A method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials

Abstract

The present invention discloses a method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials, belonging to the technical field of fiber-reinforced resin-based composite materials. The method uses an instrumental analysis method to determine the thermal weight loss apparent activation energy of the fiber-reinforced resin-based composite material. A coefficient of this activation energy is calculated as the aging activation energy of the material. An acceleration coefficient is calculated based on the aging activation energy, the accelerated aging test temperature, and the storage temperature, and then the accelerated aging time is obtained. A constant temperature and humidity accelerated aging test is conducted and the post-aging performance of the material is measured. The obtained test data is subjected to regression analysis to establish a regression equation. The calculated value of the regression equation is used to evaluate the performance of the composite material at the corresponding natural storage time. Compared with existing methods, the method has the advantages of shortening test time, improving efficiency, and saving manpower and material resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber-reinforced resin-based composite materials, and particularly relates to a method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials. Background Art

[0002] During long-term storage, fiber-reinforced resin-based composite materials will age under the influence of heat, oxygen and moisture, resulting in their macroscopic performance being unable to meet the requirements of use. Premature damage to the composite materials will cause waste of resources and may also lead to larger accidents. Therefore, the long-term storage performance evaluation of fiber-reinforced resin-based composite materials has always been a hot topic of concern.

[0003] In terms of long-term storage performance and life assessment methods for polymer materials, the methods currently commonly used include ISO 2578:1993, ISO 11346:2014, GB / T 20028-2005, GB / T 7142-2002, GJB-92.1-86, GJB-92.2-86 and HG / T 3087-2001. Among them, the four methods of ISO 2578:1993, ISO 11346:2014, GB / T 20028-2005 and GB / T 7142-2002 are similar. GB / T 7142-2002 is equivalent to ISO 2578:1993, and GB / T 20028-2005 is equivalent to ISO 11346:1997. The main contents of these methods are to carry out accelerated aging tests under no less than three temperature conditions, obtain the failure time under each temperature condition, and then process the data according to the Arrhenius law to evaluate the storage life of the material. GJB-92.1-86, GJB-92.2-86, and HG / T 3087-2001 share similar content. Accelerated aging tests are conducted at no fewer than four temperatures. Data processing involves first performing a linear regression on the logarithm of the performance retention rate versus time (lnp-tα) to determine the rate change constant, K, and other constants at different accelerating temperatures. Then, based on the Arrhenius law, a linear regression is performed on the logarithm of the rate change constant versus the inverse of the test temperature (lnK-1 / T) to determine the rate change constant at storage temperature. This allows for the development of a performance degradation model and the estimation of the material's storage life. Of these methods, GB / T 7142-2002 and ISO 2578:1993 are applicable to the lifespan assessment of plastics and can be used as a reference for fiber-reinforced resin-based composites.

[0004] None of the above methods take into account the impact of humidity on materials. When used for the long-term storage performance evaluation of fiber-reinforced resin-based composite materials, there may be a large deviation between the evaluation results and the actual test results. Moreover, the above methods all require accelerated aging tests at multiple temperature points, which not only consumes a lot of manpower and material resources, but also takes a long time. Therefore, in actual operation, it is often difficult for the testers to bear. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials. By combining instrumental analysis and accelerated aging tests at single temperature and humidity points, the long-term storage performance of fiber-reinforced resin-based composite materials can be quickly evaluated. The test cycle is usually 1 to 3 months, which is significantly shorter than the test cycle of existing evaluation methods.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: first, the temperature and humidity for accelerated aging are designed, and the thermal gravimetric apparent activation energy of the fiber-reinforced resin-based composite material is measured. The coefficient of this activation energy is calculated as the aging activation energy of the composite material; then, the acceleration coefficient is calculated based on the aging reaction activation energy, the accelerated aging test temperature and the storage temperature. The required accelerated aging time is calculated based on the obtained acceleration coefficient and the expected storage time. A constant temperature and humidity accelerated aging test is carried out, and samples are taken periodically to measure the material properties; finally, the obtained test data are subjected to regression analysis, a regression equation is established, and the calculated value of the regression equation is used to evaluate the performance of the composite material at the corresponding natural storage time.

[0007] The present invention relates to a method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material, comprising the following steps:

[0008] (1) Design accelerated aging test conditions

[0009] The test temperature is not higher than 75℃ and the test humidity is 65g / m 3 ;

[0010] (2) Determine the activation energy of the aging reaction of fiber-reinforced resin-based composites

[0011] According to the method provided by ASTM E1641, the apparent activation energy of the fiber-reinforced resin matrix composite material when the resin-air atmosphere thermal weight loss rate is 5% is determined; the coefficient of this thermal weight loss apparent activation energy is calculated as the aging reaction activation energy of the fiber-reinforced resin matrix composite material E a ;

[0012] (3) Carry out accelerated aging tests on fiber-reinforced resin-based composite materials and test the material properties after the tests

[0013] Calculate the acceleration coefficient based on the accelerated aging test temperature and aging reaction activation energy obtained in steps (1) and (2) and the expected storage temperature; then calculate the accelerated aging test time based on the obtained acceleration coefficient and the expected storage time; round the calculated result of the accelerated aging test time to an integer, carry out a constant temperature and humidity accelerated aging test, and regularly sample and test the material properties after aging;

[0014] (4) Fitting the regression equation of the change of fiber reinforced resin matrix composite material performance with accelerated aging time

[0015] A polynomial regression analysis was conducted with the accelerated aging test time as the independent variable and the performance test value of the fiber-reinforced resin-based composite material as the dependent variable, and the regression equation of the fiber-reinforced resin-based composite material performance changing with the accelerated aging time was obtained.

[0016] (5) Evaluate the performance of fiber-reinforced resin-based composite materials with the required storage time

[0017] Using the regression equation obtained in step (4), the performance of the fiber-reinforced resin-based composite material at the required storage time is evaluated.

[0018] Preferably, the test temperature of the accelerated aging test in step (1) is 75°C.

[0019] Preferably, in step (2), when calculating the apparent activation energy of thermal weight loss, the coefficient taken is 0.6-0.7.

[0020] Preferably, when calculating the acceleration coefficient in step (3), the Arrhenius equation is used:

[0021]

[0022] Where: F — acceleration factor; k 1—Aging rate constant at storage temperature; k 2—Aging rate constant under accelerated aging conditions; E a —Activation energy of aging reaction, J·mol-1; R —Gas constant, 8.314 J·K⁻¹·mol⁻¹; T 1—Storage temperature, K; T 2—Accelerated aging test temperature, K.

[0023] Preferably, the accelerated aging test time is calculated in step (3) based on the obtained acceleration factor and the expected storage time using the following formula:

[0024]

[0025] Where: t2—Accelerated aging test time, d; t 1—Expected storage time, d.

[0026] Preferably, the step (3) tests the material properties of the fiber-reinforced resin-based composite material after accelerated aging test, including flexural strength and flexural modulus.

[0027] The present invention relates to a method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials. This method combines instrumental analysis with accelerated aging tests at single temperature and humidity points to evaluate the long-term storage performance of fiber-reinforced resin-based composite materials. Compared with existing methods, this method can shorten test time, improve efficiency, and save manpower and material resources. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments, but this is not intended to limit the technical solutions of the present invention.

[0029] Example 1

[0030] Taking the long-term storage performance evaluation of carbon fiber reinforced phenolic resin-based composite materials as an example, this paper introduces the material flexural strength evaluation method of the composite material stored at room temperature of 23°C for 10 years. The specific evaluation steps are as follows:

[0031] (1) The accelerated aging test temperature is designed to be 75°C and the test humidity is 65g / m 3 .

[0032] (2) The material was subjected to air atmosphere thermal gravimetric analysis at different heating rates, namely 1°C, 2°C, 5°C and 10°C. According to the method provided by ASTM E1641, it was calculated that when the thermal weight loss rate of the resin in the composite material was 5%, the corresponding thermal weight loss apparent activation energy was 1.155×10 5 J / mol, the apparent activation energy of thermal weight loss is calculated as 0.65, which is the activation energy of the aging reaction of carbon fiber reinforced phenolic resin composite material. E a , is 7.508×10 4 J / mol.

[0033] (3) Carry out aging tests on fiber-reinforced resin-based composite materials and test the material properties after aging

[0034] Calculate the acceleration coefficient according to formula (1):

[0035] (1)

[0036] Where: F — acceleration factor; k 1—Aging rate constant at storage temperature; k2—Aging rate constant under accelerated aging conditions; E a —Activation energy of aging reaction, J·mol -1 ; R —Gas constant, 8.314 J·K -1 ·mol -1 ; T 1—Storage temperature, K; T 2—Accelerated aging test temperature, K; t 2—Accelerated aging test time, d; t 1—Expected storage time, d.

[0037] Calculate the required accelerated aging test time according to formula (2):

[0038] (2)

[0039] The calculated result of the accelerated aging test time is rounded up to 39 days.

[0040] The accelerated aging test temperature was 75°C and the test humidity was 65 g / m 3 In an environment with a temperature of 100 °C, a 39-day accelerated aging test was carried out on the carbon fiber reinforced phenolic resin matrix composite material. The flexural strength of the composite material was measured after each sampling. The test results are shown in Table 1.

[0041] Table 1 Bending strength test results

[0042]

[0043] (4) A polynomial regression analysis was performed with the accelerated aging test time as the independent variable and the flexural strength test value of the carbon fiber reinforced phenolic resin based composite material as the dependent variable to obtain the regression equation of the flexural strength of the composite material with the accelerated aging time, as shown in formula (3).

[0044] (3)

[0045] Where: y 1—Flexural strength, MPa; x-test time, d.

[0046] (5) When evaluating the flexural strength of carbon fiber reinforced phenolic resin-based composite materials stored for 8 years, the corresponding accelerated aging time is calculated as 30.7 days using formula (2). Substituting this time into formula (3), the flexural strength evaluation value of the material after 8 years of storage is calculated to be 146 MPa.

[0047] The present invention adopts a method combining instrumental analysis with accelerated aging tests at single temperature and humidity points, which can complete the flexural strength evaluation of fiber-reinforced resin-based composite materials after long-term storage in a relatively short time, with high efficiency and saving manpower and material resources.

[0048] Example 2

[0049] Taking the long-term storage performance evaluation of glass fiber reinforced epoxy resin composite materials as an example, this paper introduces the flexural strength evaluation method of the composite materials stored at room temperature of 23°C for 10 years. The specific evaluation steps are as follows:

[0050] (1) The accelerated aging test temperature is designed to be 75°C and the test humidity is 65g / m 3 .

[0051] (2) The material was subjected to air atmosphere thermogravimetric analysis at different heating rates, namely 1°C, 2°C, 5°C and 10°C. According to the method provided by ASTM E1641, when the weight loss rate of the resin in the composite material was 5%, the corresponding apparent activation energy of thermogravimetric loss was 1.285×10 5 J / mol, the apparent activation energy of thermal weight loss is calculated as the activation energy of the aging reaction of glass fiber reinforced epoxy resin matrix composite material by taking the coefficient of 0.6 E a , which is 7.71×10 4 J / mol.

[0052] (3) Calculate the acceleration coefficient according to formula (1):

[0053]

[0054] Where: F — acceleration factor; k 1—Aging rate constant at storage temperature; k 2—Aging rate constant under accelerated aging conditions; E a —Activation energy of aging reaction, J·mol -1 ; R —Gas constant, 8.314 J·K -1 ·mol -1 ; T 1—Storage temperature, K; T 2—Accelerated aging test temperature, K; t 2—Accelerated aging test time, d; t 1—Expected storage time, d. Calculate the required accelerated aging test time according to formula (2):

[0055]

[0056] The accelerated aging test temperature was 75°C and the test humidity was 65 g / m 3In an environment with a temperature of 100 °C, a 34-day accelerated aging test was carried out on the glass fiber reinforced epoxy resin matrix composite material. The flexural strength of the composite material was measured after each sampling. The test results are shown in Table 2.

[0057] Table 2 Bending strength test results

[0058]

[0059] (4) A polynomial regression analysis was performed with the accelerated aging test time as the independent variable and the flexural strength test value of the glass fiber reinforced epoxy resin matrix composite material as the dependent variable. The regression equation of the flexural strength of the composite material changing with the accelerated aging time was obtained, as shown in formula (4).

[0060] (4)

[0061] Where: y 2—Flexural strength, MPa; x—Test time, d.

[0062] (5) When evaluating the flexural strength of glass fiber reinforced epoxy resin-based composite materials stored for 8 years, the corresponding accelerated aging time is calculated as 27.2 days using formula (2). Substituting this time into formula (4), the estimated flexural strength of the material after 8 years of storage is calculated to be 299 MPa.

[0063] The present invention adopts a method combining instrumental analysis with accelerated aging tests at single temperature and humidity points, which can complete the flexural strength evaluation of fiber-reinforced resin-based composite materials after long-term storage in a relatively short time, with high efficiency and saving manpower and material resources.

[0064] Example 3

[0065] Taking the long-term storage performance evaluation of carbon fiber reinforced phenolic resin composite materials as an example, this paper introduces the evaluation method of the flexural modulus of the composite material stored at room temperature of 23°C for 10 years. The specific evaluation steps are as follows:

[0066] (1) The accelerated aging test temperature is designed to be 70°C and the test humidity is 65g / m 3 .

[0067] (2) The material was subjected to air atmosphere thermal gravimetric analysis at different heating rates, namely 1°C, 2°C, 5°C and 10°C. According to the method provided by ASTM E1641, it was calculated that when the weight loss rate of the resin in the composite material was 5%, the corresponding thermal gravimetric apparent activation energy was 1.155×10 5 J / mol, the apparent activation energy of thermal weight loss is calculated as the activation energy of the aging reaction of carbon fiber reinforced phenolic resin based composite material by taking the coefficient of 0.7 E a , is 8.085×10 4J / mol.

[0068] (3) Calculate the acceleration coefficient according to formula (1):

[0069]

[0070] Where: F — acceleration factor; k 1—Aging rate constant at storage temperature; k 2—Aging rate constant under accelerated aging conditions; E a —Activation energy of aging reaction, J·mol -1 ; R —Gas constant, 8.314 J·K -1 ·mol -1 ; T 1—Storage temperature, K; T 2—Accelerated aging test temperature, K; t 2—Accelerated aging test time, d; t 1—Expected storage time, d. Calculate the required accelerated aging test time according to formula (2):

[0071]

[0072] The calculated result of the accelerated aging test time is rounded up to 41 days.

[0073] The accelerated aging test temperature was 70°C and the test humidity was 65 g / m 3 In an environment with a temperature of 400 °C, a 41-day accelerated aging test was carried out on the carbon fiber reinforced phenolic resin matrix composite material. The flexural modulus of the composite material was measured after each sampling. The test results are shown in Table 3.

[0074] Table 3 Flexural modulus test results

[0075]

[0076] (4) A polynomial regression analysis was performed with the accelerated aging test time as the independent variable and the flexural modulus test value of the carbon fiber reinforced phenolic resin based composite material as the dependent variable to obtain the regression equation of the flexural modulus of the composite material changing with the accelerated aging time, as shown in formula (5).

[0077] (5)

[0078] Where: y 3—Flexural modulus, GPa; x-test time, d.

[0079] (5) When evaluating the flexural modulus of carbon fiber reinforced phenolic resin-based composite materials stored for 9 years, the corresponding accelerated aging time is calculated as 36.6 days using formula (2). Substituting this time into formula (5), the flexural modulus evaluation value of the material after 9 years of storage is calculated to be 21.7 GPa.

[0080] The present invention adopts a method combining instrumental analysis with accelerated aging tests at single temperature and humidity points, which can complete the flexural modulus evaluation of fiber-reinforced resin-based composite materials after long-term storage in a relatively short time, with high efficiency and saving manpower and material resources.

Claims

1. A method for evaluating the long-term storage performance of fiber-reinforced resin-based composite materials, characterized in that: The steps of this method are: (1) Design accelerated aging test conditions The test temperature is not higher than 75℃ and the test humidity is 65g / m 3 ; (2) Determine the activation energy of the aging reaction of fiber-reinforced resin-based composites According to the method provided by ASTM E1641, the apparent activation energy of the fiber-reinforced resin matrix composite material when the resin-air atmosphere thermal weight loss rate is 5% is determined; the coefficient of this thermal weight loss apparent activation energy is calculated as the aging reaction activation energy of the fiber-reinforced resin matrix composite material E a ; (3) Carry out accelerated aging tests on fiber-reinforced resin-based composite materials and test the material properties after the tests Calculate the acceleration factor based on the accelerated aging test temperature and aging reaction activation energy obtained in steps (1) and (2) and the expected storage temperature; then calculate the accelerated aging test time based on the obtained acceleration factor and the expected storage time; The calculated results of the accelerated aging test time are rounded to an integer, and accelerated aging tests are carried out at constant temperature and humidity. Samples are taken regularly and the performance of the material after aging is tested. (4) Fitting the regression equation of the change of fiber reinforced resin matrix composite material performance with accelerated aging time A polynomial regression analysis was conducted with the accelerated aging test time as the independent variable and the performance test value of the fiber-reinforced resin-based composite material as the dependent variable, and the regression equation of the fiber-reinforced resin-based composite material performance changing with the accelerated aging time was obtained. (5) Evaluate the performance of fiber-reinforced resin-based composite materials with the required storage time Using the regression equation obtained in step (4), the performance of the fiber-reinforced resin-based composite material at the required storage time is evaluated.

2. The method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material according to claim 1, wherein: The test temperature of the accelerated aging test in step (1) is 75°C.

3. The method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material according to claim 1, wherein: When calculating the apparent activation energy of thermal weight loss in step (2), the coefficient is 0.6-0.

7.

4. The method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material according to claim 1, wherein: When calculating the acceleration coefficient in step (3), the Arrhenius equation is used: Where: F — acceleration factor; k 1—Aging rate constant at storage temperature; k 2—Aging rate constant under accelerated aging conditions; E a —Activation energy of aging reaction, J·mol -1 ; R —Gas constant, 8.314 J·K -1 ·mol -1 ; T 1—Storage temperature, K; T 2—Accelerated aging test temperature, K.

5. The method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material according to claim 1, wherein: In step (3), the accelerated aging test time is calculated based on the obtained acceleration factor and the expected storage time using the following formula: Where: t 2—Accelerated aging test time, d; t 1—Expected storage time, d.

6. The method for evaluating the long-term storage performance of a fiber-reinforced resin-based composite material according to claim 1, wherein: The step (3) tests the material properties of the fiber-reinforced resin-based composite material after the accelerated aging test, including flexural strength and flexural modulus.

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