A method of repairing a composite material

Abstract

The application relates to a composite material repairing method, belonging to the technical field of composite material surface treatment, and solving the problems of low interface bonding strength of the repaired composite material and low repairing efficiency of the adhesive repairing process. The method comprises the following steps: removing the damaged part of the composite material by a mechanical removal method; scanning the interface after removal by an ultraviolet laser for multiple times to remove the mechanical damage layer generated due to the mechanical removal; cleaning the composite material after the step 2 treatment; activating the adhesive interface by a low-temperature plasma; laying and pasting an adhesive film and scraping; then laying and pasting a patch, scraping, compacting, and then packaging; heating and curing, and adopting ultrasonic radiation for auxiliary curing in the curing stage; and polishing the repaired area after heating and curing. The interface tensile shear strength of the composite material repaired by the method is increased by 38% compared with the strength of the existing single sandpaper polishing, the repairing quality is improved, and the curing time is shortened.

Description

Technical Field

[0001] This invention belongs to the field of composite material surface repair technology, and particularly relates to a method for repairing composite materials. Background Technology

[0002] Advanced resin-based composite materials have many advantages, such as high specific strength, high specific stiffness, strong designability, good fatigue fracture resistance, corrosion resistance, good dimensional stability, ability to achieve structural / functional integration, and ease of large-area integral molding. Their application in aerospace, aircraft, ships, high-speed trains, automobiles and other fields is rapidly increasing, and they have partially replaced aluminum alloys and steel, becoming one of the fastest-growing advanced materials in equipment structural materials.

[0003] One of the major problems hindering the further application of advanced composite materials is the repair of structural damage. Mechanical impact is one of the main forms of damage to composite materials. Poor impact resistance is an inherent deficiency of resin-based composite materials. When subjected to mechanical impact, metallic materials can absorb energy through plastic and elastic deformation, thereby avoiding the initiation and propagation of cracks. However, the interlaminar shear strength of resin-based composite materials is usually only tens of megapascals, far lower than the intralaminar performance. In addition, the composite material has poor ductility, therefore, it is very easy to be damaged after mechanical impact. The damage forms of composite materials usually manifest as delamination, fiber breakage, fracture, and perforation.

[0004] Composite material adhesive bonding repair technology has advantages such as not creating new stress concentrations, not significantly increasing structural weight, and providing good fatigue resistance after repair, making it a key focus of research in composite material structural damage repair technology. Currently, the repair of composite material damage and defects in aircraft and other equipment in China mainly uses traditional methods, namely mechanical grinding and pretreatment, followed by prepreg bonding and encapsulation using patching or adhesive methods, and finally heat curing using a composite material thermal repair instrument. The adhesive strength at the repair interface directly affects the quality of the repair. Existing composite material adhesive bonding repair processes result in low interfacial bond strength, long curing times, and low repair efficiency. Summary of the Invention

[0005] In view of the above analysis, the present invention proposes a method for repairing composite materials, which can at least solve one of the following technical problems: (1) the interfacial bonding strength of the composite material after repair by the existing composite material adhesive bonding repair process is low; (2) the repair efficiency of the existing composite material adhesive bonding repair process is low.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for repairing composite materials, comprising:

[0008] Step 1: Remove the damaged parts of the composite material using mechanical excavation.

[0009] Step 2: Use ultraviolet laser to scan the excavated interface multiple times to remove the mechanical damage layer caused by mechanical excavation;

[0010] Step 3: Clean the composite material after the treatment in Step 2;

[0011] Step 4: Activate the adhesive interface using low-temperature plasma;

[0012] Step 5: Apply the adhesive film and smooth it out; then apply the patch according to the size of the damaged area, smooth and compact it, and then seal it.

[0013] Step 6: Heat curing, with ultrasonic radiation used for assisted curing during the curing stage;

[0014] Step 7: After heating and curing, polish the repaired area.

[0015] In one possible design, the wavelength of the ultraviolet laser in step 2 is 355 nm.

[0016] In one possible design, in step 2, the ultraviolet laser has a power of 10-15W, a spot diameter of 20μm, a pulse width of 10ps, and a scanning speed of 1500-2000mm / s.

[0017] In one possible design, in step 2, the ultraviolet laser scans the excavated interface 15 to 20 times.

[0018] In one possible design, step 3 involves cleaning the composite material using an ultrasonic cleaner.

[0019] In one possible design, step 4, which involves activating the adhesive interface with low-temperature plasma, is as follows: a low-temperature plasma surface treatment device with a power of 30W is used, the distance between the plasma gun nozzle and the workpiece is 5-8cm, the spot movement speed is 3-5cm / s, and the scan is performed 1-2 times.

[0020] In one possible design, in step 5, after plasma treatment, the time for applying the adhesive film is controlled within 1 minute.

[0021] In one possible design, step 5, the encapsulation step includes: sequentially covering the patch with a release cloth, a heating blanket, a breathable felt, and a vacuum bag.

[0022] In one possible design, step 6, the heating and curing step, includes: turning on the composite material heat repair instrument for heating and curing, drawing a vacuum, and when the temperature reaches the insulation platform with the lowest corresponding viscosity, performing ultrasonic irradiation, and turning off the ultrasonic vibration switch after 5 to 10 minutes.

[0023] In one possible design, in step 6, the ultrasonic radiation device is a longitudinal wave probe.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] (1) In the method for repairing composite materials of the present invention, laser is used to remove the interface damage caused by the excavation of the damaged part of the composite material. This can effectively remove the resin layer with mechanical damage on the surface of the material and expose the internal carbon fiber. The ultraviolet laser does not damage the carbon fiber, so that the adhesive can directly contact the carbon fiber in the subsequent bonding process to improve the bonding effect.

[0026] (2) In the method for repairing composite materials of the present invention, laser is first used to remove the mechanically damaged layer generated after mechanical excavation of the surface layer of the composite material. This can avoid damaging the properties of the carbon fibers at the interface, such as fiber length and strength, and provide complete interface conditions for low-temperature plasma activation. Then, low-temperature plasma is used to activate the bonding interface, which can effectively improve the roughness of the bonding surface, increase surface activity, increase oxygen-containing active functional groups, and increase the proportion of chemical bonds at the bonding interface. At the same time, the uniformity of the distribution of roughness, active functional groups, and chemical bond proportions is ensured, thereby better improving the interfacial bonding strength between the repair matrix and the patch and the final repair effect.

[0027] (3) In the method for repairing composite materials of the present invention, ultrasonic irradiation is used in the curing stage. On the one hand, ultrasonic irradiation can cause bubbles to burst in liquid resin, and at the same time generate high temperature and high pressure to homogenize the blended system, reduce resin viscosity, reduce contact angle, improve resin and fiber wetting performance, increase bonding strength, and shorten curing time (the curing time of the existing epoxy system prepreg is reduced from 150 min to 130 min).

[0028] (4) The interfacial tensile shear strength between the patch, mother plate and adhesive film of the composite material repaired by the method of the present invention reaches 36.3 MPa, which is more than 38% higher than the strength of 26.3 MPa of the existing mechanical excavation method; and the uniformity of the interfacial shear strength between the patch, mother plate and adhesive film of the composite material is better, which greatly improves the repair quality.

[0029] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0030] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0031] Figure 1 This is a schematic diagram of the composite material to be repaired.

[0032] Figure 2 The morphology of the damaged area after mechanical excavation;

[0033] Figure 3 The image shows the morphology of the excavated interface after multiple ultraviolet laser scans.

[0034] Figure 4 This is a schematic diagram showing the area after the damaged part has been removed.

[0035] Figure 5 This is a schematic diagram of the packaged product;

[0036] Figure 6 This is a schematic diagram illustrating the propagation of ultrasound waves during the repair process.

[0037] Figure 7 A simplified structural diagram of a device for repairing composite materials.

[0038] Figure Labels

[0039] 1-Patch, 2-Motherboard, 3-Adhesive film, 4-Mechanical damage layer, 5-Release cloth, 6-Heating blanket, 7-Breathable felt, 8-Vacuum bag, 9-Vacuum nozzle, 10-Vacuum gauge, 11-Temperature measuring component, 12-Computer monitor, 13-PLC control unit, 14-Ultrasonic controller, 15-Ultrasonic transducer, 16-Vacuum pressure sensor, 17-Vacuum pump, 18-Heating controller, 19-Vacuum connection. Detailed Implementation

[0040] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0041] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0042] Throughout the text, the terms “top,” “bottom,” “above,” “below,” and “on top” refer to the relative positions of components of the device, such as the relative positions of the top and bottom within the device. It is understood that the device is multifunctional, regardless of its spatial orientation.

[0043] The working surface of this invention can typically be a plane or a curved surface, and can be inclined or horizontal. For ease of explanation, the embodiments of this invention are placed on a horizontal surface and used on a horizontal surface, thereby defining "height" and "vertical".

[0044] Currently, most repairs of composite material structures using adhesive bonding techniques include two methods: patching and excavation. Taking excavation repair as an example, the damaged area is typically removed first, followed by the application of adhesive film and then a patch for further repair. Excavation repair effectively restores the aerodynamic shape of the component, generates minimal repair stress, and avoids load eccentricity, making it a commonly used repair method for composite material structures. Figure 1 The diagram shows a schematic of the composite material to be repaired. The adhesive film 3 is located between the patch 1 and the base plate 2 of the composite material. The adhesive film 3 generally bears shear and lateral tensile and compressive loads, and its failure modes are peeling failure and shear failure. The patch repair aims to maximize the load-bearing capacity of the base plate 2, adhesive film 3, and patch 1 to restore the overall performance of the repaired structure to the greatest extent possible. During the repair process, the bonding strength between the base plate 2, adhesive film 3, and patch 1 directly affects the overall patch repair effect. Currently, the removal of damaged areas in composite material structures generally uses mechanical methods to process the damaged area into a conical slope with a certain length-to-thickness ratio, and to some extent, roughens the adhesive surface. This process is prone to causing secondary damage to the surface of the composite material, and also causes some damage to the strength of the repaired material. Figure 2 The image shows the morphology of the damaged area of ​​the resin-based composite material after mechanical removal. As can be seen from the figure, the surface resin has been ground away, exposing the internal carbon fibers, which have suffered multiple fractures. A significant amount of resin debris remains on the surface. This is because the uncontrollable external force during mechanical removal of the damaged area easily damages the internal carbon fibers while removing the surface resin, resulting in large resin debris. These resin residues and damaged fibers will significantly affect the bonding strength of the repair.

[0045] This invention discloses a method for repairing composite materials, comprising: using laser to remove the interface damage caused by excavation at the damaged part of the composite material; using low-temperature plasma to activate the adhesive interface; and using ultrasonic irradiation during the curing stage when using prepreg for bonding repair.

[0046] Specifically, the methods for repairing composite materials include:

[0047] Step 1: Remove the damaged parts of the composite material using mechanical excavation.

[0048] Step 2: Use ultraviolet laser to scan the excavated interface multiple times to remove the mechanical damage layer 4 caused by mechanical excavation;

[0049] Step 3: Clean the composite material after the treatment in Step 2;

[0050] Step 4: Activate the adhesive interface using low-temperature plasma;

[0051] Step 5: Apply adhesive film 3 and smooth it out; then apply patch 1 according to the size of the damaged area, smooth and compact it, and then seal it.

[0052] Step 6: Heat curing, with ultrasonic radiation used for assisted curing during the curing stage;

[0053] Step 7: After heating and curing, polish the repaired area.

[0054] Step 8: Use an ultrasonic non-destructive testing instrument to perform the inspection and complete the repair work.

[0055] Specifically, the aforementioned composite material is a resin-based composite material.

[0056] Specifically, in step 1 above, such as Figure 4 As shown, the damaged area is excavated into a circular wedge or circular stepped blind hole. Considering that although an excessively large excavation angle can reduce the stress concentration of the adhesive layer, the adhesive layer is more inclined to a tensile state rather than a shear state. At this time, the adhesive film is very prone to debonding, causing the patch to detach from the base plate, the patch to lose its load-bearing capacity, and greatly reducing the tensile strength of the joint. An excessively small angle tends to cause the base plate to break and fail. Therefore, the excavation angle is controlled to be about 3 to 6 degrees.

[0057] Specifically, because ultraviolet lasers have the characteristic of selective ablation, they can effectively remove the resin layer with mechanical damage on the surface of the material, exposing the internal carbon fibers. Ultraviolet lasers do not damage the carbon fibers, allowing the adhesive to directly contact the carbon fibers during the subsequent bonding process and improve the bonding effect. Therefore, in step 2 above, ultraviolet lasers are used to scan the interface after excavation multiple times to remove the interface damage caused by mechanical excavation. Figure 3The image shown is a topographical image of the interface after multiple scannings with ultraviolet laser after excavation.

[0058] Specifically, in step 2 above, the wavelength of the ultraviolet laser is 355nm.

[0059] Specifically, in step 2 above, the power of the ultraviolet laser is 10-15W, the spot diameter is 20μm, the pulse width is 10ps, and the scanning speed is 1500-2000mm / s.

[0060] Specifically, in step 2 above, scanning the excavated interface with ultraviolet laser too many times will damage the fiber layer; scanning it too few times will not completely remove the damaged layer; therefore, the number of times the excavated interface is scanned with ultraviolet laser should be controlled to 15 to 20 times.

[0061] Specifically, in step 3 above, an ultrasonic cleaner can be used to clean the composite material to remove debris and oil adsorbed on its surface. Industrial ethanol is used as the cleaning medium.

[0062] Specifically, in step 3 above, considering that too long a cleaning time wastes time and energy, and too short a cleaning time results in poor cleaning effect, the cleaning time is controlled to be 10 to 20 minutes.

[0063] Specifically, in step 4 above, the step of activating the adhesive interface with low-temperature plasma is as follows: using an open-type low-temperature plasma surface treatment equipment with a power of 30W, the distance between the plasma gun nozzle and the workpiece is 5-8cm, the spot movement speed is 3-5cm / s, and the scan is performed 1-2 times.

[0064] Specifically, in step 4 above, considering that if the distance between the plasma gun nozzle and the workpiece is too large, the activation effect will be weakened; if it is too small, there is a possibility of surface burn-off; therefore, the power is controlled at 30W, the distance between the plasma gun nozzle and the workpiece is 5-8cm, the spot movement speed is 3-5cm / s, and the scan is performed 1-2 times.

[0065] Specifically, in step 5 above, considering that the activation layer easily absorbs moisture from the air and is easily oxidized, thus reducing its activity, the adhesive film needs to be applied as soon as possible, with the time controlled within 1 minute.

[0066] Specifically, in step 5 above, such as Figure 5 As shown, the encapsulation steps include: sequentially covering the release cloth 5, heating blanket 6, breathable felt 7, and vacuum bag 8 on top of the patch 1.

[0067] Specifically, in step 6 above, before heat curing, an ultrasonic coupling agent is applied to a flat area adjacent to the area to be repaired (i.e., the damaged area), and the ultrasonic vibrator is placed on it and adjusted to ensure complete adhesion. Specifically, the distance between the applied ultrasonic coupling agent and the edge of the area to be repaired is less than 0.5 mm. For example, the distance between the applied ultrasonic coupling agent and the edge of the area to be repaired is 0 mm.

[0068] Specifically, in step 6 above, when the area to be repaired is large, an ultrasonic vibrating head can be added at a diagonal position of the original ultrasonic vibrating head to ensure uniform ultrasonic irradiation.

[0069] Specifically, in step 6 above, the principle of using ultrasonic irradiation to assist in the repair of composite materials lies in the fact that ultrasonic cavitation effect can generate localized high temperature, high pressure, and strong shock waves and microjets, giving ultrasound multiple functions such as strong dispersion, pulverization, and activation. Ultrasonic irradiation in the liquid resin of the patch can cause air bubbles to burst, while simultaneously generating high temperature and high pressure, achieving homogenization of the blend system, reducing resin viscosity, and decreasing the contact angle. This improves the wetting properties of the resin and fiber, increases bond strength, and shortens curing time.

[0070] It should be noted that in step 6 above, the device used for heat curing is a composite material repair instrument. The principle for setting the process parameters for heat curing is to formulate the heat curing process according to the type of resin used in the patch. The temperature plateau is set according to the temperature corresponding to the lowest viscosity point on the viscosity-temperature curve. The plateau time is usually 5-10 minutes, consistent with the ultrasonic irradiation time.

[0071] It should be noted that in step 6 above, the heating and curing steps include: turning on the heating switch of the composite material heat repair instrument to heat and cure, turning on the vacuum switch to vacuum, and when the temperature reaches the insulation platform with the lowest viscosity, turning on the ultrasonic vibration switch to perform ultrasonic irradiation, and turning off the ultrasonic vibration switch after 5 to 10 minutes.

[0072] It should be noted that in step 6 above, a longitudinal wave probe is used as the ultrasonic vibrating head. The probe power is 100W and the frequency is 28KHz.

[0073] It should be noted that in step 7 above, sanding and polishing are performed using sandpaper with a grit of ≤120. The purpose of sanding and polishing is to remove excess glue nodules and make the edges of the repaired area smooth.

[0074] It should be noted that in step 8 above, an ultrasonic non-destructive testing instrument is used to detect whether there are defects such as delamination or missing glue. If there are defects such as delamination or missing glue, steps 1-7 need to be repeated. If there are no defects such as delamination or missing glue, the repair work is completed.

[0075] Compared with existing technologies, the present invention's method for repairing composite materials uses laser to remove the interface damage caused by excavation at the damaged part of the composite material. This effectively removes the surface resin layer with mechanical damage, exposing the internal carbon fibers. The ultraviolet laser does not damage the carbon fibers, allowing the adhesive to directly contact the carbon fibers during subsequent bonding, thus improving the bonding effect. Low-temperature plasma activation of the bonding interface effectively increases the roughness of the bonding surface, enhances surface activity, and increases oxygen-containing active functional groups. This increases the proportion of chemical bonds at the bonding interface, improving the interfacial bonding strength between the repair matrix and the patch, and ultimately enhancing the repair effect. The curing stage uses ultrasonic irradiation. Ultrasonic irradiation acts on the liquid resin, causing air bubbles to burst and generating high temperature and pressure. This homogenizes the blended system, reduces resin viscosity, and lowers the contact angle, thereby improving the resin-fiber wetting properties, increasing bonding strength, and shortening the curing time (from the existing 150 minutes to 130 minutes). For example, the interfacial shear strength between the patch, mother plate, and adhesive film of the composite material repaired by the method of the present invention reaches 36.3 MPa, which is more than 38% higher than the strength of 26.3 MPa achieved by the existing mechanical removal method; furthermore, the interfacial shear strength values ​​between the patch, mother plate, and adhesive film of the composite material repaired by the method of the present invention have low dispersion, with the dispersion coefficient reduced by 66% compared to mechanical removal.

[0076] The present invention also provides an apparatus for repairing composite materials, including a laser, a low-temperature plasma surface treatment device, an ultrasonic device, and a composite material thermal repair instrument; the laser is capable of emitting laser light to remove the mechanically damaged layer of the composite material; the low-temperature plasma surface treatment device is used to spray plasma onto the surface of the composite material to achieve surface pretreatment; the area of ​​the composite material to be repaired is located within the ultrasonic irradiation area of ​​the ultrasonic device, and the ultrasonic device provides ultrasonic irradiation for the composite material thermal repair instrument to repair the area of ​​the composite material to be repaired.

[0077] Specifically, the aforementioned laser can emit ultraviolet laser light with a wavelength of 355 nm. After the damaged area of ​​the composite material is removed by mechanical excavation, the interface after excavation is scanned multiple times using an ultraviolet laser to remove the mechanical damage layer caused by mechanical excavation.

[0078] Specifically, the aforementioned low-temperature plasma surface treatment equipment can activate the adhesive interface using plasma after laser scanning.

[0079] Specifically, the aforementioned ultrasonic device includes an ultrasonic controller 14 and an ultrasonic transducer 15.

[0080] Specifically, considering that the area to be repaired of the composite material is large, the ultrasonic waves applied by a single ultrasonic transducer 15 may be uneven. Therefore, the number of ultrasonic transducers 15 is controlled to be multiple, for example, two.

[0081] Specifically, the ultrasonic transducer 15 mentioned above uses a longitudinal wave probe with a power of 100W and a frequency of 28KHz.

[0082] Specifically, the aforementioned composite material heat repair instrument includes a display unit, a control unit, and a vacuum pumping device; the control unit includes a temperature control unit, a vacuum control unit, and an ultrasonic control unit.

[0083] Specifically, the temperature control unit includes a temperature measuring component 11 and a heating controller 18.

[0084] Specifically, the vacuum control unit includes a vacuum pressure sensor 16.

[0085] Specifically, the display unit can be a computer monitor 12.

[0086] Specifically, the control unit can be a PLC control unit 13, which includes a temperature measuring component 11, a heating controller 18, and a vacuum pressure sensor 16.

[0087] Specifically, the vacuum device includes a vacuum nozzle 9, a vacuum gauge 10, a vacuum pump 17, a vacuum bag 8, a vacuum hose, and a vacuum connector 19; the vacuum bag 8 and the vacuum connector 19 are sealed and connected, and the vacuum connector 19 is connected to the vacuum pump 17 through the vacuum hose; the PLC control unit 13 can realize the following functions: heating temperature and heating time control; vacuuming and vacuum degree control; ultrasonic wave application and time control.

[0088] Specifically, the PLC control unit 13 guides the vacuum pumping device to perform vacuuming and vacuum degree control based on the detection data of the vacuum pressure sensor 16; the PLC control unit 13 guides the heating controller 18 to work based on the detection data of the temperature measuring component 11.

[0089] Specifically, the ultrasonic controller 14 is connected to the ultrasonic control unit of the PLC control unit 13, and the ultrasonic controller 14 applies ultrasonic waves and controls the time according to the data instructions of the ultrasonic control unit.

[0090] Specifically, the aforementioned PLC control unit 13 also includes a current sensor.

[0091] Specifically, the aforementioned composite material heat repair device also includes a release cloth 5, a heating blanket 6, and a breathable felt 7, which are used to encapsulate the area of ​​the composite material to be repaired.

[0092] Specifically, the temperature measuring component 11 includes multiple thermocouples.

[0093] Compared with the prior art, the beneficial effects of the device for repairing composite materials provided by the present invention are the same as those of the above-described method for repairing composite materials, and will not be repeated here.

[0094] Example 1

[0095] This embodiment provides a method for repairing composite materials, including:

[0096] Step 1: Remove the damaged parts of the composite material using mechanical excavation; specifically, excavate the damaged parts into a circular wedge shape or a circular stepped blind hole.

[0097] Step 2: Use an ultraviolet laser to scan the removed interface multiple times to remove the mechanically damaged layer 4 caused by mechanical removal; wherein the wavelength of the ultraviolet laser is 355nm, the power is 10w, the spot diameter is 20μm, the pulse width is 10ps, the scanning speed is 1500mm / s; scan 20 times.

[0098] Step 3: Use an ultrasonic cleaner to clean the composite material after step 2 to remove debris and oil adsorbed on the surface of the composite material; specifically, industrial ethanol is used as the cleaning medium.

[0099] Step 4: Activate the adhesive interface with low-temperature plasma: Use an open-type low-temperature plasma surface treatment equipment with a power of 30W. The distance between the plasma gun nozzle and the workpiece is 6cm, the spot movement speed is 4cm / s, and the scan is performed twice.

[0100] Step 5: Apply adhesive film 3 to the adhesive interface treated in step 4 and smooth it; then apply patch 1 according to the size of the damaged area, smooth and compact it, and then seal it; the sealing steps include: laying release cloth 5, heating blanket 6, breathable felt 7, and vacuum bag 8 on top of patch 1 in sequence.

[0101] Step 6: Heating and curing. Ultrasonic radiation is used to assist in curing during the curing stage. The heating and curing steps include: turning on the heating switch of the composite material heat repair instrument to heat and cure, turning on the vacuum switch to vacuum, and when the temperature reaches the insulation platform with the lowest viscosity, turning on the ultrasonic vibration switch to irradiate with ultrasonic waves. After 5 to 10 minutes, the ultrasonic vibration switch is turned off.

[0102] Step 7: After heat curing is complete, the repaired area is polished and tested with an ultrasonic non-destructive testing instrument. If there are no defects such as delamination or missing adhesive, the repair work is complete.

[0103] Example 2

[0104] This embodiment provides an apparatus for implementing the above-described method for repairing composite materials, such as... Figure 7As shown, it includes a laser, a low-temperature plasma surface treatment device, an ultrasonic device, and a composite material heat repair instrument. The ultrasonic device includes an ultrasonic controller 14 and an ultrasonic transducer 15. The ultrasonic device can provide ultrasonic irradiation when the composite material heat repair instrument repairs the area to be repaired of the composite material.

[0105] Specifically, the aforementioned composite material heat repair device includes a computer display 12, a PLC control unit 13, and a vacuum device. The PLC control unit 13 includes a temperature measuring component 11, a heating controller 18, and a vacuum pressure sensor 16. The vacuum device includes a vacuum nozzle 9, a vacuum gauge 10, a vacuum pump 17, a vacuum bag 8, a vacuum hose, and a vacuum connector 19. The vacuum bag 8 is connected and sealed to the vacuum connector 19, and the vacuum connector 19 is connected to the vacuum pump 17 through the vacuum hose. The PLC control unit 13 can perform the following functions: heating temperature and heating time control; vacuuming and vacuum degree control; ultrasonic wave application and time control.

[0106] Specifically, the PLC control unit 13 guides the vacuum pumping device to perform vacuuming and vacuum degree control based on the detection data of the vacuum pressure sensor 16; the PLC control unit 13 guides the heating controller 18 to work based on the detection data of the temperature measuring component 11.

[0107] Specifically, the ultrasonic controller 14 is connected to the PLC control unit 13, and the ultrasonic controller 14 applies ultrasonic waves and controls the time according to the data instructions of the PLC control unit 13.

[0108] Specifically, the aforementioned PLC control unit 13 also includes a current sensor.

[0109] Specifically, the aforementioned composite material heat repair device also includes a release cloth 5, a heating blanket 6, and a breathable felt 7, which are used to encapsulate the area of ​​the composite material to be repaired.

[0110] Specifically, the temperature measuring component 11 includes multiple thermocouples.

[0111] Specifically, there are two ultrasonic transducers 15.

[0112] Specifically, the ultrasonic transducer 15 mentioned above uses a longitudinal wave probe with a power of 100W and a frequency of 28KHz.

[0113] Specifically, the aforementioned computer monitor 12 is an industrial all-in-one computer.

[0114] Specifically, the aforementioned laser is capable of emitting ultraviolet laser light.

[0115] The aforementioned low-temperature plasma surface treatment equipment is used to activate the interface after laser scanning removes the interface damage caused by the excavation of damaged parts of composite materials.

[0116] The inventors of this invention conducted in-depth research and experiments on various repair methods, but none of them achieved the same repair results as the methods described above. The inventors present several repair methods they developed as comparative examples, as follows:

[0117] Comparative Example 1

[0118] This comparative example provides a method for repairing composite materials, including:

[0119] Step 1: Remove the damaged parts of the composite material using mechanical excavation.

[0120] Step 2: Use an ultrasonic cleaner to clean the composite material after the treatment in Step 1 to remove debris and oil adsorbed on the surface of the composite material.

[0121] Step 3: Apply adhesive film 3 to the adhesive interface treated in step 2 and smooth it; then apply patch 1 according to the size of the damaged area, smooth and compact it, and then seal it; the sealing steps include: laying release cloth 5, heating blanket 6, breathable felt 7, and vacuum bag 8 on top of patch 1 in sequence.

[0122] Step 4: Heating and curing. Ultrasonic radiation was not used to assist in curing during the curing stage.

[0123] Step 5: After heat curing is complete, the repaired area is polished and tested with an ultrasonic non-destructive testing instrument. If there are no defects such as delamination or missing adhesive, the repair work is complete.

[0124] Comparative Example 2

[0125] This comparative example provides a method for repairing composite materials, including:

[0126] Step 1: Remove the damaged parts of the composite material using mechanical excavation; specifically, excavate the damaged parts into a circular wedge shape or a circular stepped blind hole.

[0127] Step 2: Use ultraviolet laser to scan the excavated interface multiple times to remove the mechanical damage layer 4 caused by mechanical excavation;

[0128] Step 3: Use an ultrasonic cleaner to clean the composite material after step 2 to remove debris and oil adsorbed on the surface of the composite material; specifically, industrial ethanol is used as the cleaning medium.

[0129] Step 4: Activate the adhesive interface using low-temperature plasma;

[0130] Step 5: Apply adhesive film 3 to the adhesive interface treated in step 4 and smooth it; then apply patch 1 according to the size of the damaged area, smooth and compact it, and then seal it; the sealing steps include: laying release cloth 5, heating blanket 6, breathable felt 7, and vacuum bag 8 on top of patch 1 in sequence.

[0131] Step 6: Heat curing. Ultrasonic radiation is not used to assist curing during the curing stage.

[0132] Step 7: After heat curing is complete, the repaired area is polished and tested with an ultrasonic non-destructive testing instrument. If there are no defects such as delamination or missing adhesive, the repair work is complete.

[0133] Comparative Example 3

[0134] This comparative example provides a method for repairing composite materials, including:

[0135] Step 1: Remove the damaged parts of the composite material using mechanical excavation; specifically, excavate the damaged parts into a circular wedge shape or a circular stepped blind hole.

[0136] Step 2: Use an ultrasonic cleaner to clean the composite material after the treatment in Step 2 to remove debris and oil adsorbed on the surface of the composite material; specifically, industrial ethanol is used as the cleaning medium.

[0137] Step 3: Activate the adhesive interface using low-temperature plasma;

[0138] Step 4: Apply adhesive film 3 to the adhesive interface treated in Step 4 and smooth it out; then apply patch 1 according to the size of the damaged area, smooth and compact it, and then seal it; the sealing steps include: laying release cloth 5, heating blanket 6, breathable felt 7, and vacuum bag 8 on top of patch 1 in sequence.

[0139] Step 5: Heat curing, with ultrasonic radiation used for assisted curing during the curing stage;

[0140] Step 6: After heating and curing, the repaired area is polished and tested with an ultrasonic non-destructive testing instrument. If there are no defects such as delamination or missing adhesive, the repair work is complete.

[0141] Specifically, in Example 1 and Comparative Examples 1-3, the main resin component of the base material of the composite material is epoxy resin that cures at medium and low temperatures, and the reinforcement is carbon fiber; the material of the patch is epoxy-based carbon fiber prepreg. The adhesive film is an epoxy resin type adhesive film.

[0142] The tensile shear strength of the patches and base plates of Examples 1 and Comparative Examples 1-3 under adhesive film bonding was tested. The average interfacial shear strength of Example 1 was 36.3 MPa, and the dispersion of the interfacial shear strength values ​​between the patch, base plate, and adhesive film of the composite material was low at 0.137. The average interfacial shear strength of Comparative Example 1 was 26.3 MPa, and the dispersion of the interfacial shear strength values ​​between the patch, base plate, and adhesive film of the composite material was 0.228. The average interfacial shear strength of Comparative Example 2 was 35.2 MPa, and the interfacial shear strength between the patch, base plate, and adhesive film of the composite material was slightly lower than that of Example 1. The average interfacial shear strength of Comparative Example 3 was 30.5 MPa, and the interfacial shear strength between the patch, base plate, and adhesive film of the composite material was lower than that of Example 1. It can be seen that the method of the present invention can significantly improve the shear strength of the patch and base plate under adhesive film bonding, and the uniformity of the interfacial shear strength between the patch, base plate, and adhesive film of the composite material is better, which greatly improves the repair quality.

[0143] Furthermore, the curing time for Example 1 was approximately 130 minutes; the curing time for Comparative Example 1 was approximately 150 minutes; the curing time for Comparative Example 2 was approximately 150 minutes; and the curing time for Comparative Example 3 was approximately 140 minutes. The method of this invention can shorten the curing time and improve the repair efficiency.

[0144] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for repairing composite materials, characterized in that, The method for repairing composite materials includes: Step 1: Remove the damaged parts of the composite material using mechanical excavation. Step 2: Use ultraviolet laser to scan the excavated interface multiple times to remove the mechanical damage layer caused by mechanical excavation; Step 3: Clean the composite material after the treatment in Step 2; Step 4: Activate the adhesive interface using low-temperature plasma; Step 5: Apply the adhesive film and smooth it out; then apply the patch according to the size of the damaged area, smooth and compact it, and then seal it. Step 6: Heat curing, with ultrasonic radiation used for assisted curing during the curing stage; Step 7: After heat curing is complete, polish the repaired area. In step 1, the damaged area is excavated into a circular wedge-shaped or circular stepped blind hole, and the excavation angle is controlled to be 3~6°. In step 2, the ultraviolet laser has a power of 10W, a spot diameter of 20μm, a pulse width of 10 ps, ​​and a scanning speed of 1500~2000mm / s. The ultraviolet laser does not damage the carbon fiber, allowing the adhesive to directly contact the carbon fiber during the subsequent bonding process and improve the bonding effect. In step 4, the step of activating the adhesive interface with low-temperature plasma is as follows: a low-temperature plasma surface treatment device with a power of 30W is used, the distance between the plasma gun nozzle and the workpiece is 5~8cm, the spot movement speed is 3~5cm / s, and the scan is performed 1~2 times. In step 5, the time for applying the adhesive film should be controlled within 1 minute; In step 6, before heating and curing, an ultrasonic coupling agent is applied to a flat area adjacent to the area to be repaired, and the ultrasonic vibrating head is placed on it and adjusted to be completely in contact; the distance between the applied ultrasonic coupling agent and the edge of the area to be repaired is less than 0.5 mm. The heating and curing steps include: turning on the composite material heat repair instrument for heating and curing, drawing a vacuum, and when the temperature reaches the insulation platform with the lowest viscosity, performing ultrasonic irradiation, and turning off the ultrasonic vibration switch after 5~10 minutes. The interfacial shear strength between the patch, base plate, and adhesive film of the repaired composite material reached 36.3 MPa, and the coefficient of variation of the interfacial shear strength between the patch, base plate, and adhesive film of the repaired composite material was reduced by 66%.

2. The method for repairing composite materials according to claim 1, characterized in that, In step 2, the wavelength of the ultraviolet laser is 355nm.

3. The method for repairing composite materials according to claim 2, characterized in that, In step 2, the scanning speed of the ultraviolet laser is 1500 mm / s.

4. The method for repairing composite materials according to claim 2, characterized in that, In step 2, the ultraviolet laser scans the excavated interface 15 to 20 times.

5. The method for repairing composite materials according to claim 1, characterized in that, In step 3, an ultrasonic cleaner is used to clean the composite material.

6. The method for repairing composite materials according to claim 1, characterized in that, In step 4, the plasma gun nozzle is 6-8 cm away from the workpiece, the spot movement speed is 3-4 cm / s, and the scan is performed twice.

7. The method for repairing composite materials according to claim 1, characterized in that, In step 5, the encapsulation step includes: sequentially covering the patch with a release cloth, a heating blanket, a breathable felt, and a vacuum bag.

8. The method for repairing composite materials according to any one of claims 1-7, characterized in that, In step 6, the ultrasonic radiation device is a longitudinal wave probe.

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