A calculation method for the tensile strength of a carbon fiber metal laminate

Abstract

The present invention relates to a calculation method for the tensile strength of a carbon fiber metal laminate, including: based on the metal volume fraction theory, proposing to predict the tensile strength of the carbon fiber metal laminate by using the proportion of the metal layer thickness, and introducing the strength contribution coefficients of each component; preparing carbon fiber metal laminate specimens with different proportions of the metal layer thickness and conducting tensile experiments, measuring the correlation data between the tensile strength and the proportion of the metal layer thickness and performing curve fitting to obtain the strength contribution coefficients of the metal layer and the carbon fiber layer; determining the relationship between the proportion of the metal layer thickness and the tensile strength of the carbon fiber metal laminate; conducting verification and determining the error range. The present invention improves the traditional metal volume fraction theory and solves the problem that the prediction result is larger than the actual value due to the influence of interface delamination and residual stress not being considered in this theory.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material performance detection, and particularly relates to a calculation method for the tensile strength of a carbon fiber metal laminate. Background Art

[0002] A carbon fiber metal laminate is formed by alternately laminating and compounding high-strength metal thin plates (referred to as metal layers in the present invention) and carbon fiber reinforced resins (referred to as carbon fiber layers in the present invention). It has excellent properties such as low density, high specific strength, impact resistance, and corrosion resistance, and is widely used in fields such as aerospace, military, and transportation, such as the wing skin of the F-27 transport aircraft, the rear cabin skin of the C-17 transport aircraft, the central wing box of the Airbus A380, and the automobile anti-collision beam. Due to the particularity of the service conditions, there are very strict requirements for the mechanical properties of structural components made of carbon fiber metal laminates, and the tensile property is one of the important mechanical properties of carbon fiber metal laminates; therefore, studying the calculation method of the tensile property of carbon fiber metal laminates is of great significance for the design, manufacture, popularization, and application of fiber metal laminates.

[0003] So far, the calculation of the tensile strength of carbon fiber metal laminates mostly adopts the theory of the proportion of metal volume fraction. However, since plastic deformation will occur after the metal thin plate reaches the yield point, the analysis using linear elastic theory is not accurate enough, and this theory does not consider the influence of interface delamination and residual stress, and the prediction results are generally larger than the actual values.

[0004] In the article "Research on the Tensile Properties of Glass Fiber-Aluminum Alloy Orthogonal Laminates" (Wang Yajie et al., Journal of Materials Engineering, Vol. 43, No. 9, September 2015), aiming at the characteristics of glass fiber-aluminum alloy orthogonal laminates, considering the influence of fibers in two ply directions on the overall performance at the same time, and combining the elastic modulus mixing law of composite materials, the prediction formula obtained after correcting the MVF theory is as follows:

[0005] E lam = MVF·E met + a·E FRP1 + b·E FRP2 (1)

[0006]

[0007] In the formula: t is the thickness of the material layer; E is the tensile modulus; σ t is the tensile ultimate strength; σ 0.2is the tensile yield stress; the subscripts lam, met, and FRP1, FRP2 represent the glass fiber-aluminum alloy laminate, aluminum alloy, and 0°, 90° fiber layers, respectively. However, its conclusions include: (1) By comparing the tensile test results of two groups of specimens A and B, it can be obtained that the tensile mechanical properties of the glass fiber-aluminum alloy cross-ply laminate are not affected by the ply sequence and are only related to the volume fractions of the components in each layer; while the tensile failure mode of the material is significantly different due to different fiber ply sequences. During the entire tensile process, delamination is not obvious in specimen A, and significant delamination occurs between the aluminum alloy layer and the fiber layer in specimen B. (2) By considering the volume fractions of fiber plies at various angles and combining the composite mixture law, after modifying the MVF theory, a more accurate theoretical prediction can be made for the tensile properties of the glass fiber-aluminum alloy cross-ply laminate. Therefore, this technical solution is still based on the metal volume fraction theory.

[0008] In the article "Analysis of Tensile Strength of Fiber Metal Hybrid Laminates" (Jiang Shun, Zhao Yao, Ship Science and Technology, Vol. 33, No. 5, January 2011), based on the analysis method of classical laminate theory, the theoretical solution of fiber metal hybrid laminates was extended, and the fiber metal hybrid symmetrically laminated plates were numerically analyzed using finite element method. Comparing with the test values under unidirectional tensile conditions, it is considered that the finite element calculation can meet the requirements of engineering calculations; at the same time, the effects of ply arrangement, metal layer thickness, and metal layer material properties on tensile strength were emphatically discussed, providing a useful reference for the finite element analysis of large and complex structures. In order to study the influence of metal layer thickness on the tensile stress-strain of fiber metal hybrid laminates, the tensile stress-strain relationships of FML (fiber metal hybrid laminates) with Al layer thickness of 0.2 - 0.5 mm were numerically calculated respectively. The ply arrangement is [Al / 0 / 90 / 90 / 0 / Al]. The conclusion is that as the thickness of the Al layer increases, the yield stress point increases proportionally. Thus, it can be seen that the thickness of the metal layer has a great influence on the tensile strength of FML and increases proportionally. Therefore, the overall tensile strength of fiber metal hybrid laminates can be improved by increasing the thickness of the metal layer. However, it does not further elaborate on how to correct and calculate the tensile strength of fiber metal laminates through the proportion of metal layer thickness.

[0009] The present invention improves and modifies the existing metal volume fraction theory, and proposes a calculation method applicable to predicting the tensile strength of carbon fiber metal laminates. Summary of the Invention

[0010] The present invention provides a calculation method for the tensile strength of carbon fiber metal laminates, which improves the traditional metal volume fraction theory and solves the problem that the prediction result is larger than the actual value due to the influence of interface delamination and residual stress not being considered in this theory.

[0011] To achieve the above object, the present invention is implemented by the following technical solutions:

[0012] A calculation method for the tensile strength of a carbon fiber metal laminate, comprising the following steps:

[0013] S1. Based on the metal volume fraction theory, propose to predict the tensile strength of the carbon fiber metal laminate using the proportion of the metal layer thickness, and introduce the strength contribution coefficients of each component;

[0014] S2. Prepare carbon fiber metal laminate specimens with different proportions of metal layer thickness;

[0015] S3. Conduct a tensile experiment on the carbon fiber metal laminate specimens to measure the correlation data between the tensile strength and the proportion of the metal layer thickness;

[0016] S4. Perform curve fitting on the obtained correlation data to obtain the strength contribution coefficients of the metal layer and the carbon fiber layer;

[0017] S5. Substitute the strength contribution coefficients of the metal layer and the carbon fiber layer as constants into the tensile strength calculation formula of the carbon fiber metal laminate to determine the relationship between the only variable, i.e., the proportion of the metal layer thickness, and the dependent variable, i.e., the tensile strength of the carbon fiber metal laminate;

[0018] S6. Verify the tensile strength calculation formula of the carbon fiber metal laminate to determine the error range.

[0019] Further, in step S1, the theoretical formula for predicting the tensile strength of the carbon fiber metal laminate using the proportion of the metal layer thickness is:

[0020]

[0021] In formula (1):

[0022] σ lam —The tensile strength of the carbon fiber metal laminate;

[0023] σ met —The tensile strength of the metal layer;

[0024] V m —The volume fraction of the metal layer;

[0025] K m —The strength contribution coefficient of the metal layer;

[0026] σ CFRP —The tensile strength of the carbon fiber layer;

[0027] —The volume fraction of carbon fibers in the positive axis direction of the carbon fiber layer;

[0028] — Volume fraction of normal carbon fibers in the carbon fiber layer;

[0029] V RE — Volume fraction of reinforcing resin in the carbon fiber layer;

[0030] K CFRP — Strength contribution coefficient of the carbon fiber layer;

[0031] σ mix — Interfacial residual stress of the carbon fiber metal laminate.

[0032] Among them, σ met σ CFRP σ mix are fixed values related to the material's own properties, and the strength contribution coefficient is a constant;

[0033] Furthermore, it is obtained that:

[0034]

[0035] In Equation (2):

[0036] S—Laying area of the carbon fiber metal laminate;

[0037] h m — Total thickness of the metal layer;

[0038] V 总 — Total volume of the carbon fiber metal laminate;

[0039] Assume that in the carbon fiber metal laminate, both the metal layer and the carbon fiber layer are homogeneous layers and have exactly the same cross-sectional area; then it is obtained that:

[0040]

[0041] and

[0042] In Equations (3) and (4):

[0043] h 总 — Total thickness of the carbon fiber metal laminate;

[0044] h f+ — Thickness of carbon fibers in the positive axis direction in the carbon fiber layer;

[0045] h m — Thickness of the metal layer;

[0046] Define that in the carbon fiber metal laminate, the ratio of the thickness of the metal layer to the total thickness of the carbon fiber metal laminate is POT, then it is obtained that:

[0047]

[0048] After simplification, Equation (4) gives:

[0049]

[0050] Furthermore, in step S2, the process of preparing the carbon fiber metal laminate specimen is as follows: Process the carbon fiber reinforced resin and the high-strength metal thin plate into a carbon fiber layer specimen and a metal layer specimen respectively; Pretreat the surface of the metal layer specimen, specifically by sanding, and then alkaline washing with sodium hydroxide for 2 - 3 minutes to remove the surface oxide film; At room temperature, cure the carbon fiber layer specimen and the metal layer specimen with epoxy resin, and let it stand for more than 24 hours to obtain the carbon fiber metal laminate specimen.

[0051] Furthermore, in step S3, use a microcomputer-controlled electronic universal testing machine to conduct a tensile test, adopt GB / T228 - 2010 "Metallic materials - Tensile testing at ambient temperature" as the test standard, and the loading speed is 8 - 12 mm / min.

[0052] Compared with the prior art, the beneficial effects of the present invention are:

[0053] 1) Based on the tensile test, obtain the correlation data between the overall tensile strength of the carbon fiber metal laminate and the thickness of the metal layer. On this basis, establish a calculation formula with a unique independent variable and dependent variable between the two. In the actual application process, it can quickly select the parameters that meet the requirements, which has important guiding significance for the prediction and analysis of the tensile strength of the carbon fiber metal laminate;

[0054] 2) Improve the traditional metal volume fraction theory, and solve the problem that the prediction result is larger than the actual value because this theory does not consider the influence of interface delamination and residual stress. Description of the Drawings

[0055] The attached drawings forming a part of this application are used to provide an explanation of the process of the present invention. The experimental steps of the present invention are only used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0056] Figure 1 is a schematic diagram of the principle of a calculation method for the tensile strength of a carbon fiber metal laminate according to the present invention.

[0057] Figure 2 is a processing dimension diagram of the carbon fiber layer specimen and the metal layer specimen.

[0058] Figure 3 is the ply structure of the carbon fiber metal laminate in the embodiment of the present invention.

[0059] Figure 4 is the curve of the relationship between the test force and the displacement in the tensile test.

[0060] Figure 5 It is the fitting curve of the proportion of the metal layer thickness to the tensile strength of the carbon fiber metal laminate. Specific Embodiments

[0061] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings:

[0062] See Figure 1 , the calculation method for the tensile strength of a carbon fiber metal laminate according to the present invention includes the following steps:

[0063] S1. Based on the metal volume fraction theory, propose to predict the tensile strength of the carbon fiber metal laminate using the proportion of the metal layer thickness, and introduce the strength contribution coefficient of each component;

[0064] S2. Prepare carbon fiber metal laminate specimens with different proportions of the metal layer thickness;

[0065] S3. Conduct a tensile experiment on the carbon fiber metal laminate specimens to measure the correlation data between the tensile strength and the proportion of the metal layer thickness;

[0066] S4. Perform curve fitting on the obtained correlation data to obtain the strength contribution coefficients of the metal layer and the carbon fiber layer;

[0067] S5. Substitute the strength contribution coefficients of the metal layer and the carbon fiber layer as constants into the tensile strength calculation formula of the carbon fiber metal laminate to determine the relationship between the only variable, i.e., the proportion of the metal layer thickness, and the dependent variable, i.e., the tensile strength of the carbon fiber metal laminate;

[0068] S6. Verify the tensile strength calculation formula of the carbon fiber metal laminate to determine the error range.

[0069] Furthermore, in the step S1, the theoretical formula for predicting the tensile strength of the carbon fiber metal laminate using the proportion of the metal layer thickness is:

[0070]

[0071] In formula (1):

[0072] σ lam —The tensile strength of the carbon fiber metal laminate;

[0073] σ met —The tensile strength of the metal layer;

[0074] V m —The volume fraction of the metal layer;

[0075] K m —The strength contribution coefficient of the metal layer;

[0076] σCFRP — Tensile strength of the carbon fiber layer;

[0077] — Volume fraction of carbon fibers in the positive axis direction in the carbon fiber layer;

[0078] — Volume fraction of carbon fibers in the normal direction in the carbon fiber layer;

[0079] V RE — Volume fraction of the reinforcing resin in the carbon fiber layer;

[0080] K CFRP — Strength contribution coefficient of the carbon fiber layer;

[0081] σ mix — Interfacial residual stress of the carbon fiber metal laminate.

[0082] Among them, σ met 、σ CFRP 、σ mix are fixed values related to the material's own properties, and the strength contribution coefficient is a constant;

[0083] Further obtained:

[0084]

[0085] In Equation (2):

[0086] S—Laying area of the carbon fiber metal laminate;

[0087] h m — Total thickness of the metal layer;

[0088] V 总 — Total volume of the carbon fiber metal laminate;

[0089] Assume that in the carbon fiber metal laminate, both the metal layer and the carbon fiber layer are homogeneous layers and have exactly the same cross-sectional area; then obtained:

[0090]

[0091] And

[0092] In Equations (3) and (4):

[0093] h 总 — Total thickness of the carbon fiber metal laminate;

[0094] h f+ — Thickness of the carbon fibers in the positive axis direction in the carbon fiber layer;

[0095] h m— Thickness of the metal layer;

[0096] In the carbon fiber metal laminate, if the ratio of the thickness of the metal layer to the total thickness of the carbon fiber metal laminate is defined as POT, then:

[0097]

[0098] After simplifying Equation (4), we get:

[0099]

[0100] Furthermore, in step S2, the process of preparing the carbon fiber metal laminate specimen is as follows: Process the carbon fiber reinforced resin and the high-strength metal thin plate into a carbon fiber layer specimen and a metal layer specimen respectively; Pretreat the surface of the metal layer specimen, specifically by sanding, and then alkali-washing with sodium hydroxide for 2 - 3 minutes to remove the surface oxide film; At room temperature, cure the carbon fiber layer specimen and the metal layer specimen with epoxy resin, and let it stand for more than 24 hours to obtain the carbon fiber metal laminate specimen.

[0101] Furthermore, in step S3, use a microcomputer-controlled electronic universal testing machine to conduct a tensile test, and use GB / T228 - 2010 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature" as the test standard, with a loading speed of 8 - 12 mm / min.

[0102] The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0103]

Embodiment

[0104] As Figure 1 , in this embodiment, a calculation method for the tensile strength of a fiber metal laminate is obtained as follows:

[0105] I. The existing metal volume fraction theory.

[0106] In the literature "Vlot A, Gunnink J W. Fiber Metal Laminates[M]. Netherlands: Kluwer Academic Publishers, 2001, 73 - 75", the expression of the metal volume fraction theory is recorded:

[0107]

[0108] In Equation (7), MVF represents the volume fraction of the metal, and 0 < MVF < 1;

[0109] t met— Thickness of the single metal layer;

[0110] t frp — Thickness of the fiber metal laminate;

[0111] p — Total number of metal layers;

[0112] The metal volume fraction theory holds that: when MVF = 1, the fiber metal laminate can be regarded as a pure metal plate, and its properties are those of a pure metal; when MVF = 0, the fiber metal laminate can be regarded as a fiber laminate, and its properties are the same as those of the fiber laminate. Therefore, for the fiber metal laminate with 0 < MVF < 1, its properties can be predicted by the following formula:

[0113] E lam = MVF × E met + (1 - MVF) × E frp (8)

[0114] σ lam = MVF × σ met + (1 - MVF) × σ frp (9)

[0115] In formulas (8) and (9): E lam 、E met 、E frp represent the moduli of the fiber metal laminate, the metal layer, and the fiber layer respectively; σ lam 、σ met 、σ frp represent the tensile strengths of the fiber metal laminate, the metal layer, and the fiber layer respectively.

[0116] Since the above formulas are for unidirectional fiber layups, there is a deviation between the calculated properties of cross-ply fiber metal laminates using these formulas and the experimental results. Considering the changes in the longitudinal and transverse arrangements of the fibers, formulas (8) and (9) are modified as follows:

[0117]

[0118] In formulas (8), (9), (10), and (11):

[0119] E lam 、E met 、E frp — The moduli of the fiber metal laminate, the metal layer, and the fiber layer;

[0120] σ lam 、σ met 、σ frp — The tensile strengths of the fiber metal laminate, the metal plate, and the fiber layer;

[0121] The correction coefficient of 1 / 2 means that in the fiber metal laminate with orthogonal plies, half of the fibers are arranged transversely, and only the fibers in the direction of the normal stress affect the tensile properties of the fiber metal laminate.

[0122] Second, it is proposed to use the proportion of the metal layer thickness to predict the tensile strength of the carbon fiber metal laminate, and the strength contribution coefficients of each component are introduced;

[0123] For the carbon fiber metal laminate of the present invention, since plastic deformation will occur after the metal layer, i.e., the metal thin plate, reaches the yield point, it is not accurate enough to use the linear elastic theory for analysis. Moreover, the linear elastic theory does not consider the influence of interface delamination and residual stress, and the predicted results are generally larger than the actual values. Based on a large number of experiments, the present invention improves the metal volume fraction theory and proposes a theoretical formula suitable for predicting the tensile strength of the carbon fiber metal laminate, that is:

[0124]

[0125] In formula (1): V m —The volume fraction of the metal layer; —The volume fraction of carbon fibers in the positive axis direction and the normal direction in the carbon fiber layer; V RE —The volume fraction of the carbon fiber layer; σ CFRP —The tensile strength of the carbon fiber layer; K m 、K CFRP —The strength contribution coefficients of the metal layer and the carbon fiber layer; σ mix —The interfacial residual stress of the carbon fiber metal laminate.

[0126] In formula (1), And σ met 、σ CFRP 、σ mix Are all fixed values related to the metal material and the carbon fiber material itself that make up the carbon fiber metal laminate, and the strength contribution coefficient is a constant.

[0127] Furthermore:

[0128]

[0129] In formula (2): S—the ply area of the carbon fiber metal laminate; h m —The total thickness of the metal layer, V 总 —The total volume of the carbon fiber metal laminate.

[0130] Assuming that in the carbon fiber metal laminate, the metal layer and the fiber layer are both homogeneous layers and have exactly the same cross-sectional area, then we get:

[0131]

[0132] In Formulas (3) and (4): h 总 — the total thickness of the carbon fiber metal laminate, h f+ — the total thickness of the carbon fiber layer. In this embodiment, h f+ / h 总 = 40%.

[0133] If the ratio of the thickness of the metal layer to the total thickness of the carbon fiber metal laminate in the carbon fiber metal laminate is defined as POT (Percentage of metal thickness), then:

[0134]

[0135] Formula (4) can then be simplified to:

[0136]

[0137] III. Prepare carbon fiber metal laminate specimens with different ratios of metal layer thickness.

[0138] First, process the metal material and the carbon fiber material into corresponding tensile specimens with the shape and dimensions as Figure 2 shown.

[0139] In this embodiment, the metal material is aluminum alloy with a tensile strength of 110 MPa; the carbon fiber layer includes carbon fibers laid along the positive axis direction, carbon fibers laid along the normal direction, and reinforcing resin; among them, the tensile strength of the carbon fiber is 560 MPa, and the interfacial residual stress σ mix of the carbon fiber metal laminate is set to 60 MPa.

[0140] Pretreat the surface of the metal layer specimen: polish it with 400# sandpaper, wash it with sodium hydroxide with a concentration of 5 g / 100 ml for 2 - 3 min to remove the surface oxide film. Cure the metal layer specimen and the carbon fiber layer specimen with epoxy resin at room temperature (23 ± 2)°C and let it stand for 24 h to obtain the carbon fiber metal laminate specimen. The schematic diagram of its ply structure is as Figure 3 shown. The upper and lower layers of the specimen have the same thickness, the material is aluminum alloy, and the middle is the carbon fiber layer.

[0141] The specimen numbers and specifications are shown in Table 1:

[0142] Table 1

[0143]

[0144]

[0145] IV. Conduct a tensile experiment to measure the tensile strength of the carbon fiber metal laminate specimen and the data of the metal thickness ratio.

[0146] The tensile test was carried out using a WDW3100 microcomputer-controlled electronic universal testing machine. GB / T228-2010 “Room Temperature Test Method for Tensile Test of Metallic Materials” was selected as the test standard, and the loading speed was 10 mm / min.

[0147] 5. The test force and displacement curve obtained from the tensile test is as follows Figure 4 As shown, use formula (12) to calculate

[0148]

[0149] In formula (12), σ t represents the tensile strength of the carbon fiber metal laminate specimen; P b represents the maximum load (destructive load) borne by the carbon fiber metal laminate specimen; b represents the width of the carbon fiber metal laminate specimen; h represents the thickness of the carbon fiber metal laminate specimen.

[0150] The obtained carbon fiber metal laminate tensile strength and metal layer thickness ratio data are used to perform curve fitting through the graphical interface by calling the curve fitting tool cftool (curve fit tool) in MATLAB software. The fitting results are shown in the figure. Figure 5 As shown, the formula is expressed as:

[0151]

[0152] 6. Substituting the tensile strength of the metal layer and the tensile strength of the carbon fiber layer into formula (6) as constants, we obtain:

[0153]

[0154] Combining equation (13) with equation (14), we can determine the unique variable x (i.e., the thickness ratio of the metal layer POT) and the dependent variable y (the tensile strength σ of the carbon fiber metal laminate) in equation (13). lam ), namely, K m =-27.6, K CFRP =4.255, substituting the two coefficients into equation (6), we get:

[0155]

[0156] According to the metal layer thickness ratio POT, the tensile strength of the carbon fiber metal laminate can be calculated and predicted using formula (15).

[0157] 7. Compare and verify the predicted value obtained by the calculation method described in the present invention with the measured value, determine the error range, and judge the feasibility.

[0158] In this embodiment, the error analysis between the measured value and the predicted value is shown in Table 2: the maximum error does not exceed 10%, proving that the calculation method described in the present invention is reasonable and feasible.

[0159] Table 2

[0160]

[0161] The calculation formula (15) described in the present invention reflects the relationship between the proportion of different metal layer thicknesses and the tensile strength of the carbon fiber metal laminate. This calculation formula for the tensile strength of the carbon fiber metal laminate has important application value for the design, manufacture, popularization and application of the carbon fiber metal laminate, and can quickly and reliably provide a calculation basis.

[0162] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A calculation method for the tensile strength of a carbon fiber metal laminate, characterized in that It includes the following steps: S1. Based on the theory of metal volume fraction, a method is proposed to predict the tensile strength of carbon fiber metal laminates by using the proportion of the metal layer thickness, and the strength contribution coefficients of each component are introduced. The theoretical formula for predicting the tensile strength of carbon fiber metal laminates by using the proportion of the metal layer thickness is as follows: In formula (1): σ lam — Tensile strength of carbon fiber metal laminate; σ met — Tensile strength of the metal layer; V m — Volume fraction occupied by the metal layer; K m — Strength contribution coefficient of the metal layer; σ CFRP — Tensile strength of the carbon fiber layer; — The volume fraction of carbon fibers in the positive axis direction in the carbon fiber layer; — The volume fraction of normal carbon fibers in the carbon fiber layer; V RE — Volume fraction of reinforcing resin in the carbon fiber layer; K CFRP — Strength contribution coefficient of carbon fiber layer; σ mix — Residual stress at the interface of carbon fiber metal laminate; Among them, σ met , σ CFRP , σ mix are fixed values related to the properties of the material itself, and the strength contribution coefficient is a constant; S2. Prepare carbon fiber metal laminate specimens with different proportions of metal layer thickness. S3. Conduct tensile tests on the carbon fiber metal laminate specimens to measure the correlation data between the tensile strength and the proportion of the metal layer thickness. S4. Perform curve fitting on the obtained correlation data to obtain the strength contribution coefficients of the metal layer and the carbon fiber layer. S5. Substitute the strength contribution coefficients of the metal layer and the carbon fiber layer as constants into the calculation formula for the tensile strength of carbon fiber metal laminates to determine the relationship between the only variable, i.e., the proportion of the metal layer thickness, and the dependent variable, i.e., the tensile strength of carbon fiber metal laminates. S6. Verify the calculation formula for the tensile strength of carbon fiber metal laminates to determine the error range.

2. The calculation method of the tensile strength of a carbon fiber metal laminate according to claim 1, wherein, In step S1, based on the theoretical formula for predicting the tensile strength of carbon fiber metal laminates by using the proportion of the metal layer thickness, the following is further obtained: In formula (2): S—the laying area of the carbon fiber metal laminate; h m — Total thickness of the metal layer; V 总 — total volume of carbon fiber metal laminate; Assume that in the carbon fiber metal laminate, both the metal layer and the carbon fiber layer are homogeneous layers and have exactly the same cross-sectional area; then the following is obtained: and In formulas (3) and (4): h 总 — total thickness of the carbon fiber metal laminate; h f+ — Thickness of carbon fibers in the longitudinal axis direction in the carbon fiber layer; h m — Thickness of the metal layer; Define that in the carbon fiber metal laminate, the ratio of the thickness of the metal layer to the total thickness of the carbon fiber metal laminate is POT, then the following is obtained: After formula (4) is simplified, it is obtained:

3. The calculation method of the tensile strength of a carbon fiber metal laminate according to claim 1, wherein, In step S2, the process of preparing the carbon fiber metal laminate specimens is as follows: Process the carbon fiber reinforced resin and the high-strength metal thin plate into carbon fiber layer specimens and metal layer specimens respectively; perform surface pretreatment on the metal layer specimens, specifically by sanding, and then alkali washing with sodium hydroxide for 2 - 3 minutes to remove the surface oxide film; at room temperature, cure the carbon fiber layer specimens and the metal layer specimens with epoxy resin, and let it stand for more than 24 hours to obtain the carbon fiber metal laminate specimens.

4. The calculation method of the tensile strength of a carbon fiber metal laminate according to claim 1, characterized in that, In step S3, use a microcomputer-controlled electronic universal testing machine to conduct tensile tests, and use GB / T228-2010 "Metallic materials - Tensile testing at ambient temperature" as the test standard, and the loading speed is 8 - 12 mm / min.

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