Method for testing content of resin on surface of carbon fiber unidirectional prepreg

Abstract

The invention discloses a method for testing the content of resin on the surface of a carbon fiber unidirectional prepreg. The method comprises the following specific testing processes: cutting a prepreg sample and preparing a plurality of groups of material sheets; uncovering the isolating membrane on the surface of the prepreg, enlarging under an optical instrument, and taking a picture; acquiring a total pixel value of the picture in the step S2 by using image software; acquiring a surface resin pixel value of the picture in the step S2 by using image software; and calculating the surface resin content of the prepreg. According to the test method, through the application of simple instruments such as an optical imaging instrument or an optical microscope and in combination with picture processing software, quantitative characterization of the content of the resin on the surface of the prepreg can be simply, visually, safely and environmentally friendly, the infiltration degree of the resin in the prepreg to fibers is reflected, then formulation of a prepreg production process is guided, and the manufacturability of the prepreg is improved.

Description

Technical Field

[0001] This invention relates to the field of composite material characterization and testing technology, and specifically to a method for testing the resin content on the surface of carbon fiber unidirectional prepreg. Background Technology

[0002] Prepreg is an intermediate product of resin-based composite materials. It is made by impregnating reinforcing materials (fibers, fabrics, etc.) with matrix materials (resin) under strict control.

[0003] Resin content is one of the key physical properties of prepregs, directly affecting their layup processability, mechanical properties, and molding quality. Currently, for uncured prepregs, the resin content is generally determined according to HB 7736.5 "Test Methods for Physical Properties of Prepregs - Part 5: Determination of Resin Content". This involves using a solvent capable of completely dissolving the resin matrix without altering the mass of the reinforcing materials and fillers to dissolve or extract all the resin from the prepreg sample. The percentage difference in mass before and after treatment is then calculated to obtain the resin content. For cured prepreg composites, one common method is to estimate the resin content through metallographic observation and image processing according to GB / T 3365 "Test Methods for Pore Content and Fiber Volume Content of Carbon Fiber Reinforced Plastics". Another method is to obtain the resin content through hot liquid dissolution or high-temperature ablation according to ASTM D 3171 "Test Methods for Component Content of Composite Materials".

[0004] The resin content on the surface of a prepreg affects its surface tack and, to some extent, reflects the degree of wetting. Current common testing methods can obtain the total resin content in prepregs and composite materials, but the results cannot determine the resin content on the prepreg surface, thus failing to reflect the resin distribution. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for testing the resin content on the surface of carbon fiber unidirectional prepreg. This method utilizes simple instruments such as optical imaging devices or optical microscopes, combined with image processing software, to achieve a simple, intuitive, safe, and environmentally friendly quantitative characterization of the resin content on the surface of the prepreg. This reflects the degree of resin wetting of the fiber in the prepreg, thereby guiding the formulation of prepreg production processes and improving the processability of the prepreg.

[0006] A method for testing the resin content on the surface of unidirectional carbon fiber prepreg, the specific test procedure is as follows: S1, cut the prepreg sample and prepare multiple sets of sheets; S2, Remove the release film from the surface of the prepreg, magnify and photograph it under an optical instrument; S3, Use image processing software to obtain the total pixel value of the image from step S2. ; S4, Use image software to obtain the surface resin pixel values ​​of the image from step S2. ; S5, calculate the resin content on the surface of the prepreg, using the following formula: = .

[0007] As a preferred embodiment of the above technical solution, in step S1, multiple observation pieces are uniformly cut from the prepreg within a width.

[0008] As a preferred embodiment of the above technical solution, in step S2, an optical imager or an optical microscope is selected as the optical instrument. After removing the release film on the surface of the prepreg, the material is placed flat under the lens of the optical instrument to observe the surface morphology of the material sheet one by one and obtain clear photos.

[0009] As a preferred embodiment of the above technical solution, Photoshop is used in both steps S2 and S3.

[0010] As a preferred embodiment of the above technical solution, in step S2, the "Source" is set to "Entire Image" in the "Histogram" interface to obtain the total pixel value of the photo. .

[0011] As a preferred embodiment of the above technical solution, in step S3, click "Select" and then "Color Range" in sequence to select the surface resin area. In the "Histogram" interface, set "Source" to "Selected Layer" to obtain the surface resin pixel values. .

[0012] As a preferred embodiment of the above technical solution, there are two methods for obtaining the surface resin area, including: In the "Color Range" dialog box, set the "Selection" to "Highlight" mode, and set the "Color Tolerance" and "Range" values; In the "Color Range" dialog box, set "Select" to "Sample Color" mode, click the "Eyedropper Tool" to select the resin color in the photo, "Add" or "Subtract" the error color, and set the "Color Tolerance" value.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This method, using simple instruments such as optical imaging devices or optical microscopes combined with image processing software, provides a simple, intuitive, safe, and environmentally friendly way to quantitatively characterize the resin content on the surface of prepregs. It reflects the degree of resin wetting of the fibers and the surface tackiness of the prepreg, among other process characteristics. When the resin content of the prepreg is constant, a lower surface resin content indicates more resin penetration into the fibers, a higher degree of prepreg wetting, and lower surface tackiness. Therefore, the test results of the surface resin content of prepregs can guide the formulation and optimization of production process parameters such as production pressure and temperature, improving the processability of prepregs. Attached Figure Description

[0014] Figure 1 This is a flowchart of the testing method of the present invention.

[0015] Figure 2 This is a table of process parameters for a specific embodiment of the present invention.

[0016] Figure 3 This is a sampling diagram of the present invention.

[0017] Figure 4 This is a schematic diagram of a typical image taken in this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: like Figure 1 The method shown is for testing the resin content on the surface of carbon fiber unidirectional prepreg. The specific test procedure is as follows: S1, cut the prepreg sample and prepare multiple sets of sheets; S2, Remove the release film from the surface of the prepreg, magnify and photograph it under an optical instrument; S3, Use image processing software to obtain the total pixel value of the image from step S2. ; S4, Use image software to obtain the surface resin pixel values ​​of the image from step S2. ; S5, calculate the resin content on the surface of the prepreg, using the following formula: = .

[0020] In this embodiment, in step S1, multiple observation pieces are uniformly cut from the prepreg within a width.

[0021] In this embodiment, in step S2, an optical imager or an optical microscope is selected as the optical instrument. After removing the release film on the surface of the prepreg, the material is placed flat under the lens of the optical instrument to observe the surface morphology of the material sheet one by one and obtain clear photos.

[0022] In this embodiment, Photoshop is used for both steps S2 and S3.

[0023] In this embodiment, in step S2, the "Source" is set to "Entire Image" in the "Histogram" interface to obtain the total pixel value of the photo. .

[0024] In this embodiment, in step S3, the surface resin area is selected by clicking "Select" and then "Color Range" in sequence. In the "Histogram" interface, the "Source" is set to "Selected Layer" to obtain the surface resin pixel values. .

[0025] In this embodiment, there are two methods for obtaining the surface resin area, including: In the "Color Range" dialog box, set the "Selection" to "Highlight" mode, and set the "Color Tolerance" and "Range" values; In the "Color Range" dialog box, set "Select" to "Sample Color" mode, click the "Eyedropper Tool" to select the resin color in the photo, "Add" or "Subtract" the error color, and set the "Color Tolerance" value.

[0026] Specifically: The prepreg is a 5228A / CCF300 high-temperature curing epoxy carbon fiber unidirectional prepreg, composed of two components: 5228A resin and CCF300 carbon fiber. The manufacturing process is a two-step method: first, a high-precision film-making machine is used to produce a 5228A film; then, a high-precision prepreg machine is used to prepregate and laminate the film with the CCF300 fibers. The high-precision film-making machine can stably control the resin content of the prepreg within ±2%. By adjusting the hot roller pressure of the high-precision prepreg machine, the degree of resin impregnation on the fibers can be controlled, allowing the prepreg product to achieve surface tack, hardness, and other properties suitable for the application scenario.

[0027] All other conditions remained consistent. Three batches of 5228A / CCF300 high-temperature curing epoxy carbon fiber unidirectional prepreg were produced using three different prepreg processes. The process parameters are listed in Table 1. Figure 2 As shown.

[0028] The 5228A / CCF300 high-temperature curing epoxy carbon fiber unidirectional prepreg has a width of 1000mm. Five sheets are evenly cut within one width, with a sheet size of 100mm × 100mm. See the sampling diagram below. Figure 3 .

[0029] After removing the release liner from the prepreg surface, place it flat under the lens of an optical imaging system or optical microscope, ensuring the prepreg surface is not contaminated. Observe the surface morphology of each sample, adjusting the sample and lighting to ensure uniform illumination. Focus the lens on the center of the sample, adjusting the magnification to 1.2x to obtain a larger field of view. Adjust the focus to ensure the sample is clear in the photograph. Take a photograph; a typical photograph can be found here. Figure 4 ; Open the photo taken by the optical imager in Photoshop. In the "Histogram" interface, set the "Source" to "Entire Image" to obtain the total pixel value of the photo. Listed in Table 1, such as Figure 2 As shown; The resin and carbon fiber are clearly distinguishable in the photo. Under suitable lighting, the resin area is significantly brighter than the carbon fiber. Therefore, click "Select" - "Color Range," and in the dialog box, set "Selection" to "Highlight" mode, color tolerance 50%, and range 100%. Select the surface resin area, and in the "Histogram" interface, set "Source" to "Selected Layer" to obtain the pixel values ​​of the surface resin. Listed in Table 1, such as Figure 2 As shown; Calculate the surface resin content of 5228A / CCF300 prepreg produced by three different prepreg processes: = The results are listed in Table 1, such as Figure 2 As shown.

[0030] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing the resin content on the surface of unidirectional carbon fiber prepreg, characterized in that: The specific testing process is as follows: S1, cut the prepreg sample and prepare multiple sets of sheets; S2, Remove the release film from the surface of the prepreg, magnify and photograph it under an optical instrument; S3, Use image processing software to obtain the total pixel value of the image from step S2. ; S4, Use image software to obtain the surface resin pixel values ​​of the image from step S2. ; S5, calculate the resin content on the surface of the prepreg, using the following formula: = 。 2. The method for testing the resin content on the surface of carbon fiber unidirectional prepreg according to claim 1, characterized in that: In step S1, multiple observation pieces are uniformly cut from the prepreg within a width.

3. The method for testing the resin content on the surface of carbon fiber unidirectional prepreg according to claim 1, characterized in that: In step S2, an optical imager or optical microscope is selected as the optical instrument. After removing the release film on the surface of the prepreg, the material is placed flat under the lens of the optical instrument to observe the surface morphology of the material sheet one by one and obtain clear photos.

4. The method for testing the resin content on the surface of carbon fiber unidirectional prepreg according to claim 1, characterized in that: In both steps S2 and S3, Photoshop is used as the image software.

5. The method for testing the resin content on the surface of a unidirectional carbon fiber prepreg according to claim 4, characterized in that: In step S2, the "Source" is set to "Entire Image" in the "Histogram" interface to obtain the total pixel value of the photo. .

6. The method for testing the resin content on the surface of a unidirectional carbon fiber prepreg according to claim 4, characterized in that: In step S3, click "Select" and then "Color Range" in sequence to select the surface resin area. In the "Histogram" interface, set "Source" to "Selected Layer" to obtain the surface resin pixel values. .

7. The method for testing the resin content on the surface of a unidirectional carbon fiber prepreg according to claim 6, characterized in that: There are two methods for obtaining the surface resin area, including: In the "Color Range" dialog box, set "Selection" to "Highlight" mode, and set the "Color Tolerance" and "Range" values; In the "Color Range" dialog box, set "Select" to "Sample Color" mode, click the "Eyedropper Tool" to select the resin color in the photo, "Add" or "Subtract" the error color, and set the "Color Tolerance" value.

Images