CN114905156A - Laser stripping method for damaged layer for repairing and repairing composite material laminate - Google Patents

Laser stripping method for damaged layer for repairing and repairing composite material laminate Download PDF

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CN114905156A
CN114905156A CN202110181268.XA CN202110181268A CN114905156A CN 114905156 A CN114905156 A CN 114905156A CN 202110181268 A CN202110181268 A CN 202110181268A CN 114905156 A CN114905156 A CN 114905156A
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layer
composite material
stripping
laser
material laminate
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CN114905156B (en
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赵树森
林学春
梁晗
张志研
马文浩
梁浩
刘燕楠
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Institute of Semiconductors of CAS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/70—Auxiliary operations or equipment
    • B23K26/702—Auxiliary equipment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Abstract

The invention discloses a laser stripping method for a damaged layer for repairing and repairing a composite material laminate, wherein the composite material laminate is formed by compounding multiple layers of fiber yarns, and the stripping method comprises the following steps: detecting the composite material laminate to obtain the central position and the damage depth of the damage area; calculating the number of layers of the composite material laminate to be stripped according to the thickness and the damage depth of the single layer of the composite material laminate; judging the diameter of a stripping circle of the innermost layer to be stripped according to the damage depth; calculating to obtain the diameter of a stripping circle of each layer of the composite material laminate according to a preset oblique digging angle, the single-layer thickness of the composite material laminate and the diameter of the stripping circle of the innermost layer to be stripped; according to the central position and the diameter of each layer of stripping circle of the composite material laminate, the damaged area of the composite material laminate is scanned and stripped layer by layer from the surface layer to the inner layer by using laser, the stripping precision is high, the damage to the composite material laminate is small, the patching repair strength is improved, and the residual strength of the damaged composite material laminate is reserved.

Description

Laser stripping method for damaged layer for repairing and repairing composite material laminate
Technical Field
The invention relates to the technical field of laser processing, in particular to a laser stripping method for a damaged layer for repairing and repairing a composite material laminate.
Background
The composite material has larger and larger application proportion on airplanes and wider application in civil use, and the composite material laminate is a layered composite material, and each layer is composed of single-direction fiber yarns and resin. Pressing a plurality of fiber single-layer materials according to a certain angle. The damaged composite material layer plate structure needs to be repaired in time, the conventional repairing means of the composite material is repair, and the damaged area needs to be removed firstly during repair.
The conventional patching method mainly uses manual grinding, is low in efficiency and poor in quality controllability, depends on the working experience of operators, and greatly limits the rapid repair of the damaged composite material laminate. In addition, manual polishing is combined with numerical control machining for patching, and layer-by-layer nondestructive stripping cannot be accurately controlled. In order to avoid damaging the composite material laminate in the grinding process, the damaged composite material laminate is uniformly processed to the other surface of the laminate (penetrating all layers of the composite material laminate) according to a certain angle in manual grinding or numerical control milling processing to form a bevel hole, so that the residual strength of the composite material laminate is greatly reduced.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for stripping the strength of a composite material laminate with a small wound surface and a residual part, and discloses a method for stripping a damaged layer of the composite material laminate by laser for patching repair.
According to some embodiments of the invention, a method for laser stripping a damaged layer for patching repair of a composite laminate, the composite laminate comprising a plurality of layers of filament composite, the stripping method comprising:
detecting the composite material laminate to obtain the central position and the damage depth of the damaged area;
calculating to obtain the number of layers of the composite material laminate to be stripped according to the thickness of the single layer of the composite material laminate and the damage depth;
judging the diameter of a stripping circle of the innermost layer to be stripped according to the damage depth:
if the damage depth is smaller than the thickness of the composite material layer plate, setting the diameter of a stripping circle of the innermost layer of the layers to be stripped as a preset threshold value;
if the damage depth is equal to the thickness of the composite material layer plate, taking the minimum circumscribed circle of the damage area of the bottom layer of the composite material laminate as a stripping circle of the innermost layer needing to be stripped;
calculating to obtain the diameter of a stripping circle of each layer of the composite material laminate according to a preset oblique digging angle, the single-layer thickness of the composite material laminate and the diameter of the stripping circle of the innermost layer to be stripped;
and scanning and stripping the damaged area of the composite material laminate layer by layer from the surface layer to the inner layer by using laser according to the central position and the diameter of each stripping circle of the composite material laminate layer.
According to some embodiments of the invention, the scanning laser of the damaged area of the composite laminate layer by layer from the surface layer to the inner layer according to the center position and the diameter of each layer of the composite laminate peeling circle comprises: and removing the ablation residual substance after using the laser scanning to strip the layer.
According to some embodiments of the invention, the probing the composite plies further comprises:
obtaining the fiber yarn direction of each layer of the composite material laminate, and scanning and stripping the damaged area of the composite material laminate once or more times from the surface layer to the inner layer by using laser;
if the fiber yarn is stripped by scanning once, the scanning direction of the laser is vertical to the direction of the fiber yarn of the current stripped layer;
if the scanning stripping is carried out for a plurality of times, the scanning direction of the laser during the first scanning stripping is vertical to the direction of the fiber filament of the currently stripped layer, and the scanning direction of the laser forms an included angle of 90 degrees with the scanning direction of the laser at the last time in each follow-up scanning stripping.
According to some embodiments of the present invention, when the laser is used for scanning and peeling layer by layer from the surface layer to the inner layer, inert gas is used for protecting the scanning and peeling area so as to prevent the composite material from being heated and burnt in air.
According to some embodiments of the invention, after the calculating the number of layers of the composite material laminate to be peeled according to the single-layer thickness and the damage depth of the composite material laminate further comprises comparing the calculated number of layers to be peeled with the total number of layers of the composite material laminate:
if the calculated number of layers needing to be stripped is less than or equal to 3 subtracted from the total number of layers of the composite material laminate, taking the calculated number of layers needing to be stripped as the number of layers actually stripped;
and if the calculated number of layers needing to be stripped, subtracted from the total number of layers of the composite material laminate, is greater than 3, additionally adding 1-5 layers to the calculated number of layers needing to be stripped as the number of layers actually stripped, wherein the number of the layers left after the composite material laminate is actually stripped is greater than or equal to 3.
According to some embodiments of the invention, the scanning and peeling from the surface layer to the inner layer by layer with laser further comprises: and scanning the whole stripping area by adopting high-repetition-frequency low-power laser to clean impurities remained on the surface of the stripping step, wherein the frequency of the high-repetition-frequency low-power laser is 200-500 kHz, and the power of the high-repetition-frequency low-power laser is 5-15W.
According to some embodiments of the invention, the diameter of the stripping circle of the innermost layer to be stripped is within a preset threshold, and the preset threshold is 10mm to 15 mm.
According to some embodiments of the invention, the predetermined angle of scoop ranges from 2 ° to 6 °.
According to some embodiments of the invention, the laser layer-by-layer scan stripping from the surface layer to the inner layer comprises: and in the scanning stripping process, monitoring a scanning area, judging that the composite material laminate of the layer is stripped completely if the directions of all the fiber yarns in the monitoring area are the directions of the fiber yarns of the next layer, stripping the composite material laminate of the next layer or finishing the step and entering the next process.
According to some embodiments of the invention, the composite laminate comprises one of: the carbon fiber composite material laminate, the glass fiber composite material laminate, the carbon fiber composite material laminate containing the coating or the glass fiber composite material laminate containing the coating.
According to the technical scheme, accurate data of the part to be stripped of the damaged area of the composite material laminate are obtained through calculation, the composite material laminate is accurately stripped layer by layer through laser scanning, a step profile is formed after patching, the bonding surface area of patching repair is favorably increased, the patching repair strength of the composite material is improved, meanwhile, a parent body which is not damaged at the lower side is kept as far as possible, the residual strength of the damaged composite material laminate is greatly kept, in addition, the automated operation of patching stripping can be realized, and the controllability and the efficiency of the patching repair quality are favorably ensured.
Drawings
FIG. 1 schematically illustrates a flow chart of a damaged layer laser stripping method for repair of composite plies in accordance with an embodiment of the disclosure;
FIG. 2 schematically illustrates a structure diagram of a damaged layer after being stripped by the laser stripping method for repairing composite laminate in a patching manner according to the embodiment of the disclosure;
wherein 1 represents a center position; 2 denotes the stripping circle for innermost layer stripping; and 3 denotes a preset chamfer angle θ.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
It is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details. Furthermore, in the following description, descriptions of well-known technologies are omitted so as to avoid unnecessarily obscuring the concepts of the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "comprising" as used herein indicates the presence of the features, steps, operations but does not preclude the presence or addition of one or more other features.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
In order to solve the technical problems, the invention provides a method for stripping the strength of a composite material laminate with a small wound surface and a residual part, and discloses a method for stripping a damaged layer of the composite material laminate by laser for patching repair.
FIG. 1 schematically illustrates a flow chart of a damaged layer laser stripping method for repair of composite plies in accordance with an embodiment of the disclosure.
According to some embodiments of the invention, the invention discloses a laser stripping method for repairing damaged layers of composite material laminates, wherein the composite material laminates are formed by compounding multiple layers of fiber yarns, and as shown in figure 1, the stripping method comprises steps S1-S5.
According to some embodiments of the invention, step S1 includes: and detecting the composite material laminate to obtain the central position 1 and the damage depth of the damaged area.
According to some embodiments of the invention, the imaging difference between the damaged area and the normal area of the composite material laminate is utilized by an ultrasonic microscope to detect the specific situation of the damaged area of the composite material laminate, including the depth of the damaged area, the specific position of the damaged area, the central position of the damaged area and the like.
According to some embodiments of the invention, step S2 includes: and calculating to obtain the number of layers of the composite material laminate to be stripped according to the thickness and the damage depth of the single layer of the composite material laminate, wherein the calculated number of layers to be stripped is a theoretical value.
According to some embodiments of the invention, the number of layers that a composite laminate needs to be stripped is determined according to the following formula:
Figure BDA0002940854080000051
wherein s' is the number of layers of the composite material laminate which need to be stripped theoretically, the layers are rounded upwards, the force is the damage depth, h 0 Is the thickness of a single layer of the composite material laminate.
According to some embodiments of the present invention, although the fiber layers below the deepest part of the damaged area of the composite material laminate are not damaged, the strength of the fiber layers is affected as a directly or indirectly stressed area, and in order to ensure sufficient structural strength of the composite material laminate after repair, according to experience, 3-5 additional fiber layers are generally stripped, specifically according to the following formula:
Figure BDA0002940854080000052
according to some embodiments of the present invention, when the damaged depth of the composite material laminate is close to the thickness of the composite material laminate, for example, when the distance between the innermost layer of the damaged area of the composite material laminate and the bottom layer of the composite material laminate is 1-5 times of the thickness of a single layer, in order to avoid forming the through hole, the number of extra layers to be stripped needs to be considered in a balanced manner, and the structural strength of the remaining part of the composite material laminate is retained to the maximum extent, specifically, the number of layers to be stripped obtained by calculation is compared with the total number of layers of the composite material laminate:
if the calculated number of layers needing to be stripped is less than or equal to 3 subtracted from the total number of layers of the composite material laminate, taking the calculated number of layers needing to be stripped as the number of layers actually stripped;
and if the calculated number of layers needing to be stripped, subtracted from the total number of layers of the composite material laminate, is greater than 3, additionally adding 1-5 layers to the calculated number of layers needing to be stripped as the number of layers actually stripped, wherein the number of the layers left after the composite material laminate is actually stripped is greater than or equal to 3.
According to some embodiments of the invention, step S3 includes: the diameter of the peeling circle of the innermost layer 2 to be peeled is judged according to the damage depth:
if the damage depth is smaller than the thickness of the composite material layer, setting the diameter of a stripping circle of the innermost layer of the layers to be stripped as a preset threshold value;
if the damage depth is equal to the thickness of the composite material layer plate, the minimum circumcircle of the damage area of the bottom layer of the composite material layer plate is used as the stripping circle of the innermost layer 2 needing to be stripped.
According to some embodiments of the invention, step S4 includes: and calculating the diameter of the stripping circle of each layer of the composite material laminate according to the preset oblique digging angle, the single-layer thickness of the composite material laminate and the diameter of the stripping circle of the innermost layer 2 to be stripped.
Fig. 2 schematically shows a structure diagram of a damaged layer stripped by a laser stripping method for repairing a composite laminate in a patching mode according to an embodiment of the disclosure.
According to some embodiments of the present invention, as shown in fig. 2, the middle blank area is a stripping circle area of each layer, the plurality of stripping circles form a step shape, an angle between a vertical connection line of edges of adjacent steps and the composite material laminate is a preset inclined digging angle θ, the innermost stripping circle 2 is located below the damaged area, and an extra stripping layer is located between the lowest part of the damaged area and the innermost stripping circle 2.
According to some embodiments of the present invention, the calculation formula for the diameter of the ith layer laser ablation circle comprises:
Figure BDA0002940854080000061
wherein d is i Denotes the diameter of the laser ablation circle of the i-th layer, theta denotes the preset chamfer angle, d s Indicating the diameter of the stripping circle for the innermost layer that needs to be stripped.
According to some embodiments of the invention, step S5 includes: and scanning and stripping the damaged area of the composite material laminate layer by layer from the surface layer to the inner layer of the composite material laminate layer by using laser according to the central position 1 and the diameter of the stripping circle of each layer of the composite material laminate.
According to some embodiments of the invention, the laser light has a wavelength in the range of 355nm to 1080nm or 1.6 μm.
According to some embodiments of the present invention, the wavelength of the laser light may vary from laser to laser, for example, a solid-state laser, a laser in which trivalent neodymium ions are doped in a Yttrium Aluminum Garnet (YAG) crystal may emit near-infrared laser light having a wavelength of 1050 nm; the optical fiber laser is an ytterbium-doped high-power optical fiber laser, and a semiconductor laser of 915 nm or 975 nm is generally selected; the laser wavelength of the He-Ne laser is 632.8 nm.
According to some embodiments of the invention, the average power of the laser is 5W to 1000W.
According to some embodiments of the invention, the average power of the laser is 500W.
According to some embodiments of the present invention, the appropriate laser wavelength and power are selected based on the material of the composite plies.
According to some embodiments of the invention, the laser has a repetition rate of 5kHz to 500 kHz.
According to some embodiments of the invention, the laser has a repetition rate of 200 kHZ.
According to some embodiments of the invention, the laser has a pulse width of 4ns to 200 ns.
According to some embodiments of the invention, the laser has a pulse width of 100 ns.
According to some embodiments of the invention, the laser has a scanning speed of 50mm/s to 2000 mm/s.
According to some embodiments of the invention, the scanning speed of the laser is 500 mm/s.
According to some embodiments of the present invention, the scanning speed of the laser is related to the number of times each layer is scanned, and the appropriate laser scanning speed is selected in combination with the wavelength, power, and material of the composite laminate.
According to some embodiments of the invention, the laser spot diameter is between 10 μm and 80 μm.
According to some embodiments of the invention, the laser spot diameter is 40 μm.
According to some embodiments of the invention, the laser scan pitch is between 10 μm and 200 μm.
According to some embodiments of the invention, the laser scan pitch is 100 μm.
According to some embodiments of the invention, the scan trajectory of the laser is "bow" or "zig-zag".
According to some embodiments of the present invention, scanning the damaged area of the composite laminate using a laser layer by layer from the surface layer to the inner layer according to the center position 1 and the diameter of each layer of the composite laminate peeling circle comprises: after one layer is stripped by using laser scanning, the method also comprises the step of removing the ablation residual substance so as to prevent the ablation residual substance from influencing the stripping of the next layer.
According to some embodiments of the present invention, optionally, after one layer is removed by laser scanning, the material left by ablation on the surface is removed by using a fur brush, and after the material is removed, the next layer is removed by laser scanning.
According to some embodiments of the invention, probing the composite plies further comprises: scanning and imaging the composite material laminate through an ultrasonic microscope to obtain the fiber yarn direction of each layer of the composite material laminate, and scanning and stripping the damaged area of the composite material laminate once or for many times by using laser from the surface layer to the inner layer of the composite material laminate.
If only once scanning stripping is carried out, the scanning direction of the laser is vertical to the direction of the fiber yarn of the currently stripped layer.
If the multi-time scanning stripping is carried out, the scanning direction of the laser during the first scanning stripping is vertical to the direction of the currently stripped fiber filament, and the scanning direction of the laser for each subsequent time forms an included angle of 90 degrees with the scanning direction of the laser for the last time.
According to some embodiments of the invention, when scanning and stripping are carried out layer by layer from the surface layer to the inner layer by using a laser, inert gas is used for protecting the scanning and stripping area so as to prevent the composite material from being heated and burnt in air.
According to some embodiments of the invention, the inert gas comprises argon or nitrogen.
According to some embodiments of the invention, the flow rate of the inert gas is controlled in the range of 3-15L/min.
According to some embodiments of the present invention, the inert gas is blown from the side of the stripping operation area.
According to some embodiments of the invention, the scanning and peeling from the surface layer to the inner layer by using the laser further comprises: scanning of the entire strip area is accomplished using a high repetition frequency low power laser to clean impurities remaining on the surface of the strip step.
According to some embodiments of the invention, the high repetition frequency low power laser has a frequency of 200kHz to 500kHz and the high repetition frequency low power laser has a power of 5W to 15W.
According to some embodiments of the invention, the high repetition frequency low power laser has a frequency of 300 kHz.
According to some embodiments of the invention, the high repetition frequency low power laser has a power of 10W.
According to some embodiments of the present invention, the diameter of the stripping circle of the innermost layer 2 to be stripped is within a predetermined threshold, wherein the predetermined threshold is 10mm to 15 mm.
According to some embodiments of the invention, the preset threshold is 10 mm.
According to some embodiments of the invention, the predetermined angle of the scoop ranges from 2 ° to 6 °.
According to some embodiments of the invention, the common predetermined angle of the chamfer is, as a rule of thumb, 4 °.
According to some embodiments of the present invention, the larger the angle of the preset bevel cut angle is, the larger the diameter of the peeling circle is, the higher the structural strength after repairing is, and at the same time, the longer the peeling time and the repairing time are, the higher the cost is, in the actual operation, the comprehensive consideration of the actual conditions of the damaged area, such as the position, the influence on the surrounding parts, the size of the operable space, the requirement for implementation, the control of the cost, and the like, is needed.
According to some embodiments of the invention, scanning the peeling layer by layer using the laser from the surface layer to the inner layer comprises: and in the scanning stripping process, monitoring a scanning area, judging that the composite material laminate of the layer is stripped completely if the directions of all the fiber yarns in the monitoring area are the directions of the fiber yarns of the next layer, stripping the composite material laminate of the next layer or finishing the step and entering the next process.
According to some embodiments of the present invention, during the laser scanning stripping process, a CCD (charge coupled device) camera is used to monitor the scanning area, and the direction of the fiber filament in the stripping area is monitored to determine whether the stripping operation of the layer is completed.
According to some embodiments of the invention, the composite laminate comprises one of: the composite material comprises a carbon fiber composite material laminate, a glass fiber composite material laminate, a carbon fiber composite material laminate containing a coating or a glass fiber composite material laminate containing a coating.
The present invention is further described with reference to the following specific examples, which are only for facilitating the technical solutions of the present invention to be better understood by those skilled in the art, and are not intended to limit the scope of the present invention.
According to some embodiments of the invention, the carbon fiber composite CCF300/QY8911 is taken as an example, the composite laminate has a thickness of 3mm, and 24 layers in total, each layer having a thickness of 0.125 mm.
And detecting the damaged area through an ultrasonic microscope to obtain the central position of the damaged area, wherein the damage depth is 0.8 mm.
According to
Figure BDA0002940854080000091
Calculating to obtain s as 6.4, rounding up to 7, and taking into accountConsidering the distance from the bottom layer of the composite laminate is far, an additional 3 layers are empirically stripped, i.e. the final number of layers to be stripped is 10.
Empirically, the preset scoop angle θ is selected to be 4 °.
Empirically, the diameter d of the stripping circle of the innermost layer of the composite laminate to be stripped 10 Is 10 mm.
According to the oblique digging angle theta and the single-layer thickness h of the composite material laminate 0 Diameter d of the stripping circle of the innermost layer 10 Calculating the diameter d of the laser peeling circle of the 1 st to 9 th layers i The specific results are shown in table 1:
TABLE 1
Figure BDA0002940854080000092
Figure BDA0002940854080000101
Scanning the composite material laminate through an ultrasonic microscope to obtain the direction of each layer of the fiber yarns, and setting the scanning direction of a laser.
Setting laser parameters: the laser wavelength of the laser can be 1064 nm; average laser power: 30W; repetition frequency: 50 kHz; pulse width: 100 ns; scanning speed: 100 mm/s; laser spot diameter: 30 mu m; laser scanning interval: 0.04 mm; scanning a track: a Chinese character 'bow' shape.
Taking the damage point of the composite material laminate as the center, and the laser scanning is carried out by using d i The method comprises removing the i-th composite material layer in a circular area with a diameter, scanning with laser 1-3 times, wherein the scanning direction is perpendicular to the fiber filament direction if the scanning direction is 1 time, the scanning direction of the 1 st laser is perpendicular to the fiber filament direction if the scanning direction is multiple times, and the laser direction is changed by 90 DEG every time of scanning
In the laser scanning stripping process, the rest of the laser action is subjected to anti-oxidation protection by adopting side-blown protective gas, wherein the gas is argon, and the flow rate of the gas is 10L/min.
And when the scanning area is completely displayed as the lower layer direction fiber yarns through visual observation or synchronous detection CCD observation, the laser stripping of the layer is considered to be finished.
After the laser scanning of the current layer is finished, the residual substances of surface ablation are removed by using a soft brush, and after the removal is finished, the laser scanning stripping of the next layer can be started.
The scanning of the whole stripping area is completed by adopting high repetition frequency and low power laser to clean impurities remained on the surface of the stripping step, and the laser repetition frequency selection range is as follows: 500kHz, Power Range: 5W.
The present invention is further described with reference to another specific embodiment, it should be understood that these embodiments are only for facilitating the technical solutions of the present invention to be better understood by those skilled in the art, and are not intended to limit the scope of the present invention.
According to some embodiments of the invention, taking carbon fiber composite ZT7H/QY9611 as an example, the thickness of the composite material layer is 2mm, and the thickness of each layer is 0.125mm, and the total of 16 layers.
And detecting the damaged area through an ultrasonic microscope to obtain the central position of the damaged area, wherein the damage depth is 2mm, the damaged area is a through hole, and the diameter of the minimum circumscribed circle of the damaged area of the bottom layer of the composite material laminate is 38.6mm through measurement and calculation.
The minimum circumcircle of the damaged area of the bottom layer (16 layers) of the composite material laminate is used as a stripping circle of the innermost layer to be stripped, and the diameter of the stripping circle is 38.6 mm.
According to experience, since the damaged region is a through hole, the damage is severe, and the predetermined chamfering angle θ is empirically selected to be 2 °.
According to the oblique digging angle theta and the single-layer thickness h of the composite material laminate 0 Diameter d of the stripping circle of the innermost layer 16 Calculating the diameter d of the laser ablation circle of the 1 st to 5 th layers i The specific results are shown in table 2:
TABLE 2
Number of layers Stripping circle diameter (mm)
Layer 1 146.0
Layer 2 138.9
Layer 3 131.7
Layer 4 124.5
Layer 5 117.4
Layer 6 110.2
Layer 7 103.1
Layer 8 95.9
Layer 9 88.7
Layer 10 81.6
Layer 11 74.4
Layer 12 67.3
Layer 13 60.1
Layer 14 53.0
Layer 15 45.8
Layer 16 38.6
Scanning the composite material laminate through an ultrasonic microscope to obtain the direction of each layer of the fiber yarns, and setting the scanning direction of a laser.
Setting laser parameters: the laser wavelength of the laser can be 1064 nm; average power of laser: 30W; repetition frequency: 100 kHz; pulse width: 100 ns; scanning speed: 100 mm/s; laser spot diameter: 30 mu m; laser scanning interval: 0.04 mm; scanning a track: a Chinese character 'bow' shape.
Taking the damage point of the composite material laminate as the center, and the laser scanning is carried out by using d i The method comprises removing the i-th composite material layer in a circular area with a diameter, scanning with laser 1-3 times, wherein the scanning direction is perpendicular to the fiber filament direction if the scanning direction is 1 time, the scanning direction of the 1 st laser is perpendicular to the fiber filament direction if the scanning direction is multiple times, and the laser direction is changed by 90 DEG every time of scanning
In the laser scanning stripping process, the rest of the laser action is subjected to anti-oxidation protection by adopting side-blown protective gas, wherein the gas is argon, and the flow rate of the gas is 10L/min.
And when the scanning area is observed to be completely displayed as the fiber filaments in the lower layer direction through visual observation or synchronous detection CCD, the laser stripping of the layer is considered to be finished.
After the laser scanning of the current layer is finished, the residual substances of surface ablation are removed by using a soft brush, and after the removal is finished, the laser scanning stripping of the next layer can be started.
Scanning of the whole stripping area is completed by adopting high repetition frequency low-power laser to clean impurities remained on the surface of the stripping step, and the laser repetition frequency selection range is as follows: 500kHz, Power Range: 5W.
According to the technical scheme, the damaged area of the composite material laminate is obtained through calculation, accurate data of the part needing to be stripped are obtained, laser scanning is adopted to accurately strip the composite material laminate layer by layer, the size of the area which is stripped layer by layer can be accurately controlled, the step profile is formed after patching, the patching repair bonding surface area is increased, meanwhile, the surface of the composite material laminate which is stripped by laser is clean, and the bonding strength with the patch is improved.
The laser layer-by-layer precise stripping can effectively control the removal depth, only a plurality of layers of materials on the surface layer need to be precisely stripped for superficial damage, the undamaged parent body on the lower side is kept as far as possible, and the residual strength of the damaged composite material laminate is greatly kept.
In addition, the automatic operation of patching stripping can be realized, and the controllability and the efficiency of patching repairing quality can be ensured.
So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. In addition, the above definitions of the components are not limited to the specific structures, shapes or manners mentioned in the embodiments, and those skilled in the art may easily modify or replace them.
It is also noted that, unless otherwise indicated, the numerical parameters set forth in the specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. In particular, all numbers expressing dimensions, range conditions, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term "about". In general, the meaning of the expression is meant to encompass variations of a specified number by ± 10% in some embodiments, by ± 5% in some embodiments, by ± 1% in some embodiments, by ± 0.5% in some embodiments.
It will be appreciated by a person skilled in the art that various combinations and/or combinations of features described in the various embodiments and/or in the claims of the invention are possible, even if such combinations or combinations are not explicitly described in the invention. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present invention may be made without departing from the spirit and teachings of the invention. All such combinations and/or associations fall within the scope of the present invention.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A laser stripping method for damaged layers of composite material laminates for repairing and repairing is characterized in that the composite material laminates are formed by compounding multiple layers of fiber yarns, and the stripping method comprises the following steps:
detecting the composite material laminate to obtain the central position and the damage depth of the damage area;
calculating to obtain the number of layers of the composite material laminate needing to be stripped according to the thickness of the single layer of the composite material laminate and the damage depth;
judging the diameter of a stripping circle of the innermost layer to be stripped according to the damage depth:
if the damage depth is smaller than the thickness of the composite material layer plate, setting the diameter of a stripping circle of the innermost layer of the layers to be stripped as a preset threshold value;
if the damage depth is equal to the thickness of the composite material layer plate, taking the minimum circumscribed circle of the damaged area of the bottom layer of the composite material layer plate as a stripping circle of the innermost layer needing to be stripped;
calculating to obtain the diameter of a stripping circle of each layer of the composite material laminate according to a preset oblique digging angle, the single-layer thickness of the composite material laminate and the diameter of the stripping circle of the innermost layer to be stripped;
and scanning and stripping the damaged area of the composite material laminate layer by layer from the surface layer to the inner layer by using laser according to the central position and the diameter of each layer of stripping circle of the composite material laminate.
2. The method of claim 1, wherein scanning laser ablation of damaged areas of the composite plies from surface to interior layer by layer based on the center position and a diameter of each ablation circle of the composite plies comprises: and removing the ablation residual substance after using the laser scanning to strip the layer.
3. The method of claim 1, wherein probing the composite plies further comprises:
obtaining the fiber yarn direction of each layer of the composite material laminate, and scanning and stripping the damaged area of the composite material laminate once or more times from the surface layer to the inner layer by using laser;
if scanning stripping is carried out for one time, the scanning direction of the laser is vertical to the direction of the fiber yarn of the currently stripped layer;
if the multi-time scanning stripping is carried out, the scanning direction of the laser is perpendicular to the direction of the fiber filament of the currently stripped layer during the first scanning stripping, and the scanning direction of the laser forms an included angle of 90 degrees with the scanning direction of the laser at the last time in each follow-up time.
4. The method as claimed in claim 1, wherein the step of scanning and peeling from the surface layer to the inner layer by using the laser comprises protecting the scanning and peeling area with inert gas to prevent the composite material from burning under heat in the air.
5. The method of claim 1, wherein after calculating the number of layers of the composite laminate to be peeled based on the individual thickness of the composite laminate and the damage depth, the method further comprises comparing the calculated number of layers to be peeled to the total number of layers of the composite laminate:
if the calculated number of layers needing to be stripped is less than or equal to 3 subtracted from the total number of layers of the composite material laminate, taking the calculated number of layers needing to be stripped as the number of layers actually stripped;
and if the calculated number of layers needing to be stripped, subtracted from the total number of layers of the composite material laminate, is greater than 3, additionally adding 1-5 layers to the calculated number of layers needing to be stripped as the number of layers actually stripped, wherein the number of the layers left after the composite material laminate is actually stripped is greater than or equal to 3.
6. The method of claim 1, wherein scanning the lift-off layer by layer from the surface layer to the inner layer using a laser further comprises: and scanning the whole stripping area by adopting high-repetition-frequency low-power laser to clean impurities remained on the surface of the stripping step, wherein the frequency of the high-repetition-frequency low-power laser is 200 kHz-500 kHz, and the power of the high-repetition-frequency low-power laser is 5W-15W.
7. The method of claim 1, wherein the diameter of the stripping circle of the innermost layer to be stripped is within a predetermined threshold, and the predetermined threshold is 10mm to 15 mm.
8. The method of claim 1, wherein the predetermined angle of scoop is in the range of 2 ° to 6 °.
9. The method of claim 1, wherein scanning the lift-off layer by layer from the surface layer to the inner layer using a laser comprises: and in the scanning stripping process, monitoring a scanning area, judging that the composite material laminate of the layer is stripped completely if the directions of all the fiber yarns in the monitoring area are the directions of the fiber yarns of the next layer, stripping the composite material laminate of the next layer or finishing the step and entering the next process.
10. The method of claim 1, wherein the composite laminate comprises one of: the composite material comprises a carbon fiber composite material laminate, a glass fiber composite material laminate, a carbon fiber composite material laminate containing a coating or a glass fiber composite material laminate containing a coating.
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