A high-quality processing method for repairing damaged areas of plain-woven CFRP

Abstract

The present invention discloses a high-quality processing method for repairing damaged areas of plain-woven CFRP, comprising the following steps: step S1, ultraviolet laser ablation of plain-woven CFRP to obtain the relationship between the number of scans and the ablation depth; step S2, milling processing is performed based on the ultraviolet laser ablation performance, and a two-step processing method of ultraviolet laser post-processing is proposed, which realizes surface resin cleaning within the milling depth range of 200μm-500μm. The two-step method proposed in the present invention can meet the high-quality processing requirements for repairing damaged areas of plain-woven CFRP. The milled CFRP material is subjected to an ultraviolet laser defocusing processing method to remove surface resin, fiber fragments, resin residues, etc. After cleaning, a large number of fresh carbon fiber tubes are exposed on the surface, which can improve the repair performance during subsequent bonding.

Description

Technical Field

[0001] The present invention belongs to the technical field of processing composite materials CFRP, and in particular relates to a high-quality processing method for repairing a damaged area of ​​a plain-woven CFRP. Background Art

[0002] CFRP is widely used in aerospace, high-speed rail, automotive and other fields due to its advantages such as light weight, high strength, corrosion resistance and design flexibility. During the manufacturing process, the material is affected by temperature gradients or uneven pressure during solidification, resulting in defects such as internal holes and delamination. During service, CFRP is susceptible to damage such as scratches, cracks, and impacts due to harsh environments. However, these damages will weaken the mechanical properties of the material. Replacing structural parts in damaged areas is costly, so efficient and high-performance damaged area repair of composite materials is an important research task.

[0003] Currently, there are two main methods for repairing composite materials: mechanical connection and adhesive bonding. Compared to mechanical connection, adhesive bonding offers advantages such as reduced stress concentration, minimal weight gain, and improved fatigue resistance. Consequently, extensive research has been conducted on adhesive bonding repair of composite materials. This process first requires excavation of the damaged area, creating a stepped structure to enhance interlocking with subsequent patches and exposing the carbon fibers for reconstruction. Traditional manual sanding methods are inefficient and lack repeatability.

[0004] Currently, the literature on CFRP damage repair focuses on laminates, and there is little research on plain-woven CFRP structural components. Therefore, it is urgent to carry out research on the repair of damaged areas of plain-woven CFRP structural components and reveal the surface forming mechanism of the material.

[0005] To repair damaged areas of plain-woven CFRP structural components, the patch needs to be bonded to the excavated area. To ensure that the patch fits closely to the excavated area and restores the aerodynamic performance of the material, precise forming of the material is required. Milling, as a deterministic processing method, can meet the precision requirements. However, after milling, a large amount of resin will inevitably appear on the surface, and there will be varying degrees of damage such as fiber fragments and fiber-matrix separation, which will affect the subsequent bonding performance. Previous studies have shown that the use of ultraviolet laser defocusing processing can remove a large amount of resin on the surface without damaging the surface fiber integrity. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-quality processing method for repairing damaged areas of plain-woven CFRP, so as to solve the problems of low efficiency and lack of repeatability of manual grinding methods in the existing technology of repair by bonding, and the inevitable occurrence of fiber breakage, fiber fragmentation, resin smearing, fiber-matrix separation, etc. in milling CFRP composite materials, which will affect the bonding strength of subsequent repairs.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A high-quality processing method for repairing a damaged area of ​​a plain-woven CFRP comprises the following steps:

[0009] Step S1, first scanning a plain-woven CFRP workpiece multiple times under a focus condition to obtain a stepped workpiece with the proximity layer removed;

[0010] Step S2, scanning the surface of the ablated CFRP workpiece under a defocused condition to clean the surface resin of the CFRP workpiece;

[0011] Step S3: milling the workpiece to obtain a patch matching the pit obtained after laser ablation, and using ultraviolet laser to clean the surface resin and fiber fragments of the patch after milling;

[0012] Step S4: bonding the processed patch to the CFRP workpiece to complete the repair of the CFRP workpiece.

[0013] According to the above technical solution, in step S1, the scanning speed of the plain weave CFRP workpiece is 115 mm / s-1840 mm / s, and the filling spacing range is 5 μm-28 μm.

[0014] According to the above technical solution, in step S2, the speed range of scanning the CFRP workpiece surface under the defocus condition is 125 mm / s-750 mm / s, and the filling spacing range is 5 μm-30 μm.

[0015] According to the above technical solution, in step S2, the scanning speed parameter is adjusted according to the following formula:

[0016]

[0017] Where v is the scanning speed, f is the frequency, and d is the spot diameter.

[0018] According to the above technical solution, in step S2, the filling spacing parameter is adjusted according to the following formula:

[0019]

[0020] Where p is the fill pitch and d is the spot diameter.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The two-step method proposed in this paper achieves high-quality repair of damaged plain-weave CFRP. The milled CFRP material is then treated with a UV laser defocusing process to remove surface resin, fiber fragments, and resin debris. This cleansing exposes a large number of fresh carbon fiber tubes, enhancing repair performance during subsequent bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the relationship between ablation depth and scanning times of the present invention;

[0024] Figure 2 Schematic diagram for verification of the method of the present invention;

[0025] Figure 3 Schematic diagram of two independent surface treatment operations for focal length and defocused state of the present invention;

[0026] Figure 4 This is a schematic diagram of the laser experiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the laser experiment control of the present invention;

[0028] Figure 6 Schematic diagram of the macroscopic multi-layer three-dimensional morphology before and after laser treatment of the present invention;

[0029] Figure 7 This is a schematic diagram of the surface line profile after milling of the present invention;

[0030] Figure 8 This is a schematic diagram of the surface line profile after laser processing of the present invention;

[0031] Figure 9 This is an optical microscope image of the ablated surface after laser processing of the present invention;

[0032] Figure 10 Schematic diagram of the positive-bias laser ablation experiment of the present invention;

[0033] Figure 11 is a schematic diagram of the target sample;

[0034] Figure 12 It is a schematic diagram of the processing flow of the present invention;

[0035] Figure 13 A scanning electron microscope image of the features of the present invention;

[0036] Figure 14The surface morphology in the upper meridian direction with different milling parameters of the present invention;

[0037] Figure 15 This is the SEM image of the same position after laser treatment in the present invention;

[0038] Figure 16 This is a schematic diagram of the three-dimensional stepped geometry after laser processing according to the present invention;

[0039] Figure 17 Schematic diagram of the structure of the surface view and side view of the material of the present invention;

[0040] Figure 18 This is a schematic diagram of the laser scanning process of the present invention;

[0041] Figure 19 This is a schematic diagram of cleaning residual resin on the surface after molding by the off-focus laser processing of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] Example 1

[0044] A high-quality processing method for repairing a damaged area of ​​a plain-woven CFRP comprises the following steps:

[0045] Step S1, first scanning a plain-woven CFRP workpiece multiple times under a focus condition to obtain a stepped workpiece with the proximity layer removed;

[0046] Step S2, scanning the surface of the ablated CFRP workpiece under a defocused condition (i.e., the laser is focused to a focal point by a galvanometer) to clean the surface resin of the CFRP workpiece;

[0047] Step S201, first scan the workpiece multiple times under the focus condition to obtain a stepped workpiece with the near layer removed; since the plain weave CFRP is woven from yarns, the yarns are fiber bundles composed of a large number of carbon fiber tubes. The surface and side views of this material are as follows Figure 17 As shown, from top to bottom it is composed of yarns in two orthogonal directions, and the approach layer removal is to remove a layer of yarn, such as Figure 11 shown.

[0048] Step S202, then use the defocused laser processing method to clean the residual resin on the surface after molding (such as Figure 13shown).

[0049] In step S201, the scanning method is as follows: fill a 8mm*8mm square area of ​​the workpiece with a scanning angle of 45°, such as Figure 19 As shown in the figure, a scan is performed when a square area is completely filled, and the progressive angle is incremented by θ = 90° each time to ensure uniform ablation energy.

[0050] According to the ablation characteristics of different scanning speeds and filling spacing under focal length conditions obtained in step S1, the morphology is divided into: severe ablation, partial ablation and incomplete ablation. On this basis, according to the characteristics of strong laser energy density under focal length conditions, multiple repeated scans are performed under these conditions to obtain depth-controlled laser ablation performance. Multiple scans under severe ablation processing conditions will cause pits on the surface and fiber passivation, which seriously damages the material matrix and is not conducive to achieving depth-controlled laser ablation. Under partial ablation conditions, as the number of scans increases, the width of the fiber clusters with undulations on the surface gradually decreases, and the next layer of resin and fiber is gradually exposed. When the number of scans reaches 16 times, a layer of yarn (near layer) is almost completely removed, and new braided yarns are exposed. This phenomenon is almost reproduced when scanning 32 times, which shows that scanning 16 times under this condition can almost remove a layer of braided yarn.

[0051] In addition, under the condition of incomplete ablation, a similar process was almost reproduced because the laser energy density was low, and this process required 24 scans to achieve.

[0052] Based on the ablation results obtained by multiple laser scans under the above focal length conditions, a stepped three-dimensional structure was constructed. The processing parameters v = 805mm / s, the filling spacing d = 14μm, each layer was scanned 16 times, and three layers were processed, with a total of 48 scans. The processing flow diagram is shown below. Figure 12 As shown in the figure, the ablation area is a square of 8mm*8mm, and the circles in the middle are 2mm, 4mm, and 6mm from top to bottom respectively.

[0053] The workpiece was milled to create a matching patch for the pits created after laser ablation. UV laser treatment was then used to remove resin and fiber debris from the milled patch surface. Scanning electron microscopy images, EDS elemental analysis results, and the final three-dimensional patch surface profile data were compared between the milled and pre- and post-UV laser treatments. Because multiple scans of UV laser ablation alone were not sufficient for precise removal, milling, a deterministic machining method, was employed to achieve precise shaping of the patch surface, thereby ensuring the repair performance after the patch was bonded to the damaged area.

[0054] Step S4: bonding the processed patch to the CFRP workpiece to complete the repair of the CFRP workpiece.

[0055] The two-step method proposed in this paper achieves high-precision, high-quality surface formation of plain-weave CFRP damaged patch. After milling, the CFRP material undergoes UV laser defocusing to remove surface resin, fiber fragments, and resin debris. This cleansing exposes a large number of fresh carbon fiber tubes on the surface, enhancing the strength of the repair during subsequent bonding.

[0056] Example 2

[0057] This embodiment is a further refinement of the first embodiment.

[0058] In step S1, it is necessary to study the mechanism of action of UV laser ablation of plain woven CFRP, specifically: characterize the morphology after a single scan process by regulating the scanning speed, filling spacing and defocus amount. The specific experimental parameters are shown in Table 1. Finally, a clean surface with no surface resin residue and good fiber integrity is obtained. Since a pulsed laser is used, the overlap of the light spots will cause heat accumulation. The present invention plans the scanning speed and filling spacing parameters according to the overlap calculation formula. The overlap calculation formula along the scanning direction is as follows:

[0059]

[0060] Where v is the scanning speed, f is the frequency, and d is the spot diameter.

[0061] In addition, the calculation formula for the overlap in the filling spacing direction is as follows:

[0062]

[0063] Where p is the fill pitch and d is the spot diameter.

[0064] Based on the first step, multiple scans were performed under the focus condition to obtain the relationship between the number of scans and the ablation depth.

[0065] Table 1 UV laser scanning parameters

[0066]

[0067] Based on the above UV laser ablation performance and multiple scanning results, a hybrid processing method is proposed to combine efficient layer-by-layer removal and high-quality ablated surface, and the reliability and repeatability of UV defocus processing are verified in three-dimensional structures. First, multiple scans are performed under the focus condition to achieve a stepped three-dimensional structure with close layer removal (schematic diagram as shown in the figure). Figure 11 Then, the residual resin on the surface after molding is cleaned by using the off-focus laser processing method.

[0068] The relationship between ablation depth and scan number is shown in the following table.

[0069] Table 2 Relationship between ablation depth and scanning times

[0070]

[0071] In order to explore the performance of UV laser repair under different milling parameters, the present invention designed a total of 7 groups of experiments based on full factor variables. These full factors are milling depth, feed per tooth and cutting speed. The specific parameters are shown in Table 3. Each group of experiments was performed twice, and the second experiment was repaired with UV laser. The schematic diagram of the two-step experimental method is shown in Figure 2 As shown in (a) and (b).

[0072] Table 3 Milling experiment parameter planning

[0073]

[0074] Previous work has demonstrated that UV lasers can remove residual surface resin in a defocused state without damaging the fiber integrity. Therefore, this present invention continues the previously employed special surface treatment parameters to remove surface resin after milling to expose the carbon fibers for subsequent bonding. Specific parameters are shown in Table 4 below: frequency and pulse width are 50 kHz and 14 ns, respectively.

[0075] Table 4 Laser experiment parameter planning

[0076]

[0077] Removing surface resin and exposing a large amount of carbon fiber is beneficial to improving the subsequent repair strength. Therefore, the present invention compares the surface morphology of plain woven CFRP before and after laser repair. First, a metallographic microscope (Axio Lab.Al, ZEISS) was used to observe the brightness changes of the fiber clusters. Furthermore, a scanning electron microscope (JSM-1 T500, JEOL) with an energy dispersive spectrometer (Ultim Max, OXFORD INSTRUMENTS) was used to characterize the micromorphology, and the elemental composition of the processed surface was analyzed. Because epoxy resin is not conductive, the material was sputtered with a gold spraying device (EMACE200, LEICA) to a thickness of 15nm before taking the scanning electron microscope photo. In the final formation of the three-dimensional stepped structure, a 3D profilometer (VR-6200, KENENCE) was used to measure the removal depth and obtain the surface profile.

[0078] Previous studies have proposed a hybrid laser processing strategy to balance efficient step ablation and excellent surface quality, in which two independent surface treatment operations including on-focus and off-focus states are performed consecutively (e.g. Figure 3As shown). The former is to quickly and accurately generate the surface with laser, while the latter is to remove the residual resin and attached particles on the processed surface. In order to prove its feasibility, the laser experiment was divided into two steps, as shown in Figure 4 shown. Figure 5 The surface morphology of the same parameters but without the second step of defocusing treatment is compared. Figure 4 a3, b3 and Figure 5 c, d, it can be seen that the second step of laser cleaning and activation is necessary.

[0079] The present invention proves the reliability of the two-step method by comparing the surface morphology, EDS spectrum results and three-dimensional structure contour before and after laser treatment, providing guidance for the high-precision and high-quality manufacturing of plain-woven CFRP damaged area patches.

[0080] The same milling cutter was used to continuously process two three-dimensional stepped structures, and the results of the second experiment were specially processed by ultraviolet laser to obtain the macroscopic multi-step three-dimensional morphology before and after laser treatment, such as Figure 6 (a) is the surface morphology without treatment, (b) is the surface morphology after laser treatment, the structural diagram and flow chart are shown in Figure 2 (c) shown.

[0081] Furthermore, the surface profile of the three-dimensional structure was obtained using a 3D profilometer to analyze whether laser repair has a significant impact on the profile accuracy of the stepped surface. Figure 7 and Figure 8The surface line profiles after milling and laser treatment are shown. (a) shows the profile of section AA, and (b) shows the profile of section BB. The actual 3D structure measures 15 mm × 15 mm. To minimize errors caused by boundary conditions, the extracted line profiles are 14 mm long. Clearly, the original rough surface profile is uneven, with a top-to-bottom height difference of up to 67 μm. This is due to the inherent undulating yarns in the plain-woven CFRP material structure. In contrast, the milled surface is relatively flat, with a top-to-bottom height difference within 22 μm. Furthermore, the surface height difference after UV laser scanning remains unchanged, remaining within 21 μm. This indicates that laser treatment does not affect the accuracy of material removal depth. The 3D profiles are based on the bottom layer as a reference. Therefore, by calculating the height difference between each layer and the bottom layer, the surface ablation depth before and after laser treatment is quantitatively analyzed, as shown in Table 4. The results show that laser treatment does not affect the material removal depth, as the UV laser only removes the surface resin and debris. It's important to note that during the initial milling of the three-dimensional stepped structure, the material's inherent yarn structure can introduce errors during tool alignment, resulting in a height difference of slightly more than 500 μm between the third layer and the initial surface. This, however, does not affect the remaining results. Compared to laser ablation for removing the damaged area, milling, a deterministic method, offers superior precision, enabling the fabrication of a well-fitting three-dimensional patch structure based on the stepped structure of the damaged area.

[0082] Table 4 Cutting depth results

[0083]

[0084] Example 3

[0085] This embodiment provides a specific implementation method.

[0086] First, processing at the focal point achieves the performance of laser lift-off. Figure 9 Optical microscope images of the ablated surface after laser processing are shown. Due to the multi-scale structural characteristics of plain-woven CFRP (i.e., interwoven warp and weft yarns), an uneven surface with peaks and troughs exists in the orthogonal directions. The spaces between the warp and weft yarns are filled with a large amount of epoxy resin. Therefore, due to the inherent structure, achieving complete resin removal while maintaining fiber integrity is challenging. The results show that excessive surface energy density can lead to matrix degradation, fracture, and vaporization.

[0087] Laser ablation parameters determine the surface ablation state. Compared with scanning speed, filling spacing and scanning mode, defocus is considered to be a more important factor that directly affects the size of the laser spot diameter. A smaller spot diameter will result in a higher surface energy density (E d=P / vd, where P is the laser power, v is the scanning speed, and d is the spot diameter), which is very sensitive to process parameters and difficult to control. Based on this, a series of positive bias laser ablation experiments were conducted, such as Figure 10 shown.

[0088] Based on the above research, in order to meet the needs of complex three-dimensional geometric repair, depth-controlled ablation combined with subsequent laser processing was used to achieve high-performance manufacturing of stepped repair geometry of plain woven CFRP samples. The schematic diagram of the target sample has been Figure 11 The specific method is shown in Figure 12 As shown in the figure, the diameters of these geometric shapes are 2, 4, and 6 mm from top to bottom, respectively. The shaded area is the processing area. Its outer contour size is 8 mm × 8 mm. The plain woven CFRP samples were gradually ablated under the above-mentioned depth control conditions (v = 805 mm / s, d = 14 μm, N = 16, 32, 48). After laser stripping, the surface residue was treated by positive bias ablation. Figure 13 These detailed features are shown in scanning electron microscope images. A1-a5 have not been treated with UV laser defocusing; b1-b5 have been treated with UV laser defocusing at v = 625 mm / s, d = 20 μm, and N = 1; and c1-c5 have been treated with UV laser defocusing at v = 750 mm / s, d = 30 μm, and N = 1.

[0089] Under magnification, it was clearly observed that the fiber surface after the special laser treatment was much cleaner, with no visible resin residue. Furthermore, fiber integrity was maintained, with no damage such as fiber breakage or degradation. This demonstrates that UV defocus processing can meet cleaning requirements within a removal depth range of 200μm-500μm, providing a reference for high-quality surface formation of plain-weave CFRP three-dimensional structures.

[0090] To analyze the material removal mechanism during milling and characterize the micromorphology, scanning electron microscope images were taken under different machining conditions. Due to the characteristics of the plain weave structure, the position of the yarns must be considered when studying the material removal process, as the distribution of fibers at different locations can affect the material removal mechanism.

[0091] Figure 14 The surface topography of different feed rates per tooth in the upper meridian direction is shown. The specific milling positions are as follows: Figure 14(a). In this direction, the workpiece is squeezed, and the resin matrix is ​​smeared due to the angle between the fiber orientation and the feed direction. This phenomenon is particularly obvious at lower feed rates, as shown in Figure b1, where the surface is smooth and flat. Reducing the feed rate can reduce the generation of fiber fragments and improve the integrity of the carbon fiber. Conversely, increasing the feed per tooth will inhibit resin smearing. At the same time, fiber fragments and resin debris also increase. This is because the cutting edge contacts more material during the milling process, thereby generating greater milling force. Plain woven CFRP is an anisotropic composite material. The greater the force, the greater the tool vibration, and the more fiber fragments and resin debris are generated, as shown in Figure d2. In order to confirm the presence of a large amount of resin residue on the surface, the specific milling parameters (v c =157m / min,f z =3μm / tooth, a p Figures e and f show the processing results at a thickness of 350 μm (μm = 350 μm). In addition to the C peak, the O peak indicates the presence of a resin coating on the surface. Furthermore, the elemental distribution maps show that the distribution of O and C are nearly complementary. This is due to the resin matrix acting as an adhesive to bond the carbon fibers, resulting in a misalignment of the O and C distributions. Notably, the Au peak was generated by gold sputtering prior to acquisition of the SEM images.

[0092] UV laser post-treatment is considered to be a method that can improve the surface quality of plain woven CFRP after milling. The corresponding microscopic surface features such as Figure 15As shown in the figure, compared to the post-milling morphology, UV laser ablation completely removed residual resin, fiber fragments, and resin debris while minimizing damage to the carbon fibers. Plowing marks on the fiber surface can be seen under magnification, demonstrating that the fibers are fresh and intact. Due to the significant difference in thermodynamic properties between epoxy resin and carbon fibers, epoxy resin is easier to remove than carbon fibers. Therefore, the unit energy density achieved by defocusing the UV laser more easily captures the resin removal threshold without damaging the fibers. These carbon fibers remain intact at the microscopic level, facilitating subsequent bonding repair. Although a small number of microcracks are present at the ends of the carbon fibers, these are primarily caused by milling, and this machining damage cannot be repaired by UV laser ablation. Although the higher feed rate in the previous step resulted in poor surface quality, the fiber ends remained crack-free after laser treatment, demonstrating excellent fiber integrity. In contrast, the lower milling forces generated by the lower feed rate do not completely break the fibers, resulting in cracks at the fiber ends exposed after laser ablation. Overall, this two-step processing method may be more suitable for milling conditions with high feed rates per tooth, as it maximizes fiber integrity and improves subsequent adhesive repair performance. Similarly, EDS results after laser treatment were obtained under the same processing parameters. Clearly, the surface is almost free of elements other than carbon, indicating that the laser post-treatment has removed the surface resin, resulting in a large amount of intact carbon fibers.

[0093] Example 4

[0094] This embodiment provides a specific implementation method.

[0095] 1. First, we conducted a single-pass UV laser scanning experiment by controlling the laser scanning speed, fill spacing, and defocus, and characterized the micromorphology. The surface ablation morphology was classified into three categories: severe ablation, partial ablation, and incomplete ablation.

[0096] 2. A hybrid laser processing method is proposed to balance the efficient laser ablation under focal length conditions and the excellent surface quality obtained under off-focus conditions.

[0097] 3. Perform multiple scans under focal length conditions to obtain the relationship between cycle number and ablation depth.

[0098] To meet the needs of three-dimensional geometric repair, based on the relationship between the number of cycles and ablation depth under focal length conditions, depth-controlled ablation combined with subsequent laser defocus processing was used to achieve high-performance manufacturing of stepped repair geometry of plain-woven CFRP samples. The reliability of UV laser defocus processing in cleaning surface resin was verified within the removal depth range of 200μm-500μm.

[0099] 4. In order to meet the surface precision forming requirements of the patch in the damaged area of ​​the plain woven CFRP workpiece, the deterministic processing method of milling is used to remove the CFRP workpiece material.

[0100] 5. Milling Experiment Parameters As shown in Table 3, a total of seven experiments were designed based on single-factor variables: milling depth, feed per tooth, and cutting speed. The milling depth was determined based on the results of the UV laser repair experiment and ranged from 200 μm to 500 μm.

[0101] 6. Characterizing the micromorphology of plain-woven CFRP after milling and analyzing the material removal mechanism, it was found that reducing the feed per tooth under dry milling conditions improved fiber integrity. Furthermore, under most conditions, significant resin smearing and varying degrees of damage, including fiber fragmentation, resin debris, fiber delamination, and cracks, were unavoidable.

[0102] 7. The milled material was processed using a UV laser defocusing method and the micromorphology was characterized. The laser removed a large amount of resin, fiber fragments, and resin debris from the surface without damaging the fiber integrity.

[0103] 8. Use the same milling cutter to continuously machine two three-dimensional stepped structures, and post-process the second solid geometry using UV laser defocus processing.

[0104] 9. Use a 3D profilometer to obtain the surface profile before and after laser treatment, calculate the removal depth of milling and analyze the effect of laser repair on surface forming accuracy, such as Figure 7 and Figure 8 Obviously, the laser treatment does not affect the removal depth accuracy of the milling process, because the laser only removes the surface resin debris and fiber fragments without damaging the carbon fiber body.

[0105] 10. Characterize the three-dimensional stepped geometry after laser processing, e.g. Figure 16 As shown. According to the characteristics of the stepped three-dimensional structure, the images obtained are all at the right angles of each layer. Figure 6They are arranged in order from the upper left corner to the lower right corner, so there are a total of 6 locations displayed. Obviously, a large amount of surface resin, fiber fragments, resin residues and separated carbon fiber tubes were cleaned up after laser treatment, although a small amount of debris still remains at the end of the fiber. Compared with the laser treatment performance after single-pass milling, there are still some residues in the laser repair after three-dimensional forming. This is because the surface area to be processed of the three-dimensional structure is increased. Compared with the narrow area of ​​single-pass milling, the residual resin on the surface may not be completely removed due to insufficient heat accumulation during the UV laser scanning process, so there will be some debris on the surface. In addition, since the result of UV laser treatment is based on the second three-dimensional structure processed by the same milling cutter, the surface of the milling cutter will have the material accumulated in the previous processing adhered to it, resulting in more serious resin smearing on the surface after milling.

[0106] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0107] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high-quality processing method for repairing damaged areas of plain-woven CFRP, characterized by: The following steps are involved: Step S1: First, scan the plain-woven CFRP workpiece multiple times under the focus condition to obtain a stepped workpiece with the adjacent layer removed; the scanning speed of the plain-woven CFRP workpiece is 115 mm / s-1840 mm / s, and the filling spacing range is 5 μm-28 μm; Step S2, scanning the surface of the ablated CFRP workpiece under a defocused condition to clean the surface resin of the CFRP workpiece; the scanning speed of the CFRP workpiece under the defocused condition ranges from 125 mm / s to 750 mm / s, and the filling spacing ranges from 5 μm to 30 μm, and residual resin on the surface after molding is cleaned using a defocused laser processing method; Step S3: milling the workpiece to obtain a patch matching the pit obtained after laser ablation, and using ultraviolet laser to clean the surface resin and fiber fragments of the patch after milling; Step S4: bonding the processed patch to the CFRP workpiece to complete the repair of the CFRP workpiece.

2. A high-quality processing method for repairing a damaged area of ​​plain-woven CFRP according to claim 1, characterized in that: In step S2, the scanning speed parameter is adjusted according to the following formula: Where v is the scanning speed, f is the frequency, and d is the spot diameter.

3. A high-quality processing method for repairing a damaged area of ​​plain-woven CFRP according to claim 2, characterized in that: In step S2, the filling spacing parameter is adjusted according to the following formula: Where p is the fill pitch and d is the spot diameter.

Images