JPH0526795A - Strand compression test method and test equipment - Google Patents

Abstract

(57) [Summary] (Modified) [Construction] A fiber bundle consisting of a predetermined number of filaments is impregnated with a thermosetting resin or a thermoplastic resin, which is molded and cured to have a circular cross section with a diameter of 30 mm or less. Strands are made and the cured strands are 10 mm or more, 300
A test piece 3 is produced by cutting the strand to a predetermined length of not more than mm, and then adhering metallic cylindrical tabs to both ends of the strand using an adhesive. Both ends of the test piece are held by a lower holder 4 and an upper holder 5, and both holders 4 and 5 are guide means 6.
Is slidably guided by. [Effect] A test piece can be produced even with a small amount of discontinuous short fibers, and the test piece production and measurement operations are simple and do not require a long time, and the test piece and test jig are small and easy to handle. Excellent in reproducibility with less measurement error.
Compressive physical properties of pitch-based, PAN-based, rayon-based carbon fibers, glass fibers, and other various fibers and composite materials can be determined.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention generally relates to pitch systems, P
To obtain the compression properties of carbon fiber such as AN type and rayon type, glass fiber, and other various types of fibers, such as strength, elastic modulus and strain at the time of compression, or the compression physical properties of composite materials using such fibers as reinforcing fibers. The present invention relates to a resin-impregnated strand (hereinafter simply referred to as "strand") compression test method.

[0002]

2. Description of the Related Art For example, among pitch-based, PAN-based, rayon-based carbon fibers, in particular, high-performance carbon fibers having high tensile strength and high tensile elastic modulus are used in the space / aviation industry, energy industry, automobile industry. In various industrial fields such as the building industry, sports and leisure industries, its application is expected to be expanded as a material of a composite material that is lightweight and has high strength and high elasticity. Thus, when carbon fiber and its composite material are used as structural materials, their compressive physical properties are, as with tensile properties, sometimes more important physical properties.
Development of carbon fiber having high tensile properties and high compression properties is desired.

[0003]

However, at the present time,
The study of compressed physical properties of carbon fiber has not progressed, and many unexplained parts remain. One of the causes is
The accurate evaluation method of the compression properties, that is, the compression test method is not sufficiently prepared. Accurate evaluation of the compressed physical properties of fibers is essential for the development of carbon fibers with high compression properties.

At present, there is no standard in Japan for the compression test method of carbon fiber or carbon fiber reinforced composite material, and the compressive strength of the carbon fiber reinforced composite material is required by the test method based on the standards of Western countries. The compressed physical properties of are evaluated. However, each of these test methods has problems as described below, and has not been established.

For example, ASTM D3410 (Celanese
Method, IITRI method), a plate-shaped resin-impregnated composite material containing a specified amount of carbon fiber is used as the test piece. For example, (1) First, a unidirectional prepreg (sheet) with a width of 500 mm impregnated with an epoxy resin is manufactured,
20 pieces cut out into m × 300 mm are laminated and heat-treated at 130 ° C. for 2 hours in an autoclave to cure the resin to obtain a laminated plate having a thickness of 2 mm. (2) Next, the laminated plate is formed into a width (6.35 mm) × thickness (2
(mm) × length (140 mm) cut into strips, and FRP tabs are attached to both ends using an epoxy adhesive.
Obtained by

Further, the test piece thus obtained is mounted on a dedicated compression test jig, for example, a Celanese method compression test jig, which is installed in a material testing machine, and a compression load is applied by a crosshead. The load was applied and the compressive strength was calculated from the maximum load.

Such a compression test method (1) requires a large amount of continuous fibers for producing a test piece. (2) Molding and processing of the test piece is difficult and requires a long time. (3) Handling is inconvenient because the test pieces and jigs are large and the shapes are complicated. (4) The measurement operation is complicated and requires a long time. In addition to the above problems, (5) there is a serious problem that the dimensional accuracy of the test piece and the surface processing state are easily affected. That is, according to this test method, the portion of the test piece that receives a compressive load has a length of 1
It is 2.7 mm, and when a compressive load is applied by the crosshead, this part bends in some cases, and it is difficult to give pure uniaxial compressive stress to the test piece, and as a result, the compressive strength is small. It had the drawback of leaving.

Further, ASTM D695 is often used as a test method for evaluating the compression properties of carbon fibers. According to this method, the test piece is constrained by flat plates on both side surfaces, so that deformation due to compression is suppressed, and as a result, there is a problem that the compressive strength is relatively large.

Therefore, an object of the present invention is to solve all the problems found in the above-mentioned conventional test methods, and to make a test piece even with a small amount of discontinuous short fibers, and to make a test piece. In addition, the measurement operation is simple and does not require a long time, the test piece and the test jig are small and easy to handle, and the measurement error is small and the reproducibility is high, such as pitch type, PAN type and rayon type. It is an object of the present invention to provide a strand compression test method and a test apparatus therefor for determining the compression properties of carbon fibers, glass fibers, and various other fibers and composite materials.

[0010]

The above object can be achieved by the strand compression test method and test apparatus according to the present invention. In summary, the present invention comprises: (a) impregnating a fiber bundle having a predetermined number of filaments with a thermosetting resin or a thermoplastic resin,
This is molded and cured to produce a strand having a circular cross section with a diameter of 30 mm or less, (b) the cured strand is cut into a predetermined length of 10 mm or more and 300 mm or less, and adhered to both ends of the strand. Adhesively bonding the metallic cylindrical tabs to form a test piece, (c)
Both ends of the test piece are held by a lower holder and an upper holder and mounted on guide means for slidably guiding both holders, (d) a material test is performed on the test piece via the upper holder. Apply a compressive load with the machine crosshead and measure the compressive load and the length displacement of the test piece.
(E) A strand compression test method characterized in that the compressive physical properties of the fiber and / or the composite material are calculated based on the compression load and the amount of length displacement of the test piece.

Further, in the above strand compression test method, a fiber bundle having a predetermined number of filaments is impregnated with a thermosetting resin or a thermoplastic resin, which is molded and cured to have a diameter of 3 mm.
A strand having a circular cross section of 0 mm or less is produced, the hardened strand is cut into a predetermined length of 10 mm or more and 300 mm or less, and then a metallic cylindrical tab is adhered to both ends of the strand with an adhesive. Suitable for a strand compression test apparatus characterized by having a test piece produced by the above, a lower holder and an upper holder for holding both ends of the test piece, and guide means for slidably guiding the both holders. Will be carried out.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The strand compression test method and test equipment therefor according to the present invention will now be described in more detail with reference to the drawings. Although carbon fibers are used as the fibers in this embodiment, the present invention is not limited to this.

First, the test piece used in the present invention will be described. For example, in the case of pitch-based carbon fiber, 1000
~ 3000 filaments, in the case of PAN-based carbon fibers, a fiber bundle consisting of a small amount of carbon fibers of about 6000 filaments is impregnated with a thermosetting resin or a thermoplastic resin, which is molded and cured to obtain a diameter (D _S ) Is 30 mm or less, for example, a strand having a circular cross section of about 1 mm is produced. Then, the cured strand is 10 mm or more,
Cut to a predetermined length of 300 mm or less, usually 30 mm or more and 150 mm or less, and as shown in FIG. 1, the metallic cylindrical tabs 2 are bonded to both ends of the strand 1 using an adhesive, and the test piece 3 is It is formed. At the test piece of the present invention, the portion deformed by the compressive load (L _S) is, 100 mm or less, is preferably a 5 to 15 mm, are usually 5 mm.

The metallic cylindrical tab 2 can be made of any material, but has a length (l) of 30 mm and an inner diameter (d ₁ ) of 1.
mm, and a stainless steel pipe having an outer diameter (d ₂ ) of 3 mm can be preferably used.

As shown in FIG. 1, the strand compression test apparatus according to the present invention comprises a lower holder 4 and an upper holder 5 for holding both ends of a test piece 3 having the above-mentioned structure, and both holders. And a guide means 6 for slidably guiding 4. The lower holder 4 is a cylindrical member made of, for example, stainless steel, and has a test piece holding hole 4a formed in the upper surface thereof. Upper holder 5
Like the lower holder 4, is a columnar member made of, for example, stainless steel, has a test piece holding hole 5a opened on the lower surface, and the upper surface has a point load for the purpose described later in detail. A conical recess 5b for carrying the loading ball 7 is formed. Further, although the guide means 6 may have any configuration, in the present embodiment, it is a cylindrical sleeve made of, for example, stainless steel, so that both the cylindrical holders 4 and 5 are arranged in the cylindrical sleeve. Is slidably fitted to.

For the purpose of facilitating the understanding and not for limiting the present invention, the numerical value will be specifically described. In this embodiment, the outer diameter (D _H ) of the lower holder 4 is 15 m.
m, length (L _H ) is 40 mm, and the test piece holding hole 4a
Has a hole diameter such that the metallic cylindrical tab 2 can be smoothly inserted, and its length (L _h ) is 25 mm. Further, the upper holder 5 has the same shape and size as the lower holder 4, and only a conical recess 5b having a depth of 4 mm is formed on the upper surface. The cylindrical sleeve 6 as the guide means is provided with the holders 4, 5
The outside diameter (D _G ) is such that the hole can slide smoothly.
Was 20 mm and the length (L _G ) was 80 mm.

The test apparatus of the present invention thus constructed is installed on the fixed base 101 of the material testing machine, and the test piece 3 is mounted on the test piece 3 via the point load ball 7 and the upper holder 5.
A compressive load is applied by the crosshead 102 of the material testing machine. The moving speed of the crosshead 102 is usually 1 mm /
Minutes are suitable.

The compressive strength (σ _f ) of the fiber and the compressive strength (σ _c ) of the composite material are calculated by the following formula from the maximum load in the compression test.

Σ _f = P / A _f = (P _max + w) × ρ / T × 1000 (1) σ _c = σ _f × V _f = (P _max + w) × ρ / T × 1000 × V _f (2 ) Where P: total load (kg) P _max : maximum load (kg) w: upper jig weight (kg) A _f : total fiber cross-sectional area (mm ² ) ρ: fiber density (g / cm ^3). ) T: Fiber fineness (mg / m) V _f : Fiber volume content

If the volume content of the fiber is V _f = 60%, then σ _c = (P _max + w) × ρ / T × 1000 × 0.6 (3)

Further, the compressive elastic modulus (E _f ) and compressive strain (ε _f ) of the fiber, and the compressive elastic modulus (E _c ) and compressive strain (ε _c ) of the composite material were obtained by the above compression test. It is calculated from the load-displacement curve by the following formula. However, since the compressive strain of the fiber (ε _f ) and the compressive strain of the composite material (ε _c ) are considered to be substantially the same, ε _f = ε _c = ε.

E _f = ΔP / (A _f · Δε) (4) E _c = E _f × V _f = {ΔP / (A _f · Δε)} × V _f (5) where Δ P: Increase in load (kg) Δε: Increase in strain A _f : Total cross-sectional area of fiber (mm ² ) V _f : Volume content of fiber

Next, the present invention will be described more specifically with reference to examples.

Example 1 Pitch-based super high elasticity carbon fiber (tensile modulus of about 700 GP
a, continuous long fibers having a tensile strength of about 3.5 GPa),
JIS. Strands were produced by the method and resin impregnating apparatus defined in R7601 "Test method for carbon fiber test method 6.6.2 Test of resin-impregnated strand".

That is, a sample fiber bundle consisting of 1000 filaments under constant tension was impregnated with an epoxy resin solution. At this time, the sample fiber bundle was made to pass between the freely rotating rollers arranged in a zigzag pattern so that the epoxy resin was well permeated between the single fibers of the sample. In addition, in order to adjust the amount of resin adhered, it was passed through a die or a roller wrapped with paper, non-woven fabric or woven fabric capable of absorbing excess resin. The resin-impregnated sample fiber bundle, that is, the strand, was wound around a curing frame (winder), and the sample strand was held in a straight line and heat-cured in a dryer. Cured strands have a length of 300 mm
Disconnected. The strand had a circular cross section with a diameter of 1 mm.

Next, using epoxy adhesives on both ends of the strand 1, the length (l) is 30 mm and the inner diameter (d ₁ ).
And a metal cylindrical tab 2 formed of a stainless steel pipe having an outer diameter (d ₂ ) of 1 mm and an outer diameter (d ₂ ) of 3 mm were adhered to prepare a test piece 3. The exposed strand portion (L _S ) of the test piece 3 was 5 mm.

Both ends of the thus-prepared test piece 3 were attached to the lower holder 4 and the upper holder 5, respectively, and both holders 4 and 5 were inserted into the cylindrical sleeve 6. Both holders 4 and 5 have an outer diameter (D _H ) of 15 mm and a length (L _H ).
Was made of 40 mm stainless steel and mounted in a stainless steel cylindrical sleeve 6.

The test apparatus assembled in this way is installed on the fixed base 101 of the material tester, and the crosshead 102 of the material tester is used to insert the test piece through the point load ball 7 and the upper holder 5. A compressive load was applied to 3. The moving speed of the crosshead 102 was 1 mm / min.

As a result of calculation from the above equations (1), (3), (4) and (5), the compressive strength (σ _c ) of the composite material is 41 k.
g / mm ² , compression modulus (E _c ) is 33 ton / mm ²
Met. The time spent for the main measurement work was 8 hours for producing the test piece and 4 hours for the measurement.

Comparative Example 1 Using the same fibers as in Example 1, a unidirectional prepreg (sheet) having a width of 500 mm impregnated with an epoxy resin was manufactured, and 20 pieces cut out into 300 mm × 300 mm were laminated. The resin was cured by heat treatment at 130 ° C. for 2 hours in an autoclave to obtain a laminated plate having a thickness of 2 mm. The laminated plate is 6.6 mm x 3.8 mm x 140 mm
Was cut into strips and FRP tabs were attached to both ends using an epoxy adhesive to prepare test pieces. The test piece was mounted on a Celanese method compression test jig, installed in a material testing machine, and subjected to a compression test according to the standard of ASTM D3410. The crosshead moving speed was 1 mm / min.
The compressive strength and the compressive elastic modulus were calculated according to the above formulas (1), (3), (4) and (5). The compressive strength obtained is 4
It was 2 kg / mm ² and the compression modulus was 32 ton / mm ² . The time spent for the main measurement work was 24 hours for producing the test piece and 8 hours for the measurement.

Example 2 PAN-based high strength carbon fiber (tensile modulus of about 235 GPa,
A continuous strand fiber having a tensile strength of 3.2 GPa) was used to prepare a strand test piece under the same method and conditions as in Example 1,
A compression test was conducted in the same manner, and the compression strength and the compression elastic modulus were obtained. The compressive strength was 156 kg / mm ² , and the compressive elastic modulus was 15 ton / mm ² . The time spent for this work was 8 hours for producing the test piece and 4 hours for the measurement.

Comparative Example 2 Using the same fibers as in Example 2, a strand test piece was prepared under the same method and conditions as in Comparative Example 1, and a compression test was conducted in the same manner to determine the compression strength and compression elastic modulus. I asked. Compressive strength is 147 kg / mm ² , compressive elastic modulus is 13 ton /
It was mm ² . The time spent for this work was 24 hours for producing the test piece and 8 hours for the measurement.

Example 3 The same carbon fiber as in Example 1 was used as a discontinuous short fiber having a length of 70 mm, the fiber was dipped in an epoxy resin, and the fiber was placed in a metal or plastic strand impregnation molding apparatus. Are arranged in one direction, heat-cured as it is in a dryer, then taken out and have a circular cross section with a diameter of 1 mm,
A strand piece having a length of 70 mm was produced.

A test piece was prepared in the same manner as in Example 1 and a strand compression test was conducted under the same conditions as in Example 1. The obtained compressive strength was 40 kg / mm ² and the compressive elastic modulus was 33 ton / mm ² . The time spent for this work was 8 hours for producing the test piece and 4 hours for the measurement.

Example 4 A strand test piece was prepared in the same manner as in Example 3 using the discontinuous short fibers having a length of 70 mm of the same carbon fiber as that used in Example 2, and the same as in Example 1. A compression test was performed under the method and conditions described in 1. The compressive strength obtained is 150 kg / mm
² , the compression modulus was 14 ton / mm ² . The time spent for this work was 8 hours for producing the test piece and 4 hours for the measurement.

[0036]

As described above, according to the strand compression test method and the test apparatus according to the present invention, it is possible to prepare a test piece even with a small amount of discontinuous short fibers, and further, to prepare and measure the test piece. Carbon fiber such as pitch-based, PAN-based, rayon-based carbon fiber that is easy to operate and does not require a long time, and that the test piece and test jig are small and easy to handle, and that there are few measurement errors and high reproducibility. The compressive physical properties of glass, glass fiber, and various other fibers and composite materials can be determined.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a strand compression test test apparatus according to the present invention.

[Explanation of symbols]

1: Strand 2: Metallic cylindrical tab 3: Test piece 4, 5: Holder 6: Guide means 7: Load ball for point load

Claims (2)

[Claims] 1. (a) A fiber bundle consisting of a predetermined number of filaments is impregnated with a thermosetting resin or a thermoplastic resin, which is molded and cured to produce a strand having a circular cross section with a diameter of 30 mm or less. (B) cutting the hardened strand into a predetermined length of 10 mm or more and 300 mm or less, and adhering metal cylindrical tabs to both ends of the strand with an adhesive to prepare a test piece, c) holding both ends of the test piece by a lower holder and an upper holder, and mounting the both holders on guide means for slidably guiding them; (d) attaching the test piece to the test piece through the upper holder;
A compressive load is applied by the crosshead of the material testing machine to measure the compressive load and the length displacement of the test piece, and (e) the fiber and / or the fiber based on the compressive load and the length displacement of the test piece. A method for strand compression test, which comprises calculating a compression property of a composite material. 2. A fiber bundle having a predetermined number of filaments is impregnated with a thermosetting resin or a thermoplastic resin, and this is molded,
By curing, a strand having a circular cross section with a diameter of 30 mm or less is produced, and the cured strand is 10 mm or more,
A test piece produced by cutting a predetermined length of 300 mm or less and then adhering metallic cylindrical tabs to both ends of the strand with an adhesive, and a lower holder for holding both ends of the test piece, and A strand compression test apparatus comprising an upper holder and guide means for slidably guiding the both holders.