Laser removal method for damaged area of carbon fiber composite laminate

Abstract

The invention provides a laser removal method for a damaged area of a carbon fiber composite laminate, and belongs to the technical field of laser processing of composites. According to the method, the removal shape of the outermost layer is a chamfered regular octagon, and the outermost layer is downwards removed layer by layer in a step shape. According to the method, the removal area of each layer of carbon fiber composite material can be reduced, and the removal time of a damaged region is shortened; in addition, by means of the method, the removal volume of the carbon fiber composite material can be reduced, excessive damage-free materials are prevented from being machined and removed, and the repair strength of the patching structure is improved.

Description

Technical Field

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

[0002] Carbon fiber composite materials are widely used in aircraft structures due to their high specific strength and high specific modulus, and the proportion of materials is increasing year by year. Carbon fiber composite laminates have poor impact resistance. During the service of aircraft, especially carbon fiber composite skins, they are easily damaged by collisions, and the carbon fiber composite laminates on the aircraft need to be repaired.

[0003] At present, the main repair method for carbon fiber composite laminates is patching, that is, the damaged area is removed first, and then a patch is made, and the patch is pasted and fixed to the damaged area by gluing. This repair method can ensure that the aerodynamic shape is not affected. Removal of damaged areas is a key link in the patching repair process. The current patching method is mainly through manual grinding, but this patching 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 makes it possible to remove the special-shaped damaged areas of carbon fiber composite laminates.

[0004] At present, the commonly used method for removing the damaged area of ​​carbon fiber composite laminates is the bevel method, that is, taking the circular contour as the removal area, the damaged area is removed layer by layer according to a certain patching angle (2°~6°) and other slope steps. However, this removal method has the following disadvantages: First, the removal area of ​​each layer of carbon fiber composite material is large, which makes the removal time of the damaged area longer; second, the removal volume of the carbon fiber composite laminate is large, too much undamaged material is processed and removed, and the repair strength of the patching structure is low. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, an embodiment of the present invention proposes a laser removal method for the damaged area of ​​a carbon fiber composite material layer, which can reduce the removal area of ​​each layer of carbon fiber composite material and shorten the removal time of the damaged area; in addition, the method can reduce the removal volume of the carbon fiber composite material, avoid excessive undamaged material from being processed and removed, and improve the repair strength of the excavation and patching structure.

[0006] The embodiment of the present invention provides a laser removal method for damaged areas of carbon fiber composite material laminates, which is 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 material 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; wherein h0 is the ply thickness of the carbon fiber composite material laminate;

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

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

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

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

[0015]

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

[0017] Step 10: adjusting laser parameters, and removing the surface resin of the rounded regular octagonal processing area with 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: adjusting laser parameters, removing the area to be removed by laser, and the removal depth of the area to be removed reaches the layer thickness h0, and observing 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 fiber to form a new area to be removed, and 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, and the direction of obtaining the next layer of carbon fiber 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°-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 as follows:

[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 removal time of the damaged area.

[0028] (2) The method of the embodiment of the present invention can reduce the removal volume of the carbon fiber composite material, avoid excessive undamaged material being processed and removed, and improve the repair strength of the excavated structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A 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 cut-and-patch structure according to an embodiment of the present invention;

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

[0032] 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 position, 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 material laminate, where n=round up (h / h0)+2; where h0 is the ply thickness of the carbon fiber composite material laminate.

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

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

[0041] According to engineering experience, the selection 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 position as the center, R as the inscribed circle radius, and r as the chamfer radius.

[0046] Since the ply order of carbon fiber composite material plies usually cycles in four orthogonal directions in a certain pattern, the number of times the four orthogonal directions appear is generally 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. The laser removes the surface resin of the rounded regular octagonal processing area to expose the carbon fiber.

[0048] Step 11: The chamfered regular octagonal processing area is indented toward the center by a 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., 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 a 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., laser remove the new area to be removed, and the removal depth reaches the layer thickness h0, and 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 removal shape of the outermost layer designed by the method of the embodiment of the present invention is a regular octagon, and the removal shape of each descending layer is determined according to the removal shape of the previous layer and the direction of the carbon fibers of the current layer, and is obtained by calculation.

[0053] The following is a detailed description with reference to specific embodiments and drawings.

[0054] Example 1

[0055] The ply order of carbon fiber composite laminates is unknown, and the direction of the carbon fibers needs to be determined while laser removal is in progress. Since the ply order of carbon fiber composite laminates usually cycles in four orthogonal directions in a certain pattern, the number of occurrences of the four orthogonal directions is generally the same. Therefore, the shape of the outermost layer removed is a regular octagon with rounded corners.

[0056] The laser removal of damaged areas in carbon fiber composite laminates is a 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 position, damage depth h = 2mm, and damage size 10mm;

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

[0060] Step 4: According to the ply thickness of each layer of the carbon fiber composite material laminate h0=125 μm and the damage depth h=2 mm, the number of damaged layers n=round up (h / h0)+2=18 is calculated;

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

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

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

[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 position as the center, R = 18.27mm as the inscribed circle radius, and r = 5mm 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., remove the surface resin of the rounded regular octagonal processing area with laser, 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 next layer of carbon fiber;

[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, and the laser parameters are adjusted, including an average power of 30 W, a scanning speed of 200 mm / s, a pulse width of 100 ns, a repetition frequency of 100 kHz, a focal length of f = 100 mm, etc. The laser removes the new area to be removed, and the removal depth of the new area to be removed reaches the layer thickness h0 = 125 μm, and the direction of the next layer of carbon fiber 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 equal slope areas. Figure 2 The cross section of the patching structure of this embodiment is shown, in which the layers are removed downward in a step-like 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 layer-by-layer removal of the variable slope step removal area.

[0075] From the results of Example 1 and Comparative Example 1, the radius of the outermost circular area removed in Comparative Example 1 is 35.7 mm, which is about twice the radius of the inscribed circle of the outermost regular octagon in Example 1. Compared with Comparative Example 1, Example 1 can significantly reduce the removal area of ​​each layer of carbon fiber composite material, and the average removal area is reduced by about 50%, which can shorten the removal time of the damaged area; in addition, it can also reduce the removal volume of carbon fiber composite material, avoid excessive non-damaged material from being processed and removed, and improve the repair strength of the excavation and patching structure.

[0076] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. 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 representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

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

Claims

1. A laser removal method for damaged areas of carbon fiber composite material 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 material 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; wherein h0 is the ply thickness of the carbon fiber composite material laminate; Step 5: Design the cutting angle θ; Step 6: Calculate the step width d, d = h0 / tan(θ); Step 7: Determine the fillet radius r of the fillet regular octagonal processing area; Step 8: Calculate the radius R of the inscribed circle of the rounded regular octagonal processing area. Step 9: Draw a chamfered regular octagonal processing area with the center of the damage position as the center, R as the inscribed circle radius, and r as the chamfer radius; Step 10: adjusting laser parameters, and removing the surface resin of the rounded regular octagonal processing area with 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: adjusting laser parameters, removing the area to be removed by laser, and the removal depth of the area to be removed reaches the layer thickness h0, and observing 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 fiber to form a new area to be removed, and 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, and the direction of obtaining the next layer of carbon fiber 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°~6°.

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

4. The method according to claim 1, characterized in that: 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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