CFRP high-quality laser drilling method cooperatively assisted by hydrochloric acid and zinc plate

Abstract

The invention relates to a CFRP high-quality laser drilling method cooperatively assisted by hydrochloric acid and a zinc plate, and belongs to the technical field of composite material processing. The method comprises the following steps: S1, pretreating the surface of a sample; s2, mounting a sample and accurately positioning the sample; s3, planning a processing path and setting an aperture; s4, determining process parameters; s5, drilling is carried out according to set parameters; and S6, after machining, the heat affected zone, the roundness, the taper and the inner wall roughness of the through hole are measured. According to the method, the hydrochloric acid solution is used for strengthening heat dissipation and promoting chip discharge, meanwhile, the zinc plate is used for absorbing residual heat and regulating and controlling the appearance of an outlet through the interaction between the zinc plate and laser, and therefore the quality of the through hole is remarkably improved, the taper of the through hole is as low as 0.029, the roughness of the inner wall is only 1.097 m, the roundness of an inlet and the roundness of an outlet are as high as 99.4% and 98.1% respectively, and no thermal damage exists in an outlet area. The process is efficient and stable, high-quality through hole preparation of an advanced composite material can be achieved, the application requirement of the high-end equipment field is met, and good engineering application value is achieved.

Description

Technical Field

[0001] This invention relates to a high-quality laser drilling method for CFRP (composite material reinforced plastic) assisted by hydrochloric acid and zinc plate, belonging to the field of composite material processing technology. This invention enables the fabrication of high-quality through-holes in CFRP, facilitating its practical application in aerospace, high-end equipment, and other fields. Background Technology

[0002] Against the backdrop of an increasingly severe global energy crisis, lightweighting has become a core strategy for sustainable manufacturing. CFRP, with its superior mechanical properties, is indispensable in lightweight structures for high-end equipment such as aerospace equipment. The quality of high-precision through-holes directly affects the reliability of component connections and service life.

[0003] However, the inherent anisotropy, heterogeneity, and significant differences in thermophysical properties between components of CFRP pose serious challenges to high-quality hole fabrication. In recent years, various technologies such as mechanical drilling, electrical discharge machining (EDM), abrasive waterjet drilling, and ultrasonic vibration-assisted drilling have been used for CFRP through-hole machining. However, these methods are often limited by low processing efficiency, insufficient dimensional accuracy, or unavoidable matrix damage, making it difficult to meet the stringent quality requirements of high-performance components. In contrast, laser processing, with its high efficiency and good process controllability, has become a highly promising alternative. Nevertheless, laser drilling still has several inherent drawbacks, such as a large heat-affected zone, poor exit roundness, and significant hole taper, making it difficult to meet the stringent precision requirements of high-performance components. Furthermore, the low efficiency of debris removal during processing easily causes laser refraction and scattering, severely degrading the surface quality of the hole wall. Therefore, developing a laser drilling method to improve the quality of CFRP through-holes has significant theoretical and engineering application value. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a high-quality laser drilling method for CFRP (CFRP) synergistically assisted by hydrochloric acid and zinc plate. This method employs a fluid-assisted laser-induced plasma processing mechanism, which is significantly different from traditional laser drilling processes. In this method, the hydrochloric acid solution plays a triple synergistic role during processing: its chemical etching effect is enhanced under the high-temperature environment generated by the laser, thereby promoting material removal; its high heat absorption capacity effectively strengthens the overall heat dissipation of the processing area; and it can promptly handle the debris generated by ablation, maintaining the stability of the plasma state, thus ensuring uniform and efficient coupling between laser energy and the material. Simultaneously, it secures the material to the CFRP sample... The thermally conductive zinc plate on the sample outlet surface can actively regulate the dynamic behavior of laser-induced plasma, reshaping the morphology of the through-hole outlet while absorbing residual heat. By actively reconstructing and optimizing the laser-matter interaction environment at the inlet and outlet interfaces, this method can prepare high-quality through-holes on CFRP samples with a thickness of 2.2 mm. Specific performance indicators include: a through-hole taper as low as 0.029, an inner wall surface roughness of only 1.097 µm, and inlet and outlet roundness as high as 99.4% and 98.1%, respectively, with no thermal damage in the outlet area. Furthermore, this method is also applicable to processing high-quality through-holes on CFRP samples with more complex stacked structures.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A laser drilling method for improving the quality of through holes in carbon fiber reinforced resin matrix composites includes the following steps:

[0007] S1: Sample surface pretreatment;

[0008] The CFRP sample was ultrasonically cleaned for 20 minutes, then mechanically polished to obtain a high-quality surface, wiped with anhydrous ethanol, and left to stand at room temperature for 10 minutes to obtain a clean and dry CFRP surface.

[0009] S2: Install the sample and position it precisely;

[0010] Before drilling, the zinc plate is fastened to the back of the CFRP sample, and the hydrochloric acid solution constrained by the copper ring is placed on the upper surface of the CFRP. The whole thing is supported by four cylindrical supports and placed inside a container to prevent the hydrochloric acid solution from corroding the XY displacement platform. The XY displacement platform is operated by the control system to achieve precise alignment of the processing position.

[0011] S3: Plan the machining path and set the hole diameter;

[0012] The machining process uses a spiral scanning path and the outer diameter is set to 1mm.

[0013] S4: Determine process parameters;

[0014] Different laser powers were provided to compare the differences in drilling quality under different laser powers; other laser parameters remained constant; the pH value of the hydrochloric acid solution was 2; and the zinc plate thickness was fixed at 0.5 mm.

[0015] S5: Drilling is performed according to the set parameters;

[0016] After setting the laser processing parameters and fixing all the samples, start the drilling device to drill the CFRP sample, and turn off the drilling device after processing is completed.

[0017] S6: After machining, measure the heat-affected zone, roundness, taper, and inner wall roughness of the through hole;

[0018] After drilling, the morphology of the inlet, outlet and inner wall of the through hole was observed using a scanning electron microscope and a laser confocal microscope, and the size, roundness, taper and inner wall roughness of the heat-affected zone were quantitatively measured.

[0019] S7: Comparative verification;

[0020] Select another CFRP sample to be processed, repeat steps S3, S5 and S6, record the quantitative characterization results in step S6, and analyze the differences in hole quality between the traditional laser drilling method and the method of the present invention.

[0021] S8: Method applicability verification;

[0022] Select another CFRP sample with a more complex layered structure, repeat steps S1-S7, and compare and analyze the differences in hole quality between the traditional laser drilling method and the method of the present invention.

[0023] Furthermore, the surface roughness of the CFRP sample after mechanical polishing in step S1 is less than 90 nm.

[0024] Furthermore, the spiral scanning path described in step S3 is performed from the outside to the inside, with a scanning interval of 10µm.

[0025] Furthermore, the laser power mentioned in step S4 is 6-18W; the drilling quality is evaluated by quantitatively characterizing the size, roundness, taper, and inner wall roughness of the heat-affected zone of the through hole and observing the surface morphology; the other fixed laser parameters include: laser wavelength of 1064nm, frequency of 100kHz, scanning speed of 100mm / s, pulse width of 254fs, and laser energy distribution of Gaussian distribution.

[0026] Furthermore, the drilling device described in step S5 is a femtosecond laser processing system.

[0027] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0028] The CFRP drilling process provided by this invention has the advantages of simple operation and high efficiency. This method utilizes hydrochloric acid solution to enhance heat dissipation and promote debris removal. Simultaneously, residual heat is absorbed by a zinc plate, and the interaction between the zinc plate and the laser is used to control the exit morphology, thereby significantly improving the quality of the through-hole: the through-hole taper is as low as 0.029, the inner wall roughness is only 1.097µm, and the inlet and outlet roundness are as high as 99.4% and 98.1%, respectively, with no thermal damage in the exit area. Furthermore, the processing quality of the through-hole inner wall is also significantly improved, effectively eliminating processing defects such as micro-pits, uncut fibers, and fiber delamination. This method is also applicable to processing high-quality through-holes on CFRP samples with more complex laminated structures. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate the invention and are used to explain it, but do not constitute an undue limitation of the invention.

[0030] Figure 1 This is a schematic diagram of the processing system of the present invention.

[0031] Figure 2 The SEM images show the inlet and outlet morphologies of CFRP through holes fabricated using conventional laser drilling methods and the method of this invention, respectively, under a laser power of 18W.

[0032] Figure 3 The measurements of the heat-affected zone dimensions at the inlet and outlet of CFRP through holes produced by conventional laser drilling methods and the method of this invention, under laser power conditions of 6-18W.

[0033] Figure 4 The results show the roundness measurement of the inlet and outlet of CFRP through holes produced by the conventional laser drilling method and the method of the present invention under the condition of laser power of 6-18W.

[0034] Figure 5 The taper of the CFRP through hole produced by the conventional laser drilling method and the method of the present invention is compared under the condition of laser power of 6-18W.

[0035] Figure 6 The SEM images show the inner wall morphology of CFRP through holes prepared by conventional laser drilling and the method of the present invention under the condition of laser power of 18W.

[0036] Figure 7 The three-dimensional morphology of the inner wall of the CFRP through hole prepared by the conventional laser drilling method and the method of the present invention is shown under the condition of laser power of 18W.

[0037] Figure 8 The optical morphology of through holes made by conventional laser drilling and the method of the present invention are compared in CFRP specimens with more complex stacked structures. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0039] The method for high-quality laser drilling of CFRP synergistically assisted by hydrochloric acid and zinc plate of the present invention specifically includes the following steps:

[0040] S1: Sample surface pretreatment;

[0041] The CFRP sample was ultrasonically cleaned for 20 minutes, then mechanically polished to obtain a high-quality surface, wiped with anhydrous ethanol, and left to stand at room temperature for 10 minutes to obtain a clean and dry CFRP surface.

[0042] S2: Install the sample and position it precisely;

[0043] Before drilling, the zinc plate is fastened to the back of the CFRP sample, and the hydrochloric acid solution constrained by the copper ring is placed on the upper surface of the CFRP. The whole thing is supported by four cylindrical supports and placed inside a container to prevent the hydrochloric acid solution from corroding the XY displacement platform. The XY displacement platform is operated by the control system to achieve precise alignment of the processing position.

[0044] S3: Plan the machining path and set the hole diameter;

[0045] The machining process uses a spiral scanning path and the outer diameter is set to 1mm.

[0046] S4: Determine process parameters;

[0047] Different laser powers were provided to compare the differences in drilling quality under different laser powers; other laser parameters remained constant; the pH value of the hydrochloric acid solution was 2; and the zinc plate thickness was fixed at 0.5 mm.

[0048] S5: Drilling is performed according to the set parameters;

[0049] After setting the laser processing parameters and fixing all the samples, start the drilling device to drill the CFRP sample, and turn off the drilling device after processing is completed.

[0050] S6: After machining, measure the heat-affected zone, roundness, taper, and inner wall roughness of the through hole;

[0051] After drilling, the morphology of the inlet, outlet and inner wall of the through hole was observed using a scanning electron microscope and a laser confocal microscope, and the size, roundness, taper and inner wall roughness of the heat-affected zone were quantitatively measured.

[0052] S7: Comparative verification;

[0053] Select another CFRP sample to be processed, repeat steps S3, S5 and S6, record the quantitative characterization results in step S6, and analyze the differences in hole quality between the traditional laser drilling method and the method of the present invention.

[0054] S8: Method applicability verification;

[0055] Select another CFRP sample with a more complex layered structure, repeat steps S1-S7, and compare and analyze the differences in hole quality between the traditional laser drilling method and the method of the present invention.

[0056] Furthermore, the surface roughness of the CFRP sample after mechanical polishing in step S1 is less than 90 nm.

[0057] Furthermore, the spiral scanning path described in step S3 is performed from the outside to the inside, with a scanning interval of 10µm.

[0058] Furthermore, the laser power mentioned in step S4 is 6-18W; the drilling quality is evaluated by quantitatively characterizing the size, roundness, taper, and inner wall roughness of the heat-affected zone of the through hole and observing the surface morphology; the other fixed laser parameters include: laser wavelength of 1064nm, frequency of 100kHz, scanning speed of 100mm / s, pulse width of 254fs, and laser energy distribution of Gaussian distribution.

[0059] Furthermore, the drilling device described in step S5 is a femtosecond laser processing system.

[0060] Example 1:

[0061] A CFRP sample with a thickness of 2.2 mm was selected to compare and analyze the differences in hole quality between the traditional laser drilling method (M1) and the method of the present invention (M2). The implementation process and beneficial effects of the present invention are further illustrated by the following examples.

[0062] Figure 2The SEM morphology of the inlet and outlet of CFRP vias fabricated using M1 and M2 at a laser power of 18W is shown. It can be seen that both the inlet and outlet of the via fabricated by M1 exhibit elliptical profiles, which stems from the inherent anisotropy of heat transfer in CFRP. Specifically, heat is more easily transferred along the fiber orientation, leading to excessive resin ablation in that direction, forming a large heat-affected zone, while insufficient fiber removal ultimately results in an elliptical hole shape. In contrast, M2 breaks this limitation, achieving a near-perfect circular profile. This is mainly due to the assisted etching by hydrochloric acid solution at the inlet and the morphology reshaping caused by the laser-zinc plate interaction at the outlet.

[0063] Figure 3 The heat-affected zone dimensions of through-holes fabricated by the two methods under different laser powers (6-18W) were compared. Figure 3 As shown in (a), as the laser power increases from 6W to 18W, the size of the heat-affected zone at the entrance of the through hole prepared by M1 increases from 0.271mm² to 2.544mm², while the size of the heat-affected zone at the entrance of the through hole prepared by M2 is only 0.102mm², with a maximum reduction of 96%. Figure 3 (b) shows that as the laser power increases from 6W to 18W, the exit heat-affected zone size of the through-hole drilled by M1 increases from 0.069mm² to 3.263mm², while M2 shows no heat damage at the exit (100% elimination). The significant suppression of the heat-affected zone is mainly attributed to the effective absorption of heat by the hydrochloric acid solution and the zinc plate. These results demonstrate the significant effect of the method of the present invention in suppressing heat damage in CFRP laser drilling.

[0064] Figure 4 The results show the roundness measurement of the inlet and outlet of CFRP through-holes fabricated using M1 and M2 under laser power conditions of 6-18W. Figure 4 As shown in (a), within the tested power range, the inlet roundness of the through-hole made by M1 was consistently below 95%, while that of M2 remained above 99%, reaching a maximum of 99.4%. This is related to the aid in material removal by hydrochloric acid solution at the inlet. Figure 4 As shown in (b), as the laser power increases from 6W to 18W, the exit roundness of M1 increases from 72.4% to 88.3%, while that of M2 increases from 87.8% to 98.1%. This demonstrates the effectiveness of the method of the present invention in improving the roundness of through holes.

[0065] Figure 5 The diagram shows the taper of CFRP through-holes fabricated using M1 and M2 under laser power ranges of 6-18W. It can be seen that as the laser power increases from 6W to 18W, the taper of the through-hole fabricated with M1 decreases from 0.093 to 0.051, which is related to the enhanced material removal capability due to the higher energy input. The taper of the CFRP through-hole fabricated with M2 is further reduced, reaching a minimum of 0.029, demonstrating its advantage in controlling hole shape precision.

[0066] Figure 6 The SEM morphology of the inner wall of CFRP through-holes fabricated using M1 and M2 under a laser power of 18W is shown. It can be observed that the taper of the through-hole fabricated using M2 is significantly lower than that using M1. Furthermore, as... Figure 6 As shown in (a1)-(a3), the inner wall of the through-hole made by M1 exhibits obvious processing defects, including debris adhesion, microcracks, uncut fibers, micropits, and fiber delamination. In contrast, the inner wall of the through-hole made by M2 shows no such defects and has a smoother surface, mainly due to the timely removal of processing debris by the hydrochloric acid solution. The effective removal of debris not only improves the quality of the inner wall but also avoids unstable processing caused by laser scattering due to debris. Figure 7 The three-dimensional morphology and roughness measurement results of the corresponding area are shown. It can be seen that the surface roughness of the hole wall made by M2 is reduced by 39.5% compared with M1, further confirming the effectiveness of the present invention in improving the quality of the inner wall.

[0067] Figure 8 The optical morphology of through holes fabricated using M1 and M2 is compared on CFRP specimens with more complex stacked structures. Figure 8 (a) provides a macroscopic image of the specimen and a schematic diagram of the carbon fiber stack, showing the more complex layup arrangement of the internal carbon fibers. For example... Figure 8 As shown in (b), the through-hole processed using M1 exhibits significant thermal damage areas around both the inlet and outlet. In contrast, the through-hole processed using the method of this invention shows only a very small heat-affected zone at the inlet, and no visible thermal damage at the outlet. This comparative result fully verifies that the method of this invention also possesses excellent processing applicability for CFRP samples with complex stacked structures, and can achieve the preparation of high-quality through-holes.

[0068] The results from the examples demonstrate that the high-quality laser drilling method for CFRP using hydrochloric acid and zinc plate synergy proposed in this invention significantly improves the quality of through-holes. This is achieved by utilizing hydrochloric acid solution to enhance heat dissipation and promote debris removal, while the zinc plate absorbs residual heat and, through its interaction with the laser, regulates the exit morphology. The through-hole taper is as low as 0.029, the inner wall roughness is only 1.097µm, and the inlet and outlet roundness are as high as 99.4% and 98.1%, respectively, with no thermal damage in the exit area. Furthermore, the processing quality of the through-hole inner wall is also significantly improved, effectively eliminating processing defects such as micro-pits, uncut fibers, and fiber delamination. This method is also applicable to processing high-quality through-holes in CFRP samples with more complex laminated structures. This method is suitable for the processing requirements of high-quality through-holes in CFRP components in aerospace, high-end equipment, and other fields.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art will recognize that various modifications and variations can be made without departing from the spirit and scope of the invention. Any modifications, equivalent substitutions, and improvements made to the present invention should be included within the scope of protection of the present invention.

Claims

1. A CFRP high-quality laser drilling method assisted by hydrochloric acid and zinc plate in cooperation, characterized in that, The specific steps include: S1: sample surface pretreatment; The CFRP sample was ultrasonically cleaned for 20 min, and then the cleaned surface was mechanically polished to obtain a high-quality surface, then wiped with anhydrous ethanol, and placed at room temperature for 10 min to obtain a clean and dry CFRP surface; S2: Install the sample and accurately position it; Before drilling, the zinc plate is fastened to the back of the CFRP sample, the hydrochloric acid solution constrained by the copper ring is placed on the upper surface of the CFRP, the whole is supported by four cylindrical supports, and all are placed in a container to prevent the hydrochloric acid solution from corroding the XY displacement platform; the XY displacement platform is controlled by the control system to achieve accurate alignment of the machining position; S3: Plan the machining path and set the hole diameter; The spiral scanning path is used for machining and the outer diameter is set to 1 mm; S4: Determine the process parameters; Different laser powers are provided to compare the differences in drilling quality under different laser powers; other laser parameters remain unchanged; the pH value of the hydrochloric acid solution is 2; the thickness of the zinc plate is fixed at 0.5 mm; S5: Drill according to the set parameters; After setting the laser machining parameters and completing the fixation of all samples, the drilling device is started to drill the CFRP sample, and after machining is completed, the drilling device is turned off; S6: Measure the heat-affected zone, roundness, taper, and inner wall roughness of the through hole after machining; After drilling is completed, the scanning electron microscope and the laser confocal microscope are used to observe the morphology of the through hole entrance, exit and inner wall, and to quantitatively measure the heat-affected zone size, roundness, taper and inner wall roughness; S7: Comparison and verification; Another CFRP sample to be machined is selected, and steps S3, S5 and S6 are repeated, the quantitative characterization results in step S6 are recorded, and the differences in hole forming quality between the traditional laser drilling method and the method of the application are analyzed; S8: Verification of method applicability; Another CFRP sample with a more complex layer structure is selected, and steps S1-S7 are repeated, and the differences in hole forming quality between the traditional laser drilling method and the method of the application are compared and analyzed.

2. The method of claim 1, wherein the method is a high quality laser drilling method of CFRP assisted by hydrochloric acid and zinc plate. In step S1, the surface roughness of the CFRP sample after mechanical polishing treatment is less than 90 nm.

3. The method of claim 1, wherein the method is a high quality laser drilling method of CFRP assisted by hydrochloric acid and zinc plate. In step S3, the spiral scanning path is from the outside to the inside, and the scanning interval is 10 µm.

4. The method of claim 1, wherein the method is a high quality laser drilling method of CFRP assisted by hydrochloric acid and zinc plate. In step S4, the laser power is 6-18 W; the drilling quality is evaluated by quantitatively representing the heat-affected zone size, roundness, taper and inner wall roughness of the through hole, and observing the surface morphology; the remaining fixed laser parameters include: laser wavelength is 1064 nm, frequency is 100 kHz, scanning speed is 100 mm / s, pulse width is 254 fs, and laser energy distribution is Gaussian distribution.

5. The method of claim 1, wherein the method is a high quality laser drilling method of CFRP assisted by hydrochloric acid and zinc plate. In step S5, the drilling device is a femtosecond laser machining system.

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