Laser removal method for damaged areas of carbon fiber composite laminates

Abstract

The present invention provides a laser removal method for damaged areas in carbon fiber composite laminates, belonging to the field of composite laser processing technology. The outermost layer removed in this method is a regular octagon with rounded corners, with each layer removed in a stepped manner. This method can reduce the area removed per layer of carbon fiber composite material, shortening the time it takes to remove damaged areas. Furthermore, the method can reduce the volume of carbon fiber composite material removed, preventing excessive removal of undamaged material and improving the repair strength of the patched structure.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material laser processing, and particularly relates to a method for laser removing damaged areas of carbon fiber composite material laminates. Background Art

[0002] Carbon fiber composites, with their high specific strength and high specific modulus, are widely used in aircraft structures, and their share of the material continues to grow annually. However, carbon fiber composite laminates have poor impact resistance, making them particularly susceptible to collision damage during aircraft service, necessitating repairs to these laminates.

[0003] Currently, the main method for repairing carbon fiber composite laminates is patching. This involves first removing the damaged area, then creating a patch that is glued and fixed to the damaged area. This repair method ensures that the aerodynamic shape is not affected. Removing the damaged area is a key step in the patching process. Currently, patching is mainly done through manual grinding, but this method is inefficient and not conducive to quality control. In recent years, with the development of laser technology, composite laser precision removal technology has gradually developed, which has made it possible to remove irregularly shaped damaged areas in carbon fiber composite laminates.

[0004] The current method commonly used to remove damaged areas in carbon fiber composite laminates is the miter method, which uses a circular contour as the removal area and removes the damaged area layer by layer according to a certain patching angle (2° to 6°) and other slope steps. However, this removal method has the following disadvantages: First, the removal area of ​​each carbon fiber composite layer is large, which makes the removal time of the damaged area longer; second, the removal volume of the carbon fiber composite laminate is large, and too much undamaged material is processed and removed, resulting in a low repair strength of the patched structure. Summary of the Invention

[0005] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, embodiments of the present invention provide a laser method for removing damaged areas from carbon fiber composite laminates. This method can reduce the area removed from each layer of carbon fiber composite material and shorten the time required to remove the damaged area. Furthermore, this method can reduce the volume of carbon fiber composite material removed, preventing excessive removal of undamaged material and improving the repair strength of the patched structure.

[0006] An embodiment of the present invention provides a laser removal method for damaged areas of a carbon fiber composite material laminate, characterized by comprising the following steps:

[0007] Step 1: Remove stains from the surface of the carbon fiber composite material laminate;

[0008] Step 2: Using an ultrasonic flaw detector to test the damage position, damage depth h and damage size of the carbon fiber composite material laminate;

[0009] Step 3: Calculate the radius r0 of the damaged area of ​​the carbon fiber composite laminate, where r0 = the maximum value of the damage size in the two-dimensional direction / 2;

[0010] Step 4: Calculate the number of damaged layers n of the carbon fiber composite material laminate, where n=(h / h0)+2 rounded up; where h0 is the ply thickness of the carbon fiber composite material laminate;

[0011] Step 5: Design the patching angle θ;

[0012] Step 6: Calculate the step width d, d = h0 / tan(θ);

[0013] Step 7: Determine the fillet radius r of the filleted regular octagonal processing area;

[0014] Step 8: Calculate the inscribed circle radius R of the rounded regular octagonal processing area.

[0015]

[0016] Step 9: Draw a chamfered regular octagonal processing area with the center of the damage location as the center, R as the inscribed circle radius, and r as the chamfer radius;

[0017] Step 10: Adjust the laser parameters and remove the surface resin of the rounded regular octagonal processing area with the laser to expose the carbon fiber;

[0018] Step 11: indent the rounded regular octagonal processing area toward the center by a step width d along the direction of the exposed carbon fiber to form an area to be removed;

[0019] Step 12: Adjust the laser parameters, remove the area to be removed by laser, and remove the area to be removed to a depth that reaches the ply thickness h0, and observe the direction of the next layer of carbon fibers;

[0020] Step 13: The area to be removed is further indented toward the center by a step width d along the direction of the carbon fibers to form a new area to be removed. The laser parameters are adjusted to remove the new area to be removed by laser, and the removal depth of the new area to be removed reaches the layer thickness h0. The direction of the next layer of carbon fibers is observed.

[0021] Step 14: Repeat step S13 until the number of removed layers reaches the number of damaged layers n, and the removal process ends.

[0022] In some embodiments, in step 5, θ=2° to 6°.

[0023] In some embodiments, in step 7, r=5 mm to 10 mm.

[0024] In some embodiments, the laser parameters include average power, scanning speed, pulse width, repetition frequency, and focal length.

[0025] In some embodiments, the average power is 28W to 32W, the scanning speed is 180mm / s to 220mm / s, the pulse width is 90ns to 110ns, the repetition frequency is 90kHz to 110kHz, and the focal length is 90mm to 110mm.

[0026] The advantages and technical effects brought by the method of the embodiment of the present invention are:

[0027] (1) The method of the embodiment of the present invention can significantly reduce the removal area of ​​each layer of carbon fiber composite material and shorten the time for removing the damaged area.

[0028] (2) The method of the embodiment of the present invention can reduce the removal volume of carbon fiber composite materials, avoid excessive processing and removal of non-damaged materials, and improve the repair strength of the excavated structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a fine design for removing irregular shapes layer by layer in a patching structure according to an embodiment of the present invention;

[0030] Figure 2 A schematic cross-sectional view of a patching structure according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the detailed design of the circular removal layer by layer of the patching structure in the related technology. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0033] The embodiment of the present invention provides a laser removal method for damaged areas of a carbon fiber composite material laminate, comprising the following steps:

[0034] Step 1: Remove stains from the surface of the carbon fiber composite laminate.

[0035] Step 2: Use an ultrasonic flaw detector to test the damage location, damage depth h and damage size of the carbon fiber composite laminate.

[0036] Step 3: Calculate the radius r0 of the damaged area of ​​the carbon fiber composite laminate, where r0 = the maximum value of the damage size in the two-dimensional direction / 2.

[0037] In this step, r0 is equal to the maximum value of the damage size in the two-dimensional direction / 2. This is because: when the damaged area is circular, r0 is the radius of the circular damaged area; when the damaged area is irregular in shape, r0 is the radius of the circumscribed circle of the damaged area contour.

[0038] Step 4: Calculate the number of damaged layers n of the carbon fiber composite laminate, where n = (h / h0) + 2 rounded up; where h0 is the ply thickness of the carbon fiber composite laminate.

[0039] The ply thickness h0 is the thickness of each carbon fiber ply, such as Figure 2 Typically, multiple carbon fiber plies have the same thickness.

[0040] Step 5: Design the patching angle θ.

[0041] According to engineering experience, the range of the patching angle θ is 2° to 6°. The patching angle θ is the angle between the slope of the area to be removed and the horizontal direction. Figure 2 shown.

[0042] Step 6: Calculate the step width d, d = h0 / tan(θ);

[0043] Step 7: Determine the fillet radius r of the outermost fillet regular octagonal processing area, and the value range of r is 5mm to 10mm.

[0044] Step 8: Calculate the radius R of the inscribed circle of the outermost chamfered regular octagonal processing area. The units of d and r0 remain consistent.

[0045] Step 9: Draw a chamfered regular octagonal processing area with the center of the damage location as the center, R as the inscribed circle radius, and r as the chamfer radius.

[0046] Since the laying order of carbon fiber composite material layers usually cycles in a certain pattern in the four orthogonal directions, the number of times the four orthogonal directions appear is basically the same. Therefore, the shape of the outermost processing area is a regular octagon with rounded corners, such as Figure 1 shown.

[0047] Step 10: Adjust the laser parameters, including average power, scanning speed, pulse width, repetition frequency, focal length, etc., and remove the surface resin of the rounded regular octagonal processing area with laser to expose the carbon fiber.

[0048] Step 11: Indent the rounded regular octagonal processing area toward the center by the step width d along the direction of the exposed carbon fiber in step 10 to form an area to be removed.

[0049] Step 12: Adjust the laser parameters, including average power, scanning speed, pulse width, repetition frequency, focal length, etc., and remove the area to be removed in step 11 by laser, and the removal depth reaches the layer thickness h0, and observe the direction of the next layer of carbon fiber.

[0050] Step 13: Continue to indent the area to be removed toward the center by the step width d along the direction of the carbon fiber to form a new area to be removed. Adjust the laser parameters, including average power, scanning speed, pulse width, repetition frequency, focal length, etc., and use the laser to remove the new area to be removed, and the removal depth reaches the layer thickness h0. Observe the direction of the next layer of carbon fiber.

[0051] Step 14: Repeat step 13 until the number of removed layers reaches the number of damaged layers n, and the removal process ends.

[0052] The outermost layer removal shape designed by the method of the embodiment of the present invention is a regular octagon. The removal shape of each descending layer is determined based on the removal shape of the previous layer and the direction of the carbon fibers of the current layer, and is obtained through calculation.

[0053] The following describes the details in conjunction with specific embodiments and drawings.

[0054] Example 1

[0055] The layup order of carbon fiber composite laminates is unknown, requiring the orientation of the carbon fibers to be determined during laser removal. Since the layup order of carbon fiber composite laminates typically cycles in four orthogonal directions, with the four orthogonal directions appearing roughly evenly throughout, the outermost layer removed forms a regular octagon with rounded corners.

[0056] Laser removal of damaged areas in carbon fiber composite laminates. Layer-by-layer area planning and removal method. The specific steps are as follows:

[0057] Step 1: Remove stains from the surface of the carbon fiber composite material laminate;

[0058] Step 2: Use ultrasonic flaw detector to test the damage location, damage depth h = 2mm, and damage size 10mm;

[0059] Step 3: Divide the maximum damage size in the two-dimensional direction (10 mm) by 2 to obtain the damage area radius r0 = 5 mm;

[0060] Step 4: Based on the ply thickness h0 of each carbon fiber composite laminate layer = 125 μm and the damage depth h = 2 mm, calculate the number of damaged layers n = (h / h0) + 2 = 18;

[0061] Step 5: Design the patching angle θ, which is 3.6°.

[0062] Step 6: Based on the ply thickness h0 of each carbon fiber composite laminate layer = 125 μm and the patching angle θ = 3.6°, calculate the step width d: d = h0 / tan(θ) = 1984 μm = 1.984 mm;

[0063] Step 7: Determine the fillet radius r of the outermost fillet regular octagonal processing area, r is 5mm;

[0064] Step 8: Calculate the radius R of the inscribed circle of the outermost chamfered regular octagonal processing area.

[0065]

[0066] Step 9: Draw a chamfered regular octagonal processing area with the center of the damage location as the center, R = 18.27 mm as the inscribed circle radius, and r = 5 mm as the chamfer radius;

[0067] Step 10: Adjust the laser parameters, including average power 30W, scanning speed 200mm / s, pulse width 100ns, repetition frequency 100kHz, focal length f = 100mm, etc., and remove the surface resin of the rounded regular octagonal processing area with the laser to expose the carbon fiber and observe the direction of the obtained carbon fiber;

[0068] Step 11: Indent the rounded regular octagonal processing area toward the center along the direction of the exposed carbon fiber by a step width d = 1.984 mm to form an area to be removed;

[0069] Step 12: Adjust the laser parameters, including average power 30W, scanning speed 200mm / s, pulse width 100ns, repetition frequency 100kHz, focal length f = 100mm, etc., remove the area to be removed by laser, and the removal depth of the area to be removed reaches the layer thickness h0 = 125μm, and observe the direction of the carbon fiber of the next layer;

[0070] Step 13: The area to be removed is further indented toward the center along the direction of the carbon fiber by a step width of d = 1.984 mm to form a new area to be removed. The laser parameters are adjusted, including average power 30 W, scanning speed 200 mm / s, pulse width 100 ns, repetition frequency 100 kHz, focal length f = 100 mm, etc. The new area to be removed is removed by laser, and the removal depth of the new area to be removed reaches the layer thickness h0 = 125 μm. The direction of the carbon fiber of the next layer is observed;

[0071] Step 14: Repeat step 13 until the number of removed layers reaches 18 damaged layers, and the removal process ends.

[0072] Figure 1 The embodiment shows the step-by-step removal of the equal-slope area. Figure 2 The cross section of the patching structure of this embodiment is shown, with the patching structure being removed layer by layer in a step-by-step manner.

[0073] Comparative Example 1

[0074] The conventional layer-by-layer circular patching structure in the related art is adopted, and the patching angle is 3.6°. The radius of the outermost removed circular area is calculated to be 18×125 / tan(3.6°)=35.7 mm. Figure 3 The comparative example shows the step-by-step removal of regions with variable slopes.

[0075] The results of Example 1 and Comparative Example 1 show that the radius of the outermost circular area removed in Comparative Example 1 is 35.7 mm, approximately twice the radius of the inscribed circle of the outermost regular octagon in Example 1. Compared to Comparative Example 1, Example 1 significantly reduces the area removed per layer of carbon fiber composite material, with the average removal area reduced by approximately 50%, shortening the time required to remove the damaged area. Furthermore, it reduces the volume of carbon fiber composite material removed, preventing excessive removal of undamaged material and improving the repair strength of the patched structure.

[0076] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0077] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A laser removal method for damaged areas of carbon fiber composite laminates, characterized in that: The following steps are involved: Step 1: Remove stains from the surface of the carbon fiber composite material laminate; Step 2: Using an ultrasonic flaw detector to test the damage position, damage depth h and damage size of the carbon fiber composite material laminate; Step 3: Calculate the radius r0 of the damaged area of ​​the carbon fiber composite laminate, where r0 = the maximum value of the damage size in the two-dimensional direction / 2; Step 4: Calculate the number of damaged layers n of the carbon fiber composite material laminate, where n=(h / h0)+2 rounded up; where h0 is the ply thickness of the carbon fiber composite material laminate; Step 5: Design the patching angle θ; Step 6: Calculate the step width d, d = h0 / tan(θ); Step 7: Determine the fillet radius r of the filleted regular octagonal processing area; Step 8: Calculate the inscribed circle radius R of the rounded regular octagonal processing area. Step 9: Draw a chamfered regular octagonal processing area with the center of the damage location as the center, R as the inscribed circle radius, and r as the chamfer radius; Step 10: Adjust the laser parameters and remove the surface resin of the rounded regular octagonal processing area with the laser to expose the carbon fiber; Step 11: indent the rounded regular octagonal processing area toward the center by a step width d along the direction of the exposed carbon fiber to form an area to be removed; Step 12: Adjust the laser parameters, remove the area to be removed by laser, and remove the area to be removed to a depth that reaches the ply thickness h0, and observe the direction of the next layer of carbon fibers; Step 13: The area to be removed is further indented toward the center by a step width d along the direction of the carbon fibers to form a new area to be removed. The laser parameters are adjusted to remove the new area to be removed by laser, and the removal depth of the new area to be removed reaches the layer thickness h0. The direction of the next layer of carbon fibers is observed. Step 14: Repeat step S13 until the number of removed layers reaches the number of damaged layers n, and the removal process ends.

2. The method according to claim 1, characterized in that In step 5, θ = 2° to 6°.

3. The method according to claim 1, characterized in that In step 7, r = 5 mm to 10 mm.

4. The method according to claim 1, wherein The laser parameters include average power, scanning speed, pulse width, repetition frequency, and focal length.

5. The method according to claim 4, characterized in that The average power is 28W to 32W, the scanning speed is 180mm / s to 220mm / s, the pulse width is 90ns to 110ns, the repetition frequency is 90kHz to 110kHz, and the focal length is 90mm to 110mm.

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