Method for rapid detection of the degree of cure of carbon fiber reinforced resin-based prepreg

Abstract

This invention discloses a rapid method for detecting the degree of curing of carbon fiber reinforced resin-based prepregs. The method calculates the degree of curing based on the relationship between the heat of cross-linking reaction generated during the complete curing of the carbon fiber reinforced resin-based prepreg at different external curing times. During the heating process, the resin undergoes a curing reaction, accompanied by the generation of heat. The temperature difference between the sample and the reference material is ΔT. ΔT is eliminated by applying external power, resulting in ΔT = 0. The power difference ΔP, as it changes with the sample temperature T, generates a ΔP-T relationship curve. The peak area S of the curve is proportional to the heat of curing reaction, and the degree of curing of the prepreg is calculated by the change in S. This invention is simple, rapid, and efficient, and can be widely used for detecting the lifespan and degree of curing of carbon fiber reinforced resin-based prepregs during external curing.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of performance detection of carbon fiber reinforced resin matrix prepreg, and relates to a rapid detection method for curing degree of carbon fiber reinforced resin matrix prepreg. BACKGROUND

[0002] The carbon fiber reinforced resin matrix prepreg will have a slow curing reaction in the production, storage and application process. If the curing degree of the prepreg cannot be controlled, it will have a great impact on the application of the prepreg, such as affecting the laying, molding and mechanical properties of the composite plate. Therefore, a rapid measurement method for the curing degree of the prepreg needs to be found. Through the detection of the curing degree, the storage quality and operation life of the prepreg can be judged, which plays a good guiding role in the later application.

[0003] The traditional curing degree test method for the carbon fiber reinforced resin matrix prepreg is a solution method and a smear method. For the prepreg with high curing degree, there are problems of difficult dissolution and loss of a large amount of insoluble information, and the chemical solvent used not only has high cost, but also causes serious environmental pollution if not properly treated later. SUMMARY

[0004] The application aims to provide a rapid detection method for the curing degree of carbon fiber reinforced resin matrix prepreg.

[0005] The technical scheme for realizing the application is as follows:

[0006] The rapid detection method for the curing degree of the carbon fiber reinforced resin matrix prepreg comprises the following steps:

[0007] Step 1: An automatic sampling machine is set with n sampling points, and the sampling interval is set according to the length and width of the whole-axis prepreg;

[0008] Step 2: A stable flow rate of N2 protective gas is introduced into the detector;

[0009] Step 3: A temperature rising program is set according to a known curing process, during the test process, the automatic sampling machine puts the sample into the crucible and sends it to the detection platform of the detector, the detector is provided with an automatic sampler, during the temperature rising process, the temperature difference thermocouple transmits the temperature difference ΔT between the sample and the reference material empty crucible to the power compensator in real time, the power compensator reduces ΔT to zero by power compensation ΔP, and the signal processor tracks and records the change of the sample temperature T in the detector, and transmits the ΔP-T change trend data to the computing device, and the computing device calculates the integral area S of the ΔP-T curve by formula (1),

[0010]

[0011] The sample point resin complete curing heat release Δh nΔh is proportional to S, and is calculated by formula (2) n :

[0012] Δh n = kS (2),

[0013] wherein k is an instrument constant;

[0014] The degree of cure CD of the sampling point of the carbon fiber reinforced resin matrix prepreg is calculated by formula (3) n ,

[0015]

[0016] wherein CD n is the degree of cure of the sampling point of the carbon fiber reinforced resin matrix prepreg, Δh1 is the complete curing heat release of the resin used before the production of the prepreg, and Δh n is the complete curing heat release of the resin of the sampling point;

[0017] The average degree of cure CD of the carbon fiber reinforced resin matrix prepreg is calculated by formula (4)

[0018]

[0019] In step 1, the sampling points should be uniformly arranged, representative and complete, and the size or mass of each sampling is uniform.

[0020] In step 2, the flow rate is 50 mL / min.

[0021] In step 2, the N2 pipe connected to the detector is provided with a flow control valve, and the purity of N2 is ≥ 99.99%.

[0022] In step 3, the temperature rising program is: the temperature rising rate is 5-30 ℃ / min, and the start and end temperature is 30-400 ℃.

[0023] In step 3, the crucible is made of pure aluminum, and a heat insulation barrier is arranged around the crucible to prevent heat loss, and the heat insulation material is aluminum silicate.

[0024] In step 3, the temperature difference thermocouple is respectively buried below the two crucibles in the detector.

[0025] In step 3, the power compensator adjusts the input power size in real time according to the temperature difference change.

[0026] During the testing process of step 3, there are errors such as heating wire resistance and heat loss, so the instrument constant k is introduced to correct the deviation, k does not change with temperature and operation environment, and can be determined by standard substance, that is, by directly testing the standard substance through the correction testing program, the instrument can automatically identify the constant.

[0027] The calculation principle of the integral area S of the ΔP-T curve in step 3 is as follows: as the test temperature rises, the resin in the prepreg undergoes a curing reaction, and the reaction heat generated thereby causes a temperature difference ΔT between the sample and the reference object. At this time, the power compensator will compensate for the power, the curve will deviate, until ΔT = 0, and the curve returns to the baseline. The entire process produces a closed peak, and the peak area is calculated as S.

[0028] The detection principle of the present application is as follows: during the heating process of the carbon fiber reinforced resin-based prepreg, the resin will undergo a curing reaction, and the reaction will be accompanied by the generation of reaction heat, and the temperature difference ΔT compared with the reference object empty crucible. At this time, ΔT is eliminated by external electric power, i.e. ΔT = 0. The power difference (ΔP) will produce a ΔP-T relationship curve during the change of the sample temperature (T). The peak area S of the curve is proportional to the heat of the curing reaction, and the heat of the curing reaction at the sampling point is obtained according to the peak area S. n The heat of the curing reaction of the carbon fiber reinforced resin-based prepreg is obtained by subtracting the heat of the curing reaction at the sampling point from the heat of the complete curing reaction of the resin used before the production of the prepreg (Δh1-Δh n ), i.e. the heat of the curing reaction of the prepreg. The heat of the curing reaction of the prepreg / the heat of the complete curing reaction of the resin used before the production of the prepreg is the degree of curing of the prepreg.

[0029] Compared with the prior art, the present application has the following advantages:

[0030] (1) It has a high degree of automation. After setting the program, it can automatically sample, test and calculate the test results, which is convenient, fast, saves manpower and time required for sample preparation and data processing.

[0031] (2) The temperature difference thermocouple and the power compensator have high precision, can accurately measure the change of the reaction heat during the curing process of the prepreg, quickly obtain the average degree of curing of the carbon fiber prepreg, have low measurement cost, high precision and good reliability.

[0032] (3) The method is simple and fast, can quickly and automatically evaluate the curing condition of the whole-axis prepreg, meets the curing degree test requirements in the production, storage and use process of the prepreg, and can be widely used in the quality detection in the production, storage and application process of the carbon fiber reinforced resin-based prepreg. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flowchart of the rapid detection method of the degree of curing of the carbon fiber reinforced resin-based prepreg of the present application.

[0034] Figure 2 is a schematic diagram of the working principle of the detector. DETAILED DESCRIPTION

[0035] The present application will be further described in detail below in conjunction with the embodiments and the drawings.

[0036] The present application mainly detects the temperature difference change of the prepreg sample and the reference object by the temperature difference thermocouple, feeds back the temperature difference to the power compensator in real time, adjusts the temperature difference, and finally calculates the curing degree through the relationship curve of the power difference ΔP and the temperature T.

[0037] Before testing, the whole-axis prepreg to be tested is fixed between the feeding roller and the winding roller. The rollers will automatically feed and wind with the automatic sampler. After sampling by the automatic sampler, the sample is transmitted to the detector platform for testing. The detector automatically feeds and tests in sequence, and finally outputs the test data. The data is processed by the calculation device to obtain the result.

[0038] Embodiment

[0039] Curing degree detection of a certain specification T800 carbon fiber reinforced resin-based prepreg

[0040] 1. Test preparation:

[0041] Before testing, the whole-axis prepreg is taken out from the cold storage and placed in a constant temperature (23±2℃) and constant humidity (40-60%) clean room for at least 8 hours. After opening the packaging bag, the prepreg is fixed on the feeding roller, and the prepreg is unwound through the automatic sampler and fixed on the winding roller.

[0042] 2. Test conditions

[0043] The sample needs to be adjusted and tested under the condition that the ambient temperature reaches 23±2℃ and the relative humidity is not greater than 65%.

[0044] 3. Test procedure

[0045] 1) Set the sampling point, which can be set according to the actual situation. The sampling method is set to take 3 samples at equal intervals in the whole width, and the whole-axis prepreg is sampled every 10 meters. When the automatic sampler samples, it removes the isolation film or paper and transports it to the detector platform after being loaded into an aluminum crucible.

[0046] 2) Set the gas domain. The detector is connected to a stable flow rate N2 protective gas inside, with a flow rate of 50 mL / min;

[0047] 3) Set the temperature rising program. The temperature rising rate is set to 10℃ / min, the starting temperature is 30℃, and the terminal temperature is 350℃. The detector is equipped with an automatic feeding device. After the first sample is tested, the sample is automatically fed in sequence and tested according to the previously set temperature rising program.

[0048] 4) Start the test, during the test, the automatic sampler will put the sample into the crucible and send it to the detector platform for detection. The detector is equipped with an automatic sampler. The temperature difference thermocouple will transmit the temperature difference ΔT between the sample and the reference empty crucible to the power compensator in real time. The power compensator will reduce ΔT to zero through power compensation. At this time, the signal processor will track and record the parameter changes in the detector. Finally, the ΔP-T trend data will be transmitted to the computing device. The computing device calculates the integral area S of the ΔP-T curve by formula (1),

[0049]

[0050] Exothermic quantity Δh of the completely cured resin at the sampling point n Proportional to S, calculated by formula (2) n :

[0051] Δh n = kS (2),

[0052] Wherein, k is the instrument constant;

[0053] The degree of cure CD of the carbon fiber reinforced resin matrix prepreg at the sampling point is calculated by formula (3) n ,

[0054]

[0055] Wherein, CD n is the degree of cure of the carbon fiber reinforced resin matrix prepreg at the sampling point, Δh1 is the exothermic quantity of the completely cured resin used before the production of the prepreg, Δh n is the exothermic quantity of the completely cured resin at the sampling point;

[0056] The average degree of cure CD of the carbon fiber reinforced resin matrix prepreg is calculated by formula (4)

[0057]

Claims

1. A rapid detection method for the degree of curing of carbon fiber reinforced resin-based prepregs, characterized in that, Includes the following steps: Step 1: The automatic sampling machine is set with n sampling points. The sampling interval is set according to the length and width of the whole prepreg. The sampling points are evenly distributed and the size or quality of each sample is uniform. Step 2: Introduce a stable flow rate of N2 protective gas into the detector; Step 3: Set the temperature rise program according to the known curing process. During the test, the automatic sampler places the sample into the crucible and sends it to the detector's testing platform. The detector is equipped with an automatic sampler. During the temperature rise, the thermocouple measures the temperature difference Δ between the sample and the empty reference crucible. T Real-time transmission is sent to the power compensator, which then compensates for the power Δ. P Δ T The temperature drops to zero, while the signal processor tracks and records the sample temperature in the detector. T The change in Δ P Follow T The trend data is transmitted to the computing device, which calculates Δ using formula (1). P - T Area of ​​integral of curve S , （1）； The heat release Δ of the resin at the sampling point during complete curing h n and S Proportional, Δ can be calculated using formula (2). h n ： D h n =kS (2) in, k This is the instrument constant; The degree of curing of the carbon fiber reinforced resin prepreg sampling points was calculated using formula (3). CD n ， （3）， in, CD n Δ represents the degree of curing at the sampling points of the carbon fiber reinforced resin-based prepreg. h 1 represents the heat released during the complete curing of the resin used before prepreg production, Δ h n The heat released during the complete curing of the resin at the sampling point; The average degree of curing of the carbon fiber reinforced resin-based prepreg was calculated using formula (4). CD , （4） 。 2. The rapid detection method according to claim 1, characterized in that, In step 2, the flow rate is 50 mL / min.

3. The rapid detection method according to claim 1, characterized in that, In step 2, the N2 tube connected to the detector is equipped with a flow control valve, and the purity of N2 is ≥99.99%.

4. The rapid detection method according to claim 1, characterized in that, In step 3, the heating program is as follows: the heating rate is 5~30 ℃ / min, and the start and end temperatures are 30~400 ℃.

5. The rapid detection method according to claim 1, characterized in that, In step 3, the crucible is made of pure aluminum, and a heat insulation barrier is set around the crucible to prevent heat loss. The heat insulation material is aluminum silicate.

6. The rapid detection method according to claim 1, characterized in that, In step 3, the thermocouples are respectively embedded under the two crucibles in the detector.

7. The rapid detection method according to claim 1, characterized in that, In step 3, the power compensator adjusts the input power in real time according to the temperature difference.

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