Multi-pulse-width laser compound machining system and method for CFRP large-depth-diameter array holes

Abstract

The application discloses a kind of for CFRP big depth-diameter ratio array hole multi-pulse width laser composite processing system and method.The system includes: multi-pulse width laser generation module, for outputting two initial laser beams;Beam shaping module, for the optical axis of two initial laser beams is adjusted to coaxial, the initial laser beam is shaped, adjusts the polarization state of initial laser beam, initial laser beam is modulated into two sub laser beams, adjusts the energy distribution of two sub laser beams, two sub laser beams are converted into two mirror image symmetrical distribution in the focusing laser beam array of two sides of the CFRP matrix to be processed.The application can be applicable to the high-efficiency high-precision processing of CFRP big depth-diameter ratio array hole, and nanosecond laser is used to improve processing efficiency, and femtosecond laser is used to effectively inhibit carbon fiber delamination and thermal damage of resin matrix.

Description

Technical Field

[0001] This invention specifically relates to a multi-pulse laser composite processing system and method for large aspect ratio array holes in CFRP, belonging to the technical field of precision machining of carbon fiber reinforced composite materials (CFRP). Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) composites have become core structural materials in aerospace, new energy vehicles, medical, and high-end equipment industries due to their excellent specific strength, specific stiffness, fatigue resistance, and fracture toughness. In these applications, the processing quality of high-precision micropores (such as aircraft skin connection holes, engine cooling holes, and fuel cell bipolar plate flow channel holes) directly affects the aerodynamic performance, connection reliability, and fatigue life of components. Especially in the aerospace field, the geometric accuracy of hole positions, hole wall quality, and stringent taper requirements are key indicators for ensuring structural safety and functional realization. With the expanding application of CFRP in high-temperature components and ultra-thin structures, the demand for efficient processing of micropores without thermal damage, delamination, or taper is becoming increasingly urgent.

[0003] Currently, precision drilling of CFRP mainly relies on traditional machining and special machining technologies, but both have significant bottlenecks. While mechanical drilling is a mature and low-cost process, rapid tool wear easily leads to delamination and burr defects, and work hardening causes hole diameter deviations, making it difficult to machine micro-holes with diameters less than 0.5 mm and high aspect ratio holes. Its cutting forces can also cause edge fiber tearing, and heat accumulation can lead to resin carbonization. Furthermore, it is inefficient and lacks positioning accuracy in mass micro-hole machining. Among special machining technologies, water-guided lasers can reduce heat impact and machine deep holes, but high-pressure water jet impact can strip carbon fibers, causing deterioration of hole wall roughness, and taper control is difficult in thin-plate machining. Although electrical discharge machining is a non-contact process, the resin matrix has insulating properties, so contact occurs between the tool electrode and the resin matrix during drilling. While conventional laser processing (millisecond / nanosecond level) has the advantages of being non-contact and highly efficient, it suffers from resin ablation and fiber exposure due to thermal effects, significant taper caused by the energy attenuation of Gaussian beams, and elliptic distortion of apertures induced by the polarization sensitivity of linearly polarized light, which severely restricts the engineering application of high-precision array apertures.

[0004] Femtosecond lasers, particularly those with ultrashort pulses, can achieve "cold processing" due to their extremely high peak power and ultrafast energy deposition characteristics. Theoretically, this can overcome the processing challenges posed by the anisotropy of CFRP, avoiding heat-affected zones and delamination. However, current femtosecond laser hole-making technology still faces three core problems that restrict its application in high-precision array hole processing of CFRP. First, there's the taper issue. The Gaussian beam energy is normally distributed along the optical axis, resulting in a significantly higher inlet energy than outlet energy. When processing through holes, the hole wall undergoes varying degrees of ablation from top to bottom, forming a "trumpet-shaped" tapered hole. For CFRP micro-holes with large aspect ratios, the cumulative taper effect is even more pronounced, making it difficult to meet the requirements for pneumatic sealing or high-precision fit. Second, processing efficiency and multi-hole positioning accuracy need improvement. Femtosecond lasers sublimate the material through multiphoton ionization, producing almost no melting phase transition. While this avoids thermal damage, the volume of material removed by a single pulse is much smaller than that of a long-pulse laser. On the other hand, traditional scanning galvanometers suffer from defocusing effects when processing densely packed holes, leading to beam quality degradation at the edge holes. Meanwhile, the reflection / scattering of laser light by the material interferes with the processing of adjacent holes, causing hole position deviations and diameter fluctuations, failing to meet the positioning accuracy requirements of aerospace-grade hole groups. Finally, there is the problem of hole shape distortion caused by polarization effects. Linearly polarized lasers exhibit polarization-selective absorption with the oriented carbon fibers in CFRP, leading to differences in ablation rates in different directions. This results in asymmetric ablation during hole wall formation, causing elliptical hole shapes and uneven hole wall roughness distribution. Nanosecond lasers can significantly improve the hole-making efficiency of micro-holes with large aspect ratios. However, the strong thermal effect can lead to excessive resin ablation due to thermal diffusion, causing significant thermal damage. To comprehensively utilize the advantages of various laser types and eliminate their respective shortcomings, multi-laser composite processing has become a research trend and solution for dealing with micro-holes with large aspect ratios in micro-hole manufacturing engineering.

[0005] CN114749811A discloses a system and method for machining holes in carbon fiber composite materials based on laser dual-beam rotary cutting. It uses a DOE beam splitter to divide the output laser beam into two beams, and uses an aperture adjustment unit and an angle adjustment unit to translate and deflect the flight path of the split laser beams. Then, a Dove prism is used to form a ring-shaped region between the two laser beams to control the machining taper. WO2022142975A1 discloses a laser hole-making device and method suitable for CFRP. It uses a monochromatic semi-transparent mirror to divide the output laser beam into two beams of equal energy, and combines a scanning galvanometer to form rotating beams on both sides of the CFRP to reduce the micro-hole taper. These two methods have greatly promoted the advancement of tapered hole technology in CFRP, but some shortcomings remain. First, when dealing with large-volume micro-hole machining, the efficiency of hole-by-hole machining is low, and the positioning accuracy of hole groups still needs improvement. Second, the first method is based on lens translation of a single-sided focal point; however, when dealing with micro-holes with large aspect ratios, as the machining depth increases, the incident laser is partially blocked at the edge of the hole entrance. The second method employs a double-sided translation focus, which significantly reduces the single-sided focus compensation depth. However, the double-sided focus compensation device is mounted on a single module, resulting in the other side being out of focus when the single-sided focus is in place, thus failing to effectively utilize the advantages of double-sided focus compensation. Finally, neither method considers the influence of beam polarization state on the aperture shape. Therefore, how to utilize lasers to achieve efficient and precise machining of large-scale micro-holes with high aspect ratios in CFRP remains one of the technical problems that the industry urgently needs to solve. Summary of the Invention

[0006] The main objective of this invention is to provide a multi-pulse laser composite processing system and method for CFRP large aspect ratio array holes, thereby overcoming the shortcomings of the prior art.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] The first aspect of this invention provides a multi-pulse laser composite processing system for CFRP large aspect ratio array holes, comprising:

[0009] The multi-pulse laser generator module is used to output two initial laser beams, which have different pulse widths, different wavelengths, but the same beam color.

[0010] The beam shaping module is used to adjust the optical axes of the two initial laser beams to be coaxial, shape the initial laser beam, adjust the polarization state of the initial laser beam, modulate the initial laser beam into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and convert the two sub-laser beams into two mirror-symmetrical arrays of focused laser beams distributed on both sides of the CFRP substrate to be processed. The multiple focused laser beams contained in the two focused laser beam arrays correspond one-to-one and are coaxially set, and the wave vector directions of the focused laser beams contained in the two focused laser beam arrays are opposite.

[0011] One of the two initial laser beams works with the beam shaping module to form a pre-drilled hole array on the CFRP substrate to be processed, while the other works with the beam shaping module to process the pre-drilled hole array into a target hole array, in which the target holes are micro-holes with a large aspect ratio.

[0012] A second aspect of the present invention provides a method for processing large aspect ratio array holes for CFRP, comprising: sequentially performing a first laser processing stage and a second laser processing stage;

[0013] The first laser processing stage includes: modulating a green nanosecond laser beam into two green nanosecond sub-laser beams with the same optical axis and opposite wave vector directions, and converting the two green nanosecond sub-laser beams into two green nanosecond focused laser beam arrays that are mirror-symmetrically distributed on both sides of the CFRP substrate. The multiple green nanosecond focused laser beams contained in the two green nanosecond focused laser beam arrays correspond one-to-one and are coaxially arranged. The two green nanosecond focused laser beam arrays are used to process a pre-drilled hole array on the CFRP substrate. The pre-drilled holes contained in the pre-drilled hole array penetrate the CFRP substrate. The pre-drilled holes serve as chip removal channels for the second laser processing stage.

[0014] The second laser processing stage includes: aligning the optical axis of the green femtosecond laser beam with the optical axis of the green nanosecond laser beam; modulating the green femtosecond laser beam into two green femtosecond sub-laser beams with the same optical axis and opposite wave vector directions; converting the two green femtosecond sub-laser beams into two mirror-symmetrically distributed arrays of green femtosecond focused laser beams on both sides of the CFRP substrate; the multiple green femtosecond focused laser beams contained in the two arrays correspond one-to-one and are coaxially arranged; and the multiple green femtosecond focused laser beams correspond one-to-one with the multiple pre-made holes contained in the pre-made hole array; and using the two arrays of green femtosecond focused laser beams to process the pre-made hole array into a target hole array, wherein the target holes contained in the target hole array are micro-holes with a large aspect ratio.

[0015] The green nanosecond laser beam has a pulse width of 30ns to 120ns and a wavelength of 532nm; the green femtosecond laser beam has a pulse width of 180ns to 240ns and a wavelength of 517nm.

[0016] Compared with the prior art, the advantages of the present invention include:

[0017] The processing system and method for large aspect ratio array holes in CFRP provided in this invention rapidly form a pre-formed hole array on the CFRP substrate using a green nanosecond laser with a strong thermal effect. This improves the chip removal channel for subsequent green femtosecond laser refining of the hole shape, reduces plasma generation to improve the energy utilization rate of the green femtosecond laser, and eliminates the thermal damage left by the green nanosecond laser, thereby improving the hole quality.

[0018] The processing system and method for large aspect ratio array holes in CFRP provided by this invention maintains the consistency of the inlet and outlet dimensions of the micro-hole through a coaxial and symmetrically distributed focused laser beam array. Furthermore, a beam splitter prism can change the energy ratio of the two focused laser beam arrays to achieve the processing of micro-holes with different features (mainly taper features). In addition, a motion modulation module realizes complex relative motion trajectories of the beams and can synchronously or independently compensate for the focal points of the two beams, enabling the processing of irregularly shaped holes with arbitrary tapers. Furthermore, by combining circularly polarized light, the roundness of the micro-hole is further improved.

[0019] The processing system and method for large aspect ratio array holes in CFRP provided in this invention greatly improve the hole-making efficiency and hole group positioning accuracy of CFRP large aspect ratio micro-holes, significantly reduce or eliminate micro-hole taper and improve micro-hole roundness, and effectively reduce thermal damage during CFRP drilling. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a multi-pulse laser composite processing system for CFRP large aspect ratio array holes, provided in a typical embodiment of the present invention.

[0021] Figure 2a , Figure 2b , Figure 2c These are beam shaping effect diagrams for microlens arrays with different structures;

[0022] Figure 3 This is a schematic diagram of the motion adjustment module in a multi-pulse laser composite processing system for CFRP large aspect ratio array holes, provided in a typical embodiment of the present invention.

[0023] Figure 4a A schematic diagram showing the impact holes formed when the spot of a focused laser beam array directly irradiates the CFRP substrate to be processed.

[0024] Figure 4b , Figure 4c , Figure 4dThese are schematic diagrams illustrating different hole-making motion trajectories achieved by the linkage of the X-axis linear module and the Z-axis linear module.

[0025] Figure 5a , Figure 5b , Figure 5c These are schematic diagrams showing the states of the first and second focusing laser beam arrays, namely, dual positive defocus, dual focus, and focus compensation.

[0026] Figure 6a , Figure 6b , Figure 6c , Figure 6d These are schematic diagrams illustrating different relative motion trajectories of a spatial beam formed by the linkage of the XYZ three axes;

[0027] Figure 7a , Figure 7b , Figure 7c , Figure 7d Diagrams showing the hole-making effects of different configurations of focused laser beam arrays. Detailed Implementation

[0028] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0029] The first aspect of this invention provides a multi-pulse laser composite processing system for CFRP large aspect ratio array holes, comprising:

[0030] The multi-pulse laser generator module is used to output two initial laser beams, which have different pulse widths, different wavelengths, but the same beam color.

[0031] The beam shaping module is used to adjust the optical axes of the two initial laser beams to be coaxial, shape the initial laser beam, adjust the polarization state of the initial laser beam, modulate the initial laser beam into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and convert the two sub-laser beams into two mirror-symmetrical arrays of focused laser beams distributed on both sides of the CFRP substrate to be processed. The multiple focused laser beams contained in the two focused laser beam arrays correspond one-to-one and are coaxially set, and the wave vector directions of the focused laser beams contained in the two focused laser beam arrays are opposite.

[0032] One of the two initial laser beams works with the beam shaping module to form a pre-drilled hole array on the CFRP substrate to be processed, while the other works with the beam shaping module to process the pre-drilled hole array into a target hole array, in which the target holes are micro-holes with a large aspect ratio.

[0033] Furthermore, the multi-pulse laser generation module includes two laser sources, each providing two initial laser beams.

[0034] Furthermore, the two initial laser beams are a green nanosecond laser beam and a green femtosecond laser beam. The green nanosecond laser beam works in conjunction with the beam shaping module to process the pre-formed hole array, and the green femtosecond laser beam works in conjunction with the beam shaping module to process the pre-formed hole array into the target hole array.

[0035] The green nanosecond laser beam has a pulse width of 30ns to 120ns and a wavelength of 532nm; the green femtosecond laser beam has a pulse width of 180ns to 240ns and a wavelength of 517nm.

[0036] Furthermore, the beam shaping module includes:

[0037] The beam combining module is used to adjust two initial laser beams to propagate along the same optical path and keep them coaxial;

[0038] A collimation and beam expanding module is used to adjust the divergence angle and beam diameter of the initial laser beam;

[0039] A polarization state adjustment module is used to adjust the polarization state of the initial laser beam from linear polarization to circular polarization;

[0040] The beam splitting and energy control module is used to modulate the initial laser beam into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and guide the two sub-laser beams to both sides of the CFRP substrate to be processed, keeping them coaxial and with opposite wave vector directions.

[0041] An array conversion module is used to convert the two sub-laser beams into two focused laser beam arrays, respectively.

[0042] The beam combining module, the collimation and beam expanding module, the polarization state adjustment module, and the beam splitting and energy control module are arranged sequentially along the wave vector direction of the initial laser beam, and the beam splitting and energy control module and the array conversion module are arranged sequentially along the wave vector direction of the sub-laser beam.

[0043] Furthermore, the beam combining module includes a first dichroic mirror and a first reflecting mirror, the collimating and expanding module includes a beam expander and a collimating mirror, the polarization state adjustment module includes a quarter glass slide, the beam splitting and energy control module includes a beam splitter and a reflecting mirror group, and the array conversion module includes a first microlens array and a second microlens array.

[0044] The first dichroic mirror, the beam expander, the collimator, the quarter-glass slide, the beam splitter, the first microlens array, and the second microlens array are arranged sequentially at intervals, and the first dichroic mirror, the beam expander, the collimator, the quarter-glass slide, and the beam splitter are coaxial with the same common optical axis.

[0045] One of the two initial laser beams is directly incident on the beam expander through the first dichroic mirror, and the other is directly incident on the first reflecting mirror, and then incident on the beam expander after being reflected by the first reflecting mirror and the first dichroic mirror in sequence. The beam splitter is used to split the initial laser beam into a front sub-laser beam and a rear sub-laser beam. The reflecting mirror group is used to adjust the rear sub-laser beam to be coaxial with the front sub-laser beam and opposite in wave vector direction. The first microlens array is used to focus the front sub-laser beam to form a first focused laser beam array, and the second microlens array is used to focus the rear sub-laser beam to form a second focused laser beam array.

[0046] Furthermore, the reflector group includes a second reflector, a third reflector, and a fourth reflector. The fourth reflector is the last reflector in the reflector group, and the optical axis of the subsequent sub-laser beam reflected by the fourth reflector coincides with the common optical axis.

[0047] Furthermore, the beam splitting energy ratio of the beam splitter is 70:30, 60:40, 50:50, 40:60, or 30:70.

[0048] Furthermore, the beam splitting and energy control module also includes a first variable aperture and a second variable aperture. The first variable aperture is located between the beam splitter and the first microlens array, and the second variable aperture is located between the last reflector in the reflector group and the second microlens array. The optical axes of the first variable aperture and the second variable aperture coincide with the common optical axis.

[0049] In a typical implementation, the multi-pulse laser composite processing system for CFRP large aspect ratio array holes further includes:

[0050] A motion modulation module is used to drive a focused laser beam array to generate relative motion with the CFRP substrate to be processed. The relative motion includes linear motion along at least one of the X-axis, Y-axis, and Z-axis of a three-dimensional coordinate system, wherein the Y-axis is parallel to the common optical axis.

[0051] Furthermore, the motion modulation module includes an X-axis linear module, a Z-axis linear module, and a Y-axis linear module. The Y-axis linear module includes a Y1-axis linear module and a Y2-axis linear module. The Y1-axis linear module is used to drive the first microlens array to move along the Y-axis, and the Y2-axis linear module is used to correspondingly drive the second microlens array to move along the Y-axis. The X-axis linear module is used to drive the CFRP substrate to be processed to move along the X-axis, and the Z-axis linear module is used to drive the CFRP substrate to be processed to move along the Z-axis.

[0052] Furthermore, the X-axis linear module is also driven in conjunction with the Z-axis linear module. The X-axis linear module and the Z-axis linear module can jointly drive the CFRP substrate to be processed to move in the XZ plane of the three-dimensional coordinate system and form a specified hole cutting trajectory.

[0053] In a typical implementation, the multi-pulse laser composite processing system for CFRP large aspect ratio array holes further includes a monitoring module, which is used to locate the processing area and to observe the morphology of the processing area in real time.

[0054] A second aspect of the present invention provides a method for processing large aspect ratio array holes for CFRP, comprising: sequentially performing a first laser processing stage and a second laser processing stage;

[0055] The first laser processing stage includes: modulating a green nanosecond laser beam into two green nanosecond sub-laser beams with the same optical axis and opposite wave vector directions, and converting the two green nanosecond sub-laser beams into two green nanosecond focused laser beam arrays that are mirror-symmetrically distributed on both sides of the CFRP substrate. The multiple green nanosecond focused laser beams contained in the two green nanosecond focused laser beam arrays correspond one-to-one and are coaxially arranged. The two green nanosecond focused laser beam arrays are used to process a pre-drilled hole array on the CFRP substrate. The pre-drilled holes contained in the pre-drilled hole array penetrate the CFRP substrate. The pre-drilled holes serve as chip removal channels for the second laser processing stage.

[0056] The second laser processing stage includes: aligning the optical axis of the green femtosecond laser beam with the optical axis of the green nanosecond laser beam; modulating the green femtosecond laser beam into two green femtosecond sub-laser beams with the same optical axis and opposite wave vector directions; converting the two green femtosecond sub-laser beams into two mirror-symmetrically distributed arrays of green femtosecond focused laser beams on both sides of the CFRP substrate; the multiple green femtosecond focused laser beams contained in the two arrays correspond one-to-one and are coaxially arranged; and the multiple green femtosecond focused laser beams correspond one-to-one with the multiple pre-made holes contained in the pre-made hole array; and using the two arrays of green femtosecond focused laser beams to process the pre-made hole array into a target hole array, wherein the target holes contained in the target hole array are micro-holes with a large aspect ratio.

[0057] The green nanosecond laser beam has a pulse width of 30ns to 120ns and a wavelength of 532nm; the green femtosecond laser beam has a pulse width of 180ns to 240ns and a wavelength of 517nm.

[0058] Furthermore, the process of converting the green nanosecond laser beam into two green nanosecond sub-laser beams specifically includes:

[0059] First, the green nanosecond laser beam is expanded and collimated sequentially. Then, the polarization state of the green nanosecond laser beam is changed from linear polarization to circular polarization. Finally, the green nanosecond laser beam is divided into two green nanosecond sub-laser beams.

[0060] The process of converting a green femtosecond laser beam into two green femtosecond sub-lasers specifically includes:

[0061] First, the green femtosecond laser beam is expanded and collimated sequentially. Then, the polarization state of the green femtosecond laser beam is changed from linear polarization to circular polarization. Finally, the green femtosecond laser beam is divided into two green femtosecond sub-laser beams.

[0062] Furthermore, the energy ratio of the two green nanosecond laser beams or the two green femtosecond laser beams is 70:30, 60:40, 50:50, 40:60, or 30:70.

[0063] In a typical implementation, the method for processing large aspect ratio array holes for CFRP further includes: driving a green nanosecond focused laser beam array or a green femtosecond focused laser beam array to generate relative motion with the CFRP substrate, wherein the relative motion includes linear motion along at least one of the X-axis, Y-axis, and Z-axis of a three-dimensional coordinate system, wherein the Y-axis is parallel to the optical axis of the green nanosecond focused laser beam array or the green femtosecond focused laser beam array.

[0064] Furthermore, the processing method for large aspect ratio array holes in CFRP specifically includes: driving two green nanosecond focused laser beam arrays or two green femtosecond focused laser beam arrays to move along the Y-axis to adjust the focal position of the green nanosecond focused laser beam arrays or the green femtosecond focused laser beam arrays, thereby realizing at least one of the following processing methods for the CFRP substrate: double positive defocusing processing, double in-focusing processing, and double negative defocusing processing.

[0065] Furthermore, the processing method for large aspect ratio array holes for CFRP specifically includes: driving two green nanosecond focused laser beam arrays or two green femtosecond focused laser beam arrays to move synchronously towards each other along the Y-axis, so that the focal position of the green nanosecond focused laser beam array or the green femtosecond focused laser beam array changes with the processing depth, so that the radial dimension of the pre-made hole or the target hole remains consistent in its own axial direction.

[0066] Furthermore, the processing method for large aspect ratio array holes in CFRP specifically includes: driving the CFRP substrate to move in the XZ plane of the three-dimensional coordinate system and forming a specified hole trajectory, wherein the specified hole trajectory includes at least one of a circular trajectory, a concentric circle trajectory, and a spiral circle trajectory.

[0067] Furthermore, the method for machining large aspect ratio array holes for CFRP is implemented based on the multi-pulse laser composite machining system for machining large aspect ratio array holes for CFRP.

[0068] The following will further explain the technical solution, its implementation process and principle with reference to the accompanying drawings. Unless otherwise specified, the optical components involved in this invention, such as lasers, mirrors, beam splitters, variable apertures, dichroic mirrors, shutters, lenses, and CCD cameras, can all be obtained through commercial purchase or customized processing using known processes in the art. No specific product models or structures are limited here. The linear modules, water chillers, and industrial control computers involved in this invention are also known in the art, as are the CNC programs and circuit structures involved, which can be obtained through commercial purchase or customization.

[0069] The micropores in this invention have a depth-to-diameter ratio of 5 to 20 and a diameter of 0.5 mm to 5 mm.

[0070] The common optical axis mentioned in this invention refers to the common optical axis of the beam shaping module, specifically the common optical axis of the first dichroic mirror 8, the beam expander 10, the collimator 11, the quarter-glass slide 12, and the beam splitter 18 being coaxial.

[0071] In a typical implementation case, a multi-pulse laser composite processing system for CFRP large aspect ratio array holes includes a multi-pulse laser generation module, a beam shaping module, a motion modulation module, and a monitoring module. The multi-pulse laser generation module and the beam shaping module are the core functional modules of the multi-pulse laser composite processing system. The multi-pulse laser generation module and the beam shaping module work together to process and form the target hole array on the CFRP substrate to be processed. The motion modulation module is mainly used to work with the multi-pulse laser generation module and the beam shaping module to optimize the processing of the target hole array. The monitoring module is mainly used to locate the processing area and observe the morphology of the processing area in real time.

[0072] For details, please refer to Figure 1The multi-pulse laser generation module includes a green nanosecond laser 1 and a green femtosecond laser 4 (the green nanosecond laser 1 and the green femtosecond laser 4 are the two laser sources mentioned above). The green nanosecond laser 1 works with the beam shaping module to process the pre-formed hole array, and the green femtosecond laser 4 works with the beam shaping module to process the pre-formed hole array into the target hole array. The green nanosecond laser 1 provides a green nanosecond laser beam with a pulse width of 30ns~120ns and a wavelength of 532nm; the green femtosecond laser 4 provides a green femtosecond laser beam with a pulse width of 180ns~240ns and a wavelength of 517nm.

[0073] As a preferred embodiment, the multi-pulse laser generation module may further include a first water chiller 2 and a second water chiller 5. The first water chiller 2 is used to maintain the operating temperature of the green nanosecond laser 1, and the second water chiller 5 is used to maintain the operating temperature of the green femtosecond laser 44. The first water chiller 2 and the green nanosecond laser 1, and the second water chiller 5 and the green femtosecond laser 44 are thermally connected through structures / methods known in the art. Of course, the first water chiller 2 and the second water chiller 5 can also be replaced with other devices for temperature regulation, such as semiconductor coolers.

[0074] Specifically, the green nanosecond laser 1 and the green femtosecond laser 4 are also connected to the industrial control computer 9. The industrial control computer (an industrial control computer is a known control mechanism in the field, which can be obtained through commercial purchase or customization, and is not limited here) 9 controls the working status and working parameters of the green nanosecond laser 11 and the green femtosecond laser 44 respectively through control software (control software can be obtained through commercial purchase, and is not limited here).

[0075] Specifically, the beam shaping module includes a first reflecting mirror 7, a first dichroic mirror 8, a beam expander 10, a collimating mirror 11, a quarter-glass slide 12, a beam splitter 18, a first variable aperture (which can be called a front variable aperture) 22, a first microlens array (which can be called a front microlens array) 24, a second reflecting mirror 34, a third reflecting mirror 33, a fourth reflecting mirror 32, a second variable aperture (which can be called a rear variable aperture) 30, and a second microlens array (which can be called a rear variable aperture). The microlens array 28, the first dichroic mirror 8, the beam expander 10, the collimator 11, the quarter glass slide 12, the beam splitter 18, the first variable aperture 22, the first microlens array 24, the second microlens array 28, the second variable aperture 30, and the fourth reflector 32 are arranged sequentially at intervals. The first dichroic mirror 8, the beam expander 10, the collimator 11, the quarter glass slide 12, the beam splitter 18, the first variable aperture 22, and the second variable aperture 30 are coaxial with the same common optical axis.

[0076] It should be noted that, as is known to those skilled in the art, the beam shaping module also includes a support structure. The optical elements in the beam shaping module are mounted on the support structure, which can realize the positioning and attitude adjustment of each optical element in the beam shaping module. This will not be elaborated here.

[0077] Specifically, the processing space is between the first microlens array 24 and the second microlens array 28, and the CFRP substrate (e.g., CFRP board) 26 to be processed is located in the processing space between the first microlens array 24 and the second microlens array 28.

[0078] Specifically, the optical axis of the green nanosecond laser is coaxial with the common optical axis of the beam shaping module (i.e., the aforementioned common optical axis). The green nanosecond laser beam 3, excited and output by the green nanosecond laser, directly passes through the first dichroic mirror 8 and is incident on the beam expander 10. The green femtosecond laser beam 6, excited and output by the green femtosecond laser, is directly incident on the first reflecting mirror 7, and after being reflected by the first reflecting mirror 7 and the first dichroic mirror 8 in sequence, it is incident on the beam expander 10. Of course, it is also possible that the optical axis of the green femtosecond laser is coaxial with the beam shaping module. The modules share a common optical axis and are coaxial. The green femtosecond laser beam 6, excited and output by the green femtosecond laser, is directly incident on the beam expander 10 through the first dichroic mirror 8. The green nanosecond laser beam 3, excited and output by the green nanosecond laser, is directly incident on the first reflecting mirror 7 and then, after being reflected by the first reflecting mirror 7 and the first dichroic mirror 8, is incident on the beam expander 10. The first dichroic mirror 8 is a beam combining dichroic mirror, which can combine the green nanosecond laser beam 3 and the green femtosecond laser beam 6 into the same optical path.

[0079] The following details the process of using the initial laser beam (including green nanosecond laser beam 3 and green femtosecond laser beam 6) in conjunction with the beam shaping module to fabricate array holes:

[0080] The initial nanosecond laser beam 3, generated by the green nanosecond laser 1, enters the beam expander 10 through the first dichroic mirror 8. The initial femtosecond laser beam 6, generated by the green femtosecond laser 4, is reflected by the first reflecting mirror 7 into the first dichroic mirror 8, and then reflected into the beam expander 10. Through the adjustment of the first reflecting mirror 7, the initial femtosecond laser beam 6 and the initial nanosecond laser beam 3 are made to be on the same optical axis. It should be noted that the method / technique of adjusting the two laser beams to be on the same optical axis through reflecting mirrors is known in the art and is not specifically limited here.

[0081] The green nanosecond laser beam 3 and the green femtosecond laser beam 6 are referred to as the initial laser beam below.

[0082] The initial laser beam expands its diameter and reduces its divergence angle by passing through the center of the beam expander 10 (the specific modulation result is selected according to the parameters of the beam expander 10 and specific requirements, and is not specifically limited here). Then, it passes through the collimating lens 11 to become a collimated beam and passes through the quarter glass plate 12. The quarter glass plate 12 converts the original linearly polarized laser into a circularly polarized laser, which then enters the beam splitter prism 18 horizontally and is split into a rear sub-laser beam 19 and a front sub-laser beam 20 (the rear sub-laser beam 19 and the front sub-laser beam 20 are the two sub-beams mentioned above).

[0083] The pre-position sub-laser beam 20, after having its beam diameter adjusted by the first variable aperture 22 to match the first microlens array 24 (the specific matching relationship is known in the art and is not specifically limited here), is shaped into the first focused laser beam array (also referred to as the pre-positioned focused laser beam array) 25 after passing through the first microlens array 24. The post-position sub-laser beam 19 is then reflected sequentially by the second reflector 34, the third reflector 33, and the fourth reflector 32 and adjusted to be coaxial with the pre-position sub-laser beam 20. Subsequently, its beam diameter is adjusted by the second variable aperture 30 to match the second microlens array 28. After matching, the laser beams are shaped into a second focused laser beam array 27 (also known as a post-focused laser beam array) after passing through the second microlens array 28. The first focused laser beam array 25 and the second focused laser beam array 27 are mirror-symmetrical on both sides of the CFRP substrate 26 to be processed. The number, shape, array spacing and other parameters of the focused laser beams contained in the first focused laser beam array 25 and the second focused laser beam array 27 are the same. The first focused laser beam array 25 and the second focused laser beam array 27 simultaneously process multiple processing areas from both sides of the CFRP substrate 26 to be processed.

[0084] Specifically, the quarter-glass slide 12 converts the linearly polarized laser into a circularly polarized laser to eliminate the direction dependence of the beam on the surface absorptivity of the hole wall material, thereby improving the roundness and taper of the drilled hole. A variable aperture can adjust the beam diameter to fit the microlens array. Specifically, the beam splitter prism 18 can allocate the energy ratio between the front sub-laser beam 19 and the rear sub-laser beam 20, with a splitting energy ratio of 70 / 30, 60 / 40, 50 / 50, 40 / 60, or 30 / 70, which can be changed according to the micro-hole processing status.

[0085] Specifically, the sub-units of the first microlens array 24 and the second microlens array 28 have the same shape, size, number, and spacing. These structural parameters can be customized according to actual processing requirements. Specifically, the shape of the sub-units of the first microlens array 24 and the second microlens array 28 is one of rectangle, square, circle, or polygon. Figure 2a , Figure 2b , Figure 2cThe beam shaping effects of microlens arrays with different structures are shown. In specific applications, the sub-unit configuration of the microlens array can be customized according to the efficiency requirements of actual CFRP processing and the size of the aperture group spacing, thereby adjusting the focused laser beam array with different configurations (spacing, number, etc.) and forming different array spot distributions on the CFRP substrate 26 to be processed.

[0086] For details, please refer to the following document again. Figure 1 The optical module may also include a first shutter 21 and a second shutter 31. The first shutter 21 is located between the beam splitter prism 18 and the first variable aperture 22, and the second shutter 31 is located between the fourth reflector 32 and the second variable aperture 30. The first shutter 21 and the second shutter 31 can control the switching of the front sub-laser beam 20 and the rear sub-laser beam 19, respectively.

[0087] For details, please refer to the following document again. Figure 1 The monitoring module includes an illumination source 13, a CCD camera 15, an optical lens 16, and a second dichroic mirror 16. The second dichroic mirror 16 is positioned between the quarter-glass slide 12 and the beam splitter 18. The optical axis of the second dichroic mirror 16 coincides with the aforementioned common optical axis in the beam shaping module. The CCD camera 15 is coaxial with the illumination source 13. The visible light beam 14 provided by the illumination source 13 is reflected by the second dichroic mirror 17 through the optical lens 16 and remains coaxial with the initial laser beam in the beam shaping module. It continues to propagate along the same optical path as the initial laser beam in the beam shaping module and enters the first and second microlens arrays. Combined with the CCD camera 15, the processing position of the CFRP substrate 26 to be processed can be located, and the processing morphology of the micropores can be observed after processing. It should be noted that the structural composition of the monitoring module and its structure and method for achieving real-time monitoring are known in the art and are not specifically limited here.

[0088] Specifically, the motion modulation module is used to drive the focused laser beam array to generate relative motion with the CFRP substrate to be processed. This relative motion includes linear motion along at least one of the X, Y, and Z axes of a three-dimensional coordinate system, where the Y axis is parallel to the common optical axis. The motion modulation module enables focus compensation of the focused laser beam array and the formation of a specified hole-cutting trajectory, effectively eliminating the taper of the holes formed during processing.

[0089] Please refer to the following for details. Figure 1 and Figure 3The motion modulation module includes a motion controller 35, an X-axis linear module 37, a Z-axis linear module 38, and a Y-axis linear module 36. The X-axis linear module 37, Z-axis linear module 38, and Y-axis linear module 36 are connected to the motion controller 35. The Y-axis linear module 36 includes a Y1-axis linear module and a Y2-axis linear module. The Y1-axis linear module is used to drive the first microlens array 24 to move along the Y-axis, and the Y2-axis linear module is used to correspondingly drive the second microlens array 28 to move along the Y-axis. The X-axis linear module 37 is used to drive the CFRP substrate 26 to be processed to move along the X-axis, and the Z-axis linear module 38 is used to drive the CFRP substrate 26 to be processed to move along the Z-axis. Specifically, the motion controller 35 is used to adjust the motion state and motion parameters of the X-axis linear module 37, the Z-axis linear module 38, and the Y-axis linear module 36. The motion controller 35 is connected to the working machine 9. It should be noted that the hardware and software of the motion controller 35 can be obtained commercially, and there are no restrictions here.

[0090] As a preferred embodiment, the X-axis linear module 37 is also driven in conjunction with the Z-axis linear module 38. The X-axis linear module 37 and the Z-axis linear module 38 can jointly drive the CFRP substrate 26 to be processed to move in the XZ plane of the three-dimensional coordinate system and form a specified hole cutting trajectory. Specifically, the Y-axis linear module 36 is horizontally mounted on the bottom platform (the bottom platform is part of the support platform of the overall multi-pulse laser composite processing system; the specific structure of the support platform and the bottom platform is not limited, but it mainly serves as the support part of the system). Specifically, the Y-axis linear module 36 can be a double-slide linear module, that is, the Y1-axis linear module and the Y2-axis linear module are integrated. The X-axis linear module 37 and the Z-axis linear module 38 can be single-slide linear modules. The structure and working principle of the slide linear module are known in the art and will not be described in detail here.

[0091] As a typical implementation, the Y-axis linear module 36 has two slides that can move linearly independently, namely the Y1 slide and the Y2 slide. The first microlens array 24 is fixedly mounted on the Y1 slide mounting plate 23, and the Y1 slide mounting plate 23 is fixedly mounted on the Y1 slide. The second microlens array 28 is fixedly mounted on the Y2 slide mounting plate 29, and the Y2 slide mounting plate 29 is fixedly mounted on the Y2 slide. The Z-axis linear module 38 is fixedly mounted on the moving part (e.g., the slide) of the X-axis linear module 37. The CFRP substrate 26 to be processed is fixed on the breadboard 39 (exemplarily, the CFRP substrate 26 to be processed can be fixed on the breadboard 39 by means of clamps and bolts, and the installation position of the CFRP substrate 26 to be processed can be adjusted). The breadboard 39 is fixed on the moving part (e.g., the slide) of the Z-axis linear module 38.

[0092] In a more specific implementation, a method for processing large aspect ratio array holes for CFRP is carried out based on the aforementioned multi-pulse laser composite processing system for large aspect ratio array holes in CFRP. This processing method may specifically include the following steps:

[0093] (1) The first laser processing stage includes: fixing the CFRP substrate 26 to be processed on the moving part of the Z-axis linear module 38, turning on the green nanosecond laser 1, and the green nanosecond laser beam 3 output by the green nanosecond laser 1 passing through the beam expander 10, collimating lens 11, 1 / 4 glass plate 12, and beam splitter 18 in sequence, and being divided into a rear sub-laser beam 19 and a front sub-laser beam 20. The front sub-laser beam 20 adjusts the beam diameter to match the first microlens array 24 through the first variable aperture 22, and is shaped into a front-focused nanosecond laser beam array after passing through the first microlens array 24. The rear sub-laser beam 19 passes through the second reflector 34, the third reflector 33, and the first reflector 34 in sequence. The four reflecting mirrors 32 reflect and adjust to be coaxial with the front sub-laser beam 20. Then, the beam diameter is adjusted by the second variable aperture 30 to match the second microlens array 28. After passing through the second microlens array 28, it is shaped into a rear-focused nanosecond laser beam array. The front-focused nanosecond laser beam array and the rear-focused nanosecond laser beam array are mirror-symmetrical on both sides of the CFRP substrate 26 to be processed. The front-focused nanosecond laser beam array and the rear-focused nanosecond laser beam array simultaneously ablate the material on the CFRP substrate 26 to be processed from both sides to form a pre-formed hole array. The pre-formed holes contained in the pre-formed hole array penetrate the CFRP substrate 26 to be processed.

[0094] (2) The second laser processing stage includes: turning off the green nanosecond laser 1 and turning on the green femtosecond laser 4. The filtered femtosecond laser beam 6 output by the green femtosecond laser 4 is reflected by the first reflecting mirror 7 and the first dichroic mirror 8 and propagates along the same optical path as the green nanosecond laser beam 3, forming a pre-focused femtosecond laser beam array and a post-focused femtosecond laser beam array. The focused femtosecond laser beams contained in the pre-focused femtosecond laser beam array and the post-focused femtosecond laser beam array are respectively positioned at the center of the pre-made hole, and the pre-made hole array is further processed to form the target hole array. It should be noted that, based on the pre-made hole formed in the first laser processing stage, the volume of material removed by hole repair in the second laser processing stage is reduced, which greatly shortens the femtosecond laser processing time. At the same time, femtosecond laser processing can also improve processing accuracy and surface quality.

[0095] The pre-formed holes can serve as chip removal channels in the subsequent second laser processing stage. This not only enables the removal of debris in the second laser processing stage, but also reduces the shielding and absorption of laser energy by debris and plasma, thereby improving the utilization rate of laser energy and the processing accuracy of the target hole.

[0096] For example, the CFRP matrix 26 to be processed can be a composite material component suitable for aero-engines.

[0097] Specifically, the energy ratio of the pre-laser beam to the post-laser beam is 70:30, 60:40, 50:50, 40:60, or 30:70. Different energy ratios can yield micro-holes with varying tapers. For example, when the energy ratio of the pre-laser beam to the post-laser beam formed by a green nanosecond laser beam or a green femtosecond laser beam is 70:30 or 60:40, the resulting micro-hole is a positive taper. When the energy ratio is 50:50, the resulting micro-hole is a non-tapered hole. When the energy ratio is 40:60 or 30:70, the resulting micro-hole is an inverted taper. Of course, this invention can process irregularly shaped holes of arbitrary tapers by rationally configuring the energy ratio and scanning trajectory.

[0098] In a typical implementation scheme, during the first and second laser processing stages, the X-axis linear module and the Z-axis linear module are linked to control the movement of the CFRP substrate 26 to be processed relative to the focused laser beam array, forming a specific hole-cutting trajectory, such as... Figure 4b , Figure 4c , Figure 4d As shown, Figure 4b , Figure 4c , Figure 4d These are schematic diagrams illustrating different hole-making motion trajectories achieved by the coordinated operation of the X-axis linear module and the Z-axis linear module. When the X-axis linear module and the Z-axis linear module stop moving, as shown... Figure 4a As shown, the light spots of the first focused laser beam array 25 and the second focused laser beam array 27 directly irradiate the CFRP substrate 26 to be processed, which can form micro-holes / micro-apertures with similar inlet and outlet shapes and sizes close to the light spots. When the X-axis linear module and the Z-axis linear module are linked, the CFRP substrate 26 to be processed forms the same cutting trajectory / motion trajectory relative to the first focused laser beam array 25 and the second focused laser beam array 27, and the cutting trajectory of each hole in the array hole group is the same. For cutting holes, larger micro-apertures can be obtained, and the hole shape can be better controlled. Commonly used cutting trajectories include outer circular cutting (such as...). Figure 4b ), concentric circular holes (such as Figure 4c ) and spiral circular cut holes (such as Figure 4d ).

[0099] In a typical implementation, during the first and second laser processing stages, the first microlens array 24 and the second microlens array 28 are moved synchronously along the Y-axis by the Y1-axis linear module and the Y2-axis linear module, respectively, to adjust the focal position of the focused laser beam array in real time. During the micro-hole processing, the first microlens array 24 / second microlens array 28 moves relative to the CFRP substrate 26 to be processed along the Y-axis to adjust the focal position. This can achieve double positive defocus, double focus, and double negative defocus or a combination thereof. Furthermore, the spacing can be shortened synchronously during the laser hole making process to compensate for the focal point, thereby improving the laser energy utilization rate and eliminating the taper of the hole. Figure 5a , Figure 5b , Figure 5c The diagrams show the states of the first and second focused laser beam arrays, respectively, with double positive defocus, double focus, and focus compensation.

[0100] In a typical implementation scheme, during the first and second laser processing stages, the XYZ three-axis linkage trajectory can be achieved through the coordinated operation of the X-axis linear module 37, the Z-axis linear module 38, and the Y-axis linear module 36. Specifically, Figure 6a , Figure 6b , Figure 6c , Figure 6d Schematic diagrams are shown for different relative motion trajectories of a spatial beam formed by the linkage of the XYZ axes. Figure 6a This is a planar outer circle layered feed trajectory, which is suitable for rapid machining of shallow holes with a diameter close to 0.5 mm and a depth-to-diameter ratio close to 5, or for finishing holes based on existing pre-made holes. Figure 6b The planar concentric circle layered feed trajectory is suitable for machining micro-holes with a diameter close to 0.5 mm and a depth-to-diameter ratio of less than 10. This trajectory can extend the heat dissipation time and achieve better heat diffusion suppression effect. Figure 6c The planar spiral circular layered feed trajectory is suitable for machining micro-holes with large diameters and depth-to-diameter ratios greater than 10 but less than 20. However, the laser thermal effect is significant and can easily lead to additional thermal damage. Therefore, the planar spiral circular layered feed trajectory is only suitable for the pre-drilled hole machining stage. Figure 6d The spatial spiral circular feed trajectory is suitable for the rapid forming process of micro-holes with large depth-to-diameter ratio and has a small heat-affected zone. However, rapid feeding can easily lead to the formation of a natural positive taper. This trajectory can be used to repair holes with low-speed feeding after a positive taper hole has been formed. However, due to the complexity of the spatial spiral, this trajectory is only suitable for the processing of holes without taper and is not suitable for the processing of irregular holes with complex features.

[0101] Specifically, the X-axis linear module 37, Z-axis linear module 38, and Y-axis linear module 36 work together to form a specific motion trajectory, enabling the machining of micro-holes of arbitrary shapes. For example, by using XZ-axis linkage (achieved by the linkage of X-axis linear module 37 and Z-axis linear module 38), an outer circular trajectory is first formed. When a layer of material is removed using the first focused laser beam array 25 and the second focused laser beam array 27, the distance between the first microlens array 24, the second microlens array 28, and the CFRP substrate 26 to be processed is shortened by the Y-axis linear module 36 to perform focus compensation. This method is suitable for machining shallower micro-holes because the intermediate material is not removed. Only after cutting off the entire cylindrical material in the middle will a through hole be formed. When using concentric circle and spiral circle trajectories for hole cutting, micro-holes with large depth-to-diameter ratios can be processed. The formation process of the micro-hole is similar to the connection process of two blind holes. Specifically, the linkage motion can also realize a spatial spiral circular trajectory to further improve the hole cutting efficiency. Typically, a green nanosecond laser beam is used to punch holes to form pre-made holes, and then a green femtosecond laser beam is used for hole cutting to obtain higher processing efficiency and surface quality.

[0102] Figure 7a , Figure 7b , Figure 7c , Figure 7d The diagrams show the hole-making effects of different focused laser beam array configurations. Specifically, laser beam arrays can significantly improve hole-making efficiency. Even with focus compensation, unidirectional focused laser beam arrays (i.e., unidirectional array beams) are prone to being blocked at the hole entrance edge when processing micro-holes with large aspect ratios, resulting in the retention of the taper and the formation of positive taper array holes, such as... Figure 7a As shown; a bidirectional focused laser beam array (i.e., a bidirectional array beam) can ensure that the inlet and outlet have the same shape and size, but without focus compensation, the energy utilization near the aperture is always higher than inside the aperture. Even with a cutting trajectory, a taper will result, forming a symmetrical taper array aperture, such as... Figure 7b As shown. When a bidirectional focused laser beam array (i.e., a bidirectional array beam) is used in conjunction with bidirectional focus compensation, it can maintain high aperture-making efficiency while keeping the inlet and outlet shapes and sizes consistent, and forming a taper-free array aperture, such as... Figure 7c As shown, when a green nanosecond laser beam is used for efficient machining to form pre-drilled holes to provide a chip removal channel, and combined with a green femtosecond laser beam for hole finishing to eliminate thermal defects, high-efficiency and high-precision machining of CFRP large aspect ratio taper-free array holes can be achieved, such as... Figure 7d As shown.

[0103] The processing system and method for large aspect ratio array holes in CFRP provided in this invention rapidly form a pre-formed hole array on a CFRP substrate using a green nanosecond laser with a strong thermal effect. Based on the strong thermal effect of the green nanosecond laser, pre-formed holes can be rapidly formed on the CFRP substrate, removing most of the material volume inside the holes, significantly improving the material removal rate and leaving a heat-affected zone. The green femtosecond laser can eliminate the heat-affected zone in situ and modify the hole shape to obtain a high-quality micropore surface structure, thereby achieving high-efficiency and high-quality integrated hole fabrication.

[0104] Furthermore, the pre-formed holes rapidly created on the CFRP substrate by green nanosecond lasers also provide a chip removal channel for subsequent green femtosecond laser finishing of the hole shape, making it easier for ablated material to be discharged from the hole and reducing material adhesion at the hole opening and wall during the target hole formation process. In addition, even with focus compensation, during the hole-making process, the backflow of material vapor can easily form plasma in the hole entrance region. Material vapor and plasma absorb and shield laser energy; furthermore, plasma can cause over-ablation of the resin. Pre-formed holes can effectively reduce vapor backflow, thereby reducing plasma formation, improving the energy utilization rate of the green femtosecond laser, reducing plasma thermal ablation of material, and improving the precision control of hole shape processing.

[0105] The present invention provides a processing system and method for large aspect ratio array holes in CFRP. By using a coaxial and symmetrically distributed array of focused laser beams to maintain the consistency of the inlet and outlet dimensions of the micro-holes, and by using a beam splitter to change the energy ratio of the two focused laser beam arrays, the processing of micro-holes with different features (mainly taper features) can be realized. At the same time, a motion modulation module realizes complex relative motion trajectories of the beams and can synchronously or independently compensate for the focal points of the two beams, thereby realizing the processing of irregularly shaped holes with arbitrary taper. Furthermore, by combining circularly polarized light, the roundness of the micro-holes is further improved.

[0106] Specifically, even with single-focus compensation, the deeper the hole, the more dispersed the energy at the bottom, leading to nonlinear laser energy attenuation during the machining of micro-holes with large aspect ratios. This naturally results in a positive taper hole, causing a decrease in machining accuracy. Compared to single-focus, dual-focus control can halve the focus movement distance, improving the accuracy of laser hole making. Furthermore, based on the hole characteristics (positive taper, reverse taper, no taper, irregular hole), the laser hole making process is elevated to a powerful process that can actively and precisely control the three-dimensional cavity structure (the shape of the hole in the depth direction).

[0107] This invention provides a technical solution for a multi-pulse laser composite processing system and method for CFRP large aspect ratio array holes, but is not intended to limit it. Those skilled in the art can still modify the technical solution or make equivalent substitutions for the technical features of this invention, and such modifications or substitutions should also be considered within the scope of protection of this invention. This does not cause the essence of the corresponding technical solution to depart from the scope of the technical solutions in the embodiments of this invention.

[0108] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A multi-pulse width laser hybrid machining system for CFRP large depth-to-diameter ratio arrayed holes, characterized in that, include: The multi-pulse laser generator module is used to output two initial laser beams, which have different pulse widths, different wavelengths, but the same beam color. The beam shaping module is used to adjust the optical axes of two initial laser beams to be coaxial, shape the initial laser beam, adjust the polarization state of the initial laser beam from linear polarization to circular polarization, modulate the initial laser beam into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and convert the two sub-laser beams into two mirror-symmetrical arrays of focused laser beams distributed on both sides of the CFRP substrate to be processed. The multiple focused laser beams contained in the two focused laser beam arrays correspond one-to-one and are coaxially arranged, and the wave vector directions of the focused laser beams contained in the two focused laser beam arrays are opposite. One of the two initial laser beams works with the beam shaping module to form a pre-drilled hole array on the CFRP substrate to be processed, while the other works with the beam shaping module to process the pre-drilled hole array into a target hole array, in which the target holes are micro-holes with a large aspect ratio.

2. The multi-pulse laser composite processing system for CFRP large aspect ratio array holes according to claim 1, characterized in that: The multi-pulse laser generation module includes two laser sources, each providing two initial laser beams. And / or, the two initial laser beams are a green nanosecond laser beam and a green femtosecond laser beam, respectively. The green nanosecond laser beam works with the beam shaping module to process the pre-formed hole array, and the green femtosecond laser beam works with the beam shaping module to process the pre-formed hole array into the target hole array. The green nanosecond laser beam has a pulse width of 30ns to 120ns and a wavelength of 532nm; the green femtosecond laser beam has a pulse width of 180fs to 240fs and a wavelength of 517nm.

3. The multi-pulsewidth laser compound machining system for CFRP large depth-to-diameter ratio array holes according to claim 1 or 2, characterized in that, The beam shaping module includes: The beam combining module is used to adjust two initial laser beams to propagate along the same optical path and keep them coaxial; A collimation and beam expanding module is used to adjust the divergence angle and beam diameter of the initial laser beam; A polarization state adjustment module is used to adjust the polarization state of the initial laser beam from linear polarization to circular polarization; The beam splitting and energy control module is used to modulate the initial laser beam into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and guide the two sub-laser beams to both sides of the CFRP substrate to be processed, keeping them coaxial and with opposite wave vector directions. An array conversion module is used to convert the two sub-laser beams into two focused laser beam arrays, respectively. The beam combining module, the collimation and beam expanding module, the polarization state adjustment module, and the beam splitting and energy control module are arranged sequentially along the wave vector direction of the initial laser beam, and the beam splitting and energy control module and the array conversion module are arranged sequentially along the wave vector direction of the sub-laser beam.

4. The multi-pulse laser composite processing system for CFRP large aspect ratio array holes according to claim 3, characterized in that: The beam combining module includes a first reflecting mirror and a first dichroic mirror; the collimating and expanding module includes a beam expander and a collimating mirror; the polarization state adjustment module includes a quarter glass slide; the beam splitting and energy control module includes a beam splitter and a group of reflecting mirrors; and the array conversion module includes a first microlens array and a second microlens array. The first dichroic mirror, the beam expander, the collimator, the quarter-glass slide, the beam splitter, the first microlens array, and the second microlens array are arranged sequentially at intervals, and the first dichroic mirror, the beam expander, the collimator, the quarter-glass slide, and the beam splitter are coaxial with the same common optical axis. One of the two initial laser beams is directly incident on the beam expander through the first dichroic mirror, and the other is directly incident on the first reflector and then incident on the beam expander after being reflected by the first reflector and the first dichroic mirror in sequence. The beam splitter is used to split the initial laser beam into a front sub-laser beam and a rear sub-laser beam. The reflector group is used to adjust the rear sub-laser beam to be coaxial with the front sub-laser beam and opposite in wave vector direction. The first microlens array is used to focus the front sub-laser beam to form a first focused laser beam array, and the second microlens array is used to focus the rear sub-laser beam to form a second focused laser beam array. And / or, the reflector group includes a second reflector, a third reflector, and a fourth reflector, wherein the fourth reflector is the last reflector in the reflector group, and the optical axis of the subsequent sub-laser beam reflected by the fourth reflector coincides with the common optical axis; And / or, the beam splitting energy ratio of the beam splitter is 70:30, 60:40, 50:50, 40:60, or 30:70; And / or, the beam splitting and energy control module further includes a first variable aperture and a second variable aperture, the first variable aperture being located between the beam splitter and the first microlens array, the second variable aperture being located between the last reflector in the reflector group and the second microlens array, and the optical axes of the first variable aperture and the second variable aperture coinciding with the common optical axis.

5. The multi-pulsewidth laser compound machining system for CFRP large depth-to-diameter ratio array holes according to claim 4, characterized in that, Also includes: A motion modulation module is used to drive a focused laser beam array to generate relative motion with the CFRP substrate to be processed. The relative motion includes linear motion along at least one of the X-axis, Y-axis, and Z-axis of a three-dimensional coordinate system, wherein the Y-axis is parallel to the common optical axis.

6. The multi-pulsewidth laser compound machining system for CFRP large depth-to-diameter ratio array holes according to claim 5, characterized in that: The motion modulation module includes an X-axis linear module, a Z-axis linear module, and a Y-axis linear module. The Y-axis linear module includes a Y1-axis linear module and a Y2-axis linear module. The Y1-axis linear module is used to drive the first microlens array to move along the Y-axis, and the Y2-axis linear module is used to correspondingly drive the second microlens array to move along the Y-axis. The X-axis linear module is used to drive the CFRP substrate to be processed to move along the X-axis, and the Z-axis linear module is used to drive the CFRP substrate to be processed to move along the Z-axis. And / or, the X-axis linear module is also driven in conjunction with the Z-axis linear module, and the X-axis linear module and the Z-axis linear module can jointly drive the CFRP substrate to be processed to move in the XZ plane of the three-dimensional coordinate system and form a specified hole trajectory; And / or, the multi-pulse laser composite processing system for CFRP large aspect ratio array holes further includes: a monitoring module, which is used to locate the processing area and to observe the morphology of the processing area in real time.

7. A method for machining large-depth-to-diameter ratio array holes for CFRP, implemented based on the multi-pulsewidth laser hybrid machining system according to any one of claims 1-6, characterized in that, include: The first laser processing stage and the second laser processing stage are performed sequentially. The first laser processing stage includes: adjusting the linear polarization of a green nanosecond laser beam to circular polarization, and modulating it into two green nanosecond sub-laser beams with the same optical axis and opposite wave vector directions. The two green nanosecond sub-laser beams are then converted into two green nanosecond focused laser beam arrays that are mirror-symmetrically distributed on both sides of the CFRP substrate. The multiple green nanosecond focused laser beams contained in the two green nanosecond focused laser beam arrays correspond one-to-one and are coaxially arranged. The two green nanosecond focused laser beam arrays are used to process a pre-drilled hole array on the CFRP substrate. The pre-drilled holes contained in the pre-drilled hole array penetrate the CFRP substrate. The pre-drilled holes serve as chip removal channels for the second laser processing stage. The second laser processing stage includes: aligning the optical axis of the green femtosecond laser beam with the optical axis of the green nanosecond laser beam; adjusting the green femtosecond laser beam from linear polarization to circular polarization and modulating it into two green femtosecond sub-laser beams with the same optical axis and opposite wave vector directions; converting the two green femtosecond sub-laser beams into two mirror-symmetrically distributed arrays of green femtosecond focused laser beams on both sides of the CFRP substrate; the multiple green femtosecond focused laser beams contained in the two arrays correspond one-to-one and are coaxially arranged; and the multiple green femtosecond focused laser beams correspond one-to-one with the multiple pre-made holes contained in the pre-made hole array; and using the two arrays of green femtosecond focused laser beams to process the pre-made hole array into a target hole array, wherein the target holes contained in the target hole array are micro-holes with a large aspect ratio. The green nanosecond laser beam has a pulse width of 30ns to 120ns and a wavelength of 532nm; the green femtosecond laser beam has a pulse width of 180fs to 240fs and a wavelength of 517nm.

8. The method of claim 7, wherein the array of holes with large depth-to-diameter ratio in the CFRP is processed by, The process of converting a green nanosecond laser beam into two green nanosecond sub-lasers specifically includes: First, the green nanosecond laser beam is expanded and collimated sequentially. Then, the polarization state of the green nanosecond laser beam is changed from linear polarization to circular polarization. Finally, the green nanosecond laser beam is divided into two green nanosecond sub-laser beams. The process of converting a green femtosecond laser beam into two green femtosecond sub-lasers specifically includes: First, the green femtosecond laser beam is expanded and collimated sequentially. Then, the polarization state of the green femtosecond laser beam is changed from linear polarization to circular polarization. Finally, the green femtosecond laser beam is split into two green femtosecond sub-laser beams. And / or, the energy ratio of the two green nanosecond laser beams or the two green femtosecond laser beams is 70:30, 60:40, 50:50, 40:60, or 30:

70.

9. The method of claim 7, wherein the array of holes with large depth-to-diameter ratio is machined in the CFRP. Also includes: The green nanosecond focused laser beam array or the green femtosecond focused laser beam array is driven to generate relative motion with the CFRP substrate. The relative motion includes linear motion along at least one of the X-axis, Y-axis and Z-axis of a three-dimensional coordinate system, wherein the Y-axis is parallel to the optical axis of the green nanosecond focused laser beam array or the green femtosecond focused laser beam array. And / or, the processing method for large aspect ratio array holes for CFRP specifically includes: driving two green nanosecond focused laser beam arrays or two green femtosecond focused laser beam arrays to move along the Y-axis to adjust the focal position of the green nanosecond focused laser beam arrays or the green femtosecond focused laser beam arrays, thereby realizing at least one of the following processing methods for the CFRP substrate: double positive defocusing processing, double in-focusing processing, and double negative defocusing processing; And / or, the processing method for large aspect ratio array holes for CFRP specifically includes: driving two green nanosecond focused laser beam arrays or two green femtosecond focused laser beam arrays to move synchronously towards each other along the Y-axis, so that the focal position of the green nanosecond focused laser beam array or the green femtosecond focused laser beam array changes with the processing depth, so that the radial dimension of the pre-made hole or the target hole remains consistent in its own axial direction; And / or, the method for processing large aspect ratio array holes for CFRP specifically includes: driving the CFRP substrate to move in the XZ plane of the three-dimensional coordinate system and forming a specified hole trajectory, wherein the specified hole trajectory includes at least one of a circular trajectory, a concentric circle trajectory, and a spiral circle trajectory.

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