogenic temperatures where metallic materials cannot be used as described above, a composite material (sometimes abbreviated as FRP) comprising a fiber such as glass fiber and a matrix resin is used. Although these composite materials are superior to metal materials in terms of conductivity, magnetic susceptibility, and heat insulating properties, they cannot be said to be still satisfactory at an overall level including other properties.

[0005] For example, a glass fiber composite material (sometimes abbreviated as GFRP) is a material in which both a general matrix resin and glass fiber have a positive expansion coefficient. Although volume shrinkage at the time of lowering is unavoidable, microcracks generated at this time cause He leak, which hinders application to cryostats and duals, and furthermore, due to poor dimensional stability based on this shrinkage, various It is often difficult to use as a cryogenic member. In addition, the magnetic susceptibility of the above composite material has a considerably smaller value than that of metal, but it is still not enough in fields aiming for high sensitivity such as a skid magnetometer, leaving room for improvement with further weight reduction. is there.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of FRP as a material for cryogenic use. Another object of the present invention is to provide a high-performance FRP for cryogenic use, which has good dimensional stability, excellent microcrack resistance at cryogenic temperatures, and substantially zero magnetic susceptibility.

[0007]

SUMMARY OF THE INVENTION The fiber-reinforced plastic composite material for cryogenic use of the present invention has a gist in that it is formed by a filament winding method using high-strength polyethylene fibers as reinforcing fibers.

[0008]

The reinforcing fibers used in the present invention are high strength polyethylene fibers. Since this fiber has a much lower specific gravity than glass fiber, it is possible to obtain a high-strength, high-modulus and light reinforcing fiber, and it is also superior in magnetic susceptibility to inorganic fibers and metal materials. I have. Further, this fiber is a unique substance having a negative coefficient of expansion, and shows an increase in volume as the temperature is lowered from room temperature. Generally, since the matrix resin has a positive expansion coefficient, it becomes possible to obtain FRP with a small volume change due to temperature by compounding the above fibers. Such polyethylene fibers are disclosed in, for example, JP-A-55-107506 and JP-A-5-107506.
It can be obtained using a production method as disclosed in JP-A-6-15408.

As the form of the fiber, various types such as a twisted yarn and a spun yarn can be used. Further, in order to satisfy all of the many characteristics, other organic fibers or inorganic fibers can be mixed and used. As the organic fiber, aramid,
Examples include fibers such as PBZ polymers such as polyarylate, polybenzbisoxazole and polybenzbisthiazole, polyethylene terephthalate, polyphenylene sulfide, polyethylene naphthalate, polyamide imide, polyetheretherketone, polyetherketoneketone, and the like. Examples of the inorganic fibers include ceramic fibers such as glass, alumina, silica, zirconia, titania, silicon nitride, and silicon carbide, and metals or alloy fibers thereof such as aluminum and steel.

As a mixing method in this case, a method of tying high-strength polyethylene fibers and filaments of other organic fibers or inorganic fibers to each other, or covering one fiber core as a core with the other filament around the core. A method of manufacturing a yarn having a core-sheath structure, a method of superimposing and bundling respective filament bundles of both fibers in an opened state, and a method of manufacturing a mixed fiber using the generated filament, and the like. Inorganic fibers are significantly inferior to organic fibers in terms of magnetic susceptibility, weight, and expansion coefficient, and therefore the amount of the inorganic fibers must be considered.

As the matrix resin used in the present invention, epoxy-based, unsaturated polyester-based, vinyl ester-based, urethane-based, urethane acrylate-based resins and the like can be used. Among these, the present inventors have clarified that an epoxy resin obtained by using an alicyclic acid anhydride as a curing agent is extremely excellent in micro crack resistance. As the alicyclic acid anhydride curing agent, methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride are preferably selected, and these can be used alone or in combination. The epoxy resin is not particularly limited, but is a general-purpose bisphenol A
A mold or the like is used.

As a method of molding into a fiber-reinforced plastic composite material for cryogenic use in the present invention, a filament winding method of winding a mandrel while impregnating a thread-like fiber with a matrix resin is employed. Further, the fiber tape may be formed by a tape winding method in which the fiber is impregnated with a matrix resin and wound around a mandrel.

The mixing ratio of the fibers and the matrix resin in the composite material is expressed by the volume fraction of the fibers (may be abbreviated as Vf).
Is preferably 35 to 85%, more preferably 40 to 85%.
~ 70%. If the Vf of the fiber is less than 35%, the effect of reinforcing the fiber is not exhibited, and if it exceeds 85%, the impregnation of the matrix resin becomes insufficient, and the mechanical properties of the composite material deteriorate, which is not preferable.

[0014]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A matrix resin having the composition shown in Table 1 was mixed and wound on a mandrel (orientation angle 55 °) while impregnating high-strength polyethylene fibers by a filament winding method to form a cylindrical shape. Next, while holding this on the mandrel,
Cured at 130 ° C for 3 hours, Vf65% of fiber, 150m
A compact having a diameter of 200 mm and a thickness of 5 mm was obtained.

Comparative Examples 1 to 6 In Comparative Example 1, a glass fiber was impregnated with the vinyl ester resin shown in Table 1 and wound around a mandrel.
Time-curing molding was performed to form a pipe having the same dimensions as those of the example.
Comparative Example 2 was molded under the same conditions as in the example while impregnating the glass fiber with the epoxy resin shown in Table 1. Comparative Example 3 is shown in Table 1.
Was cured at 130 ° C. for 3 hours to form a single tube. Comparative Example 4 was made of stainless steel (SU
In S304L), pipes of the same dimensions were prepared. Comparative Example 5 was wound around a mandrel while impregnating an aramid fiber and Comparative Example 6 a polyarylate fiber with a matrix resin having the composition shown in Table 1, respectively, and molded under the same conditions as in Example 1.

[0017]

[Table 1]

Each pipe was evaluated in the following manner, and the results are shown in Table 2. (1) Crack resistance A sample pipe was placed in liquid He from a room temperature state, left standing for 30 minutes, and then pulled up to visually observe whether a crack was formed. ；: No crack is observed at all. Δ: Cracks are slightly observed. X: There are large cracks on the entire surface.

(2) He leak property First, both ends of each pipe are sealed, and a vacuum is drawn.
e Gas is introduced into the system and the standard leak rate is 5.0 × 10 ^-8 torr · l
/ sec. Next, He gas was blown onto the pipe outer cylinder width, and the He leak amount was measured. The result was shown as a ratio (%) to the standard leak amount. Then place the pipe in liquid He 3
After leaving it to stand for 0 minutes, it was taken out and the He leak amount was measured in the same manner as above.

(3) Number of Spins (Ns) ESR (Electron Spin Resonance) was measured while cooling each sample with liquid He to determine the number of spins (the number of spins is proportional to the magnetic susceptibility).

(4) Shrinkage rate The dimensional change rate of each sample from room temperature to liquid He temperature is expressed by TM
The shrinkage was calculated by measuring according to Method A (heating rate: 5 ° C /
min).

(5) Specific gravity The specific gravity was measured (25 ° C.).

(6) Flexural Strength A specimen having a thickness of 5 mm and a width of 5 mm was cut out from each specimen, and the flexural strength at room temperature and liquid He temperature was measured at a distance between fulcrums of 25 mm and a crosshead speed of 1 mm / min.

(7) Specific bending strength The specific bending strength was calculated from the bending strength and the specific gravity.

[0025]

[Table 2]

[0026]

The fiber-reinforced plastic composite material for cryogenic use obtained by the present invention is an FRP in which high-strength polyethylene fibers having a negative expansion coefficient and a matrix resin having a positive expansion coefficient are composited, so that the temperature is lowered. The shrinkage ratio becomes almost 0, and a very lightweight member excellent in micro crack resistance and dimensional stability can be obtained even at an extremely low temperature. Further, by using an epoxy resin containing a high-strength organic fiber and a specific curing agent, a cryogenic fiber-reinforced plastic composite material having excellent magnetic susceptibility and mechanical properties could be provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F16L 59/12 F16L 59/12 F17C 1/02 F17C 1/02 13/08 13/08 F25D 3/10 F25D 3/10 G01R 33 / 035 G01R 33/035 H01F 6/00 H01L 39/04 ZAA H01L 39/04 ZAA C08L 63:00 C08L 63:00 H01F 7/22 (56) References JP-A-63-115999 (JP, A) JP-A-56-116555 (JP, A) JP-A-57-195998 (JP, A) JP-A-61-64107 (JP, A) JP-A-4-196181 (JP, A) JP-A-4-266077 (JP) JP-A-4-67843 (JP, A) JP-A-4-69492 (JP, A) JP-A-4-69493 (JP, A) JP-A-3-192129 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) C08J 5/24 CFC

Claims (1)

(57) [Claims] 1. A method in which a high-strength polyethylene fiber is used as a reinforcing fiber and is formed by a filament winding method.
Cryogenic fiber-reinforced plastic, characterized in that the at is
Composites .