Method for quantifying and optimizing anisotropy of a continuous fiber reinforced composite rod

Abstract

This invention proposes a method for quantifying and optimizing the anisotropy coefficient of continuous fiber-reinforced composite rods. The quantification method includes calculating the correlation parameters between the axial ultimate / yield tensile strength, axial compressive strength, and transverse shear strength of the composite rod, and calculating the anisotropy coefficient of the composite rod based on the correlation parameters between the strengths. This method can clearly define the degree of anisotropy of the fiber composite rod, providing a theoretical basis and practical value for engineering structural design. The optimization method includes using hybrid fibers as the reinforcing phase to prepare the composite rod, wherein the hybrid fibers are composed of high-modulus carbon fibers and low-modulus glass fibers or basalt fibers; and modifying the matrix resin of the composite rod with nanofillers, wherein the nanofillers are graphene, single-walled carbon nanotubes, or multi-walled carbon nanotubes. This can effectively reduce the anisotropy coefficient of the fiber composite rod, allowing the performance of the fiber composite rod to be fully utilized and improving the utilization efficiency of the component materials.

Description

Technical Field

[0001] This invention relates to the field of continuous fiber reinforced composite materials, and in particular to a method for quantifying and optimizing the anisotropy coefficient of fiber composite rods. Background Technology

[0002] Reinforced concrete structures are a major structural form in civil engineering. However, steel corrosion leads to cracking and spalling of the concrete cover, resulting in a decrease in structural stiffness and load-bearing capacity, significantly reducing the service life of structures. Common methods for preventing steel corrosion include galvanizing, painting, applying epoxy coatings, and wrapping with composite material layers. However, these methods cannot solve the problem of steel corrosion. Therefore, there is an urgent need for a new material to replace steel bars and fundamentally solve the problem of steel corrosion in reinforced concrete structures.

[0003] Continuous fiber reinforced composite (CFRP) rods are a new type of material similar to steel bars, steel anchors, and steel strands, made by using continuous fibers as the reinforcing phase and polymer resin as the matrix phase, through pultrusion-winding processes and multi-stage high-temperature curing. They possess advantages such as lightweight, high strength, corrosion resistance, fatigue resistance, non-magnetization, and designable strength, and are considered potential replacements for metal rods. However, the mechanical properties of CFRP rods differ along and perpendicular to the continuous fiber direction. For example, the tensile strength along the continuous fiber direction is 2-4 times its compressive strength, and 4-6 times its shear strength perpendicular to the continuous fiber direction. Compared to isotropic steel products, CFRP rods are anisotropic materials in civil engineering. Taking CFRP bars as an example, the anisotropy of the material means that concrete member designs often use the lower transverse shear strength of the CFRP bars as a reference for reinforcement, inevitably resulting in a significant waste of the tensile strength of the CFRP bars along the continuous fiber direction. Currently, there is no quantitative evaluation of the anisotropy coefficient of CFRP rods. Meanwhile, the anisotropy problem of composite rods made from single fibers is particularly prominent. Although glass fiber and basalt fiber composite rods have extremely high tensile strength and low cost, their elastic modulus is low. Using them to reinforce concrete members easily leads to wide cracks and significant deformation, affecting the normal serviceability of concrete structures. Similarly, carbon fiber composite rods have extremely high tensile strength and an elastic modulus close to that of steel bars, but their cost is high and their ultimate strain is low, making their use in reinforcing concrete members cost-effective. After high-temperature curing, the matrix resin in the composite rod exhibits characteristics such as high brittleness, large shrinkage, and low toughness. Under load, it is prone to internal microcracks, affecting the synergistic stress-bearing effect between the reinforcing fibers, which to some extent leads to a reduction in the axial compressive strength and transverse shear strength of the composite rod. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for quantifying and optimizing the anisotropy coefficient of continuous fiber reinforced composite rods. This method utilizes existing technologies to reduce the differences in mechanical strength across different directions of the composite rod, thereby improving its overall performance and fully leveraging its mechanical properties in reinforcing concrete structures, maximizing material utilization. This has significant theoretical value and guiding significance for promoting the widespread application of continuous fiber reinforced composite rods in civil engineering. Furthermore, it innovatively proposes two methods for reducing the anisotropy coefficient of continuous fiber reinforced composite rods.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for quantifying the anisotropy coefficient of a continuous fiber reinforced composite rod is characterized by calculating the correlation parameters between the axial tensile strength, axial compressive strength and transverse shear strength of the composite rod, and then calculating the anisotropy coefficient of the composite rod based on the correlation parameters between the strengths.

[0007] Furthermore, the axial tensile strength includes the ultimate axial tensile strength of the composite rod or the axial yield tensile strength of the composite rod.

[0008] Furthermore, this includes methods for calculating the anisotropy coefficient based on the axial ultimate tensile strength of composite rods:

[0009] Axial compressive strength based on composite rods and axial ultimate tensile strength Calculate the correlation parameters between the axial compressive strength and the axial ultimate tensile strength of composite rods. ;

[0010] Based on the transverse shear strength of composite rods and axial ultimate tensile strength Calculate the correlation parameters between the transverse shear strength and the axial ultimate tensile strength of composite rods. ;

[0011] Based on the transverse shear strength of composite rods and axial compressive strength Calculate the correlation parameters between the transverse shear strength and axial compressive strength of composite rods. ;

[0012] Based on correlation parameters Correlation parameters and correlation parameters Calculate the anisotropy coefficient based on the axial ultimate tensile strength of the composite rod:

[0013] ;

[0014] Where n is a subscript number; when n=1, it represents unmodified fiber composite reinforcement; when n=2, it represents graphene-modified fiber composite reinforcement.

[0015] Furthermore, this includes methods for calculating the anisotropy coefficient based on the axial yield tensile strength of composite rods:

[0016] Based on the transverse shear strength of composite rods and axial compressive strength Calculate the correlation parameters between the transverse shear strength and axial compressive strength of composite rods. ;

[0017] Axial compressive strength based on composite rods and axial yield tensile strength Calculate the correlation parameters between the axial compressive strength and axial yield tensile strength of composite rods. ;

[0018] Based on the transverse shear strength of composite rods and axial yield tensile strength Calculate the correlation parameters between the transverse shear strength and axial yield tensile strength of composite rods. ;

[0019] Based on correlation parameters Correlation parameters and correlation parameters Calculate the anisotropy coefficient based on the axial yield tensile strength of the composite rod:

[0020] ;

[0021] Wherein, when n=1, it represents unmodified fiber composite reinforcement; when n=2, it represents graphene-modified fiber composite reinforcement.

[0022] Furthermore, the composite material rod is a glass fiber composite material rod, a carbon fiber composite material rod, a basalt fiber composite material rod, an aramid fiber composite material rod, or a brittle fracture hybrid fiber composite material rod.

[0023] Furthermore, the composite material rod is a hybrid fiber composite material rod that undergoes plastic failure.

[0024] A method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod is disclosed. The method involves preparing the composite rod using hybrid fibers as the reinforcing phase and then using the method for quantifying the anisotropy coefficient of the continuous fiber reinforced composite rod to quantitatively evaluate the prepared composite rod. The hybrid fibers are composed of carbon fibers and glass fibers or basalt fibers.

[0025] Furthermore, the fiber mixing ratio of the carbon fiber satisfies:

[0026] ;

[0027] Wherein, V1 is the volume fraction of carbon fiber, V2 is the volume fraction of glass fiber or basalt fiber, E1 is the elastic modulus of carbon fiber, E2 is the elastic modulus of glass fiber or basalt fiber, ε1 is the elongation of carbon fiber, and ε2 is the elongation of glass fiber or basalt fiber.

[0028] A method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod involves modifying the matrix resin of the composite rod with nanofillers to prepare the composite rod, and then using the method for quantifying the anisotropy coefficient of the continuous fiber reinforced composite rod to quantitatively evaluate the prepared composite rod. The nanofillers are graphene, single-walled carbon nanotubes, or multi-walled carbon nanotubes.

[0029] Furthermore, the amount of nanofiller is no more than 0.5%.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention proposes a method for quantifying the anisotropy coefficient of fiber composite rods and an optimization technique for reducing their anisotropy. Based on the proposed anisotropy coefficient quantification method, the difference in mechanical strength of fiber composite rods along different directions, i.e., the degree of anisotropy, can be clearly and intuitively determined, providing a reference for the application of fiber composite rods in civil engineering structural design. Simultaneously, the proposed optimization method for reducing the anisotropy of composite rods not only fundamentally solves the problems of brittle failure and cost-effectiveness imbalance in conventional composite rods, but is also simple to operate and highly effective, which can actively promote the widespread application of fiber composite rods in the field of civil engineering. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1Explanation of the abbreviation symbols for fiber composite reinforcement.

[0034] Figure 2 The stirring process for uniformly dispersing graphene in bisphenol A epoxy vinyl resin.

[0035] Figure 3 The tensile stress-strain curves of unmodified fiber composite reinforcements are shown in (a) for glass fiber reinforcements, (b) for hybrid fiber reinforcements with different carbon / glass ratios, and (c) for hybrid fiber reinforcements with different volume fractions.

[0036] Figure 4 The anisotropy coefficient of unmodified fiber composite reinforcement based on ultimate tensile strength is shown in (a) for fiber composite reinforcement with different carbon / glass ratios and (b) for hybrid fiber composite reinforcement with different volume fractions.

[0037] Figure 5 The anisotropy coefficient of unmodified fiber composite reinforcement based on yield tensile strength is shown in (a) for fiber composite reinforcement with different carbon / glass ratios and (b) for hybrid fiber composite reinforcement with different volume fractions.

[0038] Figure 6 The tensile stress-strain curves of graphene-modified fiber composite reinforcements are shown in Figure 1. (a) is a glass fiber reinforcement, (b) is a hybrid fiber reinforcement with different carbon / glass ratios, and (c) is a hybrid fiber reinforcement with different volume fractions.

[0039] Figure 7 The anisotropy coefficient of graphene-modified fiber composite reinforcement based on ultimate tensile strength is shown as the variation trend of the anisotropy coefficient compared with that of unmodified fiber composite reinforcement. (a) represents fiber composite reinforcement with different carbon / glass ratios, and (b) represents hybrid fiber composite reinforcement with different volume fractions.

[0040] Figure 8 The anisotropy coefficient of graphene-modified fiber composite reinforcement based on yield tensile strength is shown as the variation trend of the anisotropy coefficient compared with that of unmodified fiber composite reinforcement. (a) represents fiber composite reinforcement with different carbon / glass ratios, and (b) represents hybrid fiber composite reinforcement with different volume fractions. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] A method for quantifying the anisotropy coefficient of a continuous fiber reinforced composite rod is provided, which employs an anisotropy coefficient quantification method based on ultimate tensile strength, as detailed below:

[0044] Based on the definition of anisotropy and key mechanical properties of engineering materials, the axial ultimate tensile strength, axial compressive strength, and transverse shear strength of composite rods are selected as the main performance parameters. The following method for quantifying the anisotropy coefficient of composite rods is formulated:

[0045] (1);

[0046] in: (2);

[0047] In the formula: R u The anisotropy coefficient is based on the axial ultimate tensile strength of the composite bar; n is a subscript number; when n=1, it represents an unmodified fiber composite bar; when n=2, it represents a graphene-modified fiber composite bar.

[0048] N1 represents the correlation between the axial compressive strength and the axial ultimate tensile strength of the composite rod.

[0049] N2 represents the correlation between the transverse shear strength and the axial ultimate tensile strength of the composite rod.

[0050] N3 represents the correlation between the transverse shear strength and axial compressive strength of the composite rod.

[0051] σ t u The axial ultimate tensile strength (MPa) of the composite rod;

[0052] σ c The axial compressive strength (MPa) of the composite rod;

[0053] τ t The transverse shear strength (MPa) of the composite rod.

[0054] Example 2

[0055] A method for quantifying the anisotropy coefficient of a continuous fiber reinforced composite rod, employing the method for quantifying the anisotropy coefficient of yield tensile strength, is as follows:

[0056] Based on the definition of anisotropy and key mechanical properties of engineering materials, the axial yield tensile strength, axial compressive strength, and transverse shear strength of composite rods are selected as the main performance parameters. The following method for quantifying the anisotropy coefficient of composite rods is formulated:

[0057] (3);

[0058] in: (4);

[0059] In the formula: Ry is the anisotropy coefficient based on the axial yield tensile strength of the composite bar; n is a subscript number; when n=1, it represents an unmodified fiber composite bar; when n=2, it represents a graphene-modified fiber composite bar.

[0060] N3 represents the correlation between the transverse shear strength and axial compressive strength of the composite rod.

[0061] N4 represents the correlation between the axial compressive strength and the axial yield tensile strength of the composite rod.

[0062] N5 represents the correlation between the transverse shear strength and axial yield tensile strength of the composite rod.

[0063] σ t y The axial yield tensile strength (MPa) of the composite rod;

[0064] σ c The axial compressive strength (MPa) of the composite rod;

[0065] τ t The transverse shear strength (MPa) of the composite rod.

[0066] Specifically, for conventional composite material rods, such as glass fiber composite rods, carbon fiber composite rods, basalt fiber composite rods, aramid fiber composite rods, and hybrid fiber composite rods with brittle fracture, Example 1 is used to quantify their anisotropy coefficients. For hybrid fiber composite rods with plastic fracture, both Example 1 and Example 2 can be used to quantify their anisotropy coefficients according to engineering design requirements.

[0067] Example 3

[0068] A method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod is proposed. This method considers replacing some glass fibers or basalt fibers with carbon fibers to prepare hybrid fiber composite rods, thereby improving the overall performance of conventional composite rods and achieving plastic failure. This increases the elastic modulus with minimal cost increase, generates a tensile stress-strain yield plateau similar to that of steel bars, obtains tensile yield strength, and reduces the difference between axial tensile strength, axial compressive strength, and transverse shear strength, thus reducing the anisotropy of conventional composite rods.

[0069] To achieve the above design goals, in this embodiment of the application, the composite material rod is prepared by changing the fiber angle of the reinforcing phase, using hybrid fibers as the reinforcing phase. The hybrid fibers are composed of high-modulus carbon fibers and low-modulus glass fibers or basalt fibers; the fiber mixing ratio of the carbon fibers satisfies:

[0070] (5)

[0071] Wherein, V1 is the volume fraction of carbon fiber, V2 is the volume fraction of glass fiber or basalt fiber, E1 is the elastic modulus of carbon fiber, E2 is the elastic modulus of glass fiber or basalt fiber, ε1 is the elongation of carbon fiber, and ε2 is the elongation of glass fiber or basalt fiber.

[0072] Example 4

[0073] This invention discloses a method for optimizing the anisotropy coefficient of continuous fiber reinforced composite rods. Based on the force mechanism of the matrix resin providing lateral support during axial compression and transverse shear in the composite rod, the method considers modifying the matrix resin of the composite rod with nanofillers. Utilizing toughening mechanisms such as crack deflection, resin yielding, crazing, or pinning, the energy dissipation capacity of the matrix resin is improved, while its stiffness is increased. This enhances the synergistic force-bearing effect between the reinforcing fibers and improves the resistance to lateral deformation under external loads, thereby increasing the axial compressive strength and transverse shear strength of the composite rod and reducing the difference between them and the axial tensile strength, thus achieving the goal of reducing anisotropy. However, the incorporation of nanofillers does not significantly increase the viscosity of the matrix resin, nor does it reduce the resin's ability to impregnate the fibers. To obtain better toughening effects, the dosage of conventional nanofillers such as nano-SiO2, Al2O3, TiO2, ZnO, and CaCO3 in modifying the polymer resin is typically 5.0% to 20.0%, which inevitably increases the viscosity of the matrix resin, hindering the synergistic force-bearing effect between the fibers.

[0074] Therefore, in this embodiment of the application, from the perspective of improving the matrix resin of the composite fiber rod, the matrix resin of the composite rod is modified with nanofillers. By utilizing their large specific surface area and stiffness, the matrix resin can be significantly reinforced and toughened at a low dosage, while basically not increasing the economic cost of the composite rod. The nanofillers are graphene, single-walled carbon nanotubes or multi-walled carbon nanotubes, and the dosage of the nanofillers is not greater than 0.5%.

[0075] Experimental verification:

[0076] The following examples of glass fiber composite reinforcement bars, carbon / glass hybrid fiber composite reinforcement bars, graphene-modified glass fiber composite reinforcement bars, and graphene-modified carbon / glass hybrid fiber composite reinforcement bars clearly and completely describe the anisotropy coefficient quantification method and optimization technique for reducing the anisotropy coefficient proposed in this invention. The feasibility of the quantification method and optimization technique is verified using experimental results. The material types and performance parameters of the various fiber composite reinforcement bars prepared in the examples are shown in Table 1, and the performance parameters of the selected graphene nanoparticles are shown in Table 2.

[0077] Table 1 Performance parameters of component materials

[0078]

[0079] Table 2 Performance parameters of nano-graphene

[0080]

[0081] First, the experimental design schemes for the glass fiber composite reinforcement, carbon / glass hybrid fiber composite reinforcement, graphene-modified glass fiber composite reinforcement, and graphene-modified carbon / glass hybrid fiber composite reinforcement in the embodiments are shown in Tables 3 and 4. Based on equation (5) and the performance parameters of the component materials in Table 1, the critical carbon / glass ratio for achieving plastic failure and exhibiting a tensile stress-strain yield plateau in the carbon / glass hybrid fiber composite reinforcement was calculated to be 1:4.3. Therefore, the carbon / glass ratios selected in the experimental schemes were 0:1, 1:8, 1:6, and 1:4 to prepare glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement with concentrated carbon fiber distribution. When the carbon / glass ratio remained constant at 1:6, the total fiber integral was taken as 50%, 60%, and 70%, respectively. Furthermore, studies on the modification properties (tensile, compression, flexural, and fracture toughness) of the matrix resin (bisphenol A epoxy vinyl ester resin) of fiber composite reinforcements with different amounts of graphene nanoparticles (0, 0.1%, 0.3%, and 0.5%) revealed that when the amount of graphene nanoparticles was 0.3%, the viscosity of the matrix resin was not significantly altered, and the impregnation effect of the modified resin on the fiber surface was not affected. Moreover, the reinforcing and toughening effect of the graphene-modified resin was significantly improved at this concentration. Therefore, in this case study, a 0.3% (by mass) amount of graphene nanoparticles was used to modify bisphenol A epoxy vinyl ester resin to prepare graphene-modified glass fiber composite reinforcements and carbon / glass hybrid fiber composite reinforcements with concentrated distribution of graphene nanoparticles. A commercially available 10-liter dual planetary high-speed shear disperser was used to uniformly disperse the graphene nanoparticles in the bisphenol A epoxy vinyl ester resin. The dispersion process followed... Figure 2 The mixing system established in China has been completed. Figure 1 The abbreviations for fiber composite reinforcement in Table 3 are explained. All fiber composite reinforcements were prepared using a pultrusion-winding process.

[0082] Table 3 Design schemes for unmodified fiber composite reinforcement

[0083]

[0084] Table 4 Design schemes for graphene-modified fiber composite reinforcement

[0085]

[0086] Referring to standards ASTM D7205, ASTM D695 and GB / T13683, axial tensile, compression and transverse shear tests were performed on the unmodified glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement designed in Table 3. The test results are shown in Table 5.

[0087] Table 5. Results of tensile, compressive, and transverse shear tests on unmodified fiber composite reinforcement.

[0088]

[0089] at the same time, Figure 3 (ac) presents the stress-strain curves of unmodified glass fiber reinforcement and carbon / glass hybrid fiber composite reinforcement under axial tensile load. Figure 3 (a) indicates that the stress-strain relationship of glass fiber composite reinforcement under tensile load exhibits a linear elastic development trend until tensile failure. However, the stress-strain relationship of hybrid fiber composite reinforcement prepared according to the carbon / glass ratio determined by equation (5) under axial tensile load exhibits a nonlinear development trend, mainly manifested as a linear elastic segment, a yield plateau segment, and a strengthening segment, such as... Figure 3 As shown in (bc). This result verifies that hybrid fiber composite reinforcement designed based on fiber composite theory can solve the primary problem of brittle failure during tensile stress in conventional fiber composite reinforcement.

[0090] Furthermore, Example 3 was verified according to the method of Example 1.

[0091] Based on the test results of ultimate tensile strength, compressive strength and transverse shear strength in Table 5, and combined with the quantitative method of the anisotropy coefficient of fiber composite reinforcement using equations (1) and (2), the final calculated results of the anisotropy coefficients of unmodified glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement are shown in Table 6.

[0092] Table 6 Anisotropy coefficients of unmodified fiber-reinforced composite reinforcements based on ultimate tensile strength

[0093]

[0094] Based on the quantitative results of the anisotropy coefficient of the unmodified fiber composite reinforcement in Table 6, it can be found that the glass fiber composite reinforcement has the largest anisotropy coefficient. However, through "Example 3: Reducing Anisotropy by Using Fiber Hybridization," the anisotropy coefficient of the glass fiber composite reinforcement shows varying degrees of reduction, such as... Figure 4As shown in (a). For example, as the carbon-glass ratio increases from 0:1 to 1:8, 1:6, and 1:4, the anisotropy coefficient of the glass fiber composite reinforcement decreases by 3.77%, 9.28%, and 9.75%, respectively. However, when the hybrid fiber volume ratio remains constant and the total fiber fraction is changed, the anisotropy coefficient of the unmodified fiber composite reinforcement shows an increasing trend. For example, when the carbon-glass ratio remains constant at 1:6, increasing the total fiber fraction from 50% to 60% and 70% increases the anisotropy coefficient of the unmodified carbon / glass hybrid fiber composite reinforcement by 0.17% and 18.3%, respectively. Figure 4 As shown in (b). Therefore, the above results verify that when the total fiber integral is kept constant, the fiber hybridization method can effectively reduce the anisotropy coefficient of conventional fiber composite reinforcement, and the improvement of the anisotropy coefficient is more obvious as the hybridization ratio increases.

[0095] Furthermore, Example 3 was verified according to the method of Example 2.

[0096] Based on the test results of yield tensile strength, compressive strength and transverse shear strength in Table 5, and combined with the quantitative method of anisotropy coefficient of fiber composite reinforcement using equations (3) and (4), the final calculated results of anisotropy coefficient of unmodified glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement are shown in Table 7.

[0097] Table 7 Anisotropy coefficients of unmodified fiber-reinforced composite reinforcements based on yield tensile strength

[0098]

[0099] Based on the quantitative results of the anisotropy coefficient of the unmodified fiber composite reinforcement in Table 7, it can be found that the glass fiber composite reinforcement has the largest anisotropy coefficient. However, through "Example 3: Reducing Anisotropy by Using Fiber Hybridization," the anisotropy coefficient of the glass fiber composite reinforcement shows varying degrees of reduction, such as... Figure 5 As shown in (a). For example, as the carbon-glass ratio increases from 0:1 to 1:8, 1:6, and 1:4, the anisotropy coefficient of the glass fiber composite reinforcement decreases by 8.35%, 9.68%, and 4.68%, respectively, with an average decrease of 7.57%. However, when the hybrid fiber volume ratio remains constant and the total fiber fraction is changed, the anisotropy coefficient of the unmodified fiber composite reinforcement shows an increasing trend. For example, when the carbon-glass ratio remains constant at 1:6, increasing the total fiber fraction from 50% to 60% and 70% increases the anisotropy coefficient of the unmodified carbon / glass hybrid fiber composite reinforcement by 3.24% and 28.05%, respectively. Figure 5As shown in (b). Therefore, the above results verify that when the total fiber integral is kept constant, the fiber hybridization method can effectively reduce the anisotropy coefficient of conventional fiber composite reinforcement, and the anisotropy coefficient shows an improvement trend of first decreasing and then increasing as the hybridization ratio increases.

[0100] Referring to standards ASTM D7205, ASTM D695 and GB / T13683, axial tensile, compression and transverse shear tests were performed on the graphene-modified glass fiber composite tendons and carbon / glass hybrid fiber composite tendons designed in Table 4. The test results are shown in Table 8.

[0101] Table 8. Results of tensile, compressive, and transverse shear tests on graphene-modified fiber composite reinforcement.

[0102]

[0103] at the same time, Figure 6 (ac) presents the stress-strain curves of graphene-modified glass fiber reinforcement and carbon / glass hybrid fiber composite reinforcement under axial tensile load. Figure 6 (a) indicates that the stress-strain relationship of glass fiber composite reinforcement under tensile load exhibits a linear elastic development trend until tensile failure. However, the stress-strain relationship of hybrid fiber composite reinforcement prepared according to the carbon / glass ratio determined by equation (5) under axial tensile load exhibits a nonlinear development trend, mainly manifested as a linear elastic segment, a yield plateau segment, and a strengthening segment, such as... Figure 6 As shown in (bc). It is worth noting that the addition of graphene makes the yield stage of the carbon / glass hybrid fiber composite tendon more stable, and the key mechanical properties (elastic modulus, yield strength, and ultimate strength) are also improved to varying degrees. Similarly, this result once again proves that hybrid fiber composite tendons designed based on fiber composite theory can solve the primary problem of brittle fracture during tensile testing of conventional fiber composite tendons.

[0104] Furthermore, Example 4 was verified according to the method of Example 1.

[0105] Based on the test results of ultimate tensile strength, compressive strength and transverse shear strength in Table 5, and combined with the quantitative methods of formula (1) and (2) for the anisotropy coefficient of fiber composite reinforcement, the final calculated results of the anisotropy coefficients of graphene modified glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement are shown in Table 9.

[0106] Table 9 Anisotropy coefficients of graphene-modified fiber composite reinforcements based on ultimate tensile strength

[0107]

[0108] A comparison of the anisotropy coefficients of unmodified fiber composite reinforcements in Table 6 and those of graphene-modified fiber composite reinforcements in Table 9 reveals that the addition of nano-graphene filler effectively reduces the anisotropy coefficient of the fiber composite reinforcements. As the carbon-glass ratio increases from 0:1 to 1:8, 1:6, and 1:4, the anisotropy coefficients of graphene-modified fiber composite reinforcements decrease by 9.43%, 9.97%, 15.25%, and 11.85% respectively compared to unmodified fiber composite reinforcements, with an average reduction of 11.63%. Figure 7 As shown in (a). However, when the hybrid fiber volume ratio remains constant and the total fiber fraction is changed, the anisotropy coefficient of the graphene-modified fiber composite reinforcement also shows a decreasing trend compared to the unmodified fiber composite reinforcement. For example, when the carbon-glass ratio remains constant at 1:6, and the total fiber fraction increases from 50% to 60% and 70%, the anisotropy coefficient of the graphene-modified carbon / glass hybrid fiber composite reinforcement decreases by 6.94%, 15.25%, and 13.66% respectively compared to the unmodified fiber composite reinforcement, with an average decrease of 11.95%. Figure 7 As shown in (b). Therefore, the above results verify that the addition of graphene effectively reduces the anisotropy coefficient of the fiber composite reinforcement.

[0109] Example 4 was verified according to the method in Example 2.

[0110] Based on the test results of yield tensile strength, compressive strength and transverse shear strength in Table 5, and combined with the quantitative method of anisotropy coefficient of fiber composite reinforcement using equations (3) and (4), the final calculated results of anisotropy coefficient of graphene modified glass fiber composite reinforcement and carbon / glass hybrid fiber composite reinforcement are shown in Table 10.

[0111] Table 10 Anisotropy coefficients of graphene-modified fiber composite reinforcements based on yield tensile strength

[0112]

[0113] A comparison of the anisotropy coefficients of unmodified fiber composite reinforcements in Table 7 and those of graphene-modified fiber composite reinforcements in Table 10 reveals that the addition of nano-graphene filler effectively reduces the anisotropy coefficient of the fiber composite reinforcements. As the carbon-glass ratio increases from 0:1 to 1:8, 1:6, and 1:4, the anisotropy coefficients of graphene-modified fiber composite reinforcements decrease by 19.03%, 10.57%, 17.56%, and 15.59% respectively compared to unmodified fiber composite reinforcements, with an average reduction of 15.69%. Figure 8As shown in (a). However, when the hybrid fiber volume ratio remains constant and the total fiber fraction is changed, the anisotropy coefficient of the graphene-modified fiber composite reinforcement also shows a decreasing trend compared to the unmodified fiber composite reinforcement. For example, when the carbon-glass ratio remains constant at 1:6, and the total fiber fraction increases from 50% to 60% and 70%, the anisotropy coefficient of the graphene-modified carbon / glass hybrid fiber composite reinforcement decreases by 7.25%, 17.56%, and 16.85% respectively compared to the unmodified fiber composite reinforcement, with an average decrease of 13.89%. Figure 8 As shown in (b). Therefore, the above results verify that the addition of graphene effectively reduces the anisotropy coefficient of the fiber composite reinforcement.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for quantifying the anisotropy coefficient of a continuous fiber reinforced composite rod, characterized in that, Based on the axial tensile strength, axial compressive strength and transverse shear strength of the composite rod, the correlation parameters between each strength are calculated, and the anisotropy coefficient of the composite rod is calculated based on the correlation parameters between each strength.

2. The method for quantifying the anisotropy coefficient of continuous fiber reinforced composite rods according to claim 1, characterized in that, The axial tensile strength includes the ultimate axial tensile strength of the composite rod or the axial yield tensile strength of the composite rod.

3. The method for quantifying the anisotropy coefficient of continuous fiber reinforced composite rods according to claim 2, characterized in that, This includes methods for calculating the anisotropy coefficient based on the axial ultimate tensile strength of composite rods: Axial compressive strength based on composite rods and axial ultimate tensile strength Calculate the correlation parameters between the axial compressive strength and the axial ultimate tensile strength of composite rods. ; Based on the transverse shear strength of composite rods and axial ultimate tensile strength Calculate the correlation parameters between the transverse shear strength and the axial ultimate tensile strength of composite rods. ; Based on the transverse shear strength of composite rods and axial compressive strength Calculate the correlation parameters between the transverse shear strength and axial compressive strength of composite rods. ; Based on correlation parameters Correlation parameters and correlation parameters Calculate the anisotropy coefficient based on the axial ultimate tensile strength of the composite rod: ； Where n is a subscript number; when n=1, it represents unmodified fiber composite reinforcement; when n=2, it represents graphene-modified fiber composite reinforcement.

4. The method for quantifying the anisotropy coefficient of continuous fiber reinforced composite rods according to claim 2, characterized in that, This includes methods for calculating the anisotropy coefficient based on the axial yield tensile strength of composite rods: Based on the transverse shear strength of composite rods and axial compressive strength Calculate the correlation parameters between the transverse shear strength and axial compressive strength of composite rods. ; Axial compressive strength based on composite rods and axial yield tensile strength Calculate the correlation parameters between the axial compressive strength and axial yield tensile strength of composite rods. ; Based on the transverse shear strength of composite rods and axial yield tensile strength Calculate the correlation parameters between the transverse shear strength and axial yield tensile strength of composite rods. ; Based on correlation parameters Correlation parameters and correlation parameters Calculate the anisotropy coefficient based on the axial yield tensile strength of the composite rod: ； Wherein, when n=1, it represents unmodified fiber composite reinforcement; when n=2, it represents graphene-modified fiber composite reinforcement.

5. The method for quantifying the anisotropy coefficient of continuous fiber reinforced composite rods according to claim 3, characterized in that, The composite material rod is a glass fiber composite material rod, a carbon fiber composite material rod, a basalt fiber composite material rod, an aramid fiber composite material rod, or a hybrid fiber composite material rod that is prone to brittle fracture.

6. The method for quantifying the anisotropy coefficient of continuous fiber reinforced composite rods according to claim 3 or 4, characterized in that, The composite material rod is a hybrid fiber composite material rod that undergoes plastic failure.

7. A method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod, characterized in that, Composite rods were prepared using hybrid fibers as reinforcing phases, and the anisotropy coefficient of the prepared composite rods was quantitatively evaluated using the quantification method of the anisotropy coefficient of the continuous fiber reinforced composite rods. The hybrid fibers consist of carbon fibers and glass fibers or basalt fibers.

8. The method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod according to claim 7, characterized in that, The fiber mixing ratio of the carbon fiber satisfies: ； Wherein, V1 is the volume fraction of carbon fiber, V2 is the volume fraction of glass fiber or basalt fiber, E1 is the elastic modulus of carbon fiber, E2 is the elastic modulus of glass fiber or basalt fiber, ε1 is the elongation of carbon fiber, and ε2 is the elongation of glass fiber or basalt fiber.

9. A method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod, characterized in that, The matrix resin of the composite rod is modified with nanofillers to prepare the composite rod, and the anisotropy coefficient of the prepared composite rod is quantitatively evaluated using the quantification method of the anisotropy coefficient of the continuous fiber reinforced composite rod. The nanofillers are graphene, single-walled carbon nanotubes or multi-walled carbon nanotubes.

10. The method for optimizing the anisotropy coefficient of a continuous fiber reinforced composite rod according to claim 9, characterized in that, The amount of nanofiller is no more than 0.5%.

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