A method for evaluating the performance of a composite panel in a tensile test

Abstract

The application discloses a kind of composite material plate tensile test performance evaluation methods, comprising the following steps: selecting plate material and sampling: preparing test equipment and test environment;Carry out pretest, determine the optimal loading rate of test equipment;Carry out formal test, record test data: analysis test data, realize the evaluation of composite material plate tensile performance.The performance index of the material is obtained by determining the optimal loading rate, and the performance index is compared with the standard, the evaluation of composite material plate tensile performance is realized, the safety and reliability of product is improved, and the accuracy of performance evaluation is improved.

Description

Technical Field

[0001] This invention relates to the field of performance evaluation technology, and in particular to a method for evaluating the tensile performance of composite material plates. Background Technology

[0002] Carbon fiber is a special fiber mainly composed of carbon elements. Its carbon content varies depending on the type, but is generally above 90%. Carbon fiber has the characteristics of general carbon materials, such as high temperature resistance, friction resistance, electrical conductivity, thermal conductivity, and corrosion resistance. However, unlike general carbon materials, it has significant anisotropy in shape, is flexible, can be processed into various fabrics, and exhibits high strength along the fiber axis. Carbon fiber has a low specific gravity, so it has a high specific strength. In traditional applications, carbon fiber is generally not used alone except as a heat insulation material. It is mostly used as a reinforcing material added to resins, metals, ceramics, concrete, and other materials to form composite materials. Carbon fiber reinforced composite materials can be used as aircraft structural materials, electromagnetic shielding materials, artificial ligaments and other body substitutes, as well as for manufacturing rocket shells, motorboats, industrial robots, automotive leaf springs, and drive shafts.

[0003] With the increasingly widespread application of carbon fiber composite materials in various industries, the evaluation of their strength and toughness has become increasingly important. In the tensile test performance evaluation of carbon fiber composite plates, the choice of loading rate in the tensile test will affect the material behavior. Loading rates that are too fast or too slow may lead to unreliable results. Therefore, a method for evaluating the tensile test performance of composite plates is proposed to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the tensile performance of composite material plates. By determining the optimal loading rate, the performance indicators of the material are obtained, and the performance indicators are compared with the standard to evaluate the tensile performance of the composite material plates.

[0005] To solve the above technical problems, the technical solution of the present invention is: a method for evaluating the tensile performance of composite material plates, comprising the following steps: S1. Select the board material and take a sample: Select a material sheet, cut a sample from the same material sheet, and check the sample for bubbles and cracks; S2. Prepare test equipment and test environment: Select a material testing machine and install the appropriate fixtures on the machine according to the size of the sample; set up a testing environment with constant temperature and humidity. S3. Conduct preliminary tests to determine the optimal loading rate of the test equipment: Set different loading rates for the material testing machine, start the material testing machine, and conduct preliminary tests on the samples fixed in the fixture of the material testing machine at different loading rates to obtain the preliminary test results. Determine the optimal loading rate of the material testing machine based on the preliminary test results. S4. Conduct formal testing and record test data: Set the loading rate of the material testing machine to the optimal loading rate obtained in step S3, start the material testing machine, and conduct formal testing on the sample fixed in the fixture of the material testing machine in four stages, and record the test data in real time. S5. Analyze the test data: Based on the test data recorded in real time in step S4, the stress-strain curve of the sample at the optimal loading rate is determined, the performance index of the material at the optimal loading rate is obtained, and the performance index is compared with the standard to realize the evaluation of the tensile properties of the composite material plate.

[0006] Preferably, in step S1, the sample size is 250 mm. 25mm, with a thickness of 3mm.

[0007] Preferably, in step S2, the material testing machine is an electronic tensile testing machine, and the fixture is a parallel fixture.

[0008] Preferably, in step S2, the temperature of the test environment is (23±2)℃ and the humidity is (50±10)%RH.

[0009] Preferably, step S3 includes the following steps: S301. Set the loading rates of several material testing machines and determine the number of samples; S302. Fix the specimens one by one in the fixture of the material testing machine, start the material testing machine, and perform tensile pre-tests on the specimens one by one according to the different loading rates set in step S301, and record the pre-test data in real time. S303. Based on the pre-test data in step S302, determine the stress-strain curve, and obtain the yield strength, ultimate strength, elongation after fracture, and fracture mode of the material from the stress-strain curve. Compare the performance indicators of the material under different loading rates and analyze the influence of different loading rates on the material performance. S304. Based on the analysis results of step S303, evaluate the effects of different loading rates on the strength, ductility, and failure mode of the material, and determine the optimal loading rate; Preferably, in step S304, the failure mode of the material refers to whether the sample exhibits slippage, brittle fracture, and plastic deformation during the test.

[0010] Preferably, step S4 further includes setting several strain gauges on the specimen to perform multi-point testing, thereby realizing the measurement of multi-point stress and strain information.

[0011] Preferably, in step S4, the four stages include the initial stage, the yielding stage, the ultimate strength stage, and the fracture stage.

[0012] Preferably, in step S303, the yield strength The calculation formula is as follows: , in, This is the stress value. The elastic modulus of the material; The ultimate strength The calculation formula is as follows: , in, This is the stress value; The elongation after fracture The calculation formula is as follows: , in, The new length of the specimen after fracture. This is the original length of the sample.

[0013] Preferably, in step S303, the stress value The calculation formula is as follows: , in, For the applied force, This represents the original cross-sectional area of ​​the sample; strain value The calculation formula is as follows: , in, This represents the elongation of the specimen during the tensile process. This is the original length of the sample.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The material testing machine conducts pre-tests by setting different loading rates and records the stress and strain data under each loading rate to determine the optimal loading rate. Different loading rates will affect the mechanical behavior of the material, especially in terms of the yield strength, ultimate strength and elongation after fracture. By systematically analyzing the stress-strain curves under each loading rate, the performance differences of the material under different loading rates can be quickly identified, the performance characteristics of the material under different loading rates can be mastered, and the safety and reliability of the product can be improved. (2) By adopting the multi-stage loading rate method, the understanding and analysis of the mechanical behavior of materials can be significantly improved. By gradually increasing the load, the deformation response of materials under different stress levels can be clearly obtained, including elastic deformation, yielding phenomenon and final fracture. It can not only effectively identify the yield point and ultimate strength of materials, but also promptly detect any potential defects or inhomogeneities that occur under stress. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention 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.

[0016] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the preliminary test process of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings. The terminal technical solutions of the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, the present invention provides a method for evaluating the tensile performance of composite material plates, comprising the following steps: S1. Select the board material and take a sample: Select carbon fiber composite sheets and cut them to a size of 250mm from the same material sheet according to ISO 527 standard. 25mm thick and 3mm thick specimens were cut to ensure similar physical characteristics. After cutting, the specimens were carefully inspected for bubbles and cracks to ensure that the cut specimens were free of defects such as bubbles and cracks.

[0019] S2. Prepare test equipment and test environment: Select an electronic tensile testing machine with mechanical property testing functions to ensure precise control of the loading rate; install appropriate fixtures on the electronic tensile testing machine according to the size of the sample to ensure that the sample can be firmly fixed during the test and will not slip during the tensile process; set the temperature of the test environment to (23±2)℃ and the humidity to (50±10)%RH to ensure that the laboratory environment remains constant.

[0020] S3. Conduct preliminary tests to determine the optimal loading rate of the test equipment: Set different loading rates for the electronic tensile testing machine, start the machine, and conduct preliminary tests on the specimens fixed in the machine's fixture at each loading rate. Obtain the preliminary test results, and determine the optimal loading rate for the electronic tensile testing machine based on these results. Figure 2 As shown, the specific steps include the following: S301. Set the loading rates of several electronic tensile testing machines and determine the number of test specimens.

[0021] According to the ISO 527 standard, four different loading rates were set for testing: 1 mm / min, 5 mm / min, 10 mm / min and 20 mm / min. At least three identical specimens were prepared for each loading rate for preliminary testing.

[0022] S302. Fix the specimens one by one in the fixture of the electronic tensile testing machine, start the electronic tensile testing machine, and perform tensile pre-tests on the specimens one by one according to the different loading rates set in step S301, and record the pre-test data in real time.

[0023] S303. Based on the stress and strain data in the pre-test data of step S302, determine the stress-strain curve, and obtain the material's strength, elongation after fracture, and fracture mode from the stress-strain curve. Compare the material's performance indicators under different loading rates and analyze the impact of different loading rates on the material's properties. The strength includes yield strength and ultimate strength.

[0024] stress value The calculation formula is as follows: , in, For the applied force, This represents the original cross-sectional area of ​​the sample; strain value The calculation formula is as follows: , in, This represents the elongation of the specimen during the tensile process. This is the original length of the sample.

[0025] The yield strength The calculation formula is as follows: ,

[0026] in, This is the stress value. The elastic modulus of the material; The ultimate strength The calculation formula is as follows: ,

[0027] in, This is the stress value; The elongation after fracture The calculation formula is as follows: ,

[0028] in, The new length of the specimen after fracture. This is the original length of the sample.

[0029] S304. Based on the analysis results of step S303, evaluate the impact of different loading rates on the strength, ductility, and failure mode of the material, determine the optimal loading rate that provides the most consistent and repeatable performance results, and ensure the accuracy and representativeness of the test. The failure mode of the material refers to whether the specimen exhibits slip, brittle fracture, and plastic deformation during the test.

[0030] S4. Conduct formal testing and record test data: Set the loading rate of the material testing machine to the optimal loading rate obtained in step S3, start the material testing machine, and conduct formal testing on the specimen fixed in the fixture of the material testing machine in four stages. Record the test data in real time, observe the entire tensile process, and pay special attention to the failure mode of the specimen.

[0031] In this embodiment, the specimen is subjected to a four-stage progressive tensile test based on the optimal loading rate determined in step S3, ensuring that each specimen is tested at the same rate, and the test data of the specimen at different stages are recorded in real time. The four stages include the initial stage, yield stage, ultimate strength stage, and fracture stage.

[0032] (1) Initial stage: Set the optimal loading rate and gradually increase it from 0 to the elastic limit of the specimen. The elastic limit is set to 50%-70% of the yield strength of the specimen. Record the stress and strain data according to the elastic deformation of the specimen and monitor the early formation of cracks. (2) Yield stage: After the initial stage, the specimen is stretched at the same loading rate until the specimen reaches the yield point (i.e., permanent deformation begins to occur), and the stress and strain changes are recorded. (3) Ultimate strength stage: After the yield stage, continue to stretch the specimen to the ultimate strength point. The specimen will reach its maximum bearing capacity. Record the stress-strain characteristics of the specimen and monitor the necking phenomenon and surface deformation before fracture. (4) Fracture stage: The specimen fractures shortly after reaching the ultimate strength point. Tension continues until the specimen completely fractures. The final failure mode of the specimen is recorded, and the fracture characteristics of the specimen, including crack propagation and fracture surface morphology, are evaluated.

[0033] In this embodiment, multiple strain gauges can be set on the surface of the same sample to perform multi-point stress and strain measurements on the sample, so as to obtain a more comprehensive material response and effectively identify local deformation caused by material inhomogeneity.

[0034] S5. Analyze the test data: Based on the stress and strain data recorded in real time in step S4, the stress-strain curve of the specimen at the optimal loading rate is determined, the performance index of the material at the optimal loading rate is obtained, and the performance index is compared with the ISO527 standard to realize the evaluation of the tensile properties of the composite material plate. This ensures the validity and representativeness of the test data and the effectiveness of the test.

[0035] In this embodiment, the stress and strain data can be measured and collected by the data acquisition system (such as a resistance strain gauge) in the electronic tensile testing machine.

[0036] All parts not covered in this invention are the same as or implemented using existing technologies.

[0037] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for evaluating the tensile performance of composite material plates, characterized in that: Includes the following steps: S1. Select the board material and take a sample: Select a material sheet, cut a sample from the same material sheet, and check the sample for bubbles and cracks. S2. Prepare test equipment and test environment: Select a material testing machine and install the appropriate fixtures on the machine according to the size of the sample; set up a testing environment with constant temperature and humidity. S3. Conduct preliminary tests to determine the optimal loading rate of the test equipment: Set different loading rates for the material testing machine, start the material testing machine, and conduct preliminary tests on the samples fixed in the fixture of the material testing machine at different loading rates to obtain the preliminary test results. Determine the optimal loading rate of the material testing machine based on the preliminary test results. S4. Conduct formal testing and record test data: Set the loading rate of the material testing machine to the optimal loading rate obtained in step S3, start the material testing machine, and conduct formal testing on the sample fixed in the fixture of the material testing machine in four stages, and record the test data in real time. S5. Analyze the test data: Based on the test data recorded in real time in step S4, the stress-strain curve of the sample at the optimal loading rate is determined, the performance index of the material at the optimal loading rate is obtained, and the performance index is compared with the standard to realize the evaluation of the tensile properties of the composite material plate.

2. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: In step S1, the sample size is 250 mm. 25mm, with a thickness of 3mm.

3. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: In step S2, the material testing machine is an electronic tensile testing machine, and the fixture is a parallel fixture.

4. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: In step S2, the temperature of the test environment is (23±2)℃ and the humidity is (50±10)%RH.

5. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: Step S3 includes the following steps: S301. Set the loading rates of several material testing machines and determine the number of samples; S302. Fix the specimens one by one in the fixture of the material testing machine, start the material testing machine, and perform tensile pre-tests on the specimens one by one according to the different loading rates set in step S301, and record the pre-test data in real time. S303. Based on the pre-test data in step S302, determine the stress-strain curve, and obtain the yield strength, ultimate strength, elongation after fracture, and fracture mode of the material from the stress-strain curve. Compare the performance indicators of the material under different loading rates and analyze the influence of different loading rates on the material performance. S304. Based on the analysis results of step S303, evaluate the effects of different loading rates on the strength, ductility, and failure mode of the material, and determine the optimal loading rate.

6. The method for evaluating the tensile performance of composite material plates according to claim 5, characterized in that: In step S304, the failure mode of the material refers to whether the sample exhibits slippage, brittle fracture, and plastic deformation during the test.

7. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: Step S4 also includes setting several strain gauges on the specimen to perform multi-point testing, thereby realizing the measurement of multi-point stress and strain information.

8. The method for evaluating the tensile performance of composite material plates according to claim 1, characterized in that: In step S4, the four stages include the initial stage, the yielding stage, the ultimate strength stage, and the fracture stage.

9. The method for evaluating the tensile performance of composite material plates according to claim 5, characterized in that: In step S303, the yield strength The calculation formula is as follows: ， in, This is the stress value. The elastic modulus of the material; The ultimate strength The calculation formula is as follows: ， in, This represents the stress value. The elongation after fracture The calculation formula is as follows: ， in, The new length of the specimen after fracture. This is the original length of the sample.

10. The method for evaluating the tensile performance of composite material plates according to claim 5, characterized in that: In step S303, the stress value The calculation formula is as follows: ， in, For the applied force, This represents the original cross-sectional area of ​​the sample; strain value The calculation formula is as follows: ， in, This represents the elongation of the specimen during the tensile process. This is the original length of the sample.

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