A method for testing the thickness of toughening particles of carbon fiber prepreg and its composite laminate
By separating the toughening particle phase between layers using metallographic fluorescence microscopy and image analysis software, and combining this with formula calculations, the problem of inaccurate measurement of the toughening particle layer thickness in traditional methods was solved, achieving precise measurement results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHONGFU SHENYING (SHANGHAI) TECH CO LTD
- Filing Date
- 2023-03-31
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional methods cannot accurately measure the thickness of the toughening particle layer in carbon fiber prepreg and its composite laminates. In particular, the uneven distribution of toughening particles between layers is observed under a metallographic microscope, leading to inaccurate measurement results.
Metallographic fluorescence microscopy combined with LasX image analysis software was used to calculate the area percentage of the toughening particle layer by separating the interlayer toughening particle phase and the carbon fiber resin mixed phase, and the thickness of the toughening particle layer was calculated by formula.
It enables precise measurement of the thickness of toughening particle layers in carbon fiber prepregs and their composite laminates, improving the accuracy and reliability of the measurement.
Smart Images
Figure CN117007563B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of toughening particle layer thickness in carbon fiber prepreg and its composite laminates, specifically to a metallographic fluorescence microscopy processing method. Background Technology
[0002] Carbon fiber reinforced composites are non-metallic matrix composites with outstanding specific strength and specific modulus, strong designability, and good fatigue and corrosion resistance. Due to their excellent mechanical properties, they are increasingly being used as high-performance materials in various fields, especially the aerospace industry. With the widespread application of composite materials in aircraft, improving their impact resistance and other properties has gradually become a key research and development focus. Among these, interlaminar particle-reinforced composites are one of the most popular research directions.
[0003] Interlaminar particle toughening involves depositing thermoplastic resin particles onto the surface of a thermosetting resin prepreg, then preparing the resulting prepreg into a composite material. The main methods involve coating the prepreg surface with thermoplastic resin or directly adding thermoplastic resin to the resin to prepare the prepreg. This increases the contact area between the thermoplastic resin particles and the interlaminar layers, achieving interlaminar toughening and effectively preventing crack propagation, thereby improving the material's impact resistance. Since the thickness of the interlaminar toughening layer affects the type II interlaminar fracture toughness of the laminate, and the compressive strength after impact (CAI) is positively correlated with type II interlaminar fracture toughness, the thickness of the toughening layer influences the CAI performance of the laminate. Therefore, accurately measuring the thickness of the toughening layer is fundamental to the testing of composite materials.
[0004] Traditional methods for measuring the thickness of interlayer toughening particles only involve sampling from three points (left, center, and right) of the prepreg or laminate interlayer particle layer and calculating the arithmetic mean to obtain the interlayer thickness. However, under metallographic microscopy at different magnifications, both the prepreg toughening particle layer and the laminate toughening particle layer exhibit uneven distribution and discontinuity in the interlayer toughening particle layer. Therefore, traditional testing methods cannot accurately express the average thickness of a single layer or the overall average thickness of the toughening particle layer. In this case, the average thickness of a single layer and the overall average thickness can be accurately calculated using the area method by measuring the percentage of the interlayer toughening particle layer area to the observed area using metallographic fluorescence microscopy. This allows for precise measurement of the thickness of the toughening particle layer in carbon fiber prepregs and their composite laminates. Summary of the Invention
[0005] The purpose of this invention is to provide a technical method for accurately testing the thickness of the toughening particle layer in carbon fiber prepreg and its composite laminate.
[0006] A technical method for accurately testing the particle layer thickness of carbon fiber prepreg and its composite laminates, characterized by comprising the following steps:
[0007] S1. Use a cutting machine to cut a square carbon fiber prepreg or composite laminate plate with a side length of 40mm. Then use a cold mounting mold to fix it. Use wet sandpaper of coarse to fine on a grinding machine to grind its sides. At the same time, use metallographic Al2O3 polishing slurry (8-20%) to polish it to obtain the preliminary sample to be tested.
[0008] S2. After sonicating the sample for 30 minutes, place it on the stage of the fluorescence microscope, adjust the magnification of the microscope to 50 times, and adjust the distance between the sample and the objective lens until its cross-section can be clearly observed.
[0009] S3. Take a rectangular photo of the observation surface in step S2, measure the length and width of the observation surface and record them as m and n respectively, and calculate the actual area of the rectangular photo of the observation surface and record it as S.
[0010] S4. Using the LasX image analysis software of a fluorescence microscope, the interlayer toughening particle phase and the carbon fiber resin mixed phase were separated.
[0011] S5. Manually add and remove the interlayer toughening particle phase and carbon fiber resin mixture phase using the binary pre-filtering method of LasX image analysis software to obtain the percentage value of the interlayer toughening particle layer area to the observed area, denoted as k, and record the test results.
[0012] S6. Let a be the number of toughening particle layers on the observation surface, and let H be the thickness of the toughening particle layer of the carbon fiber prepreg and its composite laminate. Calculate according to formula (1):
[0013]
[0014] In the above formula:
[0015] H – Thickness of the toughening particle layer, in micrometers (μm);
[0016] S – The actual area of the rectangular photograph of the observation surface, in square micrometers (μm). 2 )
[0017] k—Percentage of the area of the interlayer toughening particle layer to the observed area, %;
[0018] m — the length of the rectangular photograph of the observation surface, in micrometers (μm);
[0019] a — Number of toughening particle layers on the observation surface, in micrometers (μm).
[0020] In some implementations, in step S1, the laminate plate is polished with 400 grit, 800 grit, or 2000 grit.
[0021] In some embodiments, in step S2, the magnification of the fluorescence microscope can also be 100x, 200x, or 500x.
[0022] In some embodiments, in step S3, the length and width of the cross-section are observed to an accuracy of 0.01 μm under fluorescence microscopy conditions.
[0023] In some implementations, step S3 can be divided into single-layer toughening particle layer thickness testing and observation surface toughening particle layer average thickness testing. The single-layer toughening particle layer thickness testing can be performed by binary processing pre-filtering to remove interfering particle layer phases and retain the target particle layer phase.
[0024] In some implementations, in step S4, the brightness thresholds of the interlayer toughening particle phase and the carbon fiber resin mixed phase are adjusted respectively. The brightness thresholds are based on the brightness differences between different phases in the captured image, and the target phase brightness threshold needs to be manually adjusted.
[0025] In some implementations, it also includes:
[0026] Throughout the testing process, the square carbon fiber prepreg or composite laminate plate must be dyed with a high concentration of water-based dye (ultrapure water: fluorescent yellow = 8:1) and heated in an oven at 80°C for 15 minutes to complete the sample preparation.
[0027] Beneficial effects:
[0028] This invention discloses a technical method for accurately testing the thickness of the toughening particle layer in carbon fiber prepreg and its composite laminates. According to this testing method, the thickness of the toughening particle layer in carbon fiber prepreg and its composite laminates can be accurately measured. Attached Figure Description
[0029] Figure 1 Figure 1 shows the test results for the prepreg particle layer thickness in Example 1.
[0030] Figure 2 The thickness test diagram of the single-layer toughening particle layer of the carbon fiber composite laminate in Example 2.
[0031] Figure 3 Average thickness test diagram of toughening particle layer in carbon fiber composite laminate in Example 3. Detailed Implementation
[0032] The present invention will be further described below with reference to embodiments. The following embodiments are only used to illustrate the performance of the present invention more clearly, and should not be limited to the embodiments described below.
[0033] Example 1:
[0034] The prepreg batch P1220602 was produced by cutting square prepreg sheets with sides of 40mm using scissors. These sheets were then fixed using a cold-mounting die. The sides were sequentially sanded using progressively finer wet sandpaper on a grinding machine, followed by polishing with an Al2O3 polishing slurry (8-20%) to obtain the initial test sample. The sample was then sonicated for 30 minutes and stained with a prepared aqueous dye. Finally, its morphology was observed and tested using a fluorescence microscope, as shown below. Figure 1 As shown, the interlayer spacing of the target particles is indicated by the arrow. Figure 1 In the image, the thickness of the toughening particle layer of prepreg batch P1220602 is shown in the figure (A: original fluorescence micrograph; B: image processed by image analyzer).
[0035] Figure 1 The image shows the test results for the toughening particle layer thickness of prepreg batch P1220602. From image A, a rectangular photograph of the observation surface can be obtained. The length and width of the observation surface are measured and recorded as 1316.67 μm and 877.70 μm, respectively. The actual area of the rectangular photograph of the observation surface is calculated and recorded as 1155641.26 μm. 2 Figure B shows the separation of the interlayer toughening particle phase and the carbon fiber resin mixture phase using image analysis software, and the percentage of the area occupied by the interlayer toughening particle phase on the observation surface is obtained, as shown in Table 1 below.
[0036] Table 1. Percentage of interlayer particle phase occupying the observation surface of our company's P1220602 prepreg.
[0037]
[0038] Therefore, the thickness of the single layer of the target toughening particle layer in the prepreg can be calculated by substituting it into formula (1), and its value is 12.99 μm.
[0039] Example 2:
[0040] The P1220801 batch of post-impact compression (CAI) plates were produced by cutting 40mm square prepreg sheets using a cutting machine. These sheets were then fixed using a cold-mounting die, and their sides were sequentially sanded with progressively finer wet sandpaper on a grinding machine. Simultaneously, they were polished with an 8-20% metallographic Al2O3 polishing slurry to obtain the preliminary test samples. The samples were then sonicated for 30 minutes and stained with a prepared aqueous dye. Finally, their morphology was observed and tested using a fluorescence microscope, as shown below. Figure 2 As shown, the spacing between the target toughening particle layers is indicated by the arrow. Figure 2In the image, the thickness of the target toughening particle layer on the CAI plate of batch P1220801 is shown in the image (A: original fluorescence micrograph; B: image processed by image analyzer).
[0041] Figure 2 The image shows the thickness test results of the target toughening particle layer on the CAI plate of batch P1220801. From image A, a rectangular photograph of the observation surface can be obtained. The length and width within the observation surface are measured and recorded as 2633.34 μm and 1755.40 μm, respectively. The actual area of the rectangular photograph of the observation surface is calculated and recorded as 4622565.04 μm. 2 Figure B shows the separation of the interlayer toughening particle phase and the carbon fiber resin mixture phase using image analysis software, and the percentage of the area occupied by the interlayer toughening particle phase on the observation surface is shown in Table 2 below.
[0042] Table 2. Percentage of interlaminar toughening particle phase occupying the observed area of our P0801 batch laminate.
[0043]
[0044] Therefore, the thickness of a single layer of the target toughening particle layer in the laminate can be calculated by substituting it into formula (1), and its value is 10.18 μm.
[0045] Example 3:
[0046] The P1220801 batch of post-impact compression (CAI) plates were produced by cutting 40mm square prepreg sheets using a cutting machine. These sheets were then fixed using a cold-mounting die, and their sides were sequentially sanded with progressively finer wet sandpaper on a grinding machine. Simultaneously, they were polished with a metallographic Al2O3 polishing slurry (8-20%) to obtain the preliminary test samples. The test samples were then sonicated for 30 minutes and stained with a prepared aqueous dye. Finally, their morphology was observed and tested using a fluorescence microscope, and the average thickness of the interparticle spacing was measured, as follows: Figure 3 As shown.
[0047] Figure 3 The image shows the overall average thickness of the toughening particle layer in batch P1220801 of the CAI plate of this invention (A: original fluorescence micrograph; B: image processed by image analyzer).
[0048] Figure 3 This is a test image showing the overall average thickness of the toughening particle layer in our P1220801 batch of CAI plates. From image A, a rectangular photograph of the observation surface can be obtained. The length and width within the observation surface are measured and recorded as 2633.34 μm and 1755.40 μm respectively. The actual area of the rectangular photograph of the observation surface is calculated and recorded as 4622565.04 μm. 2Figure B shows the separation of the interlayer toughening particle phase and the carbon fiber resin mixture phase using image analysis software, and the percentage of the area occupied by the interlayer toughening particle phase on the observation surface is shown in Table 3 below.
[0049] Table 3. Percentage of interlaminar toughening particle phase occupying the observed area of our P0801 batch laminate.
[0050]
[0051] The toughening particle layer on the observation surface has 9 layers. Therefore, the average thickness of the toughening particle layer in the laminate can be calculated by substituting it into formula (1), and its value is 14.57 μm.
[0052] This invention discloses a method for accurately testing the thickness of toughening particle layers in carbon fiber prepreg and its composite laminates. According to this invention, the average thickness of a single particle layer and the overall average thickness are accurately measured, meeting the testing requirements.
[0053] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A method for testing the thickness of toughening particle layers in carbon fiber prepreg and its composite laminates, characterized in that, Includes the following steps: S1. Use a cutting machine to cut square carbon fiber prepreg or composite laminate plates with a side length of 40mm, and then use a cold mounting mold to fix them; use wet sandpaper of coarse to fine on a grinding machine to grind the sides in sequence, and use metallographic Al2O3 polishing slurry of 8-20% to polish them to obtain the sample to be tested. S2. After sonicating the sample for 30 minutes, place it on the stage of the fluorescence microscope, adjust the magnification of the microscope to 50 times, and adjust the distance between the sample and the objective lens until its cross-section can be clearly observed. S3. Take a rectangular photo of the observation surface in step S2, measure the length and width of the observation surface and record them as m and n respectively, and calculate the actual area of the rectangular photo of the observation surface and record it as S. S4. Using the Las X image analysis software of a fluorescence microscope, the interlayer particle phase and the carbon fiber resin mixed phase were separated. S5. Manually add and remove the interlayer particle phase and carbon fiber resin mixture phase using the binary pre-filtering method of Las X image analysis software to obtain the percentage value of the interlayer particle layer area to the observed area, denoted as k, and record the test results. S6. Let a be the number of particle layers on the observation surface, and let H be the average thickness of the particle layers in the carbon fiber prepreg and its composite laminate. Calculate the thickness using formula (1): In the formula: H – Particle layer thickness, in micrometers; S—The actual area of the rectangular photograph of the observation surface, in square micrometers; k—Percentage of interlayer particle area to observed area, %; m — the length of the rectangular photograph of the observation surface, in micrometers; a — Number of particle layers on the observation surface, in micrometers.
2. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, In step S1, the laminated board is polished with 400 grit, 800 grit, and 2000 grit.
3. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, In step S2, the magnification of the fluorescence microscope can also be 100x, 200x, and 500x.
4. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, In step S3, the length and width of the cross-section are observed to an accuracy of 0.01 μm under fluorescence microscopy.
5. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, In step S3, the test is divided into single-layer toughening particle layer thickness test and observation surface toughening particle layer average thickness test. The single-layer particle layer thickness test uses a binary pre-filtering method to remove interfering particle layer phases and retain the target particle layer phase.
6. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, In step S4, the brightness thresholds of the interlayer toughening particle phase and the carbon fiber resin mixed phase are adjusted respectively. The brightness thresholds are based on the brightness differences between different phases in the captured image, and the target phase brightness threshold needs to be manually adjusted.
7. The method for testing the thickness of toughened particle layers in carbon fiber prepreg and its composite laminates according to claim 1, characterized in that, Also includes: Throughout the testing process, square carbon fiber prepreg or composite laminate plates were dyed with a high-concentration water-based dye, wherein the ratio of ultrapure water to fluorescent yellow was 8:1, in an oven at 80°C for 15 minutes to complete the sample preparation.