A method for detecting defects in carbon fiber prepreg

Abstract

The application provides a carbon fiber prepreg defect detection method, which comprises the following steps: selecting a standard carbon fiber prepreg, and measuring the thickness L of the standard carbon fiber prepreg; measuring the cold plate temperature T1 and the standard temperature T2; making the standard carbon fiber prepreg pass through a first impregnation roller and a second impregnation roller, and placing the standard carbon fiber prepreg on a cold plate; measuring the cold plate temperature T1; using the sensing end of a thermocouple to detect the standard temperature T2 of the standard carbon fiber prepreg; calculating the standard unit area heat flow density q; measuring the detection temperature T' of the carbon fiber prepreg to be detected; and judging the defect of the carbon fiber prepreg to be detected according to the detection temperature T'. The carbon fiber prepreg defect detection method provided by the application is simple to operate, reduces the labor intensity, improves the defect detection efficiency, and the detection system used has a simple structure and low investment cost, and can be used for real-time online detection of carbon fiber prepreg defects.

Description

Technical Field

[0001] This application relates to the field of carbon fiber testing technology, and in particular to a method for detecting defects in carbon fiber prepreg. Background Technology

[0002] Carbon fiber prepreg is a composite material made by bonding resin to carbon fibers using high-pressure and high-temperature technology. It consists of carbon fiber yarn, resin, release paper, and other materials, and is processed through coating, hot pressing, cooling, lamination, and winding. The production of carbon fiber prepreg generally uses the hot-melt method, where carbon fibers are impregnated in a molten resin film under heating, and then cooled and wound into carbon fiber prepreg rolls.

[0003] During the production process, carbon fiber prepreg is prone to various defects due to raw material defects, such as carbon fiber knots, insufficient resin film, and damaged release paper, or unstable processes, such as temperature fluctuations, impregnation pressure fluctuations, and tension fluctuations. These defects can result in various forms of damage, including excessive resin, insufficient resin, clumps, dry yarn, wrinkles, and cracks, leading to economic losses. Currently, the detection of defects in carbon fiber prepreg mainly relies on manual visual inspection and measurement, which is time-consuming, labor-intensive, and prone to missed detections. If specialized machines are used for inspection, the equipment is expensive, increasing production costs. Summary of the Invention

[0004] To address the problems of time-consuming, labor-intensive, and costly defect detection in carbon fiber prepregs, this application provides a carbon fiber prepreg defect detection system and method.

[0005] The first aspect of this application provides a carbon fiber prepreg defect detection system, the carbon fiber prepreg defect detection system comprising an impregnation roller assembly, a cold plate, and a thermocouple; The impregnation roller assembly includes a first impregnation roller and a second impregnation roller, with the first impregnation roller disposed upstream of the second impregnation roller along the impregnation direction; The cold plate is located between the first impregnation roller and the second impregnation roller, and the cold plate is used to support the carbon fiber prepreg to be tested; The thermocouple is positioned above the cold plate, and the sensing end of the thermocouple contacts the carbon fiber prepreg to be tested on the cold plate to detect the detection temperature of the carbon fiber prepreg.

[0006] The thermocouple includes a T-type thermocouple, the sensing end of which is used to detect the detection temperature of the carbon fiber prepreg to be tested.

[0007] The T-type thermocouple is wrapped with thermal insulation material.

[0008] The material of the cold plate includes stainless steel, aluminum, and copper.

[0009] The carbon fiber prepreg defect detection system further includes a guide roller group, which comprises multiple guide rollers positioned upstream of the first impregnation roller along the impregnation direction.

[0010] A second aspect of this application provides a method for detecting defects in carbon fiber prepreg, implemented using a carbon fiber prepreg defect detection system as described in any of the first aspects, the method comprising: Select a standard carbon fiber prepreg, which includes a carbon fiber prepreg formed by impregnating flawless carbon fibers with a resin film under constant temperature and constant pressure. Measure the thickness L of the standard carbon fiber prepreg; The cold plate temperature T1 and the standard temperature T2 are measured. The standard carbon fiber prepreg is passed through the first impregnation roller and the second impregnation roller, so that the standard carbon fiber prepreg is placed on the cold plate. The cold plate temperature T1 is measured, and the standard temperature T2 of the standard carbon fiber prepreg is detected by the sensing end of the thermocouple. Calculate the standard heat flux density per unit area, q. The detection temperature T' of the carbon fiber prepreg to be tested is measured, and the defects of the carbon fiber prepreg to be tested are determined based on the detection temperature T'.

[0011] The calculated standard heat flux density per unit area q includes: q = λ(T1 - T2) / L, λ is the thermal conductivity in Fourier's law.

[0012] The step of determining the defects of the carbon fiber prepreg to be tested based on the detection temperature T' includes: The thickness L' of the carbon fiber prepreg to be tested is L' = λ(T1 - T') / q. When T' > T2, L' > L, the thickness of the carbon fiber prepreg to be tested is too large; When T' < T2, L' < L, the thickness of the carbon fiber prepreg to be tested is too small.

[0013] When the thickness of the carbon fiber prepreg to be tested is too large, the carbon fiber prepreg to be tested has one or more of the following problems: carbon fiber clumps, resin film with excessive resin, and carbon fiber prepreg wrinkles.

[0014] When the thickness of the carbon fiber prepreg to be tested is too small, the carbon fiber prepreg to be tested has one or more of the following problems: dry carbon fibers, poor resin film, and cracks in the carbon fiber prepreg.

[0015] Compared with the prior art, the present application has the following advantages: the carbon fiber prepreg defect detection system and method of the present application are simple to operate, reduce the intensity of manual labor, improve the defect detection efficiency, and have a simple structure and low investment cost. It can be used for real-time online detection of defects in carbon fiber prepreg. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a carbon fiber prepreg defect detection system according to an exemplary embodiment. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0019] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] This application provides a carbon fiber prepreg defect detection system and method. The carbon fiber prepreg defect detection system includes an impregnation roller assembly, a cold plate, and a thermocouple. The impregnation roller assembly includes a first impregnation roller and a second impregnation roller, with the first impregnation roller positioned upstream of the second impregnation roller along the impregnation direction. The cold plate is located between the first and second impregnation rollers and is used to support the carbon fiber prepreg to be tested. The thermocouple is positioned above the cold plate, with its sensing end in contact with the carbon fiber prepreg to be tested on the cold plate to detect the detection temperature of the carbon fiber prepreg. The carbon fiber prepreg defect detection system and method of this application are simple to operate, reduce manual labor intensity, improve defect detection efficiency, and have a simple structure and low investment cost. They can be used for real-time online detection of defects in carbon fiber prepreg.

[0021] The first aspect of this application, according to an exemplary embodiment, is as follows: Figure 1 As shown, a carbon fiber prepreg defect detection system is provided, including an impregnation roller group 100, a cold plate 200, a thermocouple 300, and a guide roller group 400.

[0022] like Figure 1 As shown, the impregnation roller group 100 includes a first impregnation roller 110 and a second impregnation roller 120. Along the impregnation direction, the first impregnation roller 110 is positioned upstream of the second impregnation roller 120. A cold plate 200 is located between the first impregnation roller 110 and the second impregnation roller 120. The cold plate 200 is used to support the carbon fiber prepreg 900 to be tested. The carbon fiber prepreg 900 to be tested is a preliminary prepreg product formed after carbon fiber and resin film have been impregnated by multiple roller groups. In this embodiment, the material of the cold plate 200 can be selected from stainless steel, aluminum, and copper. All three materials have good thermal conductivity and corrosion resistance.

[0023] like Figure 1 As shown, thermocouple 300 is positioned above cold plate 200. The sensing end of thermocouple 300 contacts the carbon fiber prepreg 900 to be tested on cold plate 200 to detect the temperature of the carbon fiber prepreg 900. In this embodiment, a T-type thermocouple is selected for thermocouple 300. The T-type thermocouple is positioned perpendicular to the moving direction of the carbon fiber prepreg 900. The sensing end of the T-type thermocouple is used to detect the temperature of the carbon fiber prepreg 900. During testing, the measuring point of the T-type thermocouple is kept in contact with the upper surface of the carbon fiber prepreg 900. T-type thermocouples, also known as copper-constantan thermocouples, are an optimal base metal thermocouple for measuring low temperatures. They have advantages such as good linearity, high thermoelectric potential, high sensitivity, fast heat transfer, good stability and uniformity, and low price. The T-type thermocouple is wrapped with thermal insulation material. The thermal insulation material tightly wraps the T-type thermocouple to reduce the influence of the surrounding temperature on the T-type thermocouple, which can make its detection more accurate.

[0024] like Figure 1 As shown, the guide roller assembly 400 includes multiple guide rollers positioned upstream of the first impregnation roller 110 along the impregnation direction. The guide roller assembly 400 provides pre-pressure and guidance to the carbon fiber filaments. It clamps the carbon fiber filaments, guiding them through the impregnation tank for impregnation, and applies pressure to the impregnated filaments. Under the uniform rotation and drying action of the guide roller assembly 400, the impregnated carbon fiber filaments are guided to form a carbon fiber prepreg. This application does not limit the number of guide rollers; the actual production requirements shall prevail.

[0025] A second aspect of this application, according to an exemplary embodiment, provides a method for detecting defects in carbon fiber prepreg, the method being implemented using a carbon fiber prepreg defect detection system as described in any of the first aspects. The carbon fiber prepreg defect detection method includes: S100. Select standard carbon fiber prepreg; standard carbon fiber prepreg is carbon fiber prepreg formed by impregnating flawless carbon fibers with resin film under constant temperature and constant pressure.

[0026] Flawless carbon fiber specifically refers to carbon fiber with uniform quality, without joints or clumps. Carbon fiber prepreg prepared from flawless carbon fiber under constant temperature and pressure has stable quality.

[0027] S200. Measure the thickness L of standard carbon fiber prepreg.

[0028] The unit for material thickness L is meters (m).

[0029] S300. Measure the cold plate temperature T1 and the standard temperature T2; pass the standard carbon fiber prepreg through the first impregnation roller 110 and the second impregnation roller 120, so that the standard carbon fiber prepreg is placed on the cold plate 200, measure the cold plate temperature T1, and use the sensing end of the thermocouple 300 to detect the standard temperature T2 of the standard carbon fiber prepreg.

[0030] The unit for both the cold plate temperature T1 and the standard temperature T2 is K.

[0031] S400. Calculate the standard heat flux density per unit area, q.

[0032] q = λ(T1 - T2) / L, The unit of q is W / m 2 ; λ is the thermal conductivity in Fourier's law, and the unit of λ is W / (m*K).

[0033] S500. Measure the test temperature T' of the carbon fiber prepreg 900 to be tested, and determine the defects of the carbon fiber prepreg to be tested based on the test temperature T'.

[0034] The detection temperature T' of the carbon fiber prepreg 900 to be tested is measured using thermocouple 300. The formula for calculating the thickness L' of the carbon fiber prepreg 900 to be tested is as follows: L'=λ(T1-T') / q, Among them, when T'>T2, L'>L, the thickness of the carbon fiber prepreg to be tested is too large; When T' < T2, L' < L, the thickness of the carbon fiber prepreg to be tested is too small.

[0035] In actual production, when the thickness of the carbon fiber prepreg 900 to be tested is too large, the carbon fiber prepreg 900 to be tested may have one or more of the following problems: carbon fiber clumps, resin film with excessive resin, and carbon fiber prepreg wrinkles.

[0036] When the thickness of the carbon fiber prepreg 900 to be tested is too small, the carbon fiber prepreg 900 to be tested may have one or more of the following problems: dry carbon fibers, poor resin film, and cracks in the carbon fiber prepreg.

[0037] In summary, the carbon fiber prepreg defect detection method of this application first calculates the standard heat flux density per unit area of ​​a standard carbon fiber prepreg, and then calculates the thickness of the carbon fiber prepreg to be tested by measuring the test temperature. Based on this thickness, it can be determined whether the carbon fiber prepreg to be tested has defects such as excessive resin, insufficient resin, clumps, dry yarn, wrinkles, and cracks. The method is simple and efficient and can be used for real-time online detection of defects in carbon fiber prepreg.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A method for detecting defects in carbon fiber prepreg, characterized in that, The carbon fiber prepreg defect detection method is performed using a carbon fiber prepreg defect detection system, which includes: Impregnation roller assembly, cold plate and thermocouple; The impregnation roller assembly includes a first impregnation roller and a second impregnation roller, with the first impregnation roller disposed upstream of the second impregnation roller along the impregnation direction; The cold plate is located between the first impregnation roller and the second impregnation roller, and the cold plate is used to support the carbon fiber prepreg to be tested; The thermocouple is positioned above the cold plate, and the sensing end of the thermocouple contacts the carbon fiber prepreg to be tested on the cold plate to detect the detection temperature of the carbon fiber prepreg. The method for detecting defects in carbon fiber prepreg includes: Select a standard carbon fiber prepreg, which includes a carbon fiber prepreg formed by impregnating flawless carbon fibers with a resin film under constant temperature and constant pressure. Measure the thickness L of the standard carbon fiber prepreg; The cold plate temperature T1 and the standard temperature T2 are measured. The standard carbon fiber prepreg is passed through the first impregnation roller and the second impregnation roller, so that the standard carbon fiber prepreg is placed on the cold plate. The cold plate temperature T1 is measured, and the standard temperature T2 of the standard carbon fiber prepreg is detected by the sensing end of the thermocouple. Calculate the standard heat flux density per unit area, q. The detection temperature T' of the carbon fiber prepreg to be tested is measured, and the defects of the carbon fiber prepreg to be tested are determined based on the detection temperature T'. The method of determining the defects of the carbon fiber prepreg to be tested based on the detection temperature T' includes: The thickness L' of the carbon fiber prepreg to be tested is L' = λ(T1 - T') / q. When T' > T2, L' > L, the thickness of the carbon fiber prepreg to be tested is too large; When T' < T2, L' < L, the thickness of the carbon fiber prepreg to be tested is too small.

2. The method for detecting defects in carbon fiber prepreg according to claim 1, characterized in that, The calculated standard heat flux density per unit area q includes: q = λ(T1 - T2) / L, λ is the thermal conductivity in Fourier's law.

3. The method for detecting defects in carbon fiber prepreg according to claim 2, characterized in that, When the thickness of the carbon fiber prepreg to be tested is too large, the carbon fiber prepreg to be tested has one or more of the following problems: carbon fiber clumps, resin film with excessive resin, and carbon fiber prepreg wrinkles.

4. The method for detecting defects in carbon fiber prepreg according to claim 2, characterized in that, When the thickness of the carbon fiber prepreg to be tested is too small, the carbon fiber prepreg to be tested has one or more of the following problems: dry carbon fibers, poor resin film, and cracks in the carbon fiber prepreg.

Images