CN110057860B - Sample preparation method and device for measuring high-temperature thermal diffusion coefficient of fiber - Google Patents
Sample preparation method and device for measuring high-temperature thermal diffusion coefficient of fiber Download PDFInfo
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- CN110057860B CN110057860B CN201910234380.8A CN201910234380A CN110057860B CN 110057860 B CN110057860 B CN 110057860B CN 201910234380 A CN201910234380 A CN 201910234380A CN 110057860 B CN110057860 B CN 110057860B
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/286—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q involving mechanical work, e.g. chopping, disintegrating, compacting, homogenising
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/32—Polishing; Etching
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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Abstract
The invention discloses a sample preparation method and a device for measuring a fiber high-temperature thermal diffusion coefficient, wherein the method comprises the following steps: determination of the Linear Density of the fibers ρL(ii) a Winding the fiber on a designed winding mould or cutting the fiber into small sections so as to ensure the alignment degree of the fiber during subsequent filling; filling the fibers into a group of steel ring molds designed for overcoming high temperature, so that the fibers are filled in the molds; cutting off fibers between the steel ring molds, and polishing one surface of the steel ring mold filled with the fibers by using a polishing machine to be flat; clamping the steel ring mould by using a clamp designed to be matched with the outer diameter of the steel ring mould to polish the other surface of the steel ring mould, and simultaneously ensuring that the polished surface is kept flat so as to ensure the parallelism of the fiber sample; measuring thermal diffusion coefficient alpha of polished sample at high temperatureT. The invention also designs a corresponding winding die, a steel ring die and a matched clamp, can measure the thermal diffusion coefficient of the fiber at high temperature, can obtain the thermal conductivity through the calculation of a related formula so as to accurately reflect the thermal conductivity of the fiber, and has small heat loss in the measurement process of the thermal diffusion coefficient and small dispersibility of the measurement result.
Description
Technical Field
The invention relates to the field of fiber performance testing, in particular to a method and a device for preparing a sample for measuring a fiber high-temperature thermal diffusion coefficient.
Background
With the continuous development of scientific technology, a large number of novel varieties of fibers are developed in succession, how to accurately and comprehensively characterize the thermophysical properties of the fibers, and the method has very important reference significance for accurately evaluating the differences of different varieties of fibers and reasonably selecting the application range of the fibers.
Thermal conductivity, also called thermal conductivity, is a measure of the thermal conductivity of a substance, which is defined as the amount of heat transferred by a unit temperature gradient through a unit thermal conductive surface in a unit time, and is one of the most important thermophysical parameters of a solid material, and is commonly used to represent the thermal conductivity of the material.
There are many methods for measuring the thermal conductivity of materials, and the method can be generally divided into a steady-state method and an unsteady-state method according to a heat flow method. The steady state method mainly comprises a heat flow meter method and a protective hot plate method, and the unsteady state method mainly comprises a hot wire method and a laser flash method. The laser flash method has the advantages of small size of a required sample, high testing speed, high precision, testable thermal diffusivity, wide temperature range and the like, and can obtain the thermal conductivity through the product of the known bulk density, specific heat and the measured thermal diffusivity of the material, so the laser flash method is most commonly used for measuring the thermal conductivity of the material.
The laser flash method is widely applied to the field of materials, and the testable material system comprises metal, inorganic matters, ceramics, polymers, composite materials and the like, and the material form can be blocks, powder, liquid and the like. The principle is that under a certain set temperature, a laser source instantly emits a beam of light pulse to uniformly irradiate the lower surface of a sample, so that the temperature of the surface layer of the sample is instantly increased after the surface layer absorbs light energy, and the surface layer is used as a hot end to transmit the energy to a cold end of the upper surface in a one-dimensional heat conduction mode. And continuously measuring the corresponding temperature rise process of the central part of the upper surface by using an infrared detector so as to obtain a corresponding relation curve of temperature rise and time, and then converting to obtain the heat-conducting property of the material.
Most of common high-thermal-conductivity fibers such as carbon fibers have typical anisotropic structures, the axial thermal conductivity of the fibers is widely concerned, but due to the high length-diameter ratio of the fibers, the axial thermal conductivity of the fibers is difficult to directly test, and no clear standard exists at present.
Nowadays, the application field of fiber reinforced composite materials is more and more extensive, some fields require high service temperature of materials, the change of the temperature undoubtedly can cause the change of the performance of the fiber reinforced composite materials, and how to evaluate the change of the performance at high temperature is a problem concerned by many people at present, so the axial thermal conductivity of the fibers at high temperature is obtained by measuring the thermal diffusion coefficient of the fibers at high temperature, and the application field of the fiber reinforced composite materials can be further expanded undoubtedly.
Disclosure of Invention
The invention aims to provide a sample preparation method and a sample preparation device capable of efficiently and accurately measuring the high-temperature thermal diffusion coefficient of a fiber based on a laser flash method.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention discloses a sample preparation method for measuring a fiber high-temperature thermal diffusion coefficient, which comprises the following steps:
a. measurement of fiber Linear Density ρL；
b. Winding the fiber on a designed winding mould or cutting the fiber into small sections so as to ensure the alignment degree of the fiber during subsequent filling;
c. filling the fibers into a group of steel ring molds designed for high temperature resistance, so that the fibers are filled in the molds;
d. cutting off fibers between the steel ring molds, and polishing one surface of the steel ring mold filled with the fibers by using a polishing machine to be flat;
e. clamping the steel ring mould by using a clamp designed to be matched with the outer diameter of the steel ring mould to polish the other surface of the steel ring mould, and simultaneously ensuring that the polished surface is kept flat so as to ensure the parallelism of the fiber sample;
f. measuring thermal diffusion coefficient alpha of polished sample at high temperatureT；
Preferably, in the step a, the linear density ρ of the fibersLCalculated according to a formula shown in formula I, the total length of the taken fiber is L, and the mass of the fiber is mL：
ρL＝mLthe/L is shown as formula I.
Preferably, in the step b: for non-brittle fibers, a designed winding mold can be adopted, and the fiber collimation degree in subsequent filling can be ensured through the fiber winding mode; and for fragile fibers, the collimation degree of the fibers during subsequent filling is ensured by cutting the fragile fibers into small sections of 5-6 cm.
Preferably, in the step b, in order to ensure the volume fraction of the fibers filled in the steel ring mold in the subsequent step c
Not less than 65%, the number n of the fibers filled in the steel ring mold is calculated according to a formula shown in a formula II, and the corresponding number of turns of the fibers wound on the winding mold is at least n/2 or the fibers are cut into at least n sections:
in the formula II, the reaction solution is shown in the specification,
is the fiber volume fraction, R, filled in the steel ring mold1Is the inner diameter of the steel ring die, rhoVFor a known fiber bulk density, ρLIs the linear density of the fibers measured in step a.
Preferably, in the step c: for the fiber using the winding mold, before the fiber is cut off and taken down from one end of the winding mold, ethanol is required to be dripped into the fiber to bundle the fiber; for fibers cut into small pieces, ethanol soaking is required.
Preferably, in the step c, the adopted steel ring mold is designed, and the inner diameter R of the steel ring mold is112.7-28.56 mm, 3.5-8 mm in height h and 1mm in wall thickness b, and can be divided into a section of major arc and a section of minor arc.
Preferably, in the step d, the mesh number of the sand paper adopted by the grinding and polishing machine is not less than 600 meshes, the rotating speed of the grinding and polishing machine is 400-600 r/min, and the surface of the sand paper needs to be cleaned by water in time in the grinding and polishing process.
Preferably, in step e, the adopted clamp is designed and composed of a clamping device and a pushing device, and the diameter R of the bottom circle of the clamp is2It is necessary to satisfy the formula shown in formula III:
R2＝R1+2b formula III.
In the formula III, R1The inner diameter of the steel ring die and the wall thickness of the steel ring die are b.
Preferably, in the step f, the ground sample needs to be cleaned, a small amount of water is absorbed by an ear washing ball to remove surface impurities, then a small amount of ethanol is used for washing, and the ground sample is placed at 100-110 ℃ for at least 1h to be dried.
Preferably, in step f, the thermal diffusivity alpha is different at different temperaturesTThe measurement was carried out by laser flash.
The invention discloses a sample preparation method for measuring a fiber high-temperature thermal diffusion coefficient, which comprises the following steps: determination of the Linear Density of the fibers ρL(ii) a Winding the fiber on a designed winding mould (1) or cutting the fiber into small sections so as to ensure the alignment degree of the fiber during subsequent filling; filling the fibers into a group of steel ring molds (2) designed for overcoming high temperature, so that the fibers are fully filled in the molds; cutting off fibers between the steel ring molds (2), and polishing one surface of the steel ring mold (2) filled with the fibers by using a polishing machine; clamping the steel ring die (2) by using a clamp (3) which is designed to be matched with the outer diameter of the steel ring die (2) to polish the other surface of the steel ring die (2) to be flat, and simultaneously ensuring that the polished surface is kept flat so as to ensure the parallelism of the fiber sample (4); measuring the thermal diffusion coefficient alpha of the polished sample (4) at high temperatureT. The invention discloses a sample preparation method and a sample preparation device, wherein a corresponding winding mold (1), a steel ring mold (2) and a matched clamp (3) are designed, the thermal diffusion coefficient of a fiber at high temperature can be measured, the thermal conductivity can be obtained through calculation of a related formula so as to accurately reflect the thermal conductivity of the fiber, the heat loss in the thermal diffusion coefficient measurement process is small, and the dispersibility of a measurement result is small.
Drawings
FIG. 1 is a schematic view of a winding mold designed according to the present invention;
a is a winding mould without winding fiber; b is a winding mould for winding fibers;
FIG. 2 is a related engineering drawing of a winding mold designed according to the present invention;
a is a top view of the winding die; b is a side view of the winding die; c is a front view of the winding die; d is a three-dimensional schematic view of the winding die;
FIG. 3 is a schematic diagram of the use of the steel ring mold designed by the present invention;
a. b and c are schematic diagrams of the matching of the major arc and the minor arc of the steel ring die;
FIG. 4 is a related engineering drawing of a steel ring mold designed according to the present invention;
a is a top view of the steel ring mold; b is a side view of the steel ring mold; c is the front view of the steel ring mold; d is a three-dimensional schematic view of the steel ring mold;
FIG. 5 is a schematic diagram of the use of the clamp designed to mate with a steel ring mold of the present invention;
a is a propulsion device; b is a clamping device; c is a schematic diagram of the matching of the propelling device and the clamping device;
FIG. 6 is a related engineering drawing of a fixture designed according to the present invention;
a is a side view of the clamp; b is a front view of the clamp; c is a top view of the clamp; d is a perspective view of the clamp;
FIG. 7 is a schematic view of a fiber-filled steel ring mold of the present invention;
FIG. 8 is a schematic view of the clamp of the present invention clamping a sample.
Detailed Description
The invention discloses a sample preparation method and a device for measuring a fiber high-temperature thermal diffusion coefficient, which comprises the following steps:
a. measurement of fiber Linear Density ρL；
b. Winding the fiber on a designed winding mould (1) or cutting the fiber into small sections so as to ensure the alignment degree of the fiber during subsequent filling;
c. filling the fibers into a group of steel ring molds (2) designed for high temperature resistance, so that the interior of the molds is filled with the fibers;
d. cutting off fibers between the steel ring molds (2), and polishing one surface of the steel ring mold (2) filled with the fibers by using a polishing machine;
e. clamping the steel ring die (2) by using a clamp (3) which is designed to be matched with the outer diameter of the steel ring die (2) to polish the other surface of the steel ring die (2) to be flat, and simultaneously ensuring that the polished surface is kept flat so as to ensure the parallelism of the fiber sample (4);
f. measuring the thermal diffusion coefficient alpha of the polished sample (4) at high temperatureT：
In the present invention, in the step a shown, the linear density ρ of the fibersLThe total length of the taken fiber is L calculated according to a formula shown in formula I,mass of fiber mL：
ρL＝mLthe/L is shown as formula I.
In the present invention, the linear density ρ of the fibersLThe preferred scheme comprises the following steps: accurately measuring 3 parts of fibers with the length of 3m by using a ruler, cutting the fibers into small sections with the length of 5-6 cm by using a blade, preferably 5cm for each section in the embodiment of the invention, weighing the sections in an electronic balance, calculating the linear density, and taking the average value of the 3 parts of the linear density as the linear density rho of the fibersL。
In the present invention, in the step b: for non-brittle fibers, a designed winding die (1) can be adopted, and the fiber winding mode can ensure the alignment degree of the fibers during subsequent filling; and for the brittle fibers, the brittle fibers are preferably cut into small sections of 5-6 cm so as to ensure the collimation of the fibers during subsequent filling. In the embodiment of the invention: for non-brittle fibers, a winding die (1) is preferred to wind the fibers, and the distance between two round rods of the winding die (1) is preferably 5 cm; in the present embodiment, it is further preferable that the brittle fibers are cut into 5cm pieces.
In the invention, in the step b, in order to ensure the volume fraction of the fibers filled in the steel ring mould (2) in the subsequent step c
Not less than 65 percent, the number n of the fibers filled in the steel ring mould (2) is calculated according to a formula shown in a formula II, and the corresponding number of turns of the fibers wound on the winding mould is at least n/2 or the fibers are cut into at least n sections. In the embodiment of the invention, the winding number of the winding die (1) is preferably n/2, and the fiber cut into segments is preferably n segments:
in the formula II, the reaction solution is shown in the specification,
is the fiber volume fraction, R, filled in the steel ring mold1Is the inner diameter, rho, of the steel ring die (2)VFor a known fiber bulk density, ρLIs the linear density of the fibers measured in step a.
In the present invention, in the step c: for the fiber using the winding die (1), before the fiber is cut off from one end of the winding die (1), ethanol is required to be dripped into the fiber to bundle the fiber; for fibers cut into small pieces, ethanol soaking is required.
In the invention, in the step c, the steel ring mold (2) is designed, and the inner diameter R of the steel ring mold (2) is preferably selected112.7-28.56 mm, 3.5-8 mm in height h and not less than 1mm in wall thickness b. The inner diameter R of the steel ring die (2) in the embodiment of the invention1More preferably 13mm, and the thickness b is 1 mm.
In the step d, the number of the sand paper used by the grinding and polishing machine is not less than 600 meshes, the rotating speed of the grinding and polishing machine is 400-600 r/min, and the surface of the sand paper needs to be cleaned by water in time in the grinding and polishing process. In the embodiment of the invention, the number of the sand paper used by the grinding and polishing machine is preferably 800 meshes, and the rotating speed of the grinding and polishing machine is preferably 500 r/min.
In the invention, in the step e, the adopted clamp (3) is designed, and the inner diameter R of the clamp (3)2The formula shown in formula III is satisfied, in the embodiment of the invention, the clamp is composed of a clamping device and a propelling device, and the diameter R of the bottom circle of the clamp (3)2It is necessary to satisfy the formula shown in formula III:
R2＝R1+2b formula III.
In the formula III, R1The inner diameter of the steel ring die (2) and the wall thickness b of the steel ring die (2).
In the step f, the ground sample (4) needs to be cleaned, a small amount of water is absorbed by an ear washing ball to remove surface impurities, then a small amount of ethanol is used for washing, and the ground sample is placed at 100-110 ℃ for at least 1h to be dried. In the embodiment of the invention, the drying is preferably carried out for 1h at 105 ℃.
In the present invention, in the step f, the number of the test samples (4) is preferably 2 to 4, and in the present embodiment, it is more preferable that 2 test samples (4) are used, and the thermal diffusion system of 2 test samples (4) is testedTaking the average value as the thermal diffusion coefficient alphaT. In the present invention, the thermal diffusion coefficient α at different temperaturesTThe measurement is preferably carried out by a laser flash method, and the measurement method is not particularly limited in the invention, and the measurement can be carried out by a laser flash method which is conventional in the field.
Example 1
The method and the device for preparing the pitch-based carbon fiber sample capable of measuring the high-temperature thermal diffusion coefficient specifically comprise the following steps:
a. accurately measuring 3 parts of 3 m-long asphalt-based carbon fibers by using a ruler, cutting the asphalt-based carbon fibers into sections with the length of 5cm by using a blade, weighing each part by using an electronic balance, wherein the total length of each part is 60 small sections, and calculating the linear density of each part of fibers. The average of the linear densities ρ of 3 samples was taken as the linear density ρ of the fiberL。
b. 2 high-temperature-resistant steel ring molds with the inner diameter of 13mm, the height of 8mm and the wall thickness of 1mm are selected. According to the volume fraction of the filled fiber in the steel ring mold
The number of fibers n to be filled is calculated for 65%, n being 65%. pi.R1 2·ρV/4ρL。
c. Because pitch-based carbon fiber is fragile fiber, can't use the winding mould, so cut into 5 cm's segment with the blade with the fibre to guarantee the alignment degree of fibre when follow-up filling.
d. Fixing 2 steel ring molds by using an adhesive tape, and arranging the molds in parallel at a certain distance; and (b) when the pitch-based carbon fibers are just filled into the steel ring mold, taking 20 sections as 1 group, soaking the 1 group in ethanol, putting the 1 group into 2 steel ring molds, and then gradually reducing the number of the sections which are put into the molds each time until the fiber number calculated in the step (b) is filled.
e. Cutting off the fibers among the 2 steel ring molds by using a blade, and properly trimming the fibers outside the steel ring molds to enable the fibers exposed outside to exceed the steel ring molds by about 2 mm.
f. And (3) polishing one surface of the sample by using a polishing machine, wherein the mesh number of the abrasive paper is 800 meshes, the rotating speed of the polishing machine is 500r/min, and the abrasive paper is washed by water every 5min until one surface of the sample is polished to be flat. Due to the steel ring mold, a plane can be provided, which helps to ensure the parallelism of the test sample.
g. And (f) clamping the polished surface of the sample by using a designed clamp, and then continuously polishing the other surface until the other surface is polished to be flat according to the step f. Because anchor clamps can provide a plane, so can guarantee that the one side that originally polished is still level and smooth, the two sides depth of parallelism is all very high about the sample.
h. The surfaces of 2 samples are washed, a small amount of water is absorbed by an ear washing ball to wash away surface impurities, and then a small amount of ethanol is used for washing. Subsequently, the polished sample was placed in a glass dish, and placed in an oven at 105 ℃ for 1 hour to dry.
i. Measuring the thickness of 2 samples by a micrometer, spraying carbon on the upper and lower surfaces, measuring the thermal diffusion coefficient of 2 samples at 400 deg.C by laser flash method, and taking the average value as the thermal diffusion coefficient alpha of fiber at 400 deg.C400℃。
Example 2
The solution of example 2 differs from that of example 1 in that the test fibres are T800 grade carbon fibres. The method and the device for preparing the T800-grade carbon fiber sample capable of measuring the high-temperature thermal diffusion coefficient specifically comprise the following steps:
a. 3 parts of 3m long T800-grade carbon fiber is accurately measured by using a ruler, then the carbon fiber is cut into sections with the length of 5cm by using a blade, each section is 60 sections in total, each mass is weighed by using an electronic balance, and the linear density of each fiber is calculated. The average of the linear densities of 3 samples was taken as the linear density ρ of the fiberL。
b. 2 high-temperature-resistant steel ring molds with the inner diameter of 13mm, the height of 3mm and the wall thickness of 1mm are selected. According to the volume fraction of the filled fiber in the steel ring mold
The number of fibers n to be filled is calculated for 65%, n being 65%. pi.R1 2·ρV/4ρL。
c. The T800-grade carbon fiber is non-brittle fiber, a designed winding die is adopted, the distance between two round rods is 5cm, the fiber is wound on the winding die (the fiber which is cut into small sections for measuring the linear density rho L in the step a is not included) so as to ensure the fiber collimation degree in the subsequent filling process, and the number of winding turns is half of the number of the fibers required to be filled in the step b.
d. And dripping ethanol on the wound fibers to enable the fibers to be gathered, cutting the fibers along one side of the winding die, and taking down the fibers.
e. The 2 steel ring molds were fixed with tape, placed side-by-side at a distance apart, and the fibers were filled into the steel ring molds.
f. Cutting off the fibers among the 2 steel ring molds by using a blade, and properly trimming the fibers outside the steel ring molds to enable the fibers exposed outside to exceed the steel ring molds by about 2 mm.
g. And (3) polishing one surface of the sample by using a polishing machine, wherein the mesh number of the abrasive paper is 800 meshes, the rotating speed of the polishing machine is 500r/min, and the abrasive paper is washed by water every 5min until one surface of the sample is polished to be flat. Due to the steel ring mold, a plane can be provided, which helps to ensure the parallelism of the test sample.
h. And (g) clamping the polished surface of the sample by using a designed clamp, and then continuously polishing the other surface until the other surface is polished to be flat according to the step g. Because anchor clamps can provide a plane, so can guarantee that the one side that originally polished is still level and smooth, the two sides depth of parallelism is all very high about the sample.
i. The surfaces of 2 samples are washed, a small amount of water is absorbed by an ear washing ball to wash away surface impurities, and then a small amount of ethanol is used for washing. Subsequently, the polished sample was placed in a glass dish, and placed in an oven at 105 ℃ for 1 hour to dry.
j. Measuring the thickness of 2 samples by a micrometer, spraying carbon on the upper and lower surfaces, measuring the thermal diffusion coefficient of 2 samples at 100 deg.C by laser flash method, and taking the average value as the thermal diffusion coefficient alpha of fiber at 100 deg.C100℃。
Example 3
In the scheme of example 3, M40J-grade carbon fiber is selected to prepare a sample for measuring the high-temperature thermal diffusivity, the scheme is different from the scheme of example 2 in that the height of a steel ring die and the volume fraction of filled fibers in the steel ring die are changed, in the scheme of example 3, the height of the steel ring die is 6mm, and the steel ring die is used for measuring the high-temperature thermal diffusivityThe volume fraction of the medium filler fiber was 70%, and the thermal diffusivity alpha of the carbon fiber of M40J grade at 100 ℃ was measured by repeating the steps a to i in example 2100℃。
The results of measuring the thermal diffusivity of the pitch-based carbon fiber of example 1, the carbon fiber of grade T800 of example 2, and the carbon fiber of grade M40J of example 3 are shown in the table:
TABLE 1
| Test temperature T (. degree. C.) | Coefficient of thermal diffusion alpha (mm)2/s) | |
| Example 1 (Pitch-based carbon fiber) | 400 | 119.2 |
| Example 2(T800 grade carbon fiber) | 100 | 9.5 |
| Example 3(M40J grade carbon fiber) | 100 | 35.4 |
According to the invention, the thermal diffusion coefficient of the fiber at high temperature can be measured, the thermal conductivity can be obtained by calculating through a correlation formula so as to accurately reflect the thermal conductivity of the fiber, the heat loss in the thermal diffusion coefficient measuring process is small, and the dispersibility of the measuring result is small. Therefore, the axial thermal conductivity of the fiber at high temperature can be accurately obtained, and the application field of the fiber reinforced composite material can be further expanded undoubtedly.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A preparation method of a sample for measuring the high-temperature thermal diffusion coefficient of a fiber is characterized by comprising the following steps:
a. measurement of fiber Linear Density ρL；
b. Winding the fibers on a winding die (1) or cutting the fibers into small sections so as to ensure the alignment degree of the fibers during subsequent filling;
c. filling fibers into a group of steel ring molds (2) to enable the interior of the molds to be filled with the fibers; the steel ring die (2) is divided into a section of major arc and a section of minor arc, and the inclined planes on two sides of the major arc and the inclined planes on two sides of the minor arc are matched to form a ring;
d. cutting off fibers between the steel ring molds (2), and polishing one surface of the steel ring mold (2) filled with the fibers by using a polishing machine;
e. clamping the steel ring die (2) by using a clamp (3) matched with the outer diameter of the steel ring die (2) to polish the other surface of the steel ring die to be flat, and simultaneously ensuring that the polished surface is kept flat so as to ensure the parallelism of the fiber sample (4);
f. measuring the thermal diffusion coefficient alpha of the polished sample (4) at high temperatureT；
In the step a, the linear density rho of the fiberLCalculated according to a formula shown in formula I, the total length of the taken fiber is L, and the mass of the fiber is mL：
ρL＝mLThe formula I;
in the step b, in order to ensure that the volume fraction phi of the fibers filled in the steel ring mold (2) in the subsequent step c is not less than 65%, the number n of the fibers filled in the steel ring mold (2) needs to be calculated according to a formula shown in a formula II, and the corresponding number of winding turns on the winding mold is at least n/2 or is cut into at least n sections:
n＝φ·πR1 2·ρV/4ρLformula II;
in formula II, phi is the volume fraction of the fiber filled in the steel ring mold, R1Is the inner diameter, rho, of the steel ring die (2)VFor a known fiber bulk density, ρLIs the linear density of the fibers measured in step a.
2. The method for preparing a sample for measuring a thermal diffusivity of a fiber at a high temperature according to claim 1, wherein in the step b: for non-brittle fibers, a winding mold (1) is adopted, and the fiber collimation degree in subsequent filling is ensured through the fiber winding mode; for brittle fibers, the alignment degree of the fibers during subsequent filling is guaranteed by cutting the brittle fibers into small sections of 5-6 cm.
3. The method for preparing a sample for measuring a thermal diffusivity of a fiber at a high temperature according to claim 1, wherein in the step c: before cutting off and taking down the fiber using the winding mold (1) from one end of the winding mold (1), dripping ethanol into the fiber to bundle the fiber; for the fibers cut into small pieces, ethanol soaking was used.
4. The method for preparing a sample for measuring the thermal diffusivity of fiber at high temperature according to claim 1, wherein the inner diameter R of the steel ring mold (2) used in the step c112.7-28.56 mm, 3.5-8 mm in height h and not less than 1mm in wall thickness b.
5. The method for preparing the sample for measuring the high-temperature thermal diffusivity of the fiber according to claim 1, wherein in the step d, the number of the sand paper used by the polishing machine is not less than 600 meshes, and the rotating speed of the polishing machine is 400-600 r/min.
6. The method for preparing a sample for measuring the thermal diffusivity of fiber at high temperature according to claim 1, wherein in the step e, a clamp is used(3) Is designed and comprises a clamping device and a propelling device, wherein the diameter R of the bottom circle of the clamp (3)2It is necessary to satisfy the formula shown in formula III:
R2＝R1+2b formula III
In the formula III, R1The inner diameter of the steel ring die (2) and the wall thickness b of the steel ring die (2).
7. The method for preparing the sample for measuring the fiber high-temperature thermal diffusivity, as claimed in claim 1, wherein in the step f, the ground sample (4) needs to be cleaned, a small amount of water is absorbed by an ear washing ball to remove surface impurities, then a small amount of ethanol is used for washing, and the ground sample is placed at 100-110 ℃ for at least 1h for drying.
8. The method for preparing a sample for measuring the thermal diffusivity of a fiber at a high temperature according to claim 1, wherein the thermal diffusivity at different temperatures is α in the step fTThe measurement was carried out by laser flash.
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| CN201910234380.8A CN110057860B (en) | 2019-03-26 | 2019-03-26 | Sample preparation method and device for measuring high-temperature thermal diffusion coefficient of fiber |
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