Femtosecond laser in-situ induced carbonization composite material surface resistance value regulation and control method

Abstract

The invention discloses a femtosecond laser in-situ induced carbonization composite material surface resistance value regulation and control method, which comprises the following steps: cleaning a glass fiber composite material with absolute ethyl alcohol, airing, and placing on a three-dimensional free movement translation table; importing the drawn CAD laser scanning path pattern into a galvanometer scanning system through a computer; adjusting the distance between the three-dimensional free moving translation stage and a field lens in the galvanometer system to find a laser focus; the repetition frequency and the scanning speed of the femtosecond laser are set through the computer; the rotating motor is controlled to change the angle of the attenuation piece, and accurate and fine regulation and control are carried out within the range of not exceeding the maximum laser power which causes fiber breakage; parameters are set according to the steps, and imported patterns are processed on the surface of the glass fiber composite material through a set program. According to the method, femtosecond laser parameters are accurately controlled, a conductive carbonization layer is generated on the surface of the composite material in situ, an insulation barrier is broken, effective conduction is achieved, and continuous adjustment of a resistance value is further achieved.

Description

Technical Field

[0001] The present invention relates to the field of conductive glass fiber composites, and in particular to a method for regulating the surface resistance of a composite material by in-situ induction of carbonization with femtosecond laser. Background Art

[0002] In modern electronic devices, the problems of electromagnetic interference (EMI) and electromagnetic radiation are becoming increasingly serious. By fabricating conductive patterns with specific shapes and dimensions on the surface of a composite material, an effective electromagnetic shielding structure can be formed, which can reflect and absorb electromagnetic waves, reduce the impact of electromagnetic interference on the internal circuits of the device, and also prevent the device from radiating electromagnetic waves outward, protecting the normal operation of the surrounding environment and other devices. Conductive patterning of the composite material surface has become the core solution for advanced devices such as electromagnetic shielding, smart skin sensors, flexible electronic circuits, and aerospace stealth metasurfaces due to its customizable functional design.

[0003] Glass fiber-reinforced composite materials, with their advantages such as high specific strength, high specific modulus, low density, corrosion resistance, fatigue resistance, strong designability, and good dielectric properties, play an irreplaceable role in the radar signal transmission and protection in the fields of aerospace, military defense, etc. as the core materials of radomes. Endowing the composite material surface with conductive ability has broad application prospects. For example, it can be used as an electromagnetic shielding layer to effectively block external electromagnetic interference from entering the aircraft interior, prevent the impact on the aircraft's electronic devices and communication systems, etc., ensure the stable operation of key devices such as the flight control system and navigation system, and guarantee flight safety; utilize the characteristics such as the resistance change of the conductive composite material to integrate sensor functions. When cracks, damages, etc. occur in the composite material structure, its conductive performance will change accordingly. By monitoring these changes, the health status of the structure can be obtained in real time, facilitating the timely discovery of potential problems and maintenance, and improving the reliability and maintainability of the aircraft; enable the composite material to not only have the function of a load-bearing structure but also possess multiple functions such as conductivity and electromagnetic shielding at the same time, providing more flexibility and innovation for the design of the aircraft. For example, conductive composite materials can be used to manufacture parts such as the leading edge and trailing edge of the aircraft wing. While meeting the structural strength requirements, functions such as lightning protection and electromagnetic shielding can be realized, reducing the weight and space increase caused by the additional installation of electromagnetic shielding devices, etc.; for military aircraft, conductive composite materials can be used to adjust the electromagnetic characteristics of the aircraft surface. By reasonably designing the structure and parameters of the conductive layer, the reflection and scattering of electromagnetic waves such as radar waves by the aircraft can be reduced, improving the stealth performance of the aircraft and enhancing its survivability and penetration ability in combat. This technology has broad application prospects and is a research hotspot in the current national defense field.

[0004] Glass fiber composites are usually composed of an insulating matrix material (such as resin) and a reinforcing material (glass fiber), and their internal structure is complex and mostly in a three-dimensional intertwined state. This structure makes it difficult for electrons to form a continuous conductive path inside the material. How to break through the limitations of this complex structure and construct an effective conductive channel without damaging the original mechanical and other properties of the composite material is the key issue.

[0005] To address this challenge, researchers have adopted various strategies to endow composite materials with electrical conductivity, mainly including adding conductive fillers, surface coating, and surface modification, etc. The method of adding conductive materials is to uniformly disperse fillers with good electrical conductivity in the composite material matrix. When the fillers reach a certain content and distribution state, an electrical conduction network will be formed inside the composite material, thus enabling the surface of the composite material to have electrical conductivity. However, the method of adding conductive materials cannot precisely customize the patterned electrical conduction regions. It is difficult to achieve completely uniform dispersion of the conductive materials in the matrix, and agglomeration is likely to occur, resulting in non-uniform electrical conductivity, which affects the overall performance of the composite material. Excessive addition of conductive materials may reduce other properties of the composite material matrix, such as toughness and corrosion resistance, and will also increase the material cost. The surface coating method is to coat a layer of conductive coating on the surface of the composite material to endow the surface of the composite material with electrical conductivity. The conductive substances in the coating form a continuous conductive path to achieve current conduction. However, during the preparation by the surface coating method, the bonding force between the conductive coating and the composite material matrix may be insufficient, and phenomena such as coating peeling and flaking are likely to occur during use, affecting the electrical conductivity and service life. During long-term use, some conductive coatings may be affected by environmental factors, such as oxidation and corrosion, resulting in a decrease in electrical conductivity. Spraying is a common method, spraying the conductive coating evenly on the surface of the composite material through equipment such as a spray gun to form a conductive coating. Electroless plating is to deposit a metal coating on the surface of the composite material by using a chemical reaction. Without an external power source, metal ions are reduced to metal elements on the surface of the composite material by a reducing agent to form a conductive coating. The surface modification method is to treat the surface of the composite material by physical or chemical methods to introduce conductive groups or change the chemical structure and physical properties of the surface, thereby improving the surface electrical conductivity. For example, plasma treatment can utilize the high-energy particles in the plasma to interact with the surface of the composite material, causing the surface to generate active groups such as free radicals and double bonds. These active groups can undergo grafting reactions with conductive monomers or polymers, thus introducing conductive components on the surface. However, generally, the surface modification method can only achieve modification within a relatively shallow depth range on the surface of the composite material, and it may not be effective for cases requiring deep electrical conductivity. Many surface modification methods require strict control of process conditions, such as temperature, pressure, reaction time, etc. The operation difficulty is large, the equipment requirements are high, and some surface modification processes have problems such as low efficiency, high cost, and difficult quality control in large-scale production, which limit their wide application. Chemical vapor deposition is to decompose gaseous reactants under conditions such as high temperature and plasma, and deposit a layer of conductive film with electrical conductivity on the surface of the composite material, such as depositing conductive films such as silicon carbide and boron nitride. There is also the ultraviolet irradiation method, which causes a photochemical reaction on the surface of the composite material through ultraviolet irradiation to introduce conductive groups or initiate the polymerization of conductive polymers, thereby endowing the surface with electrical conductivity.In addition, on the surface of the composite material, through specific chemical reactions or physical processes, conductive substances are grown in-situ to form a conductive structure, and directly constructing a conductive network on the surface of the composite material is also a method to endow the surface of the composite material with conductive ability. For example, carbon nanotube arrays are grown in-situ on the surface of the composite material by chemical vapor deposition. Using gaseous carbon sources as raw materials, under the action of a catalyst, carbon nanotubes grow directionally on the surface of the composite material to form a highly ordered conductive structure, which can significantly improve the conductivity and mechanical properties of the composite material surface; however, the method of growing conductive structures in-situ requires precise control of reaction conditions such as temperature, gas flow rate, catalyst, etc., with extremely high process requirements. A slight deviation may lead to growth failure or poor performance of the conductive structure. It is difficult to achieve uniform in-situ growth on the surface of large-area and complex-shaped composite materials, and problems such as uneven growth and low coverage rate may exist; there is also the electrochemical deposition method. In an electrolyte containing metal ions, with the composite material as the working electrode, by applying a certain voltage or current, metal ions are reduced and deposited on the surface of the composite material to form a metal conductive structure, such as in-situ growing dendritic or nanowire structures of metals such as copper and silver to improve surface conductivity. In summary, these traditional processing methods all have problems such as complex processes, poor bonding force with the composite material surface, and poor precision, and are insufficient to meet the needs of large-scale production and practical applications.

[0006] Laser processing method: Long-pulse lasers use high-temperature carbonization of the laser thermal effect to prepare conductive structures. The long-pulse laser has a strong thermal effect. Under its irradiation, due to the different thermal conductivities of the fiber matrix and resin matrix of the composite material, problems such as matrix burning and gasification will occur, seriously damaging the surface. And femtosecond laser processing is an advanced manufacturing technology based on ultrashort-pulse lasers, and its pulse width is in the femtosecond order of magnitude (1 fs = 10 -15 s). Compared with traditional laser processing, femtosecond lasers have unique processing characteristics and significant advantages, and can effectively solve many technical problems in traditional strategies. The focused spot of femtosecond lasers can reach the sub-micron level (<1 μm), achieving high-precision processing; processing without physical contact avoids damage to materials caused by mechanical stress; by precisely controlling laser parameters, a conductive carbonized layer is generated in-situ on the surface of the composite material, breaking the insulation barrier to achieve effective conductivity, and further realizing continuous adjustment of the resistance value. Femtosecond laser in-situ induction can complete the endowment of the conductivity of the composite material in one step. There is no need to go through multiple steps like some other technologies, such as first performing a certain pretreatment, and then adding or depositing conductive substances. Femtosecond lasers directly induce conductive graphene in-situ through their high energy density interaction with the composite material, reducing intermediate links, lowering process complexity and costs, while also improving production efficiency and the stability of product quality.

[0007] In summary, laser in-situ induced carbonization is an ideal strategy to endow composites with electrical conductivity. However, there are still problems such as fiber fracture and substrate damage caused by thermal effects. Femtosecond lasers have the advantages of high instantaneous power and low heat-affected zone processing. However, it is still in the initial exploration stage, and the research on inducing carbonization of composites by rapid scanning of femtosecond lasers to endow composites with electrical conductivity and regulate the electrical conductivity has not been published. Summary of the Invention

[0008] In view of the above situation, the present invention provides a method for regulating the surface resistance value of a composite material induced by femtosecond laser in-situ carbonization. Through the femtosecond laser-induced carbonization technology, a micro-nano scale conductive carbonization structure can be precisely constructed on the surface of the glass fiber composite material, realizing the conductive path, electromagnetic wave regulation ability and anti-extreme environment corrosion characteristics, while maintaining the lightweight and structural load-bearing advantages of the composite material.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] In an embodiment of the present invention, a method for regulating the surface resistance value of a composite material induced by femtosecond laser in-situ carbonization is proposed. The method includes:

[0011] In a super-clean environment, use the built femtosecond laser in-situ induced carbonization processing system;

[0012] Clean and dry the glass fiber composite material with anhydrous ethanol and place it on a three-dimensional freely movable translation stage;

[0013] Import the drawn CAD laser scanning path pattern into the galvanometer scanning system through a computer;

[0014] In the optical path system, adjust the position and angle of the mirror group to ensure that the optical path output to the galvanometer is in a collimated state;

[0015] Adjust the distance between the three-dimensional freely movable translation stage and the field lens in the galvanometer system to find the laser focus;

[0016] Set the repetition frequency of the femtosecond laser and the scanning speed of the galvanometer scanning system through a computer;

[0017] Control the rotation motor through a computer to change the angle of the attenuation sheet, and perform precise and delicate regulation within the maximum laser power range that does not cause fiber fracture;

[0018] Set the parameters according to the above steps, and perform in-situ carbonization induction on the surface of the glass fiber composite material according to the imported CAD laser scanning path pattern through the program set by the computer to generate a conductive structure, and its resistance value decreases with the increase of the laser power, realizing the controllable preparation of conductive structures with different resistance values.

[0019] Furthermore, the femtosecond laser in-situ induced carbonization processing system includes: a femtosecond laser, an optical path system, a galvanometer scanning system, a three-dimensional freely movable translation stage, and a computer. The femtosecond laser used is a semiconductor-pumped fiber femtosecond laser; the optical path system includes a mirror group and a laser attenuator, which are used to precisely control the propagation path of the laser in the optical path and the laser power; the galvanometer scanning system includes a galvanometer and a field lens, which are used to focus the modulated laser onto the three-dimensional freely movable translation stage and perform rapid scanning; the three-dimensional freely movable translation stage is used to move the sample to any position through computer control; the computer is used to set the repetition frequency of the femtosecond laser and the scanning speed of the galvanometer scanning system, and control the rotation of the rotary motor and the movement of the three-dimensional freely movable translation stage along the Z-axis.

[0020] Furthermore, the laser attenuator includes a rotary motor and an attenuation sheet, which are used to assist in adjusting the power of the femtosecond laser incident on the galvanometer.

[0021] Beneficial effects:

[0022] 1. The traditional methods of endowing composite materials with electrical conductivity have problems such as uneven dispersion of conductive fillers, weak interfacial bonding, affecting performance stability; environmental factors (humidity, temperature) and mechanical damage are likely to cause conductivity attenuation; the manufacturing process is complex and it is difficult to achieve large-scale production; it is difficult to balance electrical conductivity and mechanical properties. By using femtosecond laser in-situ induction, carbonization of the resin matrix can be achieved without damaging the fiber matrix, avoiding the damage caused by long-pulse lasers due to the different thermal conductivities between the fibers and the matrix of the composite material, and endowing the originally insulating composite material with electrical conductivity.

[0023] 2. The insulating property of composite materials makes them extremely sensitive to the addition or introduction method of conductive phases. Adding a small amount of conductive phase may not effectively change its insulating state, while adding too much may cause the resistance value to drop excessively, making it difficult to achieve precise resistance value regulation. By adjusting the output power of the femtosecond laser, it is easy to achieve the electrical conductivity of the induced carbonization structure, and a smooth and precise transition from insulation to the target conductive state can be achieved.

[0024] 3. For composite materials of different batches or different preparation processes, their microstructures may be different, such as porosity, fiber distribution, etc. The femtosecond laser in-situ induction technology can adaptively induce the conductivity of materials by precisely controlling the laser output power according to the actual situation of the material microstructure. In contrast, methods such as physical vapor deposition may have relatively strict requirements for the surface flatness and microstructural uniformity of materials, and may not be able to ensure a uniform and stable conductivity endowment effect when facing composite materials with large microstructural differences. Description of the Drawings

[0025] Figure 1It is a schematic structural diagram of the femtosecond laser in-situ induced carbonization processing system of the present invention;

[0026] In the figure: 1 - femtosecond laser, 2 - galvanometer scanning system, 3 - three-dimensional freely movable translation stage, 4 - computer, 5 - mirror group, 6 - laser attenuator;

[0027] Figure 2 It is a schematic diagram of different laser output powers corresponding to different sample regions of the present invention;

[0028] Figure 3 It is Figure 2 A schematic diagram of the microscopic morphology of region A in

[0029] Figure 4 It is a curve graph of different sample regions and corresponding resistance values of the present invention;

[0030] Figure 5 It is a Raman spectrogram of the conductive structure of laser-induced carbonization of the present invention. Specific embodiments

[0031] Next, the principles and spirit of the present invention will be described with reference to several exemplary embodiments. It should be understood that these embodiments are given only to enable those skilled in the art to better understand and then design the present invention, and do not limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to be able to convey the scope of the present disclosure completely to those skilled in the art.

[0032] Those skilled in the art know that the embodiments of the present invention can be designed as a structure, device, preparation method or computer program product. Therefore, the present disclosure can be specifically designed in the following forms: completely hardware, completely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software.

[0033] According to the embodiments of the present invention, a method for regulating the surface resistance value of a composite material by femtosecond laser in-situ induced carbonization is proposed. Femtosecond laser in-situ induction generates a conductive carbonized layer in-situ on the surface of the composite material by precisely controlling laser parameters, breaks the insulation barrier to achieve effective conductivity, and further realizes continuous adjustment of the resistance value; Femtosecond laser in-situ induction can complete the imparting of conductivity to the composite material in one step, without the need for multiple steps like some other technologies, such as first performing a certain pretreatment and then adding or depositing conductive substances, etc.; Femtosecond laser directly induces conductive graphene in-situ through its high energy density interaction with the composite material, reducing intermediate links, lowering process complexity and cost, and at the same time improving production efficiency and product quality stability.

[0034] The principles and spirit of the present invention will be elaborated in detail below with reference to several representative embodiments of the present invention.

[0035] The overall solution adopted by the present invention includes two parts: the construction of a femtosecond laser in-situ induced carbonization processing system and a method for regulating the surface resistance value of a composite material by femtosecond laser in-situ induced carbonization.

[0036] 1. Construction of the femtosecond laser in-situ induced carbonization processing system

[0037] As Figure 1 shown, the femtosecond laser in-situ induced carbonization processing system includes: a femtosecond laser 1, an optical path system, a galvanometer scanning system 2, a three-dimensional freely movable translation stage 3, and a computer 4. The femtosecond laser 1 is a semiconductor-pumped fiber femtosecond laser with an output power of 20W, a central wavelength of 1030nm, and a maximum repetition frequency of 1MHz; the optical path system includes a mirror group 5 and a laser attenuator 6, which are used to precisely control the propagation path of the laser in the optical path and the laser power; the laser attenuator 6 includes a rotating motor and an attenuation sheet, which are used to assist in adjusting the power of the femtosecond laser incident on the galvanometer; the galvanometer scanning system 2 includes a galvanometer and a field lens, etc., which are used to focus the modulated laser on the three-dimensional freely movable translation stage 3 and quickly scan; the three-dimensional freely movable translation stage 3 is used to move the sample to any position through the control of the computer 4; the computer 4 is used to set the repetition frequency of the femtosecond laser 1 and the scanning speed of the galvanometer scanning system, control the rotation of the rotating motor, and move the three-dimensional freely movable translation stage 3 along the Z-axis.

[0038] 2. Method for regulating the surface resistance value of a composite material by femtosecond laser in-situ induced carbonization

[0039] The specific process is as follows:

[0040] (1) Clean and dry the glass fiber composite material (sample) with anhydrous ethanol and place it on the three-dimensional freely movable translation stage;

[0041] (2) Import the drawn CAD laser scanning path pattern into the galvanometer scanning system through the computer;

[0042] (3) Adjust the distance between the three-dimensional freely movable translation stage and the field lens in the galvanometer system to find the laser focus;

[0043] (4) Set the repetition frequency of the femtosecond laser to 1000KHZ and the scanning speed of the galvanometer scanning system to 300mm / s through the computer. It is found that the fibers of the glass fiber composite material can remain intact at 90% of the laser power, as Figure 3As shown, more than 90% of the power will cause fiber breakage. In the case where no fiber breakage occurs, the morphologies of each region are basically similar. Therefore, six parameters of 90%, 87%, 83%, 80%, 78%, and 72% are used to induce carbonization of the samples, corresponding to Figure 2 sample regions A - F in

[0044] (5) By controlling the rotation motor of the computer to change the angle of the attenuation sheet, precise and delicate regulation is carried out within the range of laser power not exceeding 90%.

[0045] (6) Set the parameters according to the above steps. Through the program set by the computer, induce carbonization on the surface of the glass fiber composite material according to the imported CAD laser scanning path pattern to generate a conductive structure, and its resistance value decreases with the increase of laser power, realizing the controllable preparation of conductive structures with different resistance values.

[0046] To ensure the accuracy and precision of processing, the above processing processes are all carried out in a super-clean environment without interruption until the processing is completed.

[0047] The resistance values of sample regions A - F are tested by a four-probe resistance meter. The results show that the resistance values of the samples after induced carbonization are positively correlated with the laser power. Among the parameters used in the test, the greater the laser power, the lower the resistance, as Figure 4 shown.

[0048] Raman spectroscopy is used to analyze the processed samples. From the test results Figure 5 it can be seen that the sample shows the unique spectral characteristic peaks of graphene, located at the D peak at about 1350 cm -1 −1, the G peak at 1582 cm -1 −1, and the 2D peak at 2700 cm -1 −1. The D peak is related to the lattice defects in the material; the G peak is the characteristic Raman peak in graphite carbon materials, representing the vibration of carbon - carbon single bonds (C - C bonds), usually appearing in graphite or graphene, reflecting the planar hexagonal structure (sp2 hybridization) characteristics of carbon atoms; the 2D peak is a characteristic peak related to the number of graphene layers, which is generated by the nonlinear scattering process triggered by two photons. The appearance of the 2D peak indicates that graphene has been successfully induced and carbonized on the surface of the composite material.

[0049] It should be noted that although the operations of the preparation method of the present invention are described in a specific order in the above embodiments and the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution.

[0050] To more clearly explain the method for regulating the surface resistance value of the composite material induced by femtosecond laser in situ carbonization, a specific embodiment is described below. However, it should be noted that this embodiment is only for better explaining the present invention and does not constitute an improper limitation to the present invention.

[0051] Step 1. Sample pretreatment

[0052] Select a glass fiber reinforced resin matrix composite material as the processing object. First, cut the composite material sample into a square with a size of 10 cm × 10 cm and a thickness of 3 mm. Since there may be contaminants such as mold release agents and dust on the material surface, anhydrous ethanol (analytical pure) is used as the cleaning medium, and the sample is immersed in ethanol and ultrasonically cleaned for 10 minutes (ultrasonic frequency is 40 kHz, power is 150 W) to remove surface impurities.

[0053] Subsequently, use deionized water to rinse the anhydrous ethanol on the sample surface clean.

[0054] After cleaning, place it in a vacuum drying oven and dry it at 30 °C and 1 standard atmospheric pressure for 2 hours to ensure that there is no residual solvent on the surface, and reserve it after drying.

[0055] Step 2. Laser-induced carbonized conductive layer

[0056] Turn on the power supplies of the computer, three-dimensional freely moving translation stage and femtosecond laser in sequence. Place the sample on the three-dimensional freely moving translation stage, and use a level to check whether the three-dimensional freely moving translation stage is horizontal. After ensuring that the three-dimensional freely moving translation stage is horizontal, proceed to the next step.

[0057] Check the optical path system, and carefully adjust the position and angle of the mirror group to ensure that the optical path output to the galvanometer is in a collimated state. This step is very important, because non-collimated incident laser will affect the processing effect and cannot achieve the expected effect of induced carbonization.

[0058] Pre-draw a 10 mm × 10 mm rectangular pattern in CAD, fill in the laser scanning path, export it in DXF format, and then import it into the software of the galvanometer scanning system. The galvanometer can scan according to the processing pattern.

[0059] Turn on the switch of the femtosecond laser, set the processing parameters as the repetition frequency of 1000 KHz, the scanning speed of 300 mm / s, and the power of 72% - 90%. And adjust the Z-axis of the three-dimensional freely moving translation stage on the computer to make the focal plane and the surface of the sample in the same plane.

[0060] Click the "Start Processing" button in the software of the galvanometer scanning system to output laser for surface-induced carbonization.

[0061] After the laser scans according to the preset pattern, the three-dimensional freely movable translation stage can be controlled by a computer to move, and then the induced processing of the next area can be carried out. Finally, conductive patterns under six different laser powers are obtained. As Figure 3 shown, Figure 3 is an enlarged image at 90% power. It can be seen that the surface is carbonized while the fibers remain intact.

[0062] Since the microstructure of composite materials in different batches or with different preparation processes may vary, such as different porosity and fiber distribution, etc., the upper limit of the power at which the laser causes fiber fracture in the composite material is also different.

[0063] It has been tested that the fibers of the composite material used in this case can remain intact at 90% laser power, and a power greater than this will cause fiber fracture. For composite materials in different batches, only the maximum power that causes fiber fracture needs to be tested, and induced processing can be carried out below this threshold to endow the material with electrical conductivity without damaging the fibers.

[0064] Step 3. Testing of surface material structure and surface resistance

[0065] Carefully remove the processed composite material sample from the three-dimensional freely movable translation stage, and then use the detection equipment to test its electrical conductivity. In this embodiment, a four-probe resistor is used to test the induced carbonized structure, and 6 regions in the embodiment are tested. The resistance test results are as Figure 4 shown. It can be seen that each sample has achieved electrical conductivity, and the resistance value decreases with the increase of laser power, realizing the controllable preparation of conductive structures with different resistance values.

[0066] Raman spectroscopy is used to test the laser-induced conductive structure. The test results are as Figure 5 shown. The 2D characteristic peak representing graphene appears, further proving that the composite material has been successfully induced to carbonize by the laser.

[0067] The advantages of a method for regulating the surface resistance of a composite material induced by femtosecond laser in situ proposed by the present invention are as follows:

[0068] 1. Traditional methods for endowing composite materials with electrical conductivity have problems such as uneven dispersion of conductive fillers, weak interfacial bonding, affecting performance stability; environmental factors (humidity, temperature) and mechanical damage easily lead to conductivity attenuation; complex manufacturing processes and difficulty in large-scale production; and it is difficult to balance electrical conductivity and mechanical properties. By in-situ induction with femtosecond laser, carbonization of the resin matrix can be achieved without damaging the fiber matrix, avoiding the damage caused by long-pulse lasers due to different thermal conductivities between the fibers and the matrix of the composite material, and endowing the originally insulating composite material with electrical conductivity.

[0069] 2. The insulating property of the composite material makes it extremely sensitive to the addition or introduction method of the conductive phase. Adding a small amount of the conductive phase may not effectively change its insulating state, while excessive addition may lead to an excessive drop in the resistance value, making it difficult to achieve precise resistance value regulation. By adjusting the output power of the femtosecond laser, it is easy to achieve the conductive ability of the induced carbonized structure, enabling a smooth and precise transition from insulation to the target conductive state.

[0070] 3. For composite materials of different batches or different preparation processes, there may be differences in their microstructures, such as porosity, fiber distribution, etc. The femtosecond laser in-situ induction technology can adaptively induce the conductivity of the material by precisely controlling the laser output power according to the actual situation of the material microstructure. In contrast, methods such as some physical vapor deposition may have relatively strict requirements for the surface flatness and microstructure uniformity of the material. When facing composite materials with large differences in microstructure, they may not be able to ensure a uniform and stable conductivity imparting effect.

[0071] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division of each aspect does not mean that the features in these aspects cannot be combined for benefit. This division is only for the convenience of expression. The present invention aims to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0072] Regarding the limitations on the protection scope of the present invention, those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for regulating the surface resistance value of a composite material induced by in-situ femtosecond laser carbonization, characterized in that, The method includes: In a super-clean environment, using the built femtosecond laser in-situ induced carbonization processing system; Clean and dry the glass fiber composite material with absolute ethanol and place it on a three-dimensional freely movable translation stage; Import the drawn CAD laser scanning path pattern into the galvanometer scanning system through a computer; In the optical path system, adjust the position and angle of the mirror group to ensure that the optical path output to the galvanometer is in a collimated state; Adjust the distance between the three-dimensional freely movable translation stage and the field lens in the galvanometer system to find the laser focus; Set the repetition frequency of the femtosecond laser and the scanning speed of the galvanometer scanning system through a computer; Control the rotation motor through a computer to change the angle of the attenuation sheet, and perform precise and delicate regulation within the maximum laser power range that does not cause fiber breakage; Set the parameters according to the above steps, and perform in-situ induced carbonization on the surface of the glass fiber composite material according to the imported CAD laser scanning path pattern through the program set by the computer to generate a conductive structure, and its resistance value decreases with the increase of the laser power, realizing the controllable preparation of conductive structures with different resistance values.

2. The method for regulating the surface resistance value of a composite material in-situ induced by femtosecond laser carbonization according to claim 1, wherein, The femtosecond laser in-situ induced carbonization processing system includes: a femtosecond laser, an optical path system, a galvanometer scanning system, a three-dimensional freely movable translation stage, and a computer. The femtosecond laser used is a semiconductor-pumped fiber femtosecond laser; the optical path system includes a mirror group and a laser attenuator, which are used to precisely control the propagation path and laser power of the laser in the optical path; the galvanometer scanning system includes a galvanometer and a field lens, which are used to focus the modulated laser on the three-dimensional freely movable translation stage and quickly scan; the three-dimensional freely movable translation stage is used to realize the movement of the sample at any position through computer control; the computer is used to set the repetition frequency of the femtosecond laser and the scanning speed of the galvanometer scanning system, control the rotation of the rotation motor and the movement of the three-dimensional freely movable translation stage along the Z axis.

3. A method for regulating the surface resistance value of a composite material induced by in-situ femtosecond laser carbonization according to claim 1, characterized in that, The laser attenuator includes a rotation motor and an attenuation sheet, which are used to assist in adjusting the power of the femtosecond laser incident on the galvanometer.

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