Method for predicting the coefficient of linear thermal expansion of hot-extruded polyethylene-reinforced fiber composite rod cables.

Abstract

This invention relates to a method for predicting the coefficient of linear thermal expansion of hot-extruded polyethylene-reinforced fiber composite rod cables. Hot-extruded polyethylene-reinforced fiber composite rod cables are rod strand bundles formed by bundling multiple reinforced fiber composite rods (1) in parallel and lightly twisting them, and are construction and bridge cable products obtained by hot-extruding polyethylene onto the surface layer (2) of the strand bundle. Reinforced fiber composite rods are composed of a substrate (e.g., epoxy resin), reinforcing fibers (e.g., carbon fibers), and the interface between the two, and the performance of the rods is determined by the volume ratio of the reinforcing fibers to the substrate and the performance of the constituent parts. This application provides support with relevant basic data for the application of cables in projects by showing a method for predicting their coefficient of linear thermal expansion, taking into account their structure and constituent materials.

Description

[Technical Field]

[0001] The present invention relates to a method for predicting the coefficient of linear thermal expansion of reinforced fiber composite rods and hot-extruded polyethylene rod cables. [Background technology]

[0002] Hot-extruded polyethylene carbon fiber reinforced composite rod cables for bridges are constructed by lightly twisting multiple carbon fiber reinforced composite rods to form a bundle of carbon fiber rods, and then hot-extruding high-density polyethylene to form a protective layer. The magnitude of the coefficient of linear expansion reflects the dimensional stability of the member in high-temperature environments; the smaller the coefficient of linear expansion, the higher the dimensional stability of the member at high temperatures, and the smaller the thermal stress generated, the better the dimensional stability of the member during temperature changes. Currently, the Changtai Yangtze River Bridge, the world's largest, is a multi-functional composite bridge with a main span of 1208 meters. Because of its large main span, long main girders, and tall towers, the wind load effect increases dramatically. To reduce the wind load effect, longitudinal restraint devices are installed between the tower girders. When this longitudinal restraint device is installed, in the case of wind loads along the bridge, most of the wind load is transmitted to the tower from the longitudinal restraint portion of the tower girder at the bridge deck, and the load acting arm is only at the height of the lower pylon, so the bending moment of the tower and the displacement of the bridge girder end generated by the wind load are greatly reduced. However, the longitudinal restraint of the tower girder limits the release of thermal deformation of the steel girder in the center of the span when the system temperature changes, generating a fairly large thermal stress. To reduce the thermal stress, the Changtai Bridge is the first in the world to adopt hot-extruded polyethylene carbon fiber reinforced composite rod cables with a relatively small coefficient of linear expansion as the horizontal restraint cables for the tower girder. These cables undergo ultra-high tensile testing in the factory before being installed on site, and have the advantages of high strength, light mass, stable structural dimensions, and ease of installation. The coefficient of thermal expansion is a crucial central parameter for the horizontal cables of the Changtai Bridge. To accurately determine this parameter, it is necessary to present a method for predicting the coefficient of thermal expansion of the relevant hot-extruded polyethylene carbon fiber reinforced composite rod cables and provide support with fundamental data related to the application of CFRP horizontal cables in the project.

[0003] Carbon fiber reinforced composite rods are advanced composite materials that achieve reinforcement through carbon fibers and their structure. They are non-uniform in their microstructure and have a clear interface between the carbon fibers and the substrate. Carbon fibers are composed of over 90% carbon. While diamond has the most regularly arranged carbon atoms, the structure of carbon fibers is closer to that of graphite, and is slightly less regular than that of diamond. They are primarily produced by removing elements other than carbon from organic fibers that have no melting point at high temperatures through solid-phase carbonization. Carbon fibers belong to a random-layer graphite structure or graphite structure. When heated, carbon atoms in the graphite layer vibrate back and forth in the vertical direction of the layer, causing expansion, and contraction occurs in the layer direction due to this vertical vibration. The higher the degree of graphitization of the carbon fibers, the smaller the coefficient of linear expansion. These characteristics mean that CFRP rod composite materials have multiple smaller coefficients of linear expansion than ordinary steel, ensuring good dimensional stability, unaffected by ambient temperature, and reducing the temperature stress of related components in environments where CFRP horizontal cables are used. However, since carbon fibers themselves are axially symmetric and not isotropic, their coefficients of thermal expansion differ in each direction, resulting in anisotropy in the coefficient of thermal expansion of CFRP rod composite materials. The axial coefficient of thermal expansion of carbon fiber composite materials is directly correlated with the coefficient of thermal expansion and elastic modulus of the carbon fibers, the coefficient of thermal expansion and elastic modulus of the resin substrate, and the volume content of carbon fibers and resin substrate. Of these, the coefficient of thermal expansion, elastic modulus, and volume content of carbon fibers have a considerable influence on the coefficient of thermal expansion of CFRP rods. Generally, CFRP rods have a relatively small coefficient of thermal expansion in the axial direction (parallel to the carbon fibers) and a relatively large coefficient of thermal expansion in the transverse direction (perpendicular to the carbon fibers).

[0004] On the one hand, the hot extrusion polyethylene carbon fiber reinforced composite bar cable is formed by twisting a plurality of carbon fiber reinforced composite bars. There are also differences in the linear expansion coefficient and elastic modulus of each bar. At the same time, after twisting the bars into a bundle, two layers of high-density polyethylene sheaths are hot extruded on the outer surface. This is a parallel composite mixed structure composed of a carbon fiber reinforced composite bar bundle with different linear expansion coefficients and elastic moduli and a high-density polyethylene sheaths, and the linear expansion coefficient is quite complex.

[0005] To solve the above problems, the present invention presents a method for predicting the linear expansion coefficient of the reinforced fiber composite bar and its hot extrusion polyethylene cable.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] In view of the composition of bar products such as fiber reinforced composite materials and the structure of their hot extrusion polyethylene cables, the inventor of the present application presents a method for predicting their linear expansion coefficients.

[0008] The hot extrusion polyethylene reinforced fiber composite bar cable (hereinafter also abbreviated as cable) is a bar twist bundle formed by bundling a plurality of reinforced fiber composite bars (hereinafter also abbreviated as bars) in parallel and gently twisting them about three times. It is a cable product for construction and bridges obtained by hot extruding polyethylene on the surface layer of the twist bundle.

[0009] Reinforced fiber composite rods are composed of a substrate (e.g., epoxy resin), reinforcing fibers (e.g., carbon fibers), and interfaces between the two. The performance of the rod is determined by the volume ratio of the reinforcing fibers to the substrate and the performance of the constituent parts. The substrate is the continuous phase in the composite material, integrally bonding the reinforcing fibers, giving the composite material a certain shape, transmitting external forces, and protecting the reinforcement from erosion by the external environment. Reinforcing fibers are constituent materials in the composite material that can enhance the mechanical properties of the substrate material, and are an important component of the composite material, playing a role in increasing the strength, toughness, and heat resistance of the composite material. The interface is a minute region between the substrate and the reinforcing fibers where the chemical composition changes significantly, forming a bond between them and performing load transmission functions.

[0010] The technical method of the present invention includes two parts: a method for predicting the coefficient of thermal expansion of a rod and a method for predicting the coefficient of thermal expansion of a cable, which are specifically as follows.

[0011] A method for predicting the coefficient of thermal expansion of a reinforced fiber composite rod, comprising the following steps:

[0012] Step 1: Calculation of the theoretical value of the axial linear expansion coefficient of the rod. The rod material includes reinforcing fibers, a substrate, and their interfaces. The reinforcing fibers are bonded to the substrate, and the reinforcing fibers are continuous fibers. The effect of the interfaces is negligible, and the theoretical value of the linear thermal expansion coefficient of the rod material is α. a The approximate calculation formula is given by equation (1-1) below.

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[0013] In the above-mentioned reinforcing fiber composite bar structure, the combination of the linear expansion coefficients of the carbon fiber tow must be considered. That is, it is agreed that the linear expansion coefficients of the fiber tow in the carbon fiber reinforced composite bar can be made to coincide, so as to prevent the carbon fiber from being cut due to thermal expansion and cold contraction. Also, due to the anisotropic linear expansion coefficient of the carbon fiber composite material, in order to obtain a stable composite structure, in all carbon fiber distributions, its central plane needs to be a symmetry plane.

[0014] Step 2: Considering the influence of the interface, calculate the interface correction coefficient K of the axial linear expansion coefficient of the bar. The interface has a certain thickness (above the nanometer level), and the structure is different due to the matrix and the reinforcing fiber, and it is a new phase - interface phase (also called the interface layer) that is clearly different from the matrix. When the reinforcing fiber and the matrix come into contact with each other, under the influence of certain conditions, chemical reactions or physicochemical actions may occur. For example, due to the mutual diffusion and dissolution of elements between the two phases, a new phase different from the original two phases is generated. Even if reactions, diffusion, and dissolution do not occur, due to the internal stress generated by the solidification and coagulation of the matrix, or the induction effect of the tissue structure, structural changes or changes in deposition density occur in the matrix near the reinforcement, resulting in the performance of this part of the matrix being different from the performance of the matrix body, and thus the interface phase is formed. Although the influence of the above-mentioned interface phase on the performance of the carbon fiber reinforced composite bar cannot be directly calculated, a comparison can be made based on the approximate calculation results and the measured results of the axial linear expansion coefficient theory of the carbon fiber composite material bar, and the interface correction coefficient can be obtained.

[0015] The present invention compares the theoretical value α a of the axial linear expansion coefficient of the bar calculated based on formula (1 - 1) with the measured value α b to obtain the interface correction coefficient K, and K = α b / α a is.

[0016] Step 3: Calculation of the measured value of the axial linear expansion coefficient of the bar The following equation (1-2) is used.

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[0017] Preferably, the reinforcing fiber is a carbon fiber, the substrate is an epoxy resin, and the axial coefficient of thermal expansion of the carbon fiber tow is α at 200°C or below. f1 (-0.1 to -1.0) × 10 -6 The temperature is / ℃, and the coefficient of linear expansion of epoxy resin is 30-80 × 10⁻⁶. -6 The temperature is / ℃, the axial tensile modulus of the carbon fiber filament is 160-290 GPa, the tensile modulus of the epoxy resin is 1.5-4.5 GPa, and the volume ratio of carbon fiber is 60-80%.

[0018] Preferably, in step 2, the method for obtaining the interface correction coefficient K of the axial linear expansion coefficient of the rod material is as follows.

[0019] Step 2.1: Measure the axial linear expansion coefficient and tensile modulus of the reinforced fiber tow. When the reinforcing fiber is carbon fiber tow, the axial linear expansion coefficient test is performed according to T / CSTM 00251-2020 - "Test Method for Average Axial Linear Expansion Coefficient of Carbon Fibers: Pushrod Differential Method". The axial tensile modulus is performed according to GB T3362-2017 - "Test Method for Tensile Performance of Carbon Fiber Multifilament". Since carbon fiber is tow fiber, each bundle consists of thousands or tens of thousands of individual fibers. However, the significance of the axial linear expansion coefficient and tensile modulus of individual fibers is not large, so the entire bundle of carbon fiber is tested, and the number of fibers in the test fiber bundle matches that of the actual rod material to determine the axial linear expansion coefficient and axial tensile modulus of the carbon fiber tow.

[0020] Step 2.2: Measure the coefficient of linear expansion and tensile modulus of the substrate. The coefficient of linear thermal expansion of the substrate is tested according to ASTM E831-14, "Test method for measuring linear thermal expansion of solid materials using thermomechanical analysis," and the tensile modulus of elasticity of the substrate is tested according to GB / T 2567-2008, "Test method for performance of resin castings."

[0021] Step 2.3: Calculate the volume ratio of reinforcing fibers in the rod. Since the lengths of the reinforcing fibers are the same, the volume ratio is the ratio of the cross-sectional area of ​​the reinforcing fibers on the cross-section of the rod to the cross-sectional area of ​​the rod, and the calculation process is as follows. The ratio of cross-sectional areas of reinforcing fibers = (cross-sectional area of ​​one reinforcing fiber * number of filaments in one bundle * number of bundles) / cross-sectional area of ​​the rod. For example, if a 7mm carbon fiber rod consists of 31 carbon fiber bundles, and each carbon fiber bundle contains 24,000 carbon fiber filaments with a diameter of 7 microns, The volume ratio = cross-sectional area ratio = area of ​​one carbon fiber filament * number of filaments in one bundle * number of bundles = 0.007 * 0.007 * 24000 * 31 / 49 = 74.4%.

[0022] Step 2.4: Calculate the theoretical value of the axial linear expansion coefficient of the bar material based on equation (1-1).

[0023] Step 2.5: Prototype the rod material. Prototype production will be carried out using the pultrusion process. Reinforcement fibers immersed in the substrate are passed through a standard mold and heated to solidify, obtaining a sample that matches the actual rod material composition and specifications.

[0024] Step 2.6: Test the coefficient of thermal expansion using several rod samples obtained in Step 2.5. The measured axial coefficient of thermal expansion is α bThe test is conducted in accordance with GB / T2572-2005 "Test Method for Average Linear Expansion Coefficient of Fiber-Reinforced Plastics". The average linear expansion coefficient refers to the average value of the relative change in sample length corresponding to a 1°C temperature change between temperatures T1 and T2. The test method involves uniformly heating the sample using a pushrod differential linear expansion coefficient tester and controlling the rate of temperature rise of the sample to accurately measure the change in sample temperature and the corresponding change in sample length, drawing an expansion curve associated with the temperature change, calculating the average linear expansion coefficient of the straight portion of the curve, or calculating the average linear expansion coefficient within a certain temperature interval upon request.

[0025] Step 2.7: The interface correction coefficient K is α b / α a That is the case.

[0026] [Table 1]

[0027] A method for predicting the coefficient of linear thermal expansion of hot-extruded polyethylene-reinforced fiber composite rod cables, A cable is a bundle of twisted rods formed by bundling multiple rods in parallel and twisting them together. A sheath is formed by hot-extruding polyethylene onto the surface of the twisted bundle, and the method for predicting the linear thermal expansion coefficient of the cable is as follows.

[0028] Step 1: Calculation of the axial linear expansion coefficient of a bundle of rods without considering torsion.

[0029] Step 1.1: Determine the volume ratio of the rods in the cable. Since the diameter of each rod is the same, its volume is the average value, and in a cable consisting of n carbon fiber reinforced composite rods, the volume ratio of one carbon fiber reinforced composite rod is 1 / n.

[0030] Step 2.2: Determine the axial linear expansion coefficient and tensile modulus of n rods in the order of α1 and E1, α2 and E3, α n and E n Measure up to this point.

[0031] Step 2.3: Axial linear expansion coefficient α of a bundle of rods without considering torsion h Calculation The formula is as follows:

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[0032] Step 2: Calculation of the radial thermal expansion coefficient of a twisted bundle of rods. The theoretical formula for calculating the coefficient of lateral linear expansion of a bundle of bar materials is as follows:

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[0033] Step 3: Axial linear expansion coefficient α of the rod bundle considering torsion. c Calculation α c =α h cosθ+α v sinθ Here, θ is the angle of twist.

[0034] Step 4, Axial linear expansion coefficient α of the cable considering hot-extruded polyethylene k Calculate The formula is as follows:

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[0035] Preferably, the radial tensile modulus of the reinforcing fiber in step 2 is 6% of the axial tensile modulus.

[0036] Preferably, the axial mean elastic modulus E of the rod material. c This involved taking a set of five rods, with the reinforcing fibers of the rods being carbon fibers. The axial tensile modulus of elasticity was measured according to T3362-2017 "Test Method for Tensile Performance of Carbon Fiber Multifilament," and then the average value was taken. [Brief explanation of the drawing]

[0037] [Figure 1] This is a cross-sectional view of the hot-extruded polyethylene carbon fiber reinforced composite rod cable of the present invention. [Figure 2] This is a cross-sectional view of the carbon fiber reinforced composite rod material of the present invention. [Figure 3] This is a cross-sectional view of the carbon fiber reinforced composite rod bundle of the present invention. [Figure 4] This is a schematic diagram illustrating the calculation of the axial thermal expansion coefficient of a bundle of rods, taking torsion into consideration.

[0038] In the diagram, 1 is a carbon fiber reinforced composite rod, 2 is an outer polyethylene sheath, 2' is an inner polyethylene sheath, 101 is a carbon fiber tow, and 102 is epoxy resin. [Modes for carrying out the invention]

[0039] The present invention is described in more detail below in conjunction with examples; however, the examples described are illustrative and intended for interpretation of the present invention, and should not be considered as limitations on the invention.

[0040] Taking a hot-extruded polyethylene carbon fiber reinforced composite rod cable with 127 strands of Φ7mm as an example, the process for predicting its coefficient of thermal expansion is as follows.

[0041] Step 1: The calculation process for predicting the axial thermal expansion coefficient per carbon fiber reinforced composite rod is as follows.

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[0042] The calculation process and results for the coefficient of thermal expansion of each carbon fiber rod constituting the cable are shown in the table below.

[0043] [Table 2] JPEG2026512766000010.jpg233157JPEG2026512766000011.jpg234157JPEG20265127660 00012.jpg233159JPEG2026512766000013.jpg236161JPEG2026512766000014.jpg198164

[0044] Step 2: Calculate the axial linear expansion coefficient of a bundle of carbon fiber reinforced composite rods, without considering the torsional angle, based on the following formula.

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[0045] Calculation of the axial linear thermal expansion coefficient of a bundle of carbon fiber reinforced composite rods without considering the torsional angle. α h = 0.23 × 10 -6 / ℃

[0046] Step 3: Calculation of the radial thermal expansion coefficient of carbon fiber reinforced composite rod bundles While carbon fibers have low coefficients of thermal expansion in the axial direction, their coefficient of thermal expansion in the radial direction is relatively large and generally positive. Therefore, the coefficient of thermal expansion in the lateral direction of carbon fiber reinforced composite rods is also considerably large, and the theoretical calculation formula is as follows.

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[0047] Based on the above theory, the coefficient of lateral linear expansion of a bundle of carbon fiber reinforced composite rods, without considering the torsional angle, is calculated as α v = 2.65 × 10 -6 It is / ℃.

[0048] Step 4: Axial linear thermal expansion coefficient of carbon fiber reinforced composite rod bundles considering the twist angle The above torsional angles are summarized, and the calculation results for the axial linear expansion coefficient of the carbon fiber reinforced composite rod bundle, taking the torsional angles into consideration, are as follows. α c =α h cosθ+α v sinθ = 0.36 × 10 -6 / ℃ Here, θ is the twist angle of the hot-extruded polyethylene carbon fiber reinforced composite rod cable, and is 3 degrees.

[0049] Step 5: After considering the influence of the high-density polyethylene sheath, the axial linear expansion coefficient of the hot-extruded polyethylene carbon fiber reinforced composite rod cable is calculated, specifically as follows.

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[0050] Considering all the factors, the calculation results for the axial linear expansion coefficient of a hot-extruded polyethylene carbon fiber reinforced composite rod cable, taking into account a high-density polyethylene sheath, are as follows. α k k = 0.55 × 10 -6 / ℃ [Explanation of symbols]

[0051] 1 is a carbon fiber reinforced composite rod, 2 is an outer polyethylene sheath, 2' is an inner polyethylene sheath, 101 is a carbon fiber tow, 102 is an epoxy resin.

Claims

1. A method for predicting the coefficient of linear thermal expansion of a reinforced fiber composite rod, comprising the following steps 1, 2, and 3, namely, Step 1 is to calculate the theoretical value of the axial linear expansion coefficient of a rod, The rod material includes reinforcing fibers, a substrate, and their interfaces. The reinforcing fibers are bonded to the substrate, and the reinforcing fibers are continuous fibers. The effect of the interfaces is negligible, and the theoretical value of the linear thermal expansion coefficient of the rod material is α. ａ The approximate calculation formula is given by the following equation (1-1): [Math 1] During the ceremony, α ａ - Theoretical value of the coefficient of linear expansion in the axial direction of the rod material, i.e., in the direction parallel to the reinforcing fibers. α ｆ１ - Axial linear expansion coefficient of reinforced fiber tow, α ｅ - Substrate's coefficient of linear expansion, E ｆ１ - Axial tensile modulus of reinforcing fiber, E ｅ - Tensile modulus of the substrate, V ｆ - Volume ratio of reinforcing fibers, Step 1 is, Step 2 involves calculating the interface correction coefficient K of the axial linear expansion coefficient of the rod material, taking into account the influence of the interface, The theoretical value α of the axial linear expansion coefficient of the bar calculated based on Equation (1-1) ａ and the measured value α ｂ are compared, and Step 2 of calculating the interface correction coefficient K by K = α ｂ / α ａ and Step 3 involves calculating the measured value of the axial linear expansion coefficient of the rod material, The calculation formula is as follows (1-2): [Math 2] During the ceremony, α ｈ - Measured value of the axial linear expansion coefficient of the rod material, K-interface correction coefficient, Step 3 is, A method for predicting the coefficient of linear thermal expansion of a reinforced fiber composite rod, characterized by including the following:

2. The reinforcing fiber is a carbon fiber, the substrate is an epoxy resin, and the axial linear expansion coefficient of the carbon fiber tow is α ｆ１ (-0.1 to -1.0) × 10 at temperatures below 200°C －６ The temperature is / °C, and the coefficient of linear expansion of epoxy resin is 30 to 80 × 10⁻⁶. －６ A method for predicting the linear expansion coefficient of a reinforced fiber composite rod according to claim 1, characterized in that the temperature is / °C, the axial tensile modulus of the carbon fiber filament is 160 to 290 GPa, the tensile modulus of the epoxy resin is 1.5 to 4.5 GPa, and the volume ratio of carbon fiber is 60% to 80%.

3. In step 2, the procedure for obtaining the interface correction coefficient K of the axial linear expansion coefficient of the rod material is as follows: Step 2.1 for measuring the axial linear expansion coefficient and tensile modulus of a reinforced fiber tow, wherein if the reinforced fiber is a carbon fiber tow, the test for the axial linear expansion coefficient is performed according to T / CSTM 00251-2020 - "Test Method for Average Axial Linear Expansion Coefficient of Carbon Fibers: Pushrod Differential Method", and the test for the axial tensile modulus is performed according to GB T3362-2017 "Test Method for Tensile Performance of Carbon Fiber Multifilament", the test is performed on a whole bundle of carbon fibers, the number of fiber bundles for the test is matched to the number of wire bundles of the actual rod material, and Step 2.1 for determining the axial linear expansion coefficient and axial tensile modulus of the carbon fiber tow, Step 2.2 involves measuring the coefficient of linear expansion and the tensile modulus of elasticity of the substrate, Step 2.2 involves testing the linear thermal expansion coefficient of the substrate according to ASTM E831-14 "Test method for measuring linear thermal expansion of solid materials using thermomechanical analysis," and testing the tensile modulus of the substrate according to GB / T 2567-2008 "Test method for performance of resin castings," Step 2.3 is to calculate the volume ratio of reinforcing fibers in the rod, and since the lengths of the reinforcing fibers are the same, the volume ratio is the ratio of the cross-sectional area of ​​the reinforcing fibers on the cross-section of the rod to the cross-sectional area of ​​the rod, and the calculation process is, Step 2.3 states that the ratio of the cross-sectional areas of the reinforcing fibers = (cross-sectional area of ​​one reinforcing fiber * number of filaments in one bundle * number of bundles) / cross-sectional area of ​​the rod, Step 2.4 involves calculating the theoretical value of the axial linear expansion coefficient of the rod based on equation (1-1), Step 2.5 involves prototyping a rod material, wherein the prototyping is carried out by a pultrusion process, in which reinforcing fibers immersed in a base material are passed through a standard mold, heated and solidified to obtain a sample that matches the actual rod material composition and specifications. The linear thermal expansion coefficient was tested on several rod samples obtained in step 2.5, and the measured axial linear thermal expansion coefficient was α ｂ The test is performed in step 2.6, based on GB / T2572-2005 "Test Method for Average Linear Expansion Coefficient of Fiber-Reinforced Plastics," The interface correction coefficient K is α ｂ / α ａ Step 2.7 is, A method for predicting the coefficient of linear expansion of a reinforced fiber composite rod according to claim 1, characterized by including the following:

4. In a method for predicting the coefficient of linear thermal expansion of hot-extruded polyethylene-reinforced fiber composite rod cables, The cable is a bundle of twisted rods formed by bundling multiple rods in parallel and twisting them together, with polyethylene hot-extruded onto the surface of the twisted bundle to form a sheath. The prediction method includes the following steps 1, 2, 3, and 4, namely, In step 1, which calculates the axial linear expansion coefficient of a bundle of rods without considering torsion, Step 1.1 determines the volume ratio of the rods in the cable, where each rod has the same diameter, so its volume is an average value, and in a cable consisting of n carbon fiber reinforced composite rods, the volume ratio of one carbon fiber reinforced composite rod is 1 / n. The axial linear expansion coefficient and tensile elastic modulus of n rods are given by α １ and E １ , α ２ and E ２ In that order, α ｎ and E ｎ Steps 1 and 2 measure up to, Axial linear thermal expansion coefficient α of a bundle of rods without considering torsion ｈ Step 1.3 for calculating, [Math 3] During the ceremony, α ｋ This is the coefficient of linear thermal expansion per rod, E ｋ Step 1.3 is the axial elastic modulus per rod, Step 1 comprises, Step 2 is to calculate the radial thermal expansion coefficient of a twisted bundle of rods, The theoretical formula for calculating the coefficient of lateral linear expansion of a bundle of bar materials is as follows: [Math 4] During the ceremony, v ｆ The Poisson ratio of the reinforcing fiber, v ｅ The Poisson's ratio of the substrate material, α ｆ２ The radial thermal expansion coefficient of the reinforcing fiber is E ｆ２ The radial tensile modulus of the reinforcing fiber is V ｆ This is the volume fraction of the reinforcing fiber. Step 2 is, Axial linear expansion coefficient α of a bundle of rods considering torsion ｃ Step 3 is to calculate, a ｃ =a ｈ ὂ὏ὂθ+α ｖ synth Here, θ is the angle of twist, in step 3, Axial linear thermal expansion coefficient α of a cable considering hot-extruded polyethylene ｋ Step 4 of the calculation, [Math 5] Here, α ｋ The coefficient of axial linear expansion of the cable is α ｃ This is the axial linear expansion coefficient of a bundle of rods, taking into account the twist angle. E ｃ The axial mean elastic modulus of the rod material is V ｃ This is the volume ratio of the carbon fiber reinforced composite rod bundle to the carbon fiber reinforced composite rod cable cord. α Ｐ This refers to the axial linear expansion coefficient of a polyethylene sheath, measured according to GB / T1036 "Method for Measuring the Linear Expansion Coefficient of Plastics". E Ｐ This is the axial tensile modulus of the polyethylene sheath, as measured by GB / T-1040.1 "Measurement of Plastic Tensile Performance". Step 4 is, A method for predicting the coefficient of linear expansion of a hot-extruded polyethylene-reinforced fiber composite rod cable, characterized by including the following:

5. A method for predicting the linear expansion coefficient of a hot-extruded polyethylene-reinforced fiber composite rod cable, characterized in that the radial tensile modulus of the reinforcing fiber in step 2 is 6% of the axial tensile modulus.

6. The axial mean modulus of elasticity E of a rod ｃ A method for predicting the linear expansion coefficient of a hot-extruded polyethylene-reinforced fiber composite rod cable, characterized in that a set of five rods is taken, the reinforcing fibers of the rods are carbon fibers, the axial tensile modulus of elasticity is measured based on T3362-2017 "Test Method for Tensile Performance of Carbon Fiber Multifilament", and then the average value is taken.

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