Method for high-quality machining of CFRP based on time-domain shaping femtosecond laser

Abstract

The present application relates to a kind of based on time domain shaping femtosecond laser high-quality processing CFRP method, belong to CFRP material processing field.The present application is based on femtosecond laser processing CFRP, traditional femtosecond laser is shaped in time domain, it is divided into double pulse with interval 0.1-100ps in time, utilize the characteristics that the material system of each component of CFRP composite material is different, by regulating pulse delay and pulse number explore its respective threshold variation law, and compare between threshold difference change trend, finally according to actual processing purpose select appropriate time domain shaping femtosecond laser processing parameter to realize the high-quality processing of CFRP.This based on time domain shaping femtosecond laser high-quality processing CFRP method, the processing result obtained is without impurity residue, processing uneven, or without layering, tearing, burr and other adverse phenomena, and simultaneously realize the dynamic regulation of different components in material, increase or reduce the difference between different components according to processing demand, to reduce the thermal damage of pre-processing surface or the heat-affected zone of hole and groove structure edge, this method shows the manufacturing capacity and application prospect of high-quality processing CFRP.

Description

Technical Field

[0001] This invention relates to a method for high-quality processing of CFRP based on time-domain shaping femtosecond laser, belonging to the field of CFRP material processing. Background Technology

[0002] Carbon fiber reinforced resin composites (CFRP) have many advantages in mechanical, thermal and chemical properties, such as lightweight, high specific modulus and specific strength, low thermal expansion, high thermal conductivity and corrosion resistance. As a result, they are widely used in the production and manufacturing of various equipment parts in the fields of aviation, aerospace and transportation. Their proportion is constantly increasing and they have gradually become the most typical, widespread and important composite material.

[0003] While the fabrication technology of CFRP materials has largely matured, significant processing requirements remain in the subsequent assembly process, primarily involving two aspects: surface pretreatment and the cutting of holes and grooves. These varying processing needs lead to different processing procedures. Surface pretreatment typically removes surface contaminants and alters the surface morphology to increase surface bonding strength; while hole and groove cutting requires ensuring cutting precision and improving processing quality. However, CFRP materials also possess anisotropy, lamination, and heterogeneity, making them typical difficult-to-machine materials. Traditional machining methods often suffer from tool limitations, resulting in residual impurities, uneven processing, delamination, tearing, burrs, and other defects, negatively impacting subsequent assembly, overall stability, and service life. Furthermore, the properties of CFRP materials during processing accelerate tool wear, reducing tool life and increasing tool consumption; and achieving high-precision pretreated surfaces or micro-hole / micro-groove structures is challenging. All of these factors limit the application prospects of CFRP materials in various fields.

[0004] Laser processing, with its high precision, non-contact operation, and wide applicability, effectively solves the problems of high tool wear and low precision in traditional machining. However, while avoiding defects such as impurity residue, uneven processing, delamination, tearing, and burrs, laser processing also introduces significant thermal damage marks on the pre-treated surface or a distinct heat-affected zone (HAZ) at the edges of the slotted structure due to the different optical and thermal properties of carbon fiber and resin materials. Therefore, controlling thermal damage on the pre-treated surface and the HAZ at the edges of the slotted structure remains a key challenge in the laser processing of CFRP materials. Summary of the Invention

[0005] The purpose of this invention is to address the problems of residual impurities, uneven processing, delamination, tearing, burrs, thermal damage to the pre-treated surface, and significant heat-affected zones at the edges of CFRP structures in existing CFRP processing methods. This invention proposes a high-quality CFRP processing method based on time-domain shaped femtosecond laser processing. Building upon femtosecond laser processing of CFRP, this invention performs time-domain shaping on the traditional femtosecond laser, dividing it into dual pulses with an interval of 0.1-100 ps. Utilizing the different material systems of the various components in the CFRP composite, the invention explores the variation patterns of their respective thresholds by adjusting the pulse delay and the number of pulses, comparing the trends of threshold differences, and finally selecting appropriate time-domain shaped femtosecond laser processing parameters according to the actual processing objectives to achieve high-quality CFRP processing. This method for high-quality CFRP processing based on time-domain shaping femtosecond lasers produces processing results free of impurities, uneven processing, or defects such as delamination, tearing, and burrs. It also achieves dynamic control of different components within the material, increasing or decreasing the differences between components according to processing requirements, thereby reducing thermal damage to the pre-treated surface or the heat-affected zone at the edge of the pore structure. This method demonstrates the manufacturing capability and application prospects of high-quality CFRP processing.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] Because CFRP is a heterogeneous composite material, with carbon fiber and resin matrix materials possessing different thermal and optical properties, high-quality laser processing is difficult to achieve. In traditional CFRP processing, if laser surface pretreatment is performed, the laser focus needs to reciprocate continuously within a plane to remove surface resin and expose the internal carbon fiber material. This results in a fixed processing trajectory and controlled spacing between trajectories. Since the laser spot has higher energy at its center, the resin removal rate and fiber thermal damage are relatively high at the center of the spot trajectory, leading to an uneven pretreated surface. Increasing the energy or decreasing the row spacing reduces resin residue but increases fiber thermal damage, potentially causing breakage. Conversely, decreasing the energy or increasing the row spacing reduces surface thermal damage while increasing resin residue. The current retention rate cannot achieve the purpose of surface pretreatment, so it cannot simultaneously increase the resin removal rate and reduce fiber thermal damage. In the process of laser direct cutting / drilling, the laser focus needs to continuously feed downwards in the thickness direction to scan layer by layer. Therefore, the size of the defocused spot on the material surface will continuously increase, and the energy will be continuously blocked and absorbed by the edge of the material cutting surface. When the accumulated energy is large enough, since the processing threshold of the resin is lower than that of the fiber, the resin material at the edge will be removed first, exposing the carbon fiber structure and forming the heat-affected zone caused by laser processing, resulting in thermal damage. Therefore, it cannot simultaneously remove the resin and carbon fiber materials.

[0008] Based on this, this invention proposes a method for high-quality processing of CFRP using time-domain shaped femtosecond lasers. By utilizing the different material systems of resin and carbon fiber materials through time-domain shaped dual-pulse lasers, and simultaneously controlling their processing thresholds to increase or decrease the threshold difference, selective etching or uniform cutting of the materials can be achieved. Specifically, the time-domain shaped optical field can effectively control the electron excitation / ionization in resin (transparent insulator) to induce significant changes in ionized electron density, resulting in a wide adjustable ablation threshold. In contrast, the intrinsic electron density of carbon fiber (metal-like conductor) remains consistently high, with minimal change in the ablation threshold. The laser scanning speed (number of irradiation pulses) can effectively control the incubation effect of the resin, causing the ablation threshold to change drastically with the number of pulses, while the ablation threshold of carbon fiber changes gradually. This further optimizes the effect of maximizing the convergence or difference in ablation thresholds between resin and carbon fiber.

[0009] A method for high-quality processing of CFRP using time-domain shaped femtosecond lasers is employed. The CFRP material consists of two parts: resin and carbon fiber. The resin is a transparent resin material, such as epoxy resin or modified cyanate ester resin, and its ablation threshold exhibits a clear variation pattern with changes in the time-domain shaped pulse delay and the number of pulses. The carbon fiber is a high-modulus carbon fiber material of M40 or M55, and its ablation threshold exhibits a distinct variation pattern with changes in the time-domain shaped pulse delay and the number of pulses, different from that of the resin.

[0010] Femtosecond lasers are time-domain shaped and divided into dual pulses with an interval of 0.1-100ps. High-quality CFRP processing is achieved by controlling the pulse delay and the number of pulses.

[0011] Based on the variation of the ablation threshold of CFRP resin and carbon fiber with changes in time-domain shaping pulse delay and pulse number, and considering the threshold differences between the two material components under the same conditions, appropriate time-domain shaping femtosecond laser processing parameters are selected according to the processing purpose. When performing surface pretreatment, time-domain shaping pulse delay and scanning speed (equivalent to the number of effective pulses) with larger threshold differences between resin and carbon fiber materials under the same conditions are used for processing. When performing cutting / drilling, time-domain shaping pulse delay and scanning speed (equivalent to the number of effective pulses) with smaller threshold differences between resin and carbon fiber materials under the same conditions are used for processing.

[0012] The femtosecond laser time-domain shaping method includes a time-domain shaping subsystem built based on the Michelson interference principle, or a time-domain shaping subsystem using a birefringent crystal that "splits" the laser into two pulses with a time interval of 0.1-100 ps.

[0013] The CFRP material used in the processing is a high-modulus CFRP multidirectional laminate with a thickness ranging from 0.2mm to 2mm.

[0014] The apparatus for implementing the above processing method includes a femtosecond laser processing subsystem, a femtosecond laser time-domain shaping subsystem, a top imaging subsystem, a computer control system, and a precision electronically controlled translation stage.

[0015] The femtosecond laser processing subsystem includes a femtosecond laser, a third ultrafast mirror group, a first aperture, a mechanical switch, an attenuator group, a second aperture, and a focusing objective lens. The femtosecond laser generates femtosecond laser light, which propagates sequentially through the aforementioned devices.

[0016] The femtosecond laser temporal shaping subsystem includes a first ultrafast mirror group, a second ultrafast mirror group, a first beam splitter, and a one-dimensional motorized translation stage. Based on the Michelson interference principle, the laser beam is proportionally split by the beam splitter and then returns to the beam splitter via the two mirrors to rejoin, forming a double-pulse beam. The computer controls the one-dimensional motorized translation stage to change the distance difference between the two mirrors and the beam splitter, thereby controlling the temporal shaping. This subsystem is placed between the femtosecond laser and the ultrafast mirror group in the femtosecond laser processing subsystem.

[0017] The top imaging subsystem consists of a dichroic mirror, a white light illumination source, a second beam splitter, and a CCD dynamic imaging unit. It is used to detect the processing position during the processing and to ensure that the focal plane coincides with the sample plane.

[0018] The so-called computer control system is used for real-time control of the femtosecond laser pulse triggering, mechanical switching, femtosecond laser time-domain shaping subsystem, precision electronically controlled translation stage, and top imaging subsystem.

[0019] A precision electronically controlled translation stage is used to place samples to be processed and to ensure that they move along a specified trajectory according to processing requirements.

[0020] The connection relationships between the above-mentioned component systems are as follows:

[0021] The femtosecond laser and mechanical switches in the femtosecond laser processing subsystem are connected to the computer control system.

[0022] The pulsed femtosecond laser generated by the femtosecond laser processing subsystem propagates through the femtosecond laser time-domain shaping subsystem.

[0023] The one-dimensional motorized translation stage in the femtosecond laser temporal shaping subsystem is connected to the computer control system. After the femtosecond laser temporal shaping subsystem, the light propagates forward along the optical path to the surface of the sample to be processed.

[0024] The top imaging subsystem uses a white light source to illuminate the surface of the sample to be processed, and the reflected light enters the CCD dynamic imaging unit to achieve real-time monitoring of the processing position.

[0025] The method for high-quality CFRP processing based on time-domain shaped femtosecond laser of the present invention includes the following steps:

[0026] Step 1: Adjust the optical path collimation of the femtosecond laser processing subsystem to ensure that the femtosecond laser passes through each device in sequence.

[0027] Step 2: Adjust the top imaging subsystem so that the laser focusing point coincides with the imaging focus point.

[0028] Step 3: Adjust the precision electronically controlled translation stage so that the laser focusing focal plane coincides with the surface of the sample to be processed.

[0029] Step 4: Adjust the femtosecond laser time-domain shaping subsystem to shape the femtosecond laser single pulse into a femtosecond laser double pulse with the required delay.

[0030] Step 5: Control the computer control system to enable the femtosecond laser to perform surface pretreatment or cutting / drilling on the sample to be processed according to the processing requirements.

[0031] It should be noted that the application of this method principle, using different types of femtosecond lasers, different processing optical path systems, different laser processing parameters, and different laser processing motion trajectories to obtain high-quality CFRP processing results by femtosecond lasers, still falls within the scope of protection of this patent.

[0032] Beneficial effects

[0033] This invention presents a method for high-quality CFRP processing based on time-domain shaped femtosecond lasers. Building upon femtosecond laser processing of CFRP, this method introduces a femtosecond laser time-domain shaped subsystem to shape single femtosecond laser pulses into dual femtosecond laser pulses with the required delay. This solves problems associated with traditional machining methods, such as residual impurities, uneven processing, delamination, tearing, burrs, and severe tool wear. It also overcomes the thermal damage to the pretreatment surface or the heat-affected zone at the edges of the hole / groove structure caused by the different optical and thermal properties of the component materials in laser processing. This method enables high-quality CFRP processing, demonstrating manufacturing capabilities and application prospects for high-quality CFRP processing. This method offers high processing quality, flexibility, simplicity, high automation, and strong designability. It is applicable to different laser types and laser processing systems, and is also suitable for high-quality processing of other fiber-reinforced composite materials besides CFRP, exhibiting broad applicability. Attached Figure Description

[0034] Figure 1This is a schematic diagram of the optical path of the femtosecond laser processing system used in this method.

[0035] Among them, 1-femtosecond laser, 2-first beam splitter, 3-first ultrafast mirror group, 4-second ultrafast mirror group, 5-one-dimensional motorized translation stage, 6-third ultrafast mirror group, 7-first aperture, 8-mechanical switch, 9-attenuator group, 10-second aperture, 11-dichroic mirror, 12-focusing objective lens, 13-sample to be processed, 14-precision electrically controlled translation stage, 15-white light illumination source, 16-second beam splitter, 17-CCD dynamic imaging unit, 18-computer.

[0036] Figure 2 The images show the processing effects before and after time-domain shaping femtosecond laser control for surface pretreatment or cutting / drilling purposes. Figure a shows a comparison of the processing effects before and after time-domain shaping femtosecond laser control for surface pretreatment; Figure b shows a comparison of the processing effects before and after time-domain shaping femtosecond laser control for cutting / drilling.

[0037] Figure 3 The images show the results of high-quality CFRP processing using time-domain shaped femtosecond laser for surface pretreatment. Figure a shows a scanning electron microscope (SEM) image of the sample surface after conventional femtosecond laser surface pretreatment; figure b shows a laser confocal image of the sample surface after conventional femtosecond laser surface pretreatment; figure c shows a scanning electron microscope (SEM) image of the sample surface after time-domain shaped femtosecond laser surface pretreatment; and figure d shows a laser confocal image of the sample surface after time-domain shaped femtosecond laser surface pretreatment.

[0038] Figure 4 The images show the results of high-quality CFRP machining using time-domain shaped femtosecond lasers for cutting / drilling purposes. Figure a shows a scanning electron microscope (SEM) image of the cutting edge structure when the conventional femtosecond laser cutting trajectory is parallel to the surface fibers; Figure b shows a SEM image of the cutting edge structure when the conventional femtosecond laser cutting trajectory is perpendicular to the surface fibers; Figure c shows a SEM image of the cutting edge structure when the time-domain shaped femtosecond laser cutting trajectory is parallel to the surface fibers; and Figure d shows a SEM image of the cutting edge structure when the time-domain shaped femtosecond laser cutting trajectory is perpendicular to the surface fibers. Detailed Implementation

[0039] To better understand the method of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the implementation of the present invention is not limited to the following embodiments.

[0040] Example 1

[0041] The processing objective of this embodiment is to pre-treat the surface of CFRP material. The goal of this processing is to achieve selective etching of the material surface, which necessitates increasing the difference in ablation thresholds among the various components of the CFRP material. By adjusting the time-domain shaping pulse delay and the number of pulses in a femtosecond laser, the ablation thresholds of the resin and carbon fiber materials under different parameters are measured, and the variation patterns of their respective ablation thresholds caused by adjusting the laser parameters are summarized. These patterns are compared to calculate the threshold differences between the two components under the same conditions, identifying the processing parameters with the greatest difference. The comparison reveals that when the time-domain shaping pulse delay is 30 ps and the number of pulses is relatively low, the threshold of the resin material is approximately four times that of the fiber material, resulting in the greatest difference in thresholds between the two components and making selective etching of the material easier to achieve. Therefore, a time-domain shaping pulse delay of 30 ps and a scanning speed of 2000 μm / s (equivalent to 8.8 effective pulses) are selected for subsequent processing.

[0042] The method for high-quality CFRP fabrication based on time-domain shaped femtosecond lasers disclosed in this embodiment includes the following specific steps:

[0043] Step 1: Adjust the optical path collimation of the femtosecond laser processing subsystem to ensure that the femtosecond laser passes through each device in sequence.

[0044] The femtosecond laser processing subsystem constructed in this embodiment is as follows: Figure 1 As shown, the system includes a femtosecond laser 1, a third ultrafast mirror group 6, a first aperture 7, a mechanical switch 8, an attenuator group 9, a second aperture 10, and a focusing objective 12. The femtosecond laser beam emitted by the femtosecond laser 1 first passes through the first beam splitter 2 in the femtosecond laser time-domain shaping subsystem, blocking one path that passes through the first ultrafast mirror group 3, preventing laser reflection. The beam then propagates through the second ultrafast mirror group 4 and the existing third ultrafast mirror group 6. By adjusting the second ultrafast mirror group 4 and the third ultrafast mirror group 6, the propagation direction of the femtosecond laser beam can be adjusted accordingly, allowing it to be collimated through the first aperture 7, mechanical switch 8, attenuator group 9, and second aperture 10. The femtosecond laser beam is then reflected by the dichroic mirror 11 and focused by the focusing objective 12 onto the sample 13 to be processed, located on the precision electronically controlled translation stage 14.

[0045] Step 2: Adjust the top imaging subsystem so that the laser focusing point coincides with the imaging focus point.

[0046] The top imaging subsystem constructed in this embodiment is as follows: Figure 1As shown, the system includes a dichroic mirror 11, a white light source 15, a second beam splitter 16, and a CCD dynamic imaging unit 17. The illumination light emitted from the uppermost white light source 15 passes through the second beam splitter 16, the dichroic mirror 11, and the focusing objective lens 12, illuminating the sample 13 to be processed. The reflected light then passes through the focusing objective lens 12 and the dichroic mirror 11 again, returning to the second beam splitter 16 and reaching the CCD dynamic imaging unit 17. By adjusting the CCD dynamic imaging unit 17, the real-time image captured by the CCD dynamic imaging unit 17 is observed, and the imaging focus is adjusted to coincide with the laser focusing position.

[0047] Step 3: Adjust the precision electronically controlled translation stage so that the laser focusing focal plane coincides with the surface of the sample to be processed.

[0048] In this embodiment, the CFRP material used in the processing is a high-modulus CFRP multidirectional laminate, consisting of 8 layers, each with a thickness of 0.125 mm. The layup sequence is 0° / +45° / -45° / 90° / 90° / -45° / +45° / 0°, with a total thickness of 1 mm.

[0049] In this embodiment, sample 13 to be processed is as follows: Figure 1 As shown, the laser is placed on a precision electronically controlled translation stage 14. The Z-axis height of the precision electronically controlled translation stage 14 is adjusted by a computer 18 so that the laser focusing focal plane coincides with the surface of the sample to be processed.

[0050] Step 4: Adjust the femtosecond laser time-domain shaping subsystem to shape the femtosecond laser single pulse into a femtosecond laser double pulse with the required delay.

[0051] The femtosecond laser temporal shaping subsystem constructed in this embodiment is as follows: Figure 1 As shown, the system includes a first ultrafast mirror group 3, a second ultrafast mirror group 4, a first beam splitter 2, and a one-dimensional motorized translation stage 5. Based on the Michelson interferometry principle, the laser beam is proportionally split by the first beam splitter 2, then returns via the first ultrafast mirror group 3 and the second ultrafast mirror group 4 to converge back at the first beam splitter 2, forming a double-pulse beam. The distance difference between the first ultrafast mirror group 3, the second ultrafast mirror group 4, and the first beam splitter 2 is changed by the one-dimensional motorized translation stage 5 to achieve time-domain shaping. During the adjustment process, the path adjusted in step one via the second ultrafast mirror group 4 remains stationary. The other path via the first ultrafast mirror group 3 is adjusted to make the two pulses spatially coincide. The computer 18 adjusts the one-dimensional motorized translation stage 5 to make the two pulses temporally coincide. Then, the computer 18 adjusts the one-dimensional electric translation stage 5 to change the distance difference between the first ultrafast reflector group 3 and the second ultrafast reflector group 4 and the first beam splitter 2, so that the pulse delay of the two pulses reaches 30ps, thus obtaining the ideal pulse delay required for surface pretreatment.

[0052] Step 5: Control the computer control system to enable the femtosecond laser to perform surface pretreatment processing on the sample to be processed according to the processing requirements.

[0053] In this embodiment, as Figure 1 The computer shown is connected to the femtosecond laser 1 and controls the opening and closing of the mechanical switch 8, controls the precision electronically controlled translation stage 14 to move according to the set program trajectory, and connects to the CCD dynamic imaging unit 17 to perform real-time imaging and monitoring of the surface of the sample 13 to be processed.

[0054] In this embodiment, a femtosecond laser direct writing process is used to pre-treat the surface of CFRP material through a pre-set motion trajectory program. The femtosecond laser is focused on the upper surface of the CFRP material, and multiple parallel linear trajectories are scanned for processing. The femtosecond laser used in this embodiment has a center wavelength of 800 nm, a pulse width of 35 fs, and a repetition frequency of 1 kHz. A 100x plano-convex objective lens is used. The laser power in this embodiment is 6 mW, and the scanning speed is 2000 μm / s. This femtosecond laser direct writing process processes 201 parallel linear trajectories, with a spacing of 5 μm between the parallel linear trajectories, and a total processing area of ​​1 mm × 1 mm.

[0055] In this embodiment, after the surface pretreatment is completed, the final processed CFRP material is cleaned, and then the pretreated surface is characterized. For example... Figure 3 As shown in c and d, the femtosecond laser pre-treated surface exhibits smooth fiber arrangement without processing damage. The fiber surface shows no processing marks, breaks, or thermal damage, and there is no residual resin or other impurities between the fibers, demonstrating significant selective resin removal. In contrast, the traditional femtosecond laser pre-treated surface suffers from processing damage, resulting in disrupted fiber arrangement, broken fibers that are lifted or pulled out, obvious thermal damage marks on the fiber surface, and a large amount of unremoved resin material remaining between the fibers. This prevents the achievement of high-quality selective etching. Figure 3 As shown in a and b. In summary, time-domain shaped femtosecond lasers can achieve selective etching in surface pretreatment, increase the threshold difference between different material compositions, and achieve the goal of high-quality processing of CFRP using time-domain shaped femtosecond lasers.

[0056] Example 2

[0057] The processing objective of this embodiment is to cut / drill CFRP material, aiming to achieve uniform cutting. Therefore, it is crucial to minimize the differences in ablation thresholds among the various CFRP components. By adjusting the femtosecond laser's time-domain shaping pulse delay and pulse count, the ablation thresholds of the resin and carbon fiber materials under different parameters were measured. The variation patterns of their respective ablation thresholds resulting from laser parameter adjustments were summarized. These patterns were compared to calculate the threshold differences between the two components under the same conditions, identifying the processing parameters with the smallest differences. The comparison revealed that when the time-domain shaping pulse delay was 10 ps and the pulse count was relatively high, the threshold values ​​of the resin and fiber materials were approximately equal, resulting in the smallest threshold difference between the two components and facilitating uniform cutting. Therefore, a time-domain shaping pulse delay of 10 ps and a scanning speed of 1000 μm / s (equivalent to 17.6 effective pulses) were selected for subsequent processing.

[0058] The method for high-quality CFRP fabrication based on time-domain shaped femtosecond lasers disclosed in this embodiment includes the following specific steps:

[0059] Step 1: Adjust the optical path collimation of the femtosecond laser processing subsystem to ensure that the femtosecond laser passes through each device in sequence.

[0060] The femtosecond laser processing subsystem constructed in this embodiment is as follows: Figure 1 As shown, the system includes a femtosecond laser 1, a third ultrafast mirror group 6, a first aperture 7, a mechanical switch 8, an attenuator group 9, a second aperture 10, and a focusing objective 12. The femtosecond laser beam emitted by the femtosecond laser 1 first passes through the first beam splitter 2 in the femtosecond laser time-domain shaping subsystem, blocking one path that passes through the first ultrafast mirror group 3, preventing laser reflection. The beam then propagates through the second ultrafast mirror group 4 and the existing third ultrafast mirror group 6. By adjusting the second ultrafast mirror group 4 and the third ultrafast mirror group 6, the propagation direction of the femtosecond laser beam can be adjusted accordingly, allowing it to be collimated through the first aperture 7, mechanical switch 8, attenuator group 9, and second aperture 10. The femtosecond laser beam is then reflected by the dichroic mirror 11 and focused by the focusing objective 12 onto the sample 13 to be processed, located on the precision electronically controlled translation stage 14.

[0061] Step 2: Adjust the top imaging subsystem so that the laser focusing point coincides with the imaging focus point.

[0062] The top imaging subsystem constructed in this embodiment is as follows: Figure 1As shown, the system includes a dichroic mirror 11, a white light source 15, a second beam splitter 16, and a CCD dynamic imaging unit 17. The illumination light emitted from the uppermost white light source 15 passes through the second beam splitter 16, the dichroic mirror 11, and the focusing objective lens 12, illuminating the sample 13 to be processed. The reflected light then passes through the focusing objective lens 12 and the dichroic mirror 11 again, returning to the second beam splitter 16 and reaching the CCD dynamic imaging unit 17. By adjusting the CCD dynamic imaging unit 17, the real-time image captured by the CCD dynamic imaging unit 17 is observed, and the imaging focus is adjusted to coincide with the laser focusing position.

[0063] Step 3: Adjust the precision electronically controlled translation stage so that the laser focusing focal plane coincides with the surface of the sample to be processed.

[0064] In this embodiment, the CFRP material used in the processing is a high-modulus CFRP multidirectional laminate, consisting of 4 layers, each with a thickness of 0.125 mm. The layup sequence is 0° / +45° / -45° / 90°, and the total thickness is 0.5 mm.

[0065] In this embodiment, sample 13 to be processed is as follows: Figure 1 As shown, the laser is placed on a precision electronically controlled translation stage 14. The Z-axis height of the precision electronically controlled translation stage 14 is adjusted by a computer 18 so that the laser focusing focal plane coincides with the surface of the sample to be processed.

[0066] Step 4: Adjust the femtosecond laser time-domain shaping subsystem to shape the femtosecond laser single pulse into a femtosecond laser double pulse with the required delay.

[0067] The femtosecond laser temporal shaping subsystem constructed in this embodiment is as follows: Figure 1 As shown, the system includes a first ultrafast mirror group 3, a second ultrafast mirror group 4, a first beam splitter 2, and a one-dimensional motorized translation stage 5. Based on the Michelson interferometry principle, the laser beam is proportionally split by the first beam splitter 2, then returns via the first ultrafast mirror group 3 and the second ultrafast mirror group 4 to converge back at the first beam splitter 2, forming a double-pulse beam. The distance difference between the first ultrafast mirror group 3, the second ultrafast mirror group 4, and the first beam splitter 2 is changed by the one-dimensional motorized translation stage 5 to achieve time-domain shaping. During the adjustment process, the path adjusted in step one via the second ultrafast mirror group 4 remains stationary. The other path via the first ultrafast mirror group 3 is adjusted to make the two pulses spatially coincide. The computer 18 adjusts the one-dimensional motorized translation stage 5 to make the two pulses temporally coincide. Then, the computer 18 adjusts the one-dimensional electric translation stage 5 to change the distance difference between the first ultrafast reflector group 3 and the second ultrafast reflector group 4 and the first beam splitter 2, so that the pulse delay of the two pulses reaches 10ps, thus obtaining the ideal pulse delay required for surface pretreatment.

[0068] Step 5: Control the computer control system to enable the femtosecond laser to cut / drill the sample according to the processing requirements.

[0069] In this embodiment, as Figure 1 The computer shown is connected to the femtosecond laser 1 and controls the opening and closing of the mechanical switch 8, controls the precision electronically controlled translation stage 14 to move according to the set program trajectory, and connects to the CCD dynamic imaging unit 17 to perform real-time imaging and monitoring of the surface of the sample 13 to be processed.

[0070] In this embodiment, a femtosecond laser direct writing process is used to cut / drill CFRP material through a pre-set motion trajectory program. The femtosecond laser is focused on the upper surface of the CFRP material, and multiple concentric circular trajectories are scanned. After the trajectories of a layer are completed, the focus is moved to the starting point of the current layer's trajectory, and then the focus is moved down a certain distance as a feed interval in the thickness direction. The same trajectory scanning process is then performed for the second layer. This process is repeated until the CFRP material with the heat protection layer is processed over its entire thickness, ultimately obtaining the desired drilled CFRP through-hole structure. In this embodiment, the femtosecond laser has a center wavelength of 800 nm, a pulse width of 35 fs, and a repetition frequency of 1 kHz. The focusing objective lens used in this embodiment is a 100x plano-convex objective lens. The laser power in this embodiment is 80 mW, and the scanning speed is 1000 μm / s. In this embodiment, during the femtosecond laser layer-by-layer scanning direct writing process, 10 concentric circle trajectories are processed per layer, with an interval of 5μm between the concentric circle trajectories and a distance of 5μm between each layer of trajectories (i.e., the feed interval in the thickness direction). The number of feed layers is 110, and the processing aperture is 1mm.

[0071] In this embodiment, after the cutting / drilling process is completed, the final processed CFRP material is cleaned, and then the cut edge portion is characterized. For example... Figure 4 As shown in c and d, the edges produced by time-domain shaping femtosecond laser cutting, regardless of the direction of the surface fibers, have smooth surface resin edges without ablation marks. The fiber edges are almost flush with the resin edges, and no obvious heat-affected zone (HAZ) is generated. Measurements show the HAZ to be approximately 1.5 μm. In contrast, the cutting edges of traditional femtosecond lasers show obvious ablation marks and are uneven at the surface resin edges, exposing the underlying fibers and forming a more pronounced HAZ. This prevents the achievement of high-quality, uniform cutting; the HAZ is approximately 8.5 μm. Figure 4 As shown in a and b. In summary, time-domain shaped femtosecond lasers can achieve uniform cutting / drilling, reduce the threshold differences between different material compositions, and achieve the goal of high-quality processing of CFRP using time-domain shaped femtosecond lasers.

[0072] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for high-quality processing of CFRP based on time-domain shaped femtosecond laser, characterized in that: Step 1: Adjust the optical path collimation of the femtosecond laser processing subsystem to ensure that the femtosecond laser passes through each device in sequence; Step 2: Adjust the top imaging subsystem so that the laser focusing point coincides with the imaging focus point; Step 3: Adjust the precision electronically controlled translation stage to make the laser focusing focal plane coincide with the surface of the sample to be processed; Step 4: Adjust the femtosecond laser time-domain shaping subsystem to shape the femtosecond laser single pulse into a femtosecond laser double pulse with the required delay; Step 5: Control the computer control system to enable the femtosecond laser to perform surface pretreatment or cutting / drilling on the sample to be processed according to the processing requirements; Based on the variation of the ablation threshold of CFRP resin and carbon fiber with changes in time-domain shaping pulse delay and pulse number, and considering the threshold differences between the two material components under the same conditions, appropriate time-domain shaping femtosecond laser processing parameters are selected according to the processing purpose. When performing surface pretreatment, time-domain shaping pulse delay and scanning speed with larger threshold differences between resin and carbon fiber materials under the same conditions are used for processing; when performing cutting / drilling, time-domain shaping pulse delay and scanning speed with smaller threshold differences between resin and carbon fiber materials under the same conditions are used for processing. The apparatus for achieving high-quality CFRP processing using femtosecond laser with time-domain shaping includes a femtosecond laser processing subsystem, a femtosecond laser time-domain shaping subsystem, a top imaging subsystem, a computer control system, and a precision electrically controlled translation stage. The femtosecond laser processing subsystem includes a femtosecond laser, a third ultrafast mirror group, a first aperture, a mechanical switch, an attenuator group, a second aperture, and a focusing objective lens. The femtosecond laser generates femtosecond laser light, which propagates sequentially through the aforementioned devices. The femtosecond laser temporal shaping subsystem includes a first ultrafast mirror group, a second ultrafast mirror group, a first beam splitter, and a one-dimensional motorized translation stage. Based on the Michelson interference principle, the laser beam is proportionally split by the beam splitter and then returns to the beam splitter via the two mirrors to rejoin, forming a double-pulse beam. The distance difference between the two mirrors and the beam splitter is changed by computer-controlled one-dimensional motorized translation stage to achieve temporal shaping control. This subsystem is placed between the femtosecond laser and the ultrafast mirror group in the femtosecond laser processing subsystem. The top imaging subsystem consists of a dichroic mirror, a white light illumination source, a second beam splitter, and a CCD dynamic imaging unit. It is used to detect the processing position during the processing and to ensure that the focal plane coincides with the sample plane. The computer control system is used for real-time control of the femtosecond laser pulse triggering, mechanical switching, femtosecond laser time-domain shaping subsystem, precision electronically controlled translation stage, and top imaging subsystem. The precision electronically controlled translation stage is used to place the sample to be processed and to ensure that it moves along a prescribed trajectory according to the processing requirements.

2. The method for high-quality CFRP processing based on time-domain shaped femtosecond laser as described in claim 1, characterized in that: The femtosecond laser and mechanical switches in the femtosecond laser processing subsystem are connected to the computer control system. The pulsed femtosecond laser generated by the femtosecond laser processing subsystem propagates through the femtosecond laser time-domain shaping subsystem. The one-dimensional electric translation stage in the femtosecond laser time-domain shaping subsystem is connected to the computer control system. After the femtosecond laser time-domain shaping subsystem, it propagates forward along the optical path to the surface of the sample to be processed. The top imaging subsystem illuminates the surface of the sample to be processed with white light from a white light source, and the reflected light enters the CCD dynamic imaging unit to realize real-time monitoring of the processing position.

3. The method for high-quality CFRP processing based on time-domain shaped femtosecond laser as described in claim 1, characterized in that: The focusing objective is a 100x plano-convex objective. The laser power range during femtosecond laser direct writing is 2mW-400mW, and the scanning speed range is 200μm / s-2000μm / s. The interval between parallel straight line trajectories in femtosecond laser direct writing for surface pretreatment is 3-15μm. In femtosecond laser layer-by-layer scanning direct writing for cutting / drilling, the interval between parallel straight line / concentric circle trajectories on each layer is 3-50μm, and the distance between each layer of trajectories is 5-20μm.

4. The method for high-quality CFRP processing based on time-domain shaped femtosecond laser as described in claim 1, characterized in that: CFRP material consists of two parts: resin and carbon fiber. The resin is a transparent resin material, such as epoxy resin or modified cyanate ester resin, and its ablation threshold varies clearly with the time-domain shaping pulse delay and the number of pulses. The carbon fiber is a high-modulus carbon fiber material of M40 or M55, and its ablation threshold varies differently from that of the resin with the time-domain shaping pulse delay and the number of pulses. Femtosecond lasers are time-domain shaped and divided into dual pulses with an interval of 0.1-100 ps. High-quality CFRP processing is achieved by controlling the pulse delay and the number of pulses.

5. The method for high-quality CFRP processing based on time-domain shaped femtosecond laser as described in claim 1, characterized in that: The CFRP material used in the processing is a high-modulus CFRP multidirectional laminate with a thickness ranging from 0.2mm to 2mm.

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