A method for determining the normalized treatment of the interface parameters between fibers and matrix

Abstract

This invention discloses a normalization method for determining the interface parameters between fibers and a matrix, comprising: conducting material-level tests and interface pull-out tests on fiber-matrix composite materials to record the force-displacement curves during the interface pull-out tests; establishing an equivalent finite element model based on the interface pull-out tests; and simulating the calculation formulas for interface parameters according to the test results of the interface pull-out tests within the finite element model to normalize the interface parameters. This method allows for direct comparison of pull-out test results for different sizes and materials, and evaluation of the interface performance of different materials. The normalized interface finite element model obtained by this invention is applicable to finite element calculations of fiber / matrix composite materials of various sizes and materials. It can apply the test result parameters obtained under experimental conditions to various complex finite element models, without being limited by mesh size or geometric dimensions, thus solving the problem that the evaluation results of existing performance evaluation methods are not applicable to changes in test dimensions.

Description

Technical Field

[0001] This invention belongs to the technical field of evaluating the basic physical properties of composite materials, specifically relating to a normalization method for determining the interface parameters between fibers and the matrix. Background Technology

[0002] Since the strength of a single matrix is ​​often insufficient to meet the strength requirements of certain structures, fibers are added to the matrix to provide reinforcement. Examples of common fiber / matrix composites include tires and carbon fiber ceramics. The strength of fiber / matrix composites depends not only on the material parameters of the fibers and matrix themselves, but also on the interfacial bonding performance between the fibers and the matrix. Composites with good interfacial bonding performance can maximize the function of each material component, achieving a synergistic effect greater than the sum of its parts (1+1>2).

[0003] In evaluating the interfacial properties of fibers / matrix, the commonly used method in engineering is the fiber / matrix pull-out test, with pull-out force used as an indicator of interfacial performance. However, pull-out force varies with the size of the specimen, so even for the same material, different specimen sizes will lead to different test conclusions. Therefore, this calculation method has significant limitations in the experimental evaluation of interfacial properties.

[0004] Furthermore, for some complex composite material structures, it is necessary to establish a finite element model to calculate and evaluate their performance. The most common method is to divide the pull-out force by the area of ​​the interface to obtain the average shear stress, and then input the average shear stress as an interface parameter into the finite element model. However, for most materials, the distribution of shear stress at the interface is not uniform, and there is usually stress concentration. Therefore, this method also has a large error. Summary of the Invention

[0005] This invention provides a normalization method for determining the interface parameters between fibers and matrix, in order to solve the problem that the evaluation results of existing performance evaluation methods are not applicable to changes in test dimensions.

[0006] A normalization method for determining interface parameters between fibers and a matrix, the method comprising the steps of:

[0007] S100. Perform material-level tests on fiber-matrix composite materials to obtain material parameters of the fiber and matrix; and conduct interface pull-out tests to record the force-displacement curves during the interface pull-out test process;

[0008] S200. An equivalent finite element model is established based on the interface pull-out test. Within the finite element model, the calculation formula of the interface parameters is simulated according to the test results of the interface pull-out test to normalize the interface parameters. This allows for direct comparison of pull-out test results of different sizes and materials, and evaluation of the interface performance of different materials.

[0009] Furthermore, during the simulation process within the finite element model, at least three sets of interface pull-out test results with different sample sizes are required. Each set of interface pull-out tests includes multiple fiber matrix composite samples with the same geometric dimensions.

[0010] Furthermore, the process of normalizing the interface parameters described in S200 is as follows:

[0011] S201. Establish a finite element model based on the sample size and test conditions for the interface pull-out test;

[0012] S202. Establish an interface model between the fiber and the matrix within the finite element model, and normalize the interface parameters of the interface model to the maximum interface stress T. max and the maximum relative displacement δ of the interface max ;

[0013] S203. Based on the results of the interface pull-out test, perform surface fitting on the interface parameters of the interface model, and confirm the unique solution of the interface parameters that can make the interface model results and the interface pull-out test results match.

[0014] Furthermore, the finite element model established in S201 can selectively establish the entire finite element model or a half of the finite element model.

[0015] Furthermore, in S202, within the interface model between the fiber and the matrix, a cohesive unit with zero thickness is set.

[0016] Furthermore, in S203, after the surface fitting, the formula for the unique solution of the interface parameters is:

[0017]

[0018] In the formula, the maximum stress at the interface is T max Interface failure displacement δ max T is a function of the pull-out force F, the pull-out displacement ΔL, and the sample size C, respectively. When parameters F, ΔL, and C change, T... max δ max It remains unchanged.

[0019] Furthermore, in S203, during the surface fitting process, considering the stress concentration effect at the interface edge, the maximum interface stress T maxIt is greater than the ratio of the pull-out force F to the interface area S.

[0020] Furthermore, the specific content of S100 is as follows:

[0021] S101. Conduct separate mechanical property tests on the fibers and matrix that make up the fiber-matrix composite material to determine the mechanical parameters of the fibers and matrix in the fiber-matrix composite material;

[0022] S102. Prepare samples of fiber matrix composite materials, conduct interface pull-out tests, and record the force-displacement curves during the pull-out process.

[0023] Furthermore, the process of the interface pull-out test is as follows: the sample includes two parallel substrates with a gap and a fiber that penetrates the two substrates and has an exposed section in the gap between the substrates. The ends of the two substrates are fixed, and the fixed ends of the substrates are used as the pull-out direction. A uniformly moving load is applied along the pull-out direction until the fiber between the two substrates is pulled out. The pull-out force and pull-out displacement during the pull-out process are recorded, and a force-displacement curve is plotted.

[0024] Furthermore, the fiber matrix composite material is selected as a rubber cord composite material. In the pull-out test of the rubber cord composite material, the calculation formula for the interface parameters is as follows, based on finite element model analysis:

[0025]

[0026] In the formula, C represents the matrix thickness and r represents the fiber radius.

[0027] Furthermore, the interface parameters of samples of the same type but with different compositions and sizes can be calculated using the aforementioned interface parameter formula to evaluate the interface properties of samples of the same type but with different compositions and sizes. The procedure is as follows:

[0028] Two fiber matrix composite samples a and b, which are of the same type but have different compositions and unknown material and interface parameters, have different matrix thicknesses C1 and C2, respectively.

[0029] Pull-out tests of the same specifications were conducted on two fiber matrix composite samples a and b, and the corresponding pull-out forces and pull-out displacements were obtained respectively.

[0030] The experimental results are imported into the interface parameter formula to obtain the corresponding interface parameters. By comparing the interface parameters, the interface properties of two fiber matrix composite samples a and b of the same type but with different composition formulations and unknown material and interface parameters can be evaluated.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The normalization method for determining the interface parameters between fibers and the matrix provided by this invention is applicable to variations in sample size after the interface parameters are normalized. Therefore, no further testing is required when the sample size changes. Furthermore, the evaluation of interface performance is not limited by sample size, and pull-out test results of different sizes and materials can be directly compared to assess the interface performance of different materials.

[0033] 2. The normalized interface finite element model obtained by the normalization processing method in this invention is applicable to finite element calculation of fiber / matrix composite materials of various sizes and materials. It can apply the test result parameters obtained from the test conditions to various complex finite element models without being limited by mesh size or geometric dimensions. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0035] Figure 1 This is a flowchart of the normalization process for determining the interface parameters between the fiber and the matrix in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the H-shaped specimen used in the fiber / matrix pull-out test in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the boundary conditions of the symmetric finite element model in an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the basic mechanical behavior curves of the cohesive unit interface used in the embodiments of the present invention:

[0039] Figure 5 This is a schematic diagram of the shape of the interface mechanical behavior curve of the cohesive unit in an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of the interface parameter fitting process of the cohesive unit in Embodiment 1 of the present invention;

[0041] Figure 7 This is a comparison chart of the results obtained by the normalization method in Embodiment 1 of the present invention and the results obtained by the traditional method;

[0042] Figure 8 This is a flowchart comparing the test sample results of different formulations and sizes obtained based on the normalization method in Embodiment 1 of the present invention.

[0043] The numbers in the diagram are: 1-matrix material, 2-fiber, 3-interface between fiber and matrix. Detailed Implementation

[0044] 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.

[0045] To overcome the limitations of sample size, the results are transformed into parameters that can be directly used for calculations in the finite element model, such as... Figure 1 As shown, this invention discloses a normalization method for determining the interface parameters between fibers and a matrix, the method comprising the following steps:

[0046] S100. Perform material-level tests on the fiber-matrix composite material to obtain the material parameters of the fiber and the matrix; and conduct an interface pull-out test to record the force-displacement curve during the interface pull-out test.

[0047] "Materials-level testing" refers to conducting separate mechanical property tests on the fibers and matrix of fiber-matrix composite materials. This is preparatory work before conducting the "interface pull-out test." The "interface pull-out test" is a test performed on fiber-matrix composite materials to assess the interfacial bonding performance between the fibers and the matrix. Therefore, its specific content is as follows:

[0048] S101. Conduct separate mechanical property tests on the fibers and matrix that make up the fiber-matrix composite material to determine the mechanical parameters of the fibers and matrix in the fiber-matrix composite material;

[0049] S102. Prepare samples of fiber matrix composite materials, conduct interface pull-out tests, and record the force-displacement curves during the pull-out process in conjunction with the mechanical parameters from the material-level tests.

[0050] In one embodiment, the interface pull-out test process is as follows: Figure 2 As shown, the sample includes two parallel substrates with a gap and a fiber that penetrates the two substrates and has an exposed section in the gap between the substrates. The ends of the two substrates are fixed, and a uniformly moving load is applied along the pulling direction with the fixed end of the substrate as the pulling direction until the fiber between the two substrates is pulled out. The pulling force and pulling displacement during the pulling process are recorded, and the force-displacement curve is plotted.

[0051] It should be noted that the interface pull-out test given in this embodiment is mainly for providing modeling data for establishing a finite element model. Other types of interface pull-out tests, if they are also for providing data for establishing a finite element model, are within the protection scope of this invention.

[0052] S200. An equivalent finite element model is established based on the interface pull-out test. Within the finite element model, the calculation formula of the interface parameters is simulated according to the test results of the interface pull-out test to normalize the interface parameters. This allows for direct comparison of pull-out test results of different sizes and materials, and evaluation of the interface performance of different materials.

[0053] The interface parameter normalization process includes the normalization of the interface model selection and the normalization of the interface parameters. The specific process is as follows:

[0054] S201. Based on the sample size and test conditions for the interface pull-out test, a finite element model is established, which can selectively establish the entire finite element model or half of the finite element model.

[0055] If the test loading conditions have symmetrical mechanical properties, a semi-three-dimensional finite element model of the specimen can be established to save computational effort.

[0056] like Figure 3 As shown, in Figure 2 In one embodiment, the upper and lower sides of the substrate 1 can be set as fixed boundaries, and a displacement load is applied to one end of the fiber 2.

[0057] S202. Establish an interface model between the fiber and the matrix within the finite element model, and normalize the interface parameters of the interface model to the maximum interface stress T. max and the maximum relative displacement δ of the interface max .

[0058] like Figure 3 As shown, in this embodiment, a microscopic interface equivalent model 3 needs to be established between the matrix 1 and the fiber 2. Considering the normalization requirement, the interface 3 is uniformly set as a cohesive element with a thickness of 0. Its mechanical behavior curve is shown in the figure. Figure 4 As shown, when the interface is subjected to a certain stress, the elements on both sides of the interface will produce relative displacement. The entire curve is divided into two stages: an ascending segment and a descending segment. In the ascending segment, the interface stiffness K remains constant, while in the descending segment, the interface stiffness continuously softens until the relative displacement of the interface reaches its maximum value δ. max The unit is then deemed damaged.

[0059] Depend on Figure 4 It can be seen that the main control parameters in the curve are T. max δ max And K, their geometric meanings are respectively Figure 4The height, base length, and slope of the left hypotenuse of the triangle formed by the mid-curves are given. In this invention, K is normalized: based on a certain number of simulation iterations, it can be verified that when T... max With δ max When K remains constant, it can fluctuate within a certain range. However, the only parameters obtained in the pull-out test are the pull-out force F and the pull-out displacement ΔL. That is, F and ΔL are two independent dependent variables, and T... max With δ max Only when K is used as two independent variables can a unique solution for the interface parameters be obtained. Therefore, in order to exclude K, the shape of the triangle must always be an isosceles triangle, i.e., K = 2T. max / δ max ,like Figure 5 As shown, this achieves the goal of reducing the number of independent variables. Thus, by using zero-thickness cohesive elements in the interface model, the multiple independent variable parameters of the interface model are reduced to two, namely the maximum interface stress T. max Maximum relative displacement δ at the interface max .

[0060] S203. Based on the results of the interface pull-out test, perform surface fitting on the interface parameters of the interface model, and confirm the unique solution of the interface parameters that can make the interface model results and the interface pull-out test results match.

[0061] Based on the normalization parameter processing in step S202, the independent variables of the finite element model include the maximum interface stress T. max and the maximum relative displacement δ of the interface max There are two dependent variables: the pull-out force F and the pull-out displacement ΔL. The latter two parameters are obtained from experiments. By fitting them together, we can solve for the unique solution of the interface parameters.

[0062] When the sample size changes, the interface parameters have a unique solution, i.e., the normalized calculation formula for the interface parameters, obtained through finite element fitting:

[0063]

[0064] In the formula, the maximum stress at the interface is T max Interface failure displacement δ max T is a function of the pull-out force F, the pull-out displacement ΔL, and the sample size C, respectively. When parameters F, ΔL, and C change, T... max δ max It remains unchanged. Moreover, through testing and verification of rubber and cord composite materials, changing the size of the sample does not change the applicability of the same set of interface parameters.

[0065] During curve fitting, the model deformation exhibits the following quantitative relationships:

[0066] ΔL=δmax +Δl 基体 +Δl1+Δl2 (2)

[0067] Where Δl 基体 Δl1 and Δl2 represent the axial deformation of the rubber, the deformation of the exposed fiber section, and the deformation of the fiber embedded in the matrix, respectively.

[0068] It should be noted that during the simulation process within the finite element model, at least three sets of interface pull-out test results with different sample sizes are required. Each set of interface pull-out tests includes multiple fiber-matrix composite material samples with the same geometric dimensions. For example, the matrix thickness of the first set of samples is 5 mm, the matrix thickness of the second set of samples is 8 mm, and the matrix thickness of the third set of samples is 10 mm.

[0069] That is, the sample size is the same within each group, but the sample size is different between each group. The conditions of the pull-out test of multiple groups of interfaces are the same, so different F and ΔL can be obtained. This makes the surface fitting in the interface model based on the test results of samples of different sizes, so as to ensure that the obtained interface parameter formula is applicable to samples of different sizes. In this way, the same interface parameters are obtained for samples of different sizes within the same interface parameter formula.

[0070] Furthermore, during fiber pull-out, the distribution of shear stress at the interface is not uniform across the entire interface, exhibiting a certain degree of stress concentration. Simulation results and literature review confirm that the shear stress in the stress concentration region is significantly greater than in other areas of the interface. Therefore, it can be approximated that during fiber pull-out, the local interface in the stress concentration region shares most of the shear stress. Consequently, in the curve fitting process of the finite element model, the maximum stress at the interface and the average stress at the interface during pull-out have the following unequal relationship:

[0071]

[0072] In the above formula, S is the area of ​​the entire interface, and the ratio of the pull-out force F to the interface area S is the average stress of the interface during pull-out. According to the stress concentration effect mentioned above, the interface area involved in most of the work should be smaller than the area S of the entire interface. Therefore, the above formula (3) holds true. By adding a condition setting for the maximum stress of the interface during the curve fitting process of the finite element model, the fitting error is reduced, which solves the problem of large error caused by directly inputting the average shear stress as an interface parameter into the finite element model in the prior art.

[0073] This invention employs a normalized interface model, applicable to various fiber / matrix composite material interfaces. It allows parameters obtained from experimental conditions to be applied to complex finite element models, unaffected by mesh size or geometric dimensions. Furthermore, this invention provides formulas for the corresponding normalized calculation of interface parameters, enabling a direct comparison of pull-out test results for different sizes and materials, and allowing for the evaluation of interface performance. This method is applicable to a variety of materials, offers accurate calculations, and has a wide range of applications, providing a basis for the study of the mechanical properties of fiber-reinforced composite materials.

[0074] Example 1

[0075] To further illustrate the normalization method for determining the interface parameters between fibers and matrix disclosed in this invention, Example 1 is provided. In this example, the fiber matrix composite material is selected as rubber cord composite material.

[0076] like Figure 2 As shown, the specimen is an H-shaped specimen, consisting of two substrates 1 and a fiber 2 that penetrates both substrates 1 and has an exposed section in the middle between the substrates 1. During the pull-out test, a special clamp is used to fix the same end of the substrate 1, and the clamp at one end is controlled to move at a constant speed along the pull-out direction until the fiber 2 is completely pulled out from either substrate 1. The force-displacement curve during this process is recorded.

[0077] Based on the fitting of experimental results to the finite element model and theoretical support, a formula for normalizing the calculation of interface parameters is given based on the pull-out test results of specimens of different sizes:

[0078]

[0079] In the formula, C represents the matrix thickness and r represents the fiber radius.

[0080] Figure 6 and Figure 7 This figure illustrates a comparison between the interface parameters obtained through normalization and those obtained using conventional methods when dealing with varying sample sizes. In this embodiment, the horizontal axis C represents the matrix thickness, and r represents the fiber radius. Figure 6 The right vertical axis t represents the average stress at the interface when the fiber is pulled out. It can be seen that when the sample size changes, the normalization method provided by this invention can make the evaluation of interface properties more accurate, regardless of the sample size d.

[0081] In addition, the interface parameters of samples of the same type but with different compositions and sizes can be calculated using formula (1) to evaluate the interface properties of samples of the same type but with different compositions and sizes.

[0082] The phrase "same type but different formulations" means: The matrix of both composite materials is rubber, but sample a is natural rubber while sample b is a type of synthetic rubber; or the matrix of both composite materials is resin, but sample a and sample b use different resin formulations. Material variations are not limited to the matrix; the same applies to fibers. For example, sample a uses No. 66 nylon fiber, while sample b uses No. 56 fiber. These all fall under the category of "same type but different formulations," but their interfacial parameter formulas are the same. Figure 8 The process of using Equation (1) to calculate the interface parameters of samples of the same type but with different compositions and sizes, and comparing and evaluating the interface performance, is demonstrated.

[0083] In conjunction with this embodiment, it can be achieved through Figure 8 The process shown uses the interface parameter formula (4) to directly compare the performance of the interface, since the core essence of interface performance evaluation is formula (1).

[0084] The specific process is as follows: two fiber / matrix composite material samples, a and b, with unknown material parameters and interface parameters, are tested. Samples a and b are of the same type but have different compositions and different matrix thicknesses C1 and C2, respectively. Pull-out tests of the same specifications are performed on them to obtain the corresponding pull-out force and pull-out displacement. At this time, due to the inconsistent sample sizes, it is not possible to directly judge the quality of the interface performance of the two materials by comparing the magnitude of the pull-out force. Therefore, the test results are applied to the normalization formula (4) to obtain the corresponding interface parameters. The quality of the interface performance can be evaluated by comparing the interface parameters.

[0085] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A normalization method for determining the interface parameters between fibers and a matrix, characterized in that, The method includes the following steps: S100. Perform material-level tests on fiber-matrix composite materials to obtain material parameters of the fiber and matrix; and conduct interface pull-out tests to record the force-displacement curves during the interface pull-out test process; Among them, material-level testing refers to conducting separate mechanical property tests on the fibers and matrix that make up the fiber-matrix composite material; The interface pull-out test is a test conducted on the fiber-matrix composite material to test the interfacial bonding performance between the fiber and the matrix. S200. An equivalent finite element model is established based on the interface pull-out test. Within the finite element model, the calculation formula of the interface parameters is simulated according to the test results of the interface pull-out test to normalize the interface parameters. This allows for direct comparison of pull-out test results of different sizes and materials, and evaluation of the interface performance of different materials. The interface parameter mentioned in S200 is the maximum interface stress T. max and the maximum relative displacement δ of the interface max For the maximum stress T at the interface max and the maximum relative displacement δ of the interface max The normalization process is as follows: S201. Establish a finite element model based on the sample size and test conditions for the interface pull-out test; S202. Establish an interface model between the fiber and the matrix within the finite element model, and normalize the interface parameters of the interface model to the maximum interface stress T. max and the maximum relative displacement δ of the interface max ; S203. Based on the results of the interface pull-out test, perform surface fitting on the interface parameters of the interface model, and confirm the unique solution of the interface parameters that can make the interface model results and the interface pull-out test results match. In S203, after surface fitting, the formula for the unique solution of the interface parameters, i.e., the formula for the interface parameters, is: ； In the formula, the maximum stress at the interface Tmax and the interface failure displacement δmax are functions of the pull-out force F, the pull-out displacement ΔL, and the matrix thickness C, respectively. When the parameters F, ΔL, and C change, Tmax and δmax remain unchanged.

2. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, During the simulation process within the finite element model, at least three sets of interface pull-out test results with different sample sizes are required. Each set of interface pull-out tests includes multiple fiber matrix composite samples with the same geometric dimensions.

3. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, The finite element model established in S201 can selectively establish the entire finite element model or half of the finite element model.

4. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, In S202, within the interface model between the fiber and the matrix, a cohesive unit with a thickness of 0 is set.

5. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, During the surface fitting process of S203, considering the stress concentration effect at the interface edge, the maximum interface stress T max It is greater than the ratio of the pull-out force F to the interface area S.

6. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, The specific content of S100 is as follows: S101. Conduct separate mechanical property tests on the fibers and matrix that make up the fiber-matrix composite material to determine the mechanical parameters of the fibers and matrix in the fiber-matrix composite material; S102. Prepare samples of fiber matrix composite materials, conduct interface pull-out tests, and record the force-displacement curves during the pull-out process.

7. The normalization method for determining the interface parameters between fibers and matrix according to claim 6, characterized in that, The interface pull-out test process is as follows: The sample includes two parallel substrates with a gap and a fiber that penetrates the two substrates and has an exposed section in the gap between the substrates. The ends of the two substrates are fixed, and the fixed ends of the substrates are used as the pull-out direction. A uniformly moving load is applied along the pull-out direction until the fiber between the two substrates is pulled out. The pull-out force and pull-out displacement during the pull-out process are recorded, and the force-displacement curve is plotted.

8. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, The fiber matrix composite material is selected as rubber cord composite material. In the pull-out test of the rubber cord composite material, the calculation formula for the interface parameters is as follows, based on finite element model analysis: ； In the formula, C represents the matrix thickness and r represents the fiber radius.

9. The normalization method for determining the interface parameters between fibers and matrix according to claim 1, characterized in that, The interface parameters of samples of the same type but with different compositions and sizes can be calculated using the aforementioned interface parameter formula to evaluate the interface properties of samples of the same type but with different compositions and sizes. The procedure is as follows: Two fiber matrix composite samples a and b, which are of the same type but have different compositions and unknown material and interface parameters, have different matrix thicknesses C1 and C2, respectively. Pull-out tests of the same specifications were conducted on two fiber matrix composite samples a and b, and the corresponding pull-out forces and pull-out displacements were obtained respectively. The experimental results are imported into the interface parameter formula to obtain the corresponding interface parameters. By comparing the interface parameters, the interface properties of two fiber matrix composite samples a and b of the same type but with different composition formulations and unknown material and interface parameters can be evaluated.

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