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

Abstract

The invention discloses a multi-pulse-width laser combined machining system and method for CFRP large depth-diameter ratio array holes. The system comprises a multi-pulse-width laser generation module used for outputting two initial laser beams; a beam shaping module, the optical axis adjusting module is used for adjusting the optical axes of the two initial laser beams to be coaxial, shaping the initial laser beams, adjusting the polarization state of the initial laser beams, modulating the initial laser beams into two sub-laser beams and adjusting the energy distribution of the two sub-laser beams; and the two sub laser beams are converted into two focused laser beam arrays which are distributed on the two sides of the CFRP base body to be machined in a mirror symmetry mode. The method can be suitable for efficient and high-precision machining of the CFRP array holes with the large depth-diameter ratio, the machining efficiency is improved through nanosecond laser, and layering of carbon fibers and thermal damage of a resin matrix are effectively restrained through femtosecond laser.

Description

TECHNICAL FIELD

[0001] The application particularly relates to a multi-pulse-width laser composite machining system and method for CFRP large-depth-diameter-ratio array holes, and belongs to the technical field of precision machining of carbon fiber reinforced composites (CFRP). BACKGROUND

[0002] Carbon fiber reinforced composites (CFRP) have become the core structural material in the fields of aerospace, new energy vehicles, medical treatment, high-end equipment, etc. due to their excellent specific strength, specific stiffness, fatigue resistance and fracture toughness. In these applications, the machining quality of high-precision micro-holes (such as aircraft skin connecting holes, engine cooling holes and fuel cell bipolar plate flow channel holes) directly affects the aerodynamic performance, connection reliability and fatigue life of the components. Especially in the field of aerospace, the geometric precision of the hole position, the quality of the hole wall and the strict taper requirement are the key indicators to ensure the safety and function of the structure. With the application of CFRP in high-temperature components and ultra-thin structures, the demand for efficient machining of non-thermal damage, non-delamination and non-taper micro-holes is increasingly urgent.

[0003] Current CFRP precision hole machining mainly relies on traditional mechanical machining and special machining technology, but both have significant bottlenecks. Mechanical drilling, although mature in technology and low in cost, can easily cause delamination and burr defects due to rapid tool wear, and the work hardening effect leads to hole diameter deviation, making it difficult to machine micro-holes with a diameter less than 0.5mm and high-depth-diameter-ratio holes. The cutting force can also cause edge fiber tearing, and heat accumulation can cause carbonization of the resin. In addition, in mass micro-hole machining, the efficiency is low and the positioning accuracy is insufficient. In special machining technology, water-guided laser can reduce thermal effects and machine deep holes, but high-pressure water jet impact can strip carbon fibers, causing deterioration of hole wall roughness, and it is difficult to control the taper in thin plate machining. Although electrical discharge machining is a non-contact machining method, the resin matrix is insulating, so contact will occur between the tool electrode and the resin matrix during drilling. Although conventional laser machining (millisecond / nanosecond level) has the advantages of non-contact and high efficiency, it causes resin ablation and fiber exposure due to thermal effects, and the taper is significantly affected by the energy decay of the Gaussian beam. In addition, the polarization sensitivity of linearly polarized light induces elliptical distortion of the hole type, which seriously restricts the engineering application of high-precision array holes.

[0004] Femtosecond laser in ultra-short pulse laser can realize 'cold machining' due to its extremely high peak power and ultrafast energy deposition characteristics, which can theoretically overcome the processing challenges of CFRP anisotropy and avoid heat-affected zone and delamination. However, there are still three major problems in current femtosecond laser drilling technology, which restrict its application in CFRP high-precision array hole machining. Firstly, the taper problem, the energy of Gaussian beam is normally distributed along the optical axis, which leads to the entrance energy significantly higher than the exit. When processing through holes, the hole wall from top to bottom experiences different degrees of ablation, forming a 'horn-shaped' tapered hole. For CFRP micro-holes with large depth-diameter ratio, the cumulative effect of taper is more significant, which is difficult to meet the aerodynamic sealing or high-precision fitting requirements. Secondly, the processing efficiency and multi-hole positioning accuracy need to be improved. Femtosecond laser removes material through multiphoton ionization, which almost does not produce melting phase change, which can avoid thermal damage, but the material removed by single pulse is much smaller than that by long pulse laser. On the other hand, the traditional scanning galvanometer causes the beam quality degradation of the edge hole due to the defocusing effect when processing dense holes. At the same time, the reflection / scattering of material to laser will interfere with the processing of adjacent holes, causing hole position deviation and hole diameter fluctuation, which cannot meet the requirements of aviation-level hole group positioning accuracy. Finally, the polarization effect causes the hole shape distortion problem. Linearly polarized laser has polarization selective absorption with the directional arrangement of carbon fibers in CFRP, which leads to the difference of ablation rate in different directions. Asymmetric ablation occurs during the formation of hole wall, causing elliptical hole type and uneven distribution of hole wall roughness. Using nanosecond laser can significantly improve the drilling efficiency of micro-holes with large depth-diameter ratio. However, the strong thermal effect will cause thermal diffusion and excessive ablation of resin, resulting in obvious thermal damage. In order to make full use of the advantages of each type of laser and eliminate their shortcomings, multi-laser composite machining has become a research trend and solution to deal with micro-holes with large depth-diameter ratio in micro-hole manufacturing engineering.

[0005] CN114749811A discloses a carbon fiber composite material hole processing system and method based on laser double-beam rotary cutting, which divides the output laser beam into two beams through a DOE beam splitter, and translates and angularly deflects the flight path of the split laser beam through an aperture adjustment unit and an angle adjustment unit, and then controls the processing taper by forming a ring-shaped area with the two laser beams through a dove prism. WO2022142975A1 discloses a laser drilling device and method suitable for CFRP, which divides the output laser into two beams of equal energy through a half-transmission half-reflection mirror of a single color, and combines a scanning galvanometer to form rotating beams on both sides of the CFRP to reduce the taper of the micro-holes. These two methods have greatly promoted the advancement of CFRP non-tapered hole process, but there are still some deficiencies. First, when dealing with large quantities of micro-holes, the efficiency of hole-by-hole processing is low and the hole group positioning accuracy still needs to be improved. Second, the first method is based on lens translation of single-side focal point, and when dealing with large depth-to-diameter ratio micro-holes, as the processing depth increases, the incident laser will be partially blocked at the edge of the hole entrance. The second method uses double-side translation focal point, which greatly reduces the single-side focal point compensation depth. However, the compensation device of the double-side focal point is installed on one module, which causes the single-side focal point to be in focus while the other side is out of focus, and cannot effectively utilize the advantages of double-side focal point compensation. Finally, both methods do not consider the influence of beam polarization state on the hole type. Therefore, how to use laser to realize efficient and precise processing of large depth-to-diameter ratio and large quantity of CFRP micro-holes is still one of the technical problems to be solved in the industry. SUMMARY

[0006] The main purpose of the present application is to provide a multi-pulse-width laser composite processing system and method for CFRP large depth-to-diameter ratio array holes, so as to overcome the deficiencies in the prior art.

[0007] To achieve the above-mentioned purposes, the technical solutions adopted by the present application include: The first aspect of the embodiment of the present application provides a multi-pulse-width laser composite processing system for CFRP large depth-to-diameter ratio array holes, which comprises: A multi-pulse-width laser generation module is used to output two initial laser beams, the pulse widths of the two initial laser beams are different, the wavelengths of the two initial laser beams are different, and the beam colors of the two initial laser beams are the same. A beam shaping module is used to adjust the optical axes of the two initial laser beams to be coaxial, shape the initial laser beams, adjust the polarization state of the initial laser beams, modulate the initial laser beams into two sub-laser beams, adjust the energy distribution of the two sub-laser beams, and convert the two sub-laser beams into two focused laser beam arrays which are mirror-symmetrically distributed on both sides of the CFRP substrate to be processed. The multiple focused laser beams included in the two focused laser beam arrays are one-to-one corresponding and coaxially arranged, and the wave vector directions of the focused laser beams included in the two focused laser beam arrays are opposite. One of the two initial laser beams cooperates with the beam shaping module to realize the machining of the preformed hole array on the CFRP substrate to be machined, and the other cooperates with the beam shaping module to realize the machining of the preformed hole array into the target hole array, the target hole contained in the target hole array being a micro-hole with a large depth-diameter ratio.

[0008] The second aspect of the embodiment of the present application provides a machining method for a large-depth-diameter ratio array hole of CFRP, which comprises sequentially performing a first laser machining stage and a second laser machining stage. The first laser machining stage comprises: 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 which 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 being one-to-one corresponding and coaxially arranged, and the two green nanosecond focused laser beam arrays being used to machine a preformed hole array on the CFRP substrate, the preformed hole contained in the preformed hole array penetrating through the CFRP substrate, and the preformed hole serving as a chip removal channel for the second laser machining stage. The second laser machining stage comprises: making the optical axis of a green femtosecond laser beam coincide 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, and converting the two green femtosecond sub-laser beams into two green femtosecond focused laser beam arrays which are mirror-symmetrically distributed on both sides of the CFRP substrate, the multiple green femtosecond focused laser beams contained in the two green femtosecond focused laser beam arrays being one-to-one corresponding and coaxially arranged, and the multiple green femtosecond focused laser beams being one-to-one corresponding to the multiple preformed holes contained in the preformed hole array, and the two green femtosecond focused laser beam arrays being used to machine the preformed hole array into a target hole array, the target hole contained in the target hole array being a micro-hole with a large depth-diameter ratio. The pulse width of the green nanosecond laser beam is 30ns-120ns, and the wavelength is 532nm; the pulse width of the green femtosecond laser beam is 180ns-240ns, and the wavelength is 517nm.

[0009] Compared with the prior art, the advantages of the present application include: The machining system and machining method for a large-depth-diameter ratio array hole of CFRP provided by the embodiment of the present application quickly form a preformed hole array on the CFRP substrate by using a green nanosecond laser with strong heat effect, provide a chip removal channel for subsequent green femtosecond laser fine machining, reduce the generation of plasma to improve the energy utilization rate of the green femtosecond laser, and eliminate the thermal damage left by the green nanosecond laser by using the green femtosecond laser, thereby improving the hole machining quality.

[0010] The machining system and machining method for CFRP large-depth-diameter array holes provided by the embodiment of the present application greatly improve the hole making efficiency and hole group positioning accuracy of CFRP large-depth-diameter micro holes, greatly reduce or eliminate the micro hole taper and improve the micro hole roundness, and effectively reduce the thermal damage during CFRP drilling.

[0011] The machining system and machining method for CFRP large-depth-diameter array holes provided by the embodiment of the present application greatly improve the hole making efficiency and hole group positioning accuracy of CFRP large-depth-diameter micro holes, greatly reduce or eliminate the micro hole taper and improve the micro hole roundness, and effectively reduce the thermal damage during CFRP drilling. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural schematic diagram of a multi-pulse-width laser composite machining system for CFRP large-depth-diameter array holes provided in a typical embodiment of the present application; Figure 2a 、 Figure 2b 、 Figure 2c are light beam shaping effect diagrams of micro lens arrays of different structures; Figure 3 is a structural schematic diagram of a motion adjustment module in a multi-pulse-width laser composite machining system for CFRP large-depth-diameter array holes provided in a typical embodiment of the present application; Figure 4a is a schematic diagram of an impact hole formed by directly irradiating a spot of a focused laser beam array on a CFRP substrate to be machined; Figure 4b 、 Figure 4c 、 Figure 4d are schematic diagrams of different hole making motion trajectories realized by linkage of an X-axis linear module and a Z-axis linear module; Figure 5a 、 Figure 5b 、 Figure 5c are state schematic diagrams of double positive defocus, double in-focus and focal point compensation of the first focused laser beam array and the second focused laser beam array; Figure 6a 、 Figure 6b 、 Figure 6c 、 Figure 6d are schematic diagrams of different relative motion trajectories of space beams formed by linkage of XYZ three axes; Figure 7a 、 Figure 7b 、 Figure 7c 、 Figure 7dThe hole forming effect diagram of different configuration forms of the array of focused laser beams. DETAILED DESCRIPTION

[0013] In view of the deficiencies in the prior art, the present inventors have long studied and practiced to come up with the technical solution of the present application. The technical solution, its implementation process and principles will be further explained as follows.

[0014] A first aspect of the embodiment of the present application provides a multi-pulse-width laser composite machining system for CFRP large-depth-diameter-ratio array holes, which comprises: a multi-pulse-width laser generation module for outputting two initial laser beams, the two initial laser beams being different in pulse width and wavelength and the same in beam color; a beam shaping module for adjusting the optical axes of the two initial laser beams to be coaxial, shaping the initial laser beams, adjusting the polarization states of the initial laser beams, modulating the initial laser beams into two sub-laser beams, adjusting the energy distribution of the two sub-laser beams, and converting the two sub-laser beams into two arrays of focused laser beams which are mirror-symmetrically distributed on both sides of a CFRP substrate to be machined, the multiple focused laser beams included in the two arrays of focused laser beams being one-to-one corresponding and coaxially arranged, and the wave vector directions of the focused laser beams included in the two arrays of focused laser beams being opposite; wherein one of the two initial laser beams cooperates with the beam shaping module to form a preformed hole array on the CFRP substrate to be machined, and the other cooperates with the beam shaping module to machine the preformed hole array into a target hole array, the target holes included in the target hole array being micro-holes with large depth-diameter ratio.

[0015] Further, the multi-pulse-width laser generation module comprises two laser sources, and the two laser sources respectively provide the two initial laser beams.

[0016] Further, the two initial laser beams are green nanosecond laser beams and green femtosecond laser beams, the green nanosecond laser beam cooperates with the beam shaping module to machine the preformed hole array, and the green femtosecond laser beam cooperates with the beam shaping module to machine the preformed hole array into the target hole array. wherein the pulse width of the green nanosecond laser beam is 30ns-120ns, and the wavelength is 532nm; the pulse width of the green femtosecond laser beam is 180ns-240ns, and the wavelength is 517nm.

[0017] Further, the beam shaping module comprises: a beam combining module for adjusting the two initial laser beams to propagate along the same optical path and keep the same optical axis; a collimation and beam expansion module for adjusting the divergence angle and beam diameter of the initial laser beams; a polarization state adjusting module, configured to adjust the polarization state of the initial laser beam from linear polarization to circular polarization; a beam splitting and energy control module, configured 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 the two sides of the CFRP substrate to be processed while keeping coaxial and opposite wave vector directions; an array conversion module, configured to convert the two sub laser beams into two focused laser beam arrays respectively; The beam combining module, the collimating and expanding beam module, the polarization state adjusting module, and the beam splitting and energy control module are sequentially arranged along the wave vector direction of the initial laser beam, and the beam splitting and energy control module and the array conversion module are sequentially arranged along the wave vector direction of the sub laser beam.

[0018] Further, the beam combining module comprises a first dichroic mirror and a first mirror, the collimating and expanding beam module comprises an expanding beam mirror and a collimating mirror, the polarization state adjusting module comprises a 1 / 4 plate, the beam splitting and energy control module comprises a beam splitter prism and a mirror group, and the array conversion module comprises a first microlens array and a second microlens array. The first dichroic mirror, the expanding beam mirror, the collimating mirror, the 1 / 4 plate, and the beam splitter prism are coaxial on a same common optical axis. One of the two initial laser beams directly transmits through the first dichroic mirror to the expanding beam mirror, and the other directly transmits to the first mirror and then is reflected by the first mirror and the first dichroic mirror to the expanding beam mirror, the beam splitter prism is configured to split the initial laser beam into a front sub laser beam and a rear sub laser beam, the mirror group is configured 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 configured to focus the front sub laser beam to form a first focused laser beam array, and the second microlens array is configured to focus the rear sub laser beam to form a second focused laser beam array.

[0019] Further, the mirror group comprises a second mirror, a third mirror, and a fourth mirror, the fourth mirror is the last mirror in the mirror group, and the optical axis of the rear sub laser beam reflected by the fourth mirror coincides with the common optical axis.

[0020] Further, the beam splitting ratio of the beam splitter prism is 70:30, 60:40, 50:50, 40:60, or 30:70.

[0021] Further, the beam splitting and energy control module further comprises a first variable aperture and a second variable aperture, the first variable aperture is located between the beam splitter prism and the first microlens array, the second variable aperture is located between the last mirror of the mirror group and the second microlens array, the optical axis of the first variable aperture and the second variable aperture coincides with the common optical axis.

[0022] In a more typical embodiment, the multi-pulse-width laser compound machining system for CFRP large depth-diameter array holes further comprises: a motion modulation module for driving the focused laser beam array to produce relative motion with the CFRP substrate to be machined, the relative motion comprising 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.

[0023] Further, the motion modulation module comprises an X-axis linear module, a Z-axis linear module and a Y-axis linear module, the Y-axis linear module comprises 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, 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 machined to move along the X-axis, and the Z-axis linear module is used to drive the CFRP substrate to be machined to move along the Z-axis.

[0024] Further, the X-axis linear module is further transmission matched 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 machined to move in the XZ plane of the three-dimensional coordinate system and form a specified hole cutting track.

[0025] In a more typical embodiment, the multi-pulse-width laser compound machining system for CFRP large depth-diameter array holes further comprises a monitoring module for positioning a machining area and observing the topography of the machining area in real time.

[0026] The second aspect of the embodiment of the present application provides a machining method for CFRP large depth-diameter array holes, which comprises sequentially performing a first laser machining stage and a second laser machining stage. The first laser processing stage comprises: modulating the 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 which 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 are one-to-one corresponding and coaxially arranged, and the two green nanosecond focused laser beam arrays are used to process a preformed hole array on the CFRP substrate, the preformed holes contained in the preformed hole array penetrate through the CFRP substrate, and the preformed holes serve as the chip removal channels in the second laser processing stage; The second laser processing stage comprises: 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, and converting the two green femtosecond sub-laser beams into two green femtosecond focused laser beam arrays which are mirror-symmetrically distributed on both sides of the CFRP substrate, the multiple green femtosecond focused laser beams contained in the two green femtosecond focused laser beam arrays are one-to-one corresponding and coaxially arranged, and the multiple green femtosecond focused laser beams correspond to the multiple preformed holes contained in the preformed hole array one-to-one, and the two green femtosecond focused laser beam arrays are used to process the preformed hole array into a target hole array, the target holes contained in the target hole array are micro-holes with a large depth-diameter ratio; The pulse width of the green nanosecond laser beam is 30ns-120ns, and the wavelength is 532nm; the pulse width of the green femtosecond laser beam is 180ns-240ns, and the wavelength is 517nm.

[0027] Further, the process of converting the green nanosecond laser beam into two green nanosecond sub-laser beams comprises: First, the green nanosecond laser beam is expanded and collimated in sequence, and then the polarization state of the green nanosecond laser beam is converted from linear polarization to circular polarization, and then the green nanosecond laser beam is divided into two green nanosecond sub-laser beams; The process of converting the green femtosecond laser beam into two green femtosecond sub-laser beams comprises: First, the green femtosecond laser beam is expanded and collimated in sequence, and then the polarization state of the green femtosecond laser beam is converted from linear polarization to circular polarization, and then the green femtosecond laser beam is divided into two green femtosecond sub-laser beams.

[0028] Further, the energy ratio of the two green nanosecond sub-laser beams or the two green femtosecond sub-laser beams is 70:30, 60:40, 50:50, 40:60 or 30:70.

[0029] In a more typical embodiment, the method for processing the large-depth-to-diameter array hole of CFRP further comprises: driving the green nanosecond focused laser beam array or the green femtosecond focused laser beam array to have relative motion with the CFRP substrate, the relative motion comprising linear motion along at least one of the X-axis, the Y-axis and the 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.

[0030] Further, the method for processing the large-depth-to-diameter array hole of CFRP specifically comprises: driving the two green nanosecond focused laser beam arrays or the two green femtosecond focused laser beam arrays to move along the Y-axis to adjust the focal point positions of the green nanosecond focused laser beam arrays or the green femtosecond focused laser beam arrays, so as to realize at least one of the double positive defocusing processing, the double in-focus processing and the double negative defocusing processing of the CFRP substrate.

[0031] Further, the method for processing the large-depth-to-diameter array hole of CFRP specifically comprises: driving the two green nanosecond focused laser beam arrays or the two green femtosecond focused laser beam arrays to move along the Y-axis to adjust the focal point positions of the green nanosecond focused laser beam arrays or the green femtosecond focused laser beam arrays, so as to realize at least one of the double positive defocusing processing, the double in-focus processing and the double negative defocusing processing of the CFRP substrate.

[0032] Further, the method for processing the large-depth-to-diameter array hole of CFRP specifically comprises: driving the CFRP substrate to move in the XZ plane of the three-dimensional coordinate system and form a specified hole cutting track, the specified hole cutting track comprising at least one of a circular track, a concentric circular track and a spiral circular track.

[0033] Further, the method for processing the large-depth-to-diameter array hole of CFRP is implemented based on the multi-pulse-width laser composite processing system for the large-depth-to-diameter array hole of CFRP.

[0034] The technical scheme, implementation process and principles thereof will be further explained in the following with reference to the accompanying drawings. Unless specifically stated, the laser, the mirror, the beam splitter, the variable diaphragm, the dichroic mirror, the shutter, the lens, the CCD camera and other optical components involved in the present application can be obtained by market purchase or known processes in the art, and their specific product models and structures are not limited herein. The linear module, the water cooling machine and the industrial computer involved in the present application are also known in the art, and the numerical control program and the circuit structure thereof are also known in the art, which can be obtained by market purchase or customization.

[0035] The micro-holes in the present application have a depth-to-diameter ratio of 5-20 and a diameter of 0.5-5 mm.

[0036] The common optical axis mentioned in the present application refers to the common optical axis of the first dichroic mirror 8, the beam expander 10, the collimator 11, the 1 / 4 wave plate 12, and the beam splitter prism 18.

[0037] In a more typical embodiment, a multi-pulse-width laser composite processing system for CFRP large-depth-diameter array holes includes a multi-pulse-width laser generating module, a beam shaping module, a motion modulation module, and a monitoring module. The multi-pulse-width laser generating module and the beam shaping module are the core functional modules of the multi-pulse-width laser composite processing system. The multi-pulse-width laser generating module and the beam shaping module cooperate to form a target hole array on the CFRP substrate to be processed. The motion modulation module is mainly used to cooperate with the multi-pulse-width laser generating module and the beam shaping module to optimize the processing of the target hole array. The monitoring module is mainly used for positioning the processing area and observing the morphology of the processing area in real time.

[0038] Specifically, please refer to Figure 1 The multi-pulse-width laser generating 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 aforementioned laser sources). The green nanosecond laser 1 cooperates with the beam shaping module to process a preformed hole array. The green femtosecond laser 4 cooperates with the beam shaping module to process the preformed hole array into a target hole array. The green nanosecond laser beam provided by the green nanosecond laser 1 has a pulse width of 30 ns to 120 ns and a wavelength of 532 nm. The green femtosecond laser beam provided by the green femtosecond laser 4 has a pulse width of 180 ns to 240 ns and a wavelength of 517 nm.

[0039] As a preferred solution, the multi-pulse-width laser generating module can further include a first water chiller 2 and a second water chiller 5. The first water chiller 2 is used to maintain the use temperature of the green nanosecond laser 1, and the second water chiller 5 is used to maintain the use 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 heat-conducting cooperations through structures / methods known in the art. Of course, the first water chiller 2 and the second water chiller 5 can also be replaced by other temperature-regulating devices, such as semiconductor refrigerators, etc.

[0040] Specifically, the green nanosecond laser 1 and the green femtosecond laser 4 are further connected to an industrial computer 9. The industrial computer (which is a control mechanism known in the art and can be obtained by purchase or customization, and is not limited here) 9 controls the working state and working parameters of the green nanosecond laser 1 and the green femtosecond laser 4 through control software (which can be obtained by purchase, and is not limited here).

[0041] Specifically, the light beam shaping module includes a first mirror 7, a first dichroic mirror 8, a beam expander 10, a collimator 11, a 1 / 4 wave plate 12, a beam splitter prism 18, a first variable aperture (which can be referred to as a front variable aperture) 22, a first microlens array (which can be referred to as a front microlens array) 24, a second mirror 34, a third mirror 33, a fourth mirror 32, a second variable aperture (which can be referred to as a rear variable aperture) 30, and a second microlens array (which can be referred to as a rear microlens array) 28. The first dichroic mirror 8, the beam expander 10, the collimator 11, the 1 / 4 wave plate 12, the beam splitter prism 18, the first variable aperture 22, the first microlens array 24, the second microlens array 28, and the second variable aperture 30 are sequentially and spacedly arranged, and the first dichroic mirror 8, the beam expander 10, the collimator 11, the 1 / 4 wave plate 12, the beam splitter prism 18, the first variable aperture 22, and the second variable aperture 30 are coaxial on a same common optical axis.

[0042] It should be noted that, as known to those skilled in the art, the light beam shaping module of course also includes a support structure, and the optical elements in the light beam shaping module are mounted on the support structure, which can realize positioning and attitude adjustment of the optical elements in the light beam shaping module, and details are not described herein.

[0043] Specifically, a machining space is arranged between the first microlens array 24 and the second microlens array 28, and the CFRP substrate (for example, a CFRP plate) 26 to be machined is located in the machining space between the first microlens array 24 and the second microlens array 28.

[0044] Specifically, the optical axis of the green nanosecond laser is coaxial with the common optical axis (i.e., the aforementioned common optical axis) of the light beam shaping module, and the green nanosecond laser beam 3 excited and output by the green nanosecond laser directly transmits through the first dichroic mirror 8 to be incident on the beam expander 10. The green femtosecond laser beam 6 excited and output by the green femtosecond laser directly enters the first mirror 7 and is sequentially reflected by the first mirror 7 and the first dichroic mirror 8 to be incident on the beam expander 10. Of course, the optical axis of the green femtosecond laser can also be coaxial with the common optical axis of the light beam shaping module, and the green femtosecond laser beam 6 excited and output by the green femtosecond laser directly transmits through the first dichroic mirror 8 to be incident on the beam expander 10. The green nanosecond laser beam 3 excited and output by the green nanosecond laser directly enters the first mirror 7 and is sequentially reflected by the first mirror 7 and the first dichroic mirror 8 to be 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.

[0045] The process of the initial laser beam (including the green nanosecond laser beam 3 and the green femtosecond laser beam 6) cooperating with the light beam shaping module to realize array hole machining is specifically introduced as follows: The initial nanosecond laser beam 3 emitted by the green nanosecond laser 1 passes through the first dichroic mirror 8 and enters the beam expander 10. The initial femtosecond laser beam 6 emitted by the green femtosecond laser 4 passes through the first mirror 7, the first dichroic mirror 8, and the beam expander 10. The initial femtosecond laser beam 6 and the initial nanosecond laser beam 3 are coaxial by adjusting the first mirror 7. It should be noted that the method / technology of adjusting the two laser beams to be coaxial by using a mirror is known in the art, and will not be specifically limited here.

[0046] The green nanosecond laser beam 3 and the green femtosecond laser beam 6 are collectively referred to as initial laser beams.

[0047] The initial laser beams pass through the center of the beam expander 10 to expand the beam diameter and reduce the divergence angle (the specific modulation results are selected according to the parameters of the beam expander 10 and specific requirements, and will not be specifically limited here), and then pass through the collimator 11 to become a collimated beam that passes through the 1 / 4 plate 12. The 1 / 4 plate 12 converts the original linearly polarized laser into 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 aforementioned sub-beams); The front sub-laser beam 20 passes through the first variable aperture 22 to adjust the beam diameter to match the first microlens array 24 (the specific matching relationship is known in the art, and will not be specifically limited here). After passing through the first microlens array 24, it is reshaped into a first focused laser beam array (also referred to as a front focused laser beam array) 25. The rear sub-laser beam 19 is reflected and adjusted to be coaxial with the front sub-laser beam 20 by the second mirror 34, the third mirror 33, and the fourth mirror 32 in turn. Then, the beam diameter is adjusted to match the second microlens array 28 by the second variable aperture 30. After passing through the second microlens array 28, it is reshaped into a second focused laser beam array 27 (also referred to as a rear focused laser beam array). The first focused laser beam array 25 and the second focused laser beam array 27 are mirror images on both sides of the CFRP substrate 26 to be processed. The number, shape, and array spacing of the focused laser beams included 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 regions from both sides of the CFRP substrate 26 to be processed.

[0048] Specifically, the 1 / 4 glass 12 converts linearly polarized laser into circularly polarized laser to eliminate the direction dependence of the beam and the surface absorption rate of the hole wall material, thereby improving the roundness and taper of the drilled hole. The variable diaphragm can adjust the diameter of the light beam to adapt to the microlens array. Specifically, the light splitting prism 18 can allocate the energy proportion of the front and rear sub-laser beams 19 and 20, and the light splitting energy proportion is one of 70 / 30, 60 / 40, 50 / 50, 40 / 60, 30 / 70, which is specifically replaced according to the actual processing state.

[0049] Specifically, the sub-unit shapes, sizes, numbers, and pitches of the first and second microlens arrays 24 and 28 are the same, and these structural parameters can be customized according to actual processing needs. Specifically, the shapes of the sub-units of the first and second microlens arrays 24 and 28 are one of rectangular, square, circular, and polygonal. Figure 2a 、 Figure 2b 、 Figure 2c The beam shaping effects of microlens arrays with different structures are shown respectively. In the specific application process, the sub-unit configuration form of the microlens array can be customized according to the efficiency requirements of the actual CFRP processing and the size of the hole group pitch, so as to adjust the focused laser beam array with different configuration forms (pitch, number, etc.) and form different array spot distributions on the CFRP substrate 26 to be processed.

[0050] Specifically, please refer to Figure 1 , the optical module can further include a first shutter 21 and a second shutter 31. The first shutter 21 is arranged between the light splitting prism 18 and the first variable diaphragm 22, and the second shutter 31 is arranged between the fourth mirror 32 and the second variable diaphragm 30. The first shutter 21 and the second shutter 31 can control the on-off of the front and rear sub-laser beams 20 and 19, respectively.

[0051] Specifically, please refer to Figure 1 , the monitoring module includes an illumination light source 13, a CCD camera 15, an optical lens 16, and a second dichroic mirror 16. The second dichroic mirror 16 is arranged between the 1 / 4 glass 12 and the light splitting prism 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 and the illumination light source 13 are coaxial. The visible light beam 14 provided by the illumination light source 13 is reflected by the optical lens 16 and the second dichroic mirror 17, and is coaxial with the initial laser beam in the beam shaping module. The visible light beam 14 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. In combination 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 micro-holes can be observed after processing. It should be noted that the structure and method of the monitoring module for realizing real-time monitoring are known in the art, and are not limited here.

[0052] Specifically, the motion modulation module is specifically configured to drive the focused laser beam array to have relative motion with the CFRP substrate to be processed, and the relative motion includes linear motion along at least one of an X axis, a Y axis and a Z axis of a three-dimensional coordinate system, wherein the Y axis is parallel to the common optical axis. Through the motion modulation module, the focal point compensation of the focused laser beam array and the formation of a specified hole cutting track can be realized, so as to effectively eliminate the hole taper formed by processing.

[0053] Specifically, please refer to Figure 1 and Figure 3 together, the 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, the Z-axis linear module 38 and the Y-axis linear module 36 are connected with 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 configured to drive the first microlens array 24 to move along the Y axis. The Y2-axis linear module is configured to correspondingly drive the second microlens array 28 to move along the Y axis. The X-axis linear module 37 is configured to drive the CFRP substrate 26 to be processed to move along the X axis. The Z-axis linear module 38 is configured to drive the CFRP substrate 26 to be processed to move along the Z axis. Specifically, the motion controller 35 is configured 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 with the working condition machine 9. It should be noted that the hardware and software parts of the motion controller 35 can be obtained by purchase, and are not limited herein.

[0054] As a more preferred embodiment, the X-axis linear module 37 is further in transmission cooperation 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 track. Specifically, the Y-axis linear module 36 is horizontally installed on a bottom end platform (the bottom end platform is part of a support table of the whole multi-pulse-width laser composite processing system, and the specific structure of the support table and the bottom end platform is not limited, and the main function is to support the system). Specifically, the Y-axis linear module 36 can be a double slide table 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 a single slide table linear module. The structure and working principle of the slide table linear module are known in the art, and are not described herein.

[0055] As a typical embodiment, the Y-axis linear module 36 has two independently linearly movable slides, namely Y1 slide and Y2 slide, the first microlens array 24 is fixedly installed on the Y1 slide adapter plate 23, the Y1 slide adapter plate 23 is fixedly installed on the Y1 slide, the second microlens array 28 is fixedly installed on the Y2 slide adapter plate 29, and the Y2 slide adapter plate 29 is fixedly installed on the Y2 slide; the Z-axis linear module 38 is fixedly installed on the moving part (for example, slide) of the X-axis linear module 37, and the CFRP substrate 26 to be processed is fixed on the breadboard 39 (for example, the CFRP substrate 26 to be processed can be fixed on the breadboard 39 through a clamping plate cooperating with a bolt, and the installation position of the CFRP substrate 26 to be processed can be adjusted), and the breadboard 39 is fixed on the moving part (for example, slide) of the Z-axis linear module 38.

[0056] In a more specific embodiment, a method for processing a large-depth-to-diameter ratio array hole of CFRP is implemented based on the foregoing laser composite processing system for processing a large-depth-to-diameter ratio array hole of CFRP, and the method can specifically include the following processes: (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 adjusting the green nanosecond laser beam 3 output by the green nanosecond laser 1 to match the first microlens array 24 through the beam expander 10, the collimating mirror 11, the 1 / 4 glass 12, the light splitting prism 18, the second reflecting mirror 34, the third reflecting mirror 33, the fourth reflecting mirror 32, and the second variable aperture 30, and then passing through the first microlens array 24 to be shaped into a front focusing nanosecond laser beam array, and passing through the second microlens array 28 to be shaped into a rear focusing nanosecond laser beam array, wherein the front focusing nanosecond laser beam array and the rear focusing nanosecond laser beam array are mirror images on both sides of the CFRP substrate 26 to be processed, and the front focusing nanosecond laser beam array and the rear focusing nanosecond laser beam array are synchronized on the CFRP substrate 26 to be processed from both sides of the CFRP substrate 26 to be processed to quickly ablate materials on the CFRP substrate 26 to be processed to form a prefabricated hole array, and the prefabricated hole array contains prefabricated holes that penetrate the CFRP substrate 26 to be processed.

[0057] (2) the second laser processing stage comprises: 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 propagates along the same light path as the green nanosecond laser beam 3 after being reflected by the first mirror 7 and the first dichroic mirror 8, and forms 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 preformed hole, and the preformed hole array is further processed to form the target hole array. It should be noted that based on the preformed hole formed in the first laser processing stage, the material volume removed in the second laser processing stage is reduced, which greatly shortens the femtosecond laser processing time, and at the same time, the femtosecond laser processing can also improve the processing precision and surface quality.

[0058] The preformed hole formed by processing can be used as a chip removal channel in the subsequent second laser processing stage, which not only can realize the discharge of debris in the second laser processing stage, but also can reduce the shielding and absorption of laser energy by debris and plasma, improve the utilization rate of laser energy, and improve the processing precision of the target hole.

[0059] For example, the CFRP substrate 26 to be processed can be suitable for an aero-engine composite material component.

[0060] Specifically, the energy ratio of the pre-sub-laser beam and the post-sub-laser beam is 70:30, 60:40, 50:50, 40:60, 30:70, and different splitting energy ratios can obtain micro-holes with different tapers, for example, when the energy ratio of the pre-sub-laser beam and the post-sub-laser beam formed by the green nanosecond laser beam or the green femtosecond laser beam is 70:30 or 60:40, the micro-hole obtained by processing is a positive taper hole; when the energy ratio of the pre-sub-laser beam and the post-sub-laser beam is 50:50, the micro-hole obtained by processing is a non-taper hole; when the energy ratio of the pre-sub-laser beam and the post-sub-laser beam is 40:60 or 30:70, the micro-hole obtained by processing is an inverted taper hole. Of course, the present application can process special-shaped holes with any taper by reasonably configuring the energy ratio and the scanning track.

[0061] In a more typical embodiment, in the first laser processing stage and the second laser processing stage, the CFRP substrate 26 to be processed is moved relative to the focused laser beam array to form a specific hole cutting track through the linkage control of the X-axis linear module and the Z-axis linear module, as shown in Figure 4b 、 Figure 4c 、 Figure 4d , Figure 4b 、 Figure 4c 、 Figure 4d , respectively, different hole making motion track schematic diagrams realized by the linkage 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 in Figure 4aAs 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 ).

[0062] 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.

[0063] 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 6cFor the planar helical circular layered feed track, the planar helical circular layered feed track is suitable for micro-hole machining with large diameter and large depth-diameter ratio greater than 10 and less than 20, but the laser thermal effect is significant, which is easy to cause additional thermal damage, so the planar helical circular layered feed track is only suitable for the pre-hole machining stage. Figure 6d For the spatial helical circular feed track, the spatial helical circular feed track is suitable for rapid forming process of micro-hole with large depth-diameter ratio, and the heat affected zone is small, but the fast feed is easy to cause natural positive taper formation, which can be used for low-speed feed hole repair based on the positive tapered hole formed by machining, but due to the complexity of the spatial spiral, this track is only suitable for the machining of non-tapered holes, and is not suitable for the machining of special-shaped holes with complex features.

[0064] Specifically, the X-axis linear module 37, the Z-axis linear module 38 and the Y-axis linear module 36 are linked to form a specific motion track, which can realize the machining of micro-holes of any shape. For example, the XZ-axis linkage (X-axis linear module 37 and Z-axis linear module 38 linkage) is used to form an outer circular track, and when a layer of material is removed by using the first focused laser beam array 25 and the second focused laser beam array 27, the Y-axis linear module 36 is used to shorten the distance between the first microlens array 24, the second microlens array 28 and the CFRP substrate 26 to be machined to compensate for the focal point. This method is suitable for relatively shallow micro-hole machining, because the intermediate material is not removed, and only after the entire cylindrical intermediate material is cut off, a through hole will be formed. When using concentric circle and helical circle track to cut holes, micro-holes with large depth-diameter ratio can be machined, and the formation process of the micro-holes is similar to the connection process of two blind holes. Specifically, the linkage motion can also realize the spatial helical circular track to further improve the hole cutting efficiency. Generally, green nanosecond laser beam is used to punch a pre-hole, and then green femtosecond laser beam is used to cut the hole to obtain higher machining efficiency and surface quality.

[0065] Figure 7a 、 Figure 7b 、 Figure 7c 、 Figure 7d The hole forming effect diagrams of different configurations of focused laser beam arrays are shown respectively. Specifically, the laser beam array can significantly improve the hole forming efficiency. Even if focal compensation is used, the unidirectional focused laser beam array (i.e. unidirectional array beam) is easy to be blocked at the edge of the hole entrance when dealing with micro-holes with large depth-diameter ratio, which leads to the retention of taper and the formation of positive taper array holes, as shown in Figure 7a The bidirectional focused laser beam array (i.e. bidirectional array beam) can ensure the same shape and size of the entrance and exit, but in the case of no focal compensation, the energy utilization rate near the hole is always higher than that inside the hole, which will lead to taper even if the hole cutting track is used, forming a symmetrical taper array hole, as shown in Figure 7bAs shown. When the bidirectional focusing laser beam array (i.e. bidirectional array beam) is matched with bidirectional focal point compensation, the entry and exit shapes and sizes can be kept consistent while ensuring high hole making efficiency, and the array holes without taper can be formed, such as Figure 7c As shown. When the green nanosecond laser beam is used to form a preformed hole to provide a chip removal channel, and the green femtosecond laser beam is used to repair the hole to eliminate thermal defects, high-efficiency and high-precision machining of CFRP large-depth-diameter ratio array holes can be realized, such as Figure 7d As shown.

[0066] The machining system and method for CFRP large-depth-diameter ratio array holes provided by the embodiment of the present application can quickly form a preformed hole array on the CFRP substrate by using a green nanosecond laser with strong thermal effect. Based on the strong thermal effect of the green nanosecond laser, a preformed hole can be quickly formed on the CFRP substrate, most of the hole material volume can be removed, the material removal rate can be significantly improved, and a heat affected zone is left. The green femtosecond laser can eliminate the heat affected zone in situ and repair the hole type to obtain a high-quality micro-hole surface structure, thereby realizing high-efficiency and high-quality comprehensive hole making.

[0067] Further, the preformed hole quickly formed on the CFRP substrate by the green nanosecond laser also provides a chip removal channel for subsequent green femtosecond laser fine repair of the hole type, so that the ablated material is more easily discharged outside the hole, and the adhesion of the material in the hole opening and hole wall during the formation of the target hole is reduced. In addition, even if focal point compensation is used, due to the backflow of material vapor during hole making, plasma is easily formed in the hole entrance area. The material vapor and plasma will absorb and shield the laser energy. In addition, the plasma will also cause the resin to be over-ablated. The preformed hole can effectively reduce the vapor backflow, thereby reducing the formation of plasma, improving the energy utilization rate of the green femtosecond laser, and reducing the thermal ablation of the plasma material, and improving the precision control effect of hole type machining.

[0068] The machining system and method for CFRP large-depth-diameter ratio array holes provided by the embodiment of the present application can keep the size consistency of the micro-hole entry and exit by using coaxial and symmetrically distributed focused laser beam arrays, and the energy ratio of the front and rear focused laser beam arrays can be changed by using a beam splitting prism to realize the machining of micro-holes with different characteristics (mainly taper characteristics). At the same time, through the motion modulation module, complex beam relative motion trajectories can be realized, and the focal points of the front and rear beams can be compensated synchronously or independently, thereby realizing the machining of special-shaped holes with any taper, and further improving the roundness of the micro-holes in combination with circularly polarized light. Specifically, even if a single focal point is compensated, the deeper the hole depth, the more dispersed the energy at the bottom, resulting in nonlinear laser energy attenuation when machining large depth-diameter ratio micro-holes, thus naturally forming a positive taper hole, leading to a decline in machining precision. Double focal control can halve the focal point movement distance compared to single focal control, improving laser drilling precision. In addition, according to the requirements of hole characteristics (positive taper, reverse taper, no taper, special-shaped hole), the laser drilling process is upgraded to a powerful process means that can actively and accurately control the three-dimensional cavity structure (the shape in the depth direction of the hole).

[0069] The embodiments of the present application provide a kind of related technical solutions of multi-pulse width laser composite machining system and method for CFRP large depth-diameter ratio array hole, not limit to it, the ordinary skilled in the art can still modify or equivalent replace the technical features of the technical solutions of the present application, and these modifications or replacements should also be regarded as the protection scope of the present application.The essence of the corresponding technical solution does not deviate from the scope of the technical solutions of the embodiments of the present application.

[0070] It should be understood that the above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and cannot limit the protection scope of the present application.Any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A multi-pulse laser composite processing system for CFRP large aspect ratio array 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 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. 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 180ns to 240ns and a wavelength of 517nm.

3. The multi-pulse laser composite processing system for CFRP large aspect 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-pulse laser composite processing system for CFRP large aspect 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-pulse laser composite processing system for CFRP large aspect 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 aspect ratio array holes for CFRP, characterized in that, include: The first laser processing stage and the second laser processing stage are performed sequentially. 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. 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. 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.

8. The method for processing large aspect ratio array holes for CFRP according to claim 7, characterized in that, 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 for machining large aspect ratio array holes for CFRP according to claim 7, characterized in that, 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.

10. The method for processing large aspect ratio array holes for CFRP according to claim 7, 8, or 9, characterized in that: The method for fabricating large aspect ratio array holes for CFRP is implemented based on the multi-pulse laser composite processing system for large aspect ratio array holes for CFRP as described in any one of claims 1-6.

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