Method for evaluating seawater resistance of cyanate ester-based composite material for structural material

Abstract

The invention discloses a method for evaluating seawater resistance of a cyanate ester-based composite material for a structural material, and belongs to the field of material performance testing, and the method comprises the following steps: S1, preparing a sample plate of the cyanate ester-based composite material for seawater resistance testing, and cutting the sample plate into a sample sheet I, a sample sheet II and a sample sheet III; s2, soaking the sample piece I, the sample piece II and the sample piece III, and sampling and testing at different time nodes; s3, obtaining a fitting equation about the water absorption rate, the interlayer shear strength and the glass transition temperature; s4, converting into a long-time fitting equation; s5, calculating an evaluation score; s6, comparing the evaluation score S with the required score of the allowable value of the cyanate ester matrix composite to obtain an evaluation conclusion; the evaluation score is calculated through fitting equations corresponding to the water absorption rate, the interlaminar shear strength and the glass transition temperature, and the method is used for predicting the seawater resistance of the cyanate ester matrix composite for the structural material.

Description

Technical Field

[0001] This invention relates to the field of material performance testing, and specifically to a method for evaluating the seawater resistance of cyanate ester-based composites for structural materials. Background Technology

[0002] With the rapid development of structural components, the storage characteristics of the main structural component materials have gradually attracted attention, especially the impact of the environment on materials during storage and use in marine environments, which directly affects the quality and reliability of structural components. Cyanate ester resin materials have good temperature resistance, as well as extremely low properties and dielectric constant, making them very suitable for structural components or integrated structural and functional parts that are used for a long time in marine environments.

[0003] Compared to normal aging under humid heat, the aging factors of resin-based composites in seawater environments are more complex. In addition to temperature and humidity as the main corrosive aging factors under normal conditions, they are also affected by factors such as salinity. Ions in salt can cause chemical corrosion, while seawater, as a polar molecule, can accelerate the breakdown of large molecules into smaller molecule leachates.

[0004] Currently, structural components are made from either metal-based or resin-based materials. Compared to the comprehensive testing and evaluation methods for metal-based corrosion, resin-based composites lack universal testing standards and evaluation methods for damp heat aging and corrosion. For example, GB / 1462, a commonly used test method for the water absorption of fiber-reinforced plastics, specifies the sample size but does not address the impact of seawater salinity on the material, and the pH environment used in the test is not suitable for marine environments. Therefore, a new testing environment design is needed to simulate the storage and operating conditions of structural components. Furthermore, there are few reports on the seawater resistance of cyanate ester-based composites used in structural components. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to calculate the evaluation score by fitting equations corresponding to water absorption rate, interlaminar shear strength and glass transition temperature, and use it to predict the seawater resistance of cyanate ester matrix composites for structural materials.

[0006] The technical solution adopted by this invention to solve the technical problem is: a method for evaluating the seawater resistance of cyanate ester-based composites for structural materials, comprising the following steps:

[0007] S1: Prepare a sample of the cyanate matrix composite for seawater resistance testing, and cut the sample to form sample one for water absorption testing, sample two for interlaminar shear strength testing, and sample three for DMA dynamic thermomechanical analysis testing.

[0008] S2: The sample 1, sample 2 and sample 3 are all immersed in the seawater test solution for seawater resistance testing, and samples are taken multiple times at different time points after immersion.

[0009] S3: Obtain the sampling data of sample one, plot the soaking time-water absorption rate relationship graph, and obtain the short-time fitting equation M for water absorption rate based on the soaking time-water absorption rate relationship graph. r =f1(d), obtain the sampling data of the second sample, plot the relationship between immersion time and interlaminar shear strength, and obtain the short-time fitting equation τ for interlaminar shear strength based on the relationship between immersion time and interlaminar shear strength. M =f2(d), obtain the sampling data of the sample three, plot the relationship between immersion time and glass transition temperature, and obtain the short-time fitting equation for glass transition temperature T = f3(d) based on the relationship between immersion time and glass transition temperature;

[0010] Among them, M r τ is the water absorption rate. M Where is the interlaminar shear strength, T is the glass transition temperature, and d is the short-time days;

[0011] S4: Multiply the short-time days d corresponding to the short-time fitting equations for water absorption rate, interlaminar shear strength, and glass transition temperature by the doubling factor K to obtain the long-time fitting equation M for water absorption rate. r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-term fitting equation for the glass transition temperature T = F3(D), where D is the number of long-term days;

[0012] S5: Calculate the evaluation score S, S = W1*A1 + W2*A2 + W3*A3;

[0013] Where W1 is the water absorption rate weight, W2 is the interlaminar shear strength weight, W3 is the glass transition temperature weight, W1+W2+W3=1, and A1 is the water absorption rate normalization value, which is obtained through M. r =F1(D) is the water absorption rate obtained from the calculation, and A2 is the normalized value of interlaminar shear strength, which is obtained by τ M =F2(D) is the interlaminar shear strength obtained by calculation, and A3 is the normalized value of the glass transition temperature, which is obtained by calculation of the glass transition temperature obtained by T=F3(D);

[0014] S6: Compare the evaluation score S with the required score of the allowable value of the cyanate ester matrix composite to obtain the evaluation conclusion.

[0015] As a preferred embodiment of the present invention, the water absorption rate normalization value A1 = (B max1 -B1) / (B max1 -B mix1 ), where B max1 B is the critical water absorption rate. mix1 B1 represents the initial water absorption rate before soaking, and B1 represents the long-term fitting equation M based on the water absorption rate. r =F1(D) is the water absorption rate at point D calculated by the interlaminar shear strength normalized value A2 = (B2 - B mix2 ) / (B max2 -B mix2 ), where B mix2 B is the critical interlaminar shear strength. max2 B1 represents the initial interlaminar shear strength before soaking, and B2 represents the long-term fitting equation τ based on the interlaminar shear strength. M =F2(D) is the interlaminar shear strength at time D calculated by F2(D), and the normalized value of the glass transition temperature A3 = (B3 - B mix3 ) / (B max3 -B mix3 ), where B mix3 B is the critical glass transition temperature. max3 B3 is the initial glass transition temperature before immersion, and B3 is the glass transition temperature at point D calculated using the long-term fitting equation T = F3(D) based on the glass transition temperature.

[0016] As a preferred embodiment of the present invention: the doubling factor K is obtained using an empirical formula for moisture absorption, wherein the empirical formula for moisture absorption is: Where C is the empirical coefficient, T1, T2 represents the actual ocean temperature and corresponding relative humidity. t1 represents the immersion temperature and corresponding relative humidity under test, t2 represents the time corresponding to the short-time fitting equation under accelerated testing, and t1 represents the exposure time in the actual marine environment.

[0017] As a preferred embodiment of the present invention, the soaking time-water absorption rate relationship graph utilizes the water absorption rate test formula. Obtain, where △m r The value is the water absorption rate, m0 is the mass of sample 1 before soaking, and m is the mass of samples taken and weighed at different time points.

[0018] As a preferred embodiment of the present invention, the immersion time-interlaminar shear strength relationship diagram utilizes the interlaminar shear strength formula: Obtain, where τ M denoted as interlaminar shear strength, F as failure load or maximum load, b as specimen width, and h as specimen thickness.

[0019] As a preferred technical solution of the present invention, the glass transition temperature relationship graph is obtained by obtaining the glass transition temperature through dynamic thermomechanical analysis and combining it with the immersion time. The dynamic thermomechanical analysis is performed by three-point bending vibration, and the arithmetic mean of the temperature values ​​corresponding to the highest tanδ value obtained by the test is taken as the critical glass transition temperature.

[0020] As a preferred embodiment of the present invention, the soaking time-water absorption rate relationship graph uses soaking time as the abscissa and water absorption rate as the ordinate; the soaking time-interlaminar shear strength relationship graph uses soaking time as the abscissa and interlaminar shear strength as the ordinate; and the soaking time-glass transition temperature relationship graph uses soaking time as the abscissa and glass transition temperature as the ordinate.

[0021] As a preferred embodiment of the present invention, the cyanate-based composite material includes, but is not limited to, bisphenol A, bisphenol E, tetramethylbisphenol F, hexafluorobisphenol A, and bisphenol M.

[0022] As a preferred embodiment of the present invention, the first sample has a length range of 45-60mm, a width range of 45-60mm, and a thickness range of 1-4mm; the second sample has a length range of 15-30mm, a width range of 5-15mm, and a thickness range of 1-3mm; and the third sample has a length range of 55-70mm, a width range of 4-7mm, and a thickness range of 0.5-3mm.

[0023] As a preferred embodiment of the present invention, immersing the first, second, and third samples in a seawater test solution for seawater resistance testing specifically includes:

[0024] Several of the aforementioned sample 1, sample 2, and sample 3 are suspended in a container containing seawater test solution. The volume ratio of the seawater test solution to the volume of sample 1, sample 2, and sample 3 is ≥800. A water bath containing distilled water is preheated and kept at 70°C. A thin film is covered at the mouth of the container to prevent moisture evaporation. The container is then placed in the water bath.

[0025] The beneficial effects of this invention are reflected in:

[0026] 1. This method is simple, comprehensive, and reproducible. It can intuitively reflect the seawater resistance of cyanate ester resin-based composites through dynamic thermomechanical analysis, changes in mechanical properties, and water absorption data. By fitting various exponential functions, it can determine the number of days the material can be stored under different temperatures and humidity levels under the allowable design values, as well as the expected performance of the material under specific future storage days. This is of great significance for studying the seawater resistance of cyanate ester-based structural components stored and used in long-term seawater environments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the test environment;

[0028] Figure 2 These are curves showing the relationship between soaking time and water absorption rate, and the relationship between soaking time and interlaminar shear strength, obtained by fitting data points using an exponential function equation.

[0029] Figure 3 These are curves showing the relationship between soaking time and water absorption rate, and the relationship between soaking time and glass transition temperature, obtained by fitting data points using an exponential function equation.

[0030] Figure 4 This is a flowchart of the method of the present invention. Detailed Implementation

[0031] The invention will now be described in further detail with reference to the accompanying drawings.

[0032] Combined with appendix Figure 4 As shown, a method for evaluating the seawater resistance of cyanate-based composites for structural materials is characterized by the following steps:

[0033] S1: Prepare a sample of the cyanate ester matrix composite for seawater resistance testing, and cut the sample to form sample 1 for water absorption testing, sample 2 for interlaminar shear strength testing, and sample 3 for DMA dynamic thermomechanical analysis testing. Preferably, sample 1, sample 2, and sample 3 are divided into test group and control group to meet the requirements of test rigor, and the test is mainly based on the test group.

[0034] Specifically:

[0035] The cyanate ester-based composites include, but are not limited to, bisphenol A, bisphenol E, tetramethylbisphenol F, hexafluorobisphenol A, bisphenol M, or other corrosion-resistant resin-based composites;

[0036] The length of sample one ranges from 45 to 60 mm, the width ranges from 45 to 60 mm, and the thickness ranges from 1 to 4 mm. The ratio between the longest side and the shortest side of sample one is not less than 8. The length of sample two ranges from 15 to 30 mm, the width ranges from 5 to 15 mm, and the thickness ranges from 1 to 3 mm. The length of sample three ranges from 55 to 70 mm, the width ranges from 4 to 7 mm, and the thickness ranges from 0.5 to 3 mm.

[0037] S2: The sample 1, sample 2 and sample 3 are all immersed in the seawater test solution for seawater resistance testing, and samples are taken multiple times at different time points after immersion.

[0038] Specifically:

[0039] The seawater test solution is made of simulated seawater, real seawater, or 5% NaCl solution. Several of the sample pieces 1, 2, and 3 are suspended in a container containing the seawater test solution. The volume ratio of the seawater test solution to the volume of sample pieces 1, 2, and 3 is ≥800. A water bath containing distilled water is preheated and kept at 70°C. A thin film is covered at the mouth of the container to prevent water evaporation. The container is then placed in the water bath.

[0040] S3: Obtain the sampling data of sample one, plot the soaking time-water absorption rate relationship graph, and obtain the short-time fitting equation M for water absorption rate based on the soaking time-water absorption rate relationship graph. r =f1(d), obtain the sampling data of the second sample, plot the relationship between immersion time and interlaminar shear strength, and obtain the short-time fitting equation τ for interlaminar shear strength based on the relationship between immersion time and interlaminar shear strength. M =f2(d), obtain the sampling data of the sample three, plot the relationship between immersion time and glass transition temperature, and obtain the short-time fitting equation for glass transition temperature T = f3(d) based on the relationship between immersion time and glass transition temperature;

[0041] Among them, M r τ is the water absorption rate. M Where is the interlaminar shear strength, T is the glass transition temperature, and d is the short-time days;

[0042] Before measuring the glass transition temperature and interlaminar shear strength, the interval between taking the sample and conducting the test should never exceed 12 hours.

[0043] Specifically:

[0044] The soaking time-water absorption rate relationship graph uses the water absorption rate test formula. Obtain, where △m rThe water absorption rate is given by m0, where m is the mass of sample 1 before soaking, and m is the mass of samples taken and weighed at different time points.

[0045] The immersion time-interlaminar shear strength relationship diagram utilizes the interlaminar shear strength formula: Obtain, where τ M denoted as interlaminar shear strength, F as failure load or maximum load, b as specimen width, and h as specimen thickness;

[0046] The immersion time-glass transition temperature relationship graph is obtained by combining the glass transition temperature with the immersion time through dynamic thermomechanical analysis test. The dynamic thermomechanical analysis test is carried out by three-point bending vibration, and the arithmetic mean of the temperature values ​​corresponding to the highest tanδ value obtained by the test is used as the critical glass transition temperature.

[0047] The soaking time-water absorption rate relationship graph uses soaking time as the horizontal axis and water absorption rate as the vertical axis; the soaking time-interlaminar shear strength relationship graph uses soaking time as the horizontal axis and interlaminar shear strength as the vertical axis; the soaking time-glass transition temperature relationship graph uses soaking time as the horizontal axis and glass transition temperature as the vertical axis.

[0048] S4: Multiply the short-time days d corresponding to the short-time fitting equations for water absorption rate, interlaminar shear strength, and glass transition temperature by the doubling factor K to obtain the long-time fitting equation M for water absorption rate. r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-time fitting equation for the glass transition temperature T = F3(D), specifically, the short-time fitting equation for the water absorption rate M r =f1(d), short-time fitting equation for interlaminar shear strength τ M =f2(d) and the short-time fitting equation for glass transition temperature T = f3(d) are multiplied by the doubling factor K to obtain the long-time fitting equation for water absorption rate M. r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-term fitting equation for glass transition temperature T = F3(D), where D is the number of long-term days. The short-term fitting equation is the fitting equation obtained under the experimental accelerated testing environment. Due to the limitations of the testing environment, the value of d is recommended not to exceed 150. The long-term fitting equation is the fitting equation obtained with the actual marine environment as the background, in order to predict the performance at a certain time in the actual marine environment.

[0049] Long-term fitting equation for water absorption rate M r =F1(D) is used for water absorption prediction, and the long-term fitting equation for interlaminar shear strength is τ. M=F2(D) is used to predict interlaminar shear strength and judge the mechanical property degradation based on the prediction results. The long-term fitting equation for glass transition temperature T=F3(D) is used to predict glass transition temperature and judge the temperature property degradation based on the prediction results.

[0050] Specifically:

[0051] The doubling factor K is obtained using an empirical formula for moisture absorption. The empirical formula for moisture absorption is: Where C is an empirical coefficient, preferably 81.5, for temperatures ≥60℃, T1, T2 represents the actual ocean temperature and corresponding relative humidity. t2 represents the immersion temperature and corresponding relative humidity under test, t2 represents the time corresponding to the short-time fitting equation under accelerated testing, which is selected based on the number of days of the experimental test, and t1 represents the exposure time in the actual marine environment, which is selected based on the number of days to be predicted in the actual marine environment.

[0052] S5: Calculate the evaluation score S, S = W1*A1 + W2*A2 + W3*A3;

[0053] Where W1 is the water absorption rate weight, W2 is the interlaminar shear strength weight, W3 is the glass transition temperature weight, W1+W2+W3=1, and A1 is the water absorption rate normalization value, which is obtained through M. r =F1(D) is the water absorption rate obtained from the calculation, and A2 is the normalized value of interlaminar shear strength, which is obtained by τ M =F2(D) is the interlaminar shear strength obtained by calculation, and A3 is the normalized value of the glass transition temperature, which is obtained by calculation of the glass transition temperature obtained by T=F3(D);

[0054] Specifically:

[0055] The normalized value of water absorption rate A1 = (B max1 -B1) / (B max1 -B mix1 ), where B max1 B is the critical water absorption rate. mix1 B1 represents the initial water absorption rate before soaking, and B1 represents the long-term fitting equation M based on the water absorption rate. r =F1(D) is the water absorption rate at point D calculated by the interlaminar shear strength normalized value A2 = (B2 - B mix2 ) / (B max2 -B mix2 ), where B mix2 B is the critical interlaminar shear strength. max2B1 represents the initial interlaminar shear strength before soaking, and B2 represents the long-term fitting equation τ based on the interlaminar shear strength. M =F2(D) is the interlaminar shear strength at time D calculated by F2(D), and the normalized value of the glass transition temperature A3 = (B3 - B mix3 ) / (B max3 -B mix3 ), where B mix3 B is the critical glass transition temperature. max3 B3 is the initial glass transition temperature before immersion, and B3 is the glass transition temperature at point D calculated using the long-term fitting equation T = F3(D) for the glass transition temperature.

[0056] S6: Compare the evaluation score S with the required score of the allowable value of the cyanate ester matrix composite to obtain the evaluation conclusion.

[0057] Combined with appendix Figure 1-3 As shown:

[0058] Example 1:

[0059] For example, for cyanate ester matrix composites with permissible design requirements of moisture absorption ≤0.55%, interlaminar shear strength ≥90MPa, glass transition temperature ≥225℃, and storage and attendance environment of 30℃ and 60% relative humidity, the critical moisture absorption is 0.55%, the critical interlaminar shear strength is 90MPa, and the critical glass transition temperature is 225℃.

[0060] Based on historical experience, the weights for water absorption rate (W1), interlaminar shear strength (W2), and glass transition temperature (W3) in the evaluation of this cyanate ester matrix composite are 0.5, 0.4, and 0.1, respectively. The seawater resistance performance is predicted to be 1 year (365 days) after storage. Based on experience, an evaluation score of 0 (excluding) to 0.2 is considered average, 0.2 to 0.5 is considered good, and >0.5 is considered excellent.

[0061] Prepare sample one, which is 50mm*50mm*2mm in size. Wipe the surface with alcohol and then put them in the same batch into the oven for 6 hours at 90℃. After taking them out, let them cool to room temperature. Then, weigh all test samples within 30 minutes.

[0062] Prepare sample two, which is 20mm*10mm*2mm in size. Wipe the surface with alcohol and then put them in the same batch into the oven for 6 hours at 90℃. After taking them out, let them cool to room temperature. Then, weigh all test samples within 30 minutes.

[0063] Prepare sample three, which is 60mm*5mm*1mm in size. Wipe the surface with alcohol and then put them in the same batch into the oven for 6 hours at 90℃. After taking them out, let them cool to room temperature. Then, weigh all test samples within 30 minutes.

[0064] Preheat a water bath containing distilled water to 70°C and keep it warm.

[0065] Add simulated or real seawater, which will be used as the seawater test solution, to the beaker. The composition of the seawater is shown in Table 1. Suspend sample 1, sample 2 and sample 3 in the beaker and immerse them in the seawater test solution. Cover the mouth of the beaker with a protective film to prevent water evaporation. Then place the beaker in a preheated water bath.

[0066] Following the principle of prioritizing denser samples over sparser ones, samples of sample 1 were taken at different time points on days 2, 4, 8, 16, 24, 30, 50, 80, and 128. Each time, 5 samples of sample 1 were taken. After each sampling, the samples were wiped, dried, and placed at room temperature for weighing. The weight was accurate to 0.0001g. The average weight of the 5 samples of sample 1 was then calculated.

[0067] Using the water absorption rate test formula Obtain the relationship between soaking time and water absorption rate, where Δm r Let m be the water absorption rate under this test, m be the average weight of each sample, and m0 be the weight before soaking. A graph showing the relationship between soaking time and water absorption rate is plotted with soaking time on the x-axis and water absorption rate on the y-axis. Based on this graph, the short-time fitting equation for the water absorption rate, M, is obtained. r =f1(d);

[0068] Specifically, M r = 0.15462 + 0.2293(1 - exp(-d / 1.94483)) + 0.19153(1 - exp(-d / 19.57094)), where M r The equation has a good fit of 0.9972, where d is the water absorption rate and d is the number of short-term days.

[0069] Following the principle of prioritizing denser samples over sparser ones, samples of sample two were taken at different time points on days 2, 4, 8, 16, 24, 30, 50, 80, and 128. Five samples of sample two were taken each time. After each sampling, the samples were wiped clean, dried, and placed at room temperature for interlaminar shear strength measurement. A three-point loading method with a small span-to-thickness ratio was used for measurement. Specifically, a rectangular cross-section rod was used as a simply supported beam, placed on two supports, and a bending load was applied at the center of the supports to induce interlaminar shear failure. Measurements were taken along the fiber direction with a span of 10 mm and a test speed of 1 ± 0.2 mm / min. The sample should exhibit a reasonable failure mode such as single-layer or multi-layer shear. The maximum load or destructive load experienced by sample two after shear failure was recorded, and the interlaminar shear strength was calculated.

[0070] Using the interlaminar shear strength formula: Obtain the immersion time-interlaminar shear strength relationship diagram, where τ M Interlaminar shear strength is expressed in megapascals (MPa), F is the breaking load or maximum load in newtons (N), b is the specimen width in mm, and h is the specimen thickness in mm. A graph showing the relationship between immersion time and interlaminar shear strength is plotted with immersion time on the x-axis and water absorption rate on the y-axis. Combining this with the water absorption rate test results, a second graph is plotted with water absorption rate on the y-axis to obtain... Figure 2 The curve shown is used to obtain the short-time fitting equation τ for interlaminar shear strength based on the immersion time-interlaminar shear strength relationship graph. M =f2(d);

[0071] Specifically, τ M =102.495-7.15609*(1-exp(-d / 18.53862))-7.15609*(1-exp(-d / 18.5386)), where τ M The interlaminar shear strength is expressed in megapascals (MPa), d is the short-term duration in days, and the goodness of fit of the equation is 0.9968.

[0072] Following the principle of prioritizing denser samples over sparser ones, samples of sample three were taken at different time points on days 2, 4, 8, 16, 24, 30, 50, 80, and 128. Each time, three groups of sample three were taken, with two samples in each group. After each sampling, the sample was wiped clean, dried, and placed at room temperature for glass transition temperature measurement. Dynamic thermomechanical analysis was performed using a three-point bending vibration method with a heating rate of 3°C / min and a vibration frequency of 5Hz. The test range was room temperature to 350°C. The arithmetic mean of the temperature values ​​corresponding to the highest tanδ value obtained from the test was taken as the critical glass transition temperature.

[0073] A graph showing the relationship between immersion time and glass transition temperature was plotted with immersion time as the x-axis and the glass transition temperature obtained from dynamic thermomechanical analysis as the y-axis. Combined with the water absorption rate test results, a second y-axis graph was then plotted with the water absorption rate. Figure 3 The curve shown is based on the relationship between immersion temperature and glass transition temperature. The short-time fitting equation for the glass transition temperature is T = f3(d).

[0074] Specifically, T = 344.48 - 83.947 * (1 - exp(-d / 0.867)) - 37.876 * (1 - exp(-d / 18.471)), where T is the glass transition temperature in degrees Celsius, d is the short-term number of days in days, and the goodness of fit of the equation is 0.99784;

[0075] Using the empirical formula for moisture absorption Obtain the doubling factor K, where C is an empirical coefficient whose value is related to the actual temperature. Specifically, for temperatures ≥60℃, C is 81.5, T1, The actual ocean temperature and corresponding relative humidity are 30℃ and 60%, respectively. (T2, ...) The immersion temperature and corresponding relative humidity under test are 70℃ and 100%, respectively. t2 is the time corresponding to the short-time fitting equation under the experimental accelerated test, which is selected according to the number of days of the experimental test. t1 is the exposure time in the actual marine environment, which is selected according to the number of days to be predicted in the actual marine environment. The calculated K value is 28.67 days, that is, 1 day in the test is equivalent to 28.67 days in the actual marine environment.

[0076] The short-time fitting equation M for the water absorption rate r =f1(d), short-time fitting equation for interlaminar shear strength τ M =f2(d) and the short-time fitting equation for glass transition temperature T = f3(d) are multiplied by the doubling factor K to obtain the long-time fitting equation for water absorption rate M. r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-term fitting equation for the glass transition temperature T = F3(D), where D is the number of long-term days;

[0077] Based on the short-time fitting equation M for water absorption rate r =f1(d), short-time fitting equation for interlaminar shear strength τ M=f2(d) and the critical values ​​of the short-time fitting equation T = f3(d) for the glass transition temperature, combined with the doubling factor K, it can be seen that the number of days to reach the critical water absorption rate, critical interlaminar shear strength and critical glass transition temperature in the actual marine environment are 1118.13 days for water absorption rate, 1089.46 days for interlaminar shear strength and 1462.17 days for glass transition temperature. That is, the number of days that the material can be stored under the minimum requirements of the corresponding indicators are 1118.13 days, 1089.46 days and 1462.17 days respectively. Taking the minimum value as the constraint, the material can be stored for 1089.46 days in the actual marine environment.

[0078] Predict the seawater resistance of the material for one year, calculate the evaluation score S, and use S = W1*A1 + W2*A2 + W3*A3;

[0079] Among them, according to the long-term fitting equation M of water absorption rate r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-term fitting equation for the glass transition temperature T = F3(D), the water absorption rate over one year (365 days) is 0.47%, the interlaminar shear strength is 95.38 MPa, and the glass transition temperature is 241.7℃. The initial water absorption rate before immersion is 0.155%, the initial interlaminar shear strength before immersion is 102 MPa, and the initial glass transition temperature before immersion is 344℃. Substituting these values ​​into the numerical calculations, we can see that:

[0080] S=0.5*(0.55-0.47) / (0.55-0.155)+0.4*(95.38-90) / (102-90)+0.1*(241.7-225) / (344-225)=0.293;

[0081] The evaluation score S was compared with the required score of the allowable value of the cyanate ester matrix composite. The score of 0.293 is in the good performance range.

[0082] Example 2:

[0083] The difference from Example 1 is:

[0084] Taking a cyanate-based composite material with permissible design requirements of moisture absorption ≤0.58%, interlaminar shear strength ≥86.54MPa, and glass transition temperature ≥221.2℃ as an example, and with storage and attendance environments of 25℃ and 65% relative humidity, the critical moisture absorption is 0.58%, the critical interlaminar shear strength is 86.54MPa, and the critical glass transition temperature is 221.2℃.

[0085] Based on historical experience, the weights for water absorption rate (W1), interlaminar shear strength (W2), and glass transition temperature (W3) in the evaluation of this cyanate ester matrix composite are 0.2, 0.5, and 0.3, respectively. According to experience, when the evaluation score is 0-0.3, its performance is rated as average; when it is 0.3-0.8, its performance is rated as good; and when it is 0.8-1, its performance is rated as excellent. The predicted storage time is 5 years (365*5 days) for seawater resistance.

[0086] The dimensions of sample one are 60*60*4mm;

[0087] The dimensions of sample two are 30*15*3mm;

[0088] Sample 3 measures 70*7*3mm;

[0089] The seawater test solution is a 5% NaCl solution;

[0090] Following the principle of prioritizing denser samples over sparser ones, samples 1, 2, and 3 were taken on days 1, 2, 4, 8, 16, 32, 64, 96, and 128.

[0091] Accordingly, the short-time fitting equation M for water absorption rate is obtained. r =f1(d);

[0092] Specifically, M r =0.1431+0.307(1-exp(-d / 2.484))+0.149(1-exp(-d / 37.928)), the goodness of fit of this equation is 0.9982;

[0093] Accordingly, the short-time fitting equation τ for interlaminar shear strength is obtained. M =f2(d);

[0094] Specifically, τ M =111.076-12.116*(1-exp(-d / 46.093))-14.654*(1-exp(-d / 1.283)), the goodness of fit of this equation is 0.9825;

[0095] Accordingly, the short-time fitting equation for the glass transition temperature is obtained as T = f3(d);

[0096] Specifically, T = 245.48 - 17.493*(1-exp(-d / 5.928)) - 10.577*(1-exp(-d / 76.028)), and the goodness of fit of this equation is 0.985.

[0097] Accordingly, using the empirical formula for moisture absorption, we choose C = 81.5, T1, The actual ocean temperature and corresponding relative humidity are 25℃ and 65%, respectively. (T2, ...) The immersion temperature and corresponding relative humidity under test are 70℃ and 100%, respectively. t2 is the time corresponding to the short-time fitting equation under the experimental accelerated test, which is selected according to the number of days of the experimental test. t1 is the exposure time in the actual marine environment, which is selected according to the number of days to be predicted in the actual marine environment. The obtained doubling factor K is 46.8, that is, 1 day in the test is equivalent to 46.8 days in the actual marine environment.

[0098] Predict the seawater resistance of the material over five years, calculate the evaluation score S, and use S = W1*A1 + W2*A2 + W3*A3;

[0099] Among them, according to the long-term fitting equation M of water absorption rate r =F1(D), Long-term fitting equation for interlaminar shear strength τ M =F2(D) and the long-term fitting equation for the glass transition temperature T = F3(D), the water absorption rate after five years (365*5 days) is 0.546%, the interlaminar shear strength is 89.5 MPa, and the glass transition temperature is 223.8℃. The initial water absorption rate before immersion is 0.1431%, the initial interlaminar shear strength before immersion is 111.1 MPa, and the initial glass transition temperature before immersion is 245.48℃. Substituting these values ​​into the numerical calculations, we can see that:

[0100] S=0.2*(0.58-0.546) / (0.58-0.1431)+0.5*(89.5-86.54) / (111.1-86.54)+0.3*(223.8-221.2) / (245.48-221.2)=0.11;

[0101] The evaluation score S was compared with the required score of the allowable value of the cyanate ester matrix composite, and the result of 0.11 indicates that the performance is within the general range.

[0102] Table 1. Simulated seawater composition (neutral wt%)

[0103] Types / Ingredients NaCl <![CDATA[MgCl2]]> <![CDATA[CaCO3]]> <![CDATA[MgSO4·7H2O]]> <![CDATA[CaSO4·2H2O]]> NaCl concentration / % seawater 21 2.51 0.1 1.51 2.43 2

[0104] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the seawater resistance of a cyanate-based composite material for structural materials, characterized by: It comprises the following steps: S1: prepare the cyanate ester matrix composite sample for seawater resistance test, and cut the sample to form sample one for water absorption test, sample two for interlaminar shear strength test, and sample three for DMA dynamic mechanical analysis test; S2: place the sample one, sample two and sample three in seawater test solution for seawater resistance test, and take multiple samples of the soaked sample one, sample two and sample three at different time nodes; S3: obtaining the sample data of the sample one to draw an immersion time-water absorption rate relation graph, and obtaining a water absorption rate short-time fitting equation M = f1(d) according to the immersion time-water absorption rate relation graph r = f2(d), obtaining the sample data of the sample two to draw an immersion time-interlaminar shear strength relation graph, and obtaining an interlaminar shear strength short-time fitting equation τ = f2(d) according to the immersion time-interlaminar shear strength relation graph M = f3(d); obtaining the sample data of the sample three to draw an immersion time-glass transition temperature relation graph, and obtaining a glass transition temperature short-time fitting equation T = f3(d) according to the immersion time-glass transition temperature relation graph; wherein M r is the water absorption, τ M is the interlaminar shear strength, T is the glass transition temperature, and d is the short-term days; S4: multiplying the short-time days d corresponding to the short-time fitting equations of the water absorption, interlaminar shear strength and glass transition temperature respectively by the doubling coefficient K to obtain the long-time fitting equation M of water absorption r = F1(D), the long-time fitting equation τ of interlaminar shear strength M = F2(D) and the long-time fitting equation T = F3(D) of glass transition temperature, wherein D is the long-time days; S5: calculate the evaluation score S, S=W1*A1+W2*A2+W3*A3; wherein W1 is a water absorption weight, W2 is an interlaminar shear strength weight, W3 is a glass transition temperature weight, W1+W2+W3=1, A1 is a water absorption normalized value, the water absorption normalized value is calculated by M r = F1(D) learned water absorption, A2 is an interlaminar shear strength normalized value, the interlaminar shear strength normalized value is calculated by τ M = F2(D) learned interlaminar shear strength, A3 is a glass transition temperature normalized value, the glass transition temperature normalized value is calculated by T = F3(D) learned glass transition temperature; S6: compare the evaluation score S with the required score of the cyanate ester matrix composite allowable value, and obtain the evaluation conclusion.

2. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: the water absorption normalized value A1 = (B max1 -B max1 ) / (B mix1 ), where B max1 is the critical water absorption, B mix1 is the initial water absorption without soaking, and B1 is the water absorption at D calculated using the long-time fitting equation M r = F1(D) for the water absorption, the interlaminar shear strength normalized value A2 = (B2-B mix2 ) / (B max2 -B mix2 ), where B mix2 is the critical interlaminar shear strength, B max2 is the initial interlaminar shear strength without soaking, and B2 is the interlaminar shear strength at D calculated using the long-time fitting equation τ M = F2(D) for the interlaminar shear strength, and the glass transition temperature normalized value A3 = (B3-B mix3 ) / (B max3 -B mix3 ), where B mix3 is the critical glass transition temperature, B max3 is the initial glass transition temperature without soaking, and B3 is the glass transition temperature at D calculated using the long-time fitting equation T = F3(D) for the glass transition temperature.

3. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The doubling factor K is obtained using a hygroscopic empirical formula, which is where C is an empirical coefficient, T1, is the actual temperature of the sea and the corresponding relative humidity, T2, is the immersion temperature under test and the corresponding relative humidity, t2 is the time corresponding to the short-term fitting equation under experimental accelerated test, and t1 is the time of exposure under actual marine environment.

4. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The soaking time-water absorption rate graph utilizes a water absorption test formula is obtained, where Δm r is the water absorption rate, m0is the mass of the sample piece before soaking, and m is the mass of the sample taken for weighing at different time points.

5. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The soak time-interlaminar shear strength graph utilizes the interlaminar shear strength formula: is obtained, where τ M is the interlaminar shear strength, F is the failure load or maximum load, b is the specimen width, and h is the specimen thickness.

6. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The soaking time-glass transition temperature relationship diagram is obtained by dynamic mechanical analysis test, and the arithmetic mean of the temperature values corresponding to the highest tan delta values obtained by the test is taken as the critical glass transition temperature.

7. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The soaking time-water absorption rate relationship diagram takes soaking time as the abscissa and water absorption rate as the ordinate, the soaking time-interlaminar shear strength relationship diagram takes soaking time as the abscissa and interlaminar shear strength as the ordinate, and the soaking time-glass transition temperature relationship diagram takes soaking time as the abscissa and glass transition temperature as the ordinate.

8. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The cyanate ester matrix composite includes but is not limited to bisphenol A type, bisphenol E type, tetramethyl bisphenol F type, hexafluorobisphenol A type, and bisphenol M type.

9. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 1, characterized by: The length of the sample one ranges from 45 to 60 mm, the width ranges from 45 to 60 mm, and the thickness ranges from 1 to 4 mm; the length of the sample two ranges from 15 to 30 mm, the width ranges from 5 to 15 mm, and the thickness ranges from 1 to 3 mm; the length of the sample three ranges from 55 to 70 mm, the width ranges from 4 to 7 mm, and the thickness ranges from 0.5 to 3 mm.

10. The method for evaluating the seawater resistance of a cyanate-based composite material for structural materials according to claim 9, characterized by: The soaking of the sample one, sample two and sample three in seawater test solution for seawater resistance test specifically comprises: A plurality of sample one, sample two and sample three are placed in a container containing seawater test solution in a suspended manner, the volume ratio of the solution of the seawater test solution to the volume of the sample one, sample two and sample three is ≥800, a water bath containing distilled water is preheated, and the water bath is heated to 70℃ for insulation, a film is covered on the container opening to prevent water evaporation, and then the container is placed in the water bath.

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