Comprehensive evaluation method for paint removal effect of composite aircraft skin

Abstract

The invention discloses a comprehensive evaluation method for a paint removal effect of a composite material aircraft skin, and relates to the technical field of paint removal of the composite material aircraft skin. In a paint layer residual information evaluation stage, regions are divided before paint removal, and an infrared spectral imager is used for scanning and imaging after paint removal to obtain spectral data of pixel points; comprise the paint layer characteristic absorption peak intensity value and the pixel point number, the paint layer residue condition can be accurately quantified, the average paint layer characteristic absorption peak intensity value is used as an important index, the relative degree of paint layer residue in each area can be accurately judged, and the accuracy of paint layer residue detection is improved. By calculating the spectral characteristic abnormal area proportion of the paint layer and determining the included angle deviation between the distribution direction of the paint layer residues and the stress direction of the fibers, the structural characteristics of the composite material can be fully considered, and the potential influence of the paint layer residues on the stress performance of the skin can be predicted in advance by analyzing the included angle deviation. And the problem of stress concentration caused by unreasonable distribution of paint layer residues is avoided.

Description

Technical Field

[0001] This invention relates to the field of paint removal technology for composite aircraft skin, and specifically to a comprehensive evaluation method for the paint removal effect of composite aircraft skin. Background Technology

[0002] With the increasing application of composite materials in aircraft skin, the evaluation of paint removal effect has become increasingly important. Traditional paint removal evaluation methods are difficult to meet the requirements of composite material characteristics. Accurately assessing the paint removal effect can ensure the performance of aircraft skin and the quality of subsequent coating, ensuring flight safety and service life. At the same time, the development of advanced testing technology has made it possible to comprehensively evaluate the paint removal effect of composite aircraft skin based on paint layer residue information, structural damage and other aspects.

[0003] The current comprehensive evaluation method for paint removal effect of composite aircraft skin has the following problems: 1. Previous comprehensive evaluation methods for paint removal effect of composite aircraft skin lack analysis of the relationship between paint residue distribution and the stress direction of composite fiber. The stress direction of composite fiber has a key impact on its overall performance. If the paint residue is at an unreasonable angle with the stress direction of fiber, it will not be conducive to the uniform transmission of stress on the skin under the complex stress during aircraft flight. This will lead to local stress concentration, reduce the fatigue life and structural strength of the skin, and even cause safety hazards.

[0004] 2. Existing evaluation methods for paint removal effects on composite aircraft skin lack in-depth research on changes in characteristic chemical bonds after paint removal. Composite materials and paint layers contain a variety of characteristic chemical bonds, and the paint removal process can alter or destroy these bonds. Due to a lack of analysis, it is difficult to accurately determine the impact of paint removal on the chemical structure of the composite matrix and paint layer. This is not conducive to the effective bonding between the paint layer and the matrix during subsequent coating, and can lead to insufficient adhesion of the new paint layer, resulting in problems such as peeling and blistering, which affect the appearance and protective performance of the aircraft.

[0005] 3. Traditional evaluation methods for the paint removal effect of composite aircraft skin lack a comprehensive consideration of the microstructural damage during the paint removal process. The microstructure of composite materials, such as fiber orientation and porosity, will change during paint removal. The lack of assessment of microstructural changes, microdefect growth, and the proportion of damage to the paint layer and matrix interface makes it difficult to accurately grasp the degree of damage to the microstructure performance of the skin during paint removal. This can lead to misjudgment of the actual performance status of the skin. During long-term aircraft operation, the deterioration of the microstructure can accelerate the degradation of skin performance, increasing maintenance costs and flight risks. Summary of the Invention

[0006] The purpose of this invention is to provide a comprehensive evaluation method for the paint removal effect of composite material aircraft skin, which solves the problems existing in the background art.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention provides a comprehensive evaluation method for the paint removal effect of composite aircraft skin, including: Step 1, paint layer residue information assessment: Before the paint removal operation is performed on the composite aircraft skin, the composite aircraft skin is divided into various regions, and then the paint layer residue information of each region after the paint removal operation is analyzed.

[0008] Step 2: Assessment of paint residue status: Based on the paint residue information corresponding to each area, the paint residue assessment coefficient for each area of ​​the composite aircraft skin is calculated to determine the paint residue status in each area, and areas that do not meet the paint residue requirements are recorded as preliminary paint residue areas.

[0009] Step 3: Analysis of paint layer residue: Analyze the areas affected by interfering factors in each preliminary paint layer residue area, and record the remaining preliminary paint layer residue areas as each paint layer residue area, and then calculate the paint layer residue degree assessment coefficient corresponding to each paint layer residue area.

[0010] Step 4: Microstructural damage assessment: By assessing the impact of paint removal on the performance of the composite aircraft skin structure, the microstructural damage assessment coefficient corresponding to each paint layer residue area is calculated.

[0011] Step 5: Comprehensive paint removal effect evaluation: Based on the paint residue evaluation coefficient, paint residue degree evaluation coefficient, and microstructure damage evaluation coefficient of each paint residue area, the comprehensive paint removal effect evaluation index corresponding to each paint residue area is calculated to determine whether the paint removal effect of the composite material aircraft skin meets the paint removal requirements.

[0012] The beneficial effects of this invention are as follows: 1. This invention provides a comprehensive evaluation method for the paint removal effect of composite aircraft skin. In the paint residue information assessment stage, by dividing the area before paint removal and scanning it with an infrared spectral imager after paint removal, the spectral data of the pixels are obtained, including the intensity value of the characteristic absorption peak of the paint layer and the number of pixels. This is beneficial for accurately quantifying the paint residue situation. Using the average intensity value of the characteristic absorption peak of the paint layer as an important indicator helps to accurately judge the relative degree of paint residue in each area, calculate the proportion of abnormal area of ​​the paint layer spectral characteristics, and determine the angle deviation between the distribution direction of the paint residue and the direction of fiber stress. This is beneficial for fully considering the structural characteristics of composite materials. Since the performance of composite materials is closely related to the direction of fiber stress, analyzing the angle deviation helps to predict the potential impact of paint residue on the stress performance of the skin in advance, avoid stress concentration caused by unreasonable distribution of paint residue, and ensure the structural stability and safety of the aircraft skin during flight.

[0013] 2. In the paint residue assessment stage of this invention, the paint residue assessment coefficient is obtained by calculation formula and compared with the standard reference threshold. This helps to establish a scientific and objective paint residue judgment standard, making the assessment results more reliable and comparable. Through clear quantitative indicators, preliminary paint residue areas that do not meet the paint residue requirements are efficiently screened out, providing accurate targets for subsequent analysis, reducing unnecessary detection and analysis workload, and improving the efficiency of the entire evaluation process.

[0014] 3. In the process of analyzing the paint layer residue, the present invention analyzes the number of characteristic chemical bonds and the intensity values ​​of related characteristic peaks through chemical analysis, and monitors the paint layer thickness with an ultrasonic thickness gauge. This is beneficial to explore in depth the impact of paint removal on the chemical structure and physical thickness of the composite material and the paint layer, and helps to ensure that the new paint layer has good bonding performance with the composite material matrix, ensuring that the paint layer thickness is uniform and appropriate, thereby improving the protective performance and appearance quality of the aircraft skin.

[0015] 4. In the microstructure damage assessment stage of this invention, by acquiring characteristic parameter information before and after paint removal and calculating the microstructure damage assessment coefficient, it is beneficial to fully understand the degree of change of the microstructure of the composite material caused by the paint removal process. Considering the changes in characteristic parameter information, as well as the growth ratio of micro defects and the damage ratio of the paint layer and the substrate interface, it is beneficial to promptly detect potential micro-damage caused by the paint removal operation, take targeted repair or improvement measures in advance, and extend the service life of the aircraft skin.

[0016] 5. In the comprehensive paint removal effect evaluation, the embodiments of the present invention comprehensively calculate the comprehensive paint removal effect evaluation index, which is conducive to evaluating the paint removal effect from multiple dimensions in a comprehensive and systematic way, avoiding the one-sidedness of single indicator evaluation, and helping to provide comprehensive and accurate data support for the optimization of aircraft skin paint removal process, quality control and maintenance decisions. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the implementation steps of the present invention. Detailed Implementation

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] Please see Figure 1 As shown, the present invention provides a comprehensive evaluation method for the paint removal effect of composite aircraft skin. The method includes: Step 1, paint layer residue information assessment: Before the paint removal operation is performed on the composite aircraft skin, the composite aircraft skin is divided into various regions, and then the paint layer residue information of each region after the paint removal operation is analyzed.

[0021] In a specific embodiment, the analysis of residual paint information in each region after paint removal is performed as follows: The composite aircraft skin after paint removal is divided into regions according to the aircraft's structural characteristics and functional areas. Each region of the composite aircraft skin after paint removal is scanned and imaged using an infrared spectral imager to obtain spectral data corresponding to each pixel in the image. The spectral data includes the number of pixels i and the intensity value of the paint layer's characteristic absorption peak, i = 1, 2, ..., n, where n is the total number of pixels and n is a positive integer. The average intensity value of the paint layer's characteristic absorption peak corresponding to each pixel in each region is calculated by averaging the values. The result is the average intensity value of the paint layer's characteristic absorption peak corresponding to each region. j is the number corresponding to each region, j = 1, 2, ..., m, m is the total number of regions, and m is a positive integer.

[0022] The database is used to retrieve the characteristic absorption peak intensity ranges of the paint layer corresponding to the composite aircraft skin. The characteristic absorption peak intensity values ​​of the paint layer for each pixel within each region are compared with the corresponding ranges. The number of pixels in each region that do not fall within the ranges is counted, along with the total number of pixels in each region. The result of dividing the number of pixels in each region that do not fall within the ranges by the total number of pixels in each region is the proportion of the spectral anomaly area of ​​the paint layer for each region, denoted as S. j The direction of fiber stress is set as the reference direction. The angle deviation between the direction of residual paint layer distribution and the direction of fiber stress in each region is calculated by a geometric algorithm and denoted as θ. j .

[0023] It should be noted that structural features and functional areas refer to different parts such as wings and fuselages, as well as the layup direction of composite materials. By extracting the contour lines of the paint layer residual distribution boundary and the straight line features of the fiber stress direction, respectively, they are converted into slope or vector form. The geometric algorithm is used to calculate the angle deviation between the two by using the slope difference and angle relationship or the vector dot product formula. The geometric calculation process is the mathematical calculation formula of the vector angle, which will not be elaborated on here.

[0024] Step 2: Assessment of paint residue status: Based on the paint residue information corresponding to each area, the paint residue assessment coefficient for each area of ​​the composite aircraft skin is calculated to determine the paint residue status in each area, and areas that do not meet the paint residue requirements are recorded as preliminary paint residue areas.

[0025] In a specific embodiment, the calculation of the paint layer residue assessment coefficient for each region of the composite aircraft skin is carried out as follows: The calculation formula is as follows:

[0026] The residual paint layer evaluation coefficient PL1 for each region of the composite aircraft skin was obtained. j ,in These are the weighting factors corresponding to the set spectral characteristics, the weighting factor corresponding to the proportion of abnormal area of ​​the spectral characteristics of the paint layer, and the weighting factor corresponding to the angle deviation between the direction of residual distribution of the paint layer and the direction of fiber stress, respectively. ji Let a be the intensity value of the paint layer feature absorption peak corresponding to the i-th pixel in the j-th region. j Let a1 + a2 + ... + a be the number of pixels in the j-th region. j =n.

[0027] It should be noted that, The values ​​are all greater than 0 and less than 1. If a specific spectral feature is associated with key components of the paint layer and affects important skin performance, such as corrosion resistance, the spectral feature weighting factor is set to 0.4. If it is a general feature, the corresponding weighting factor is set to a lower value, such as 0.2. If it is a business jet skin with high requirements for appearance integrity, the weighting factor for the proportion of abnormal area of ​​the paint layer spectral feature can be set to 0.35. If it is a military transport aircraft skin with relatively low requirements, it can be set to 0.25. In high-stress areas such as the wing root, the weighting factor for the angle deviation between the paint layer residual distribution direction and the fiber stress direction can be set to 0.25. In low-stress areas such as non-critical parts inside the fuselage, it can be set to 0.1. Finally, the actual weighting factor value is obtained by combining expert opinions and the type of composite aircraft.

[0028] In a specific embodiment, the process of determining the paint residue status in each region is as follows: The standard control paint residue assessment coefficient threshold corresponding to the composite aircraft skin is obtained from the database. The paint residue assessment coefficient for each region of the composite aircraft skin is compared with the standard control paint residue assessment coefficient threshold. If the paint residue assessment coefficient for a certain region of the composite aircraft skin is greater than the standard control paint residue assessment coefficient threshold, it indicates that the paint residue status in that region does not meet the paint residue requirements. If the paint residue assessment coefficient for a certain region of the composite aircraft skin is less than or equal to the standard control paint residue assessment coefficient threshold, it indicates that the paint residue status in that region meets the paint residue requirements. This process is used to obtain the paint residue status in each region.

[0029] In the paint residue assessment stage of this invention, a paint residue assessment coefficient is obtained through a calculation formula and compared with a standard reference threshold. This helps to establish a scientific and objective standard for judging paint residue, making the assessment results more reliable and comparable. Through clear quantitative indicators, preliminary paint residue areas that do not meet the paint residue requirements are efficiently screened out, providing accurate targets for subsequent analysis, reducing unnecessary detection and analysis workload, and improving the efficiency of the entire evaluation process.

[0030] Step 3: Analysis of paint layer residue: Analyze the areas affected by interfering factors in each preliminary paint layer residue area, and record the remaining preliminary paint layer residue areas as each paint layer residue area, and then calculate the paint layer residue degree assessment coefficient corresponding to each paint layer residue area.

[0031] In a specific embodiment, the process of analyzing the areas affected by interfering factors in each preliminary paint layer residue area is as follows: each monitoring point is set in each preliminary paint layer residue area, and each monitoring point is detected by a micro-area Raman spectrometer, thereby screening out each preliminary paint layer residue area affected by interfering factors, and thus obtaining each paint layer residue area.

[0032] The types of composite materials and paint layers were obtained from the database. Then, chemical analysis was used to detect the number of characteristic chemical bonds in each paint layer residue area. The characteristic peak intensity values ​​of each characteristic chemical bond in each paint layer residue area of ​​the composite aircraft skin before paint removal were obtained from the database and denoted as P′. jq q represents the number corresponding to each type of characteristic chemical bond, q = 1, 2, ..., b, where b is the total number of types of characteristic chemical bonds and b is a positive integer. The residual areas of each paint layer after the paint removal operation are detected using an infrared spectrometer, and the characteristic peak intensity values ​​of each characteristic chemical bond corresponding to each residual area of ​​the paint layer after the paint removal operation are obtained, denoted as P. jqThe characteristic peak intensities of each characteristic chemical bond corresponding to the residual areas of each paint layer before the paint removal operation were sorted in descending order, and the characteristic peak intensity value with the highest ranking was selected and denoted as .

[0033] The paint layer thickness at each monitoring point in each residual paint area was monitored using an ultrasonic thickness gauge. The paint layer thickness at each monitoring point was then selected as the thickest paint layer at that point. The paint layer thickness at each monitoring point corresponding to each paint layer residue area was calculated by averaging the values, and the result was recorded as the paint layer thickness of each paint layer residue area, denoted as H. j .

[0034] It should be noted that interfering factors include environmental factors such as humidity and temperature changes during the paint removal process, as well as impurities generated during the paint removal process. Composite materials include, but are not limited to, carbon fiber reinforced composite materials, glass fiber reinforced composite materials, and aramid fiber reinforced composite materials. Paint types include nitrocellulose coatings, alkyd coatings, polyurethane coatings, and fluorocarbon coatings. Chemical analysis methods include, but are not limited to, infrared spectroscopy, X-ray photoelectron spectroscopy, and mass spectrometry. Characteristic chemical bonds include ester bonds in the paint layer and ether bonds in the matrix.

[0035] In a specific embodiment, the calculation process for the paint layer residue assessment coefficient corresponding to each paint layer residue area is as follows: The calculation formula is:

[0036] The paint residue level assessment coefficient PL2 corresponding to each paint residue area was obtained. j Where μ is the correction factor corresponding to the degree of paint residue, b j Let b1+b2+......+b be the number of characteristic chemical bonds corresponding to the j-th region. j =b.

[0037] It should be noted that, for example, taking a certain type of carbon fiber composite aircraft skin as an example, when the thickness of the residual paint layer after paint removal is 0-5 micrometers and the similarity of the main components exceeds 90%, if the area is located in a non-critical part of the fuselage, the paint layer residue correction factor can be set to 0.8, because the requirements for paint layer residue in this part are relatively lenient. However, in critical parts such as the leading edge of the wing, even if the thickness of the residual paint layer is 0-3 micrometers and the similarity of the main components reaches 95%, the paint layer residue correction factor is only set to 0.3. This is because it has a great impact on aerodynamic performance, and even small differences in residue can lead to serious consequences. Through the analysis of different residue conditions in different parts and the summary by experts, the paint layer residue correction factor value is determined to accurately assess the degree of paint layer residue.

[0038] In the process of analyzing the paint layer residue, this invention analyzes the number of characteristic chemical bonds and the intensity values ​​of related characteristic peaks through chemical analysis, and monitors the paint layer thickness using an ultrasonic thickness gauge. This helps to explore in depth the impact of paint removal on the chemical structure and physical thickness of the composite material and the paint layer, and helps to ensure that the new paint layer has good bonding performance with the composite material matrix, ensuring that the paint layer thickness is uniform and appropriate, thereby improving the protective performance and appearance quality of the aircraft skin.

[0039] Step 4: Microstructural damage assessment: By assessing the impact of paint removal on the performance of the composite aircraft skin structure, the microstructural damage assessment coefficient corresponding to each paint layer residue area is calculated.

[0040] In a specific embodiment, the evaluation of the performance impact of the paint removal process on the composite aircraft skin structure is carried out as follows: Characteristic parameter information of the residual paint layer areas of the composite aircraft skin before the paint removal operation is obtained from the database, denoted as G′. jg Let g be the index of the parameter information contained in the feature parameter information, g = 1, 2, ..., c, and c be the total number of parameter information contained in the feature parameter information, where c is a positive integer. The feature parameter acquisition device detects the residual areas of each paint layer after the paint removal operation, obtaining the feature parameter information corresponding to each residual area of ​​the paint layer after the paint removal operation, denoted as G. jg And the maximum value of the corresponding parameter information contained in the feature parameter information is recorded as .

[0041] It should be noted that the characteristic parameter information includes characteristic parameters such as fiber orientation degree and porosity, and the characteristic parameter acquisition equipment includes, but is not limited to, automatic fiber orientation degree measuring instruments and mercury porosimeters.

[0042] In a specific embodiment, the calculation process for the microstructural damage assessment coefficient corresponding to each residual area of ​​the paint layer is as follows: The calculation formula is:

[0043] The microstructural damage assessment coefficient PL3 ​​corresponding to the residual areas of each paint layer was obtained. j Where γ1, γ2, and γ3 are the weighting factors corresponding to the characteristic parameter information, the weighting factor corresponding to the micro-defect growth ratio, and the weighting factor corresponding to the paint layer-substrate interface damage ratio, D j 、E j G represents the growth rate of micro-defects and the damage rate of the paint layer-substrate interface in the j-th region, respectively. j Let c1+c2+......+c be the number of characteristic chemical bonds corresponding to the j-th region. j =c.

[0044] It should be noted that the micro-defect growth rate is obtained by imaging the microstructure of each paint layer residue area before and after paint removal using an electron microscope, counting the number of newly added micro-defects in each paint layer residue area after paint removal, and then dividing it by the baseline number of micro-defects in each paint layer residue area before paint removal. The paint layer-substrate interface damage rate is obtained by observing the interface damage in each paint layer residue area using a scanning acoustic microscope, counting the area or length of the damaged interface in each paint layer residue area, and dividing it by the total area or total length of the interfaces in each paint layer residue area.

[0045] It should also be noted that the values ​​of γ1, γ2, and γ3 are all greater than 0 and less than 1, and the process of setting γ1, γ2, and γ3 is the same as... The setup process is the same, so I won't go into too much detail here. (1-γ2*D) j In this context, when there is no micro-defect growth, i.e., D... j When = 0, then (1-γ2*D j ) = 1, indicating that there was no damage to the microstructure of the composite aircraft skin in terms of micro-defect growth, when D j When it increases, (1-γ2*D j A decrease in the value of ) indicates that the more micro-defects grow, the greater the damage to the microstructure of the composite aircraft skin.

[0046] In the microstructure damage assessment stage, this invention obtains characteristic parameter information before and after paint removal and calculates the microstructure damage assessment coefficient. This helps to fully understand the degree of change in the microstructure of the composite material caused by the paint removal process. Considering the changes in characteristic parameter information, as well as the growth ratio of micro defects and the damage ratio of the paint layer and the substrate interface, it is beneficial to promptly detect potential micro-damage caused by the paint removal operation and take targeted repair or improvement measures in advance to extend the service life of the aircraft skin.

[0047] Step 5: Comprehensive paint removal effect evaluation: Based on the paint residue evaluation coefficient, paint residue degree evaluation coefficient, and microstructure damage evaluation coefficient of each paint residue area, the comprehensive paint removal effect evaluation index corresponding to each paint residue area is calculated to determine whether the paint removal effect of the composite material aircraft skin meets the paint removal requirements.

[0048] In a specific embodiment, the calculation of the comprehensive paint removal effect evaluation index corresponding to each paint layer residue area is as follows: Substitute the paint layer residue evaluation coefficient, paint layer residue degree evaluation coefficient, and microstructure damage evaluation coefficient of each paint layer residue area into the calculation formula: PL=(PL1) -1*η1+PL2*η2+PL3*η3 yields the comprehensive paint removal effect evaluation index PL corresponding to each paint layer residue area. η1, η2, and η3 are the weight factors corresponding to the set paint layer residue evaluation coefficient, the paint layer residue degree evaluation coefficient, and the microstructure damage evaluation coefficient, respectively.

[0049] It should be noted that the values ​​of η1, η2, and η3 are all greater than 0 and less than 1, and the setting process of η1, η2, and η3 is the same as... The setup process is the same, so I won't go into too much detail here.

[0050] In a specific embodiment, the process of determining whether the paint removal effect of the composite aircraft skin meets the paint removal requirements is as follows: The standard control comprehensive paint removal effect evaluation index threshold for the composite aircraft skin during the paint removal process is obtained from the database. The comprehensive paint removal effect evaluation index corresponding to each paint layer residue area is compared with the standard control comprehensive paint removal effect evaluation index threshold. If the comprehensive paint removal effect evaluation index corresponding to a certain paint layer residue area is greater than the standard control comprehensive paint removal effect evaluation index threshold, it indicates that the paint removal effect of the composite aircraft skin meets the paint removal requirements; otherwise, it indicates that the paint removal effect of the composite aircraft skin does not meet the paint removal requirements.

[0051] In the comprehensive paint removal effect evaluation, the embodiments of the present invention comprehensively calculate the comprehensive paint removal effect evaluation index, which is conducive to evaluating the paint removal effect from multiple dimensions in a comprehensive and systematic way, avoiding the one-sidedness of evaluation by a single indicator, and helping to provide comprehensive and accurate data support for the optimization of aircraft skin paint removal process, quality control and maintenance decisions.

[0052] This invention provides a comprehensive evaluation method for the paint removal effect of composite aircraft skin. In the paint residue information assessment stage, the method divides the area before paint removal and then scans it with an infrared spectral imager after removal to obtain the spectral data of each pixel, including the intensity value of the characteristic absorption peak of the paint layer and the number of pixels. This method is beneficial for accurately quantifying the paint residue situation. Using the average intensity value of the characteristic absorption peak of the paint layer as an important indicator helps to accurately determine the relative degree of paint residue in each area. The method also calculates the proportion of abnormal areas of the paint layer spectral characteristics and determines the angular deviation between the distribution direction of paint residue and the direction of fiber stress. This method is beneficial for fully considering the structural characteristics of composite materials. Since the performance of composite materials is closely related to the direction of fiber stress, analyzing the angular deviation helps to predict the potential impact of paint residue on the stress performance of the skin in advance, avoid stress concentration caused by unreasonable distribution of paint residue, and ensure the structural stability and safety of the aircraft skin during flight.

[0053] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined in this specification, they should all fall within the scope of protection of the present invention.

Claims

1. A comprehensive evaluation method for the paint removal effect of composite material aircraft skin, characterized in that, include: Step 1: Assessment of paint residue information: Before the paint removal operation is carried out on the composite aircraft skin, the composite aircraft skin is divided into various areas, and then the paint residue information of each area after the paint removal operation is analyzed. Step 2: Assessment of paint residue: Based on the paint residue information of each area, the paint residue assessment coefficient of each area of ​​the composite aircraft skin is calculated to determine the paint residue status of each area, and areas that do not meet the paint residue requirements are recorded as preliminary paint residue areas. Step 3: Analysis of paint layer residue: Analyze the areas affected by interfering factors in each preliminary paint layer residue area, and record the remaining preliminary paint layer residue areas as each paint layer residue area, and then calculate the paint layer residue degree assessment coefficient corresponding to each paint layer residue area. Step 4: Microstructure damage assessment: By assessing the impact of paint removal on the performance of the composite aircraft skin structure, the microstructure damage assessment coefficient corresponding to each paint layer residual area is calculated. Step 5: Comprehensive paint removal effect evaluation: Based on the paint residue evaluation coefficient, paint residue degree evaluation coefficient, and microstructure damage evaluation coefficient of each paint residue area, the comprehensive paint removal effect evaluation index corresponding to each paint residue area is calculated to determine whether the paint removal effect of the composite material aircraft skin meets the paint removal requirements.

2. The comprehensive evaluation method for paint removal effect of composite aircraft skin according to claim 1, characterized in that, The analysis of residual paint layer information in each area after the paint removal operation is carried out in the following specific process: The depainted composite aircraft skin was divided into regions according to the aircraft's structural characteristics and functional areas. Infrared spectral imagers were used to scan and image each region of the depainted composite aircraft skin, obtaining spectral data for each pixel in the image. The spectral data included the number of pixels *i* and the intensity value of the paint layer's characteristic absorption peak, where *i* = 1, 2, ..., n, where *n* is the total number of pixels and *n* is a positive integer. The average intensity value of the paint layer's characteristic absorption peak for each pixel in each region was calculated by averaging the values. j is the number corresponding to each region, j = 1, 2, ..., m, m is the total number of regions, and m is a positive integer; The database is used to retrieve the characteristic absorption peak intensity ranges of the paint layer corresponding to the composite aircraft skin. The characteristic absorption peak intensity values ​​of the paint layer for each pixel within each region are compared with the corresponding ranges. The number of pixels in each region that do not fall within the ranges is counted, along with the total number of pixels in each region. The result of dividing the number of pixels in each region that do not fall within the ranges by the total number of pixels in each region is the proportion of the spectral anomaly area of ​​the paint layer for each region, denoted as S. j The direction of fiber stress is set as the reference direction. The angle deviation between the direction of residual paint layer distribution and the direction of fiber stress in each region is calculated by a geometric algorithm and denoted as θ. j .

3. The comprehensive evaluation method for paint removal effect of composite material aircraft skin according to claim 2, characterized in that, The specific process for calculating the paint layer residue assessment coefficient for each region of the composite aircraft skin is as follows: Calculation formula: The residual paint layer evaluation coefficient PL1 for each region of the composite aircraft skin was obtained. j ,in These are the weighting factors corresponding to the set spectral characteristics, the weighting factor corresponding to the proportion of abnormal area of ​​the spectral characteristics of the paint layer, and the weighting factor corresponding to the angle deviation between the direction of residual distribution of the paint layer and the direction of fiber stress, respectively. ji Let a be the intensity value of the paint layer feature absorption peak corresponding to the i-th pixel in the j-th region. j Let a1 + a2 + ... + a be the number of pixels in the j-th region. j =n.

4. The comprehensive evaluation method for paint removal effect of composite material aircraft skin according to claim 3, characterized in that, The specific process for determining the paint residue in each area is as follows; The standard control paint residue assessment coefficient threshold is obtained from the database for the composite aircraft skin. The paint residue assessment coefficient of each region of the composite aircraft skin is compared with the standard control paint residue assessment coefficient threshold. If the paint residue assessment coefficient of a certain region of the composite aircraft skin is greater than the standard control paint residue assessment coefficient threshold, it indicates that the paint residue of that region does not meet the paint residue requirements. If the paint residue assessment coefficient of a certain region of the composite aircraft skin is less than or equal to the standard control paint residue assessment coefficient threshold, it indicates that the paint residue of that region meets the paint residue requirements. In this way, the paint residue status of each region is obtained.

5. The comprehensive evaluation method for paint removal effect of composite aircraft skin according to claim 4, characterized in that, The specific process for analyzing the areas affected by interfering factors in the residual areas of each preliminary paint layer is as follows: Monitoring points were set up in each preliminary paint layer residue area, and each monitoring point was detected by micro-area Raman spectroscopy to screen out each preliminary paint layer residue area affected by interfering factors, and thus obtain each paint layer residue area. The types of composite materials and paint layers were obtained from the database. Then, chemical analysis was used to detect the number of characteristic chemical bonds in each paint layer residue area. The characteristic peak intensity values ​​of each characteristic chemical bond in each paint layer residue area of ​​the composite aircraft skin before paint removal were obtained from the database and denoted as P′. jq q represents the number corresponding to each type of characteristic chemical bond, q = 1, 2, ..., b, where b is the total number of types of characteristic chemical bonds and b is a positive integer. The residual areas of each paint layer after the paint removal operation are detected using an infrared spectrometer, and the characteristic peak intensity values ​​of each characteristic chemical bond corresponding to each residual area of ​​the paint layer after the paint removal operation are obtained, denoted as P. jq The characteristic peak intensities of each characteristic chemical bond corresponding to the residual areas of each paint layer before the paint removal operation were sorted in descending order, and the characteristic peak intensity value with the highest ranking was selected and denoted as . The paint layer thickness at each monitoring point in each residual paint area was monitored using an ultrasonic thickness gauge. The paint layer thickness at each monitoring point was then selected as the thickest paint layer at that point. The paint layer thickness at each monitoring point corresponding to each paint layer residue area was calculated by averaging the values, and the result was recorded as the paint layer thickness of each paint layer residue area, denoted as H. j .

6. The comprehensive evaluation method for paint removal effect of composite material aircraft skin according to claim 5, characterized in that, The specific calculation process for the evaluation coefficient of paint layer residue degree corresponding to each paint layer residue area is as follows: Through calculation formula The paint residue level assessment coefficient PL2 corresponding to each paint residue area was obtained. j Where μ is the correction factor corresponding to the degree of paint residue, b j Let b1+b2+......+b be the number of characteristic chemical bonds corresponding to the j-th region. j =b.

7. The comprehensive evaluation method for paint removal effect of composite material aircraft skin according to claim 6, characterized in that, The specific process for assessing the impact of paint removal on the performance of composite aircraft skin structures is as follows: The characteristic parameter information of each paint layer residual area of ​​the composite aircraft skin before paint removal is obtained from the database and denoted as G′. jg Let g be the index of the parameter information contained in the feature parameter information, g = 1, 2, ..., c, and c be the total number of parameter information contained in the feature parameter information, where c is a positive integer. The feature parameter acquisition device detects the residual areas of each paint layer after the paint removal operation, obtaining the feature parameter information corresponding to each residual area of ​​the paint layer after the paint removal operation, denoted as G. jg And the maximum value of the corresponding parameter information contained in the feature parameter information is recorded as .

8. The comprehensive evaluation method for paint removal effect of composite aircraft skin according to claim 7, characterized in that, The specific calculation process for the microstructural damage assessment coefficient corresponding to the residual area of ​​each paint layer is as follows: Through calculation formula The microstructural damage assessment coefficient PL3 ​​corresponding to the residual areas of each paint layer was obtained. j Where γ1, γ2, and γ3 are the weighting factors corresponding to the characteristic parameter information, the weighting factor corresponding to the micro-defect growth ratio, and the weighting factor corresponding to the paint layer-substrate interface damage ratio, D j E j G represents the growth rate of micro-defects and the damage rate of the paint layer-substrate interface in the j-th region, respectively. j Let c1+c2+......+c be the number of characteristic chemical bonds corresponding to the j-th region. j =c.

9. A comprehensive evaluation method for paint removal effect of composite material aircraft skin according to claim 8, characterized in that, The calculation yields a comprehensive paint removal effect evaluation index for each paint layer residue area. The specific calculation process is as follows: Substitute the paint residue assessment coefficient, paint residue degree assessment coefficient, and microstructure damage assessment coefficient for each paint residue area into the calculation formula PL=(PL1). -1 *η1+PL2*η2+PL3*η3 yields the comprehensive paint removal effect evaluation index PL corresponding to each paint layer residue area. η1, η2, and η3 are the weight factors corresponding to the set paint layer residue evaluation coefficient, the paint layer residue degree evaluation coefficient, and the microstructure damage evaluation coefficient, respectively.

10. A comprehensive evaluation method for paint removal effect of composite aircraft skin according to claim 9, characterized in that, The specific process for determining whether the paint removal effect of the composite material aircraft skin meets the paint removal requirements is as follows: The comprehensive paint removal effect evaluation index threshold corresponding to the standard control in the paint removal process of composite aircraft skin is obtained from the database. The comprehensive paint removal effect evaluation index corresponding to each paint layer residual area is compared with the comprehensive paint removal effect evaluation index threshold of the standard control. If the comprehensive paint removal effect evaluation index corresponding to a certain paint layer residual area is greater than the comprehensive paint removal effect evaluation index threshold of the standard control, it indicates that the paint removal effect of the composite aircraft skin meets the paint removal requirements; otherwise, it indicates that the paint removal effect of the composite aircraft skin does not meet the paint removal requirements.

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