Laser Paint Removal Research Articles

Comparative study of infrared nanosecond laser surface paint removal for carbon fiber reinforced polymer and glass fiber reinforced polymer

Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) are widely used in aerospace applications due to their excellent properties. Green and efficient laser cleaning technology has a broad development prospect in the paint removal treatment of aerospace composites. However, the lack of theoretical analysis and guidance has prevented the industrial application of laser paint removal technology. An infrared nanosecond laser is used to clean the paint layer on the surface of CFRP and GFRP, and the best paint removal process parameters are explored. Surface micromorphology and 3D morphology of CFRP and GFRP after cleaning are observed to reveal the cleaning quality. The FTIR spectrum is used to verify the cleanliness of the paint layer. In addition, the contact angle and bonding force are tested, and the experimental results show that the surface wettability of both surfaces is enhanced after cleaning, and the paint adhesion of both surfaces is improved after repainting. Temperature monitoring, acoustic signal monitoring and high-speed photography monitoring are used to monitor the two cleaning processes respectively. The temperature, amplitude intensity, and plasma size of the two in the cleaning process are compared and analyzed. Based on the monitoring results, it is found that the cleaning mechanism of fiber-reinforced composites includes thermal ablation, vibration effect and plasma impact effect.

Application of pulsed laser ablation thermal model in nanosecond pulsed laser removal of the epoxy resin paint film

The effect of laser surface paint removal depends on the mechanism of paint removal. The mechanism of nanosecond laser removal of epoxy resin paint film on aluminum alloy surfaces was studied theoretically and experimentally. Firstly, a laser thermal paint removal model was established based on the heat conduction equation, Hertz-Knudsen equation, and Hooke's law. The adsorption relationship between the paint film and the aluminum alloy substrate molecules and the adsorption force between the paint film and the substrate were analyzed and calculated. A laser thermal paint removal model was solved using COMSOL finite element software. By analyzing the changes in temperature and thermal stress with laser fluence, we obtained the theoretical threshold for laser paint removal. Subsequently, experimental research was conducted on laser paint removal. Through theoretical and experimental studies, it was found that the paint removal threshold of nanosecond pulse laser is 0.47 J/cm2. The primary mechanism of nanosecond laser paint removal is thermal stress stripping. When the laser fluence is low, the nanosecond pulse laser can only ablate the paint on the surface, and the thermal stress between the paint film and the substrate makes it difficult to remove the paint film. As the laser fluence increases, the nanosecond laser will ablate the surface paint film, and the thermal stress between the paint film and the substrate will cause the stripping of the underlying paint film and the substrate. The primary mechanism of laser paint removal is stripping.

Research on LIBS online monitoring criteria for aircraft skin laser paint removal based on OPLS-DA.

Online monitoring technology plays a pivotal role in advancing the utilization of laser paint removal in aircraft maintenance and automation. Through the utilization of a high-frequency infrared pulse laser paint removal laser-induced breakdown spectroscopy (LIBS) online monitoring platform, this research conducted data collection encompassing 60 sets of LIBS spectra during the paint removal process. Classification and identification models were established employing principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least squares discriminant analysis (OPLS-DA). These models served as the foundation for creating criteria and rules for the online LIBS monitoring of the controlled paint removal process for aircraft skin. In this research, 12 selected characteristic spectral lines were used to construct the OPLS-DA model, with a predictive root mean square error (RMSEP) of 0.2873. Both full spectrum and feature spectral line data achieved a predictive accuracy of 94.4%. The selection of feature spectral lines maintains predictive performance while significantly reducing the amount of input data. Consequently, this research offers a methodological reference for further advancements in online monitoring technology for laser paint removal in aircraft skin.

Simulation and Experimental Study on Continuous Wave Fiber Laser Removal of Epoxy Resin Paint Film on the Surface of 6061 Aluminum Alloy

Paint removal is an essential process in the industrial field. Laser technology provides an effective method of paint removal to replace traditional mechanical and chemical methods. This paper establishes a continuous wave (CW) laser thermal paint removal model based on heat conduction theory and Arrhenius’ law. The paint stripping process of epoxy paint film on the surface of 6061 aluminum alloy via CW laser was studied through simulation and experiment. We found that the carbonization of the paint film during the CW laser paint removal process will inhibit the laser paint removal process. Therefore, the paint removal efficiency of the CW laser is limited. The depth of CW laser paint removal increases linearly with the CW laser power density. However, during the CW laser paint removal process, due to the pyrolysis of the paint film and the reflection of the laser by the substrate, the surface temperature of the material first increases and then decreases. In addition, after laser paint removal, the surface roughness of the material after paint removal is reduced due to the melting of the base material. The model established in this article can provide a theoretical reference for studying the CW laser paint removal process.

Formation and effect of rough surface in pulsed laser removal of thick paint layer on 2024 aluminum

When using pulsed laser to remove a thick paint layer from a 2024 aluminum alloy substrate, the paint layer should be removed layer by layer, and the substrate should remain intact after the paint layer is completely removed. In this process, the formation of a rough surface on the paint increases laser absorption, changing the removal mechanism, which becomes an unstable factor for nondestructive paint removal. This study investigated the laser paint removal mechanism of fluorocarbon paint and found that when the laser fluence was 0.91 J/cm2, the main removal mechanisms were thermal stress and combustion-decomposition removal, while at 94.36 J/cm2, the main mechanism was sputtering removal. The study also investigated the relationship between surface roughness and the number of laser scans, which showed a positive linear correlation. Additionally, an equivalent model of a rough surface was established to analyze the changes in absorption, though this model has yet to be verified and further research and validation is required to confirm our findings.

Research on online monitoring of aircraft skin laser paint removal thickness using standard curve method and PCA-SVR based on LIBS.

High-frequency pulse lasers, applied in the form of rapid scanning, act upon the surface of aircraft skin paint layers, thereby removing the paint layers, exhibiting characteristics of efficiency and eco-friendliness. Real-time monitoring of the paint removal effect and prevention of substrate damage necessitates the continuous monitoring of paint removal thickness. Combining Laser-Induced Breakdown Spectroscopy (LIBS) online monitoring technology enables laser-controlled paint removal under multiple effects coupling, meeting the requirements of airworthiness maintenance. This paper, based on a high-frequency nanosecond infrared pulse laser paint removal LIBS monitoring platform, conducts research on laser paint removal thickness LIBS online monitoring of aluminum alloy plates coated with dual-layer paint. Spectra corresponding to the removal thickness of each group are collected and, respectively, paint removal thickness monitoring models based on LIBS spectra are established using the standard curve method and Principal Component Analysis-Support Vector Regression (PCA-SVR) algorithm. When monitoring paint removal thickness using the standard curve method, the intensity of five Ti element characteristic spectral lines selected is correlated with the paint removal thickness, and segmented curve fitting according to the paint layer structure satisfies the segmented curve fitting of topcoat and topcoat + primer. Among them, the average coefficient of the curve fitting of the Ti II 589.088 nm characteristic spectral line is 0.89, and the root mean square error (RMSE) is 12.28 μm. Its performance is superior in the five standard curves; thus, its fitting equation is used as the criterion for paint removal thickness monitoring. To further improve monitoring accuracy, research on paint removal thickness monitoring models based on PCA-SVR is conducted. Compared to the traditional univariate standard curve method, the PCA-SVR model does not require segmented monitoring. After parameter optimization, the average fitting coefficient reaches 0.97, and the RMSE is 2.92 μm. The results indicate that the PCA-SVR-based paint removal thickness monitoring model has higher accuracy, thereby forming the basis for paint removal thickness monitoring. Through comparative research on paint removal thickness monitoring models, two types of paint removal thickness monitoring criteria are obtained, providing model solutions for high-precision monitoring and automation of aircraft skin laser paint removal thickness.

Simulation and experimental study of the evolution of shock waves during laser paint removal

This paper studies the spatiotemporal evolution of shock waves during laser paint removal. In order to study the evolution process of laser-induced plasma shock waves, we developed a laser-plasma shock wave evolution model based on the mass, momentum, and energy conservation theory. The evolution process of laser-induced plasma is studied by simulation and experiment. The simulation and experimental results show that the simulation model can accurately simulate the evolution of the plasma shock wave. In addition, by comparing the ablation depth and paint film thickness, we found that stripping is the primary mechanism of nanosecond pulsed laser paint removal. The ablation is the secondary paint removal mechanism. In summary, this study provides a new way of studying the evolution process of acoustic waves during laser removal paint.

Simulation Study of the Mechanism of Action in the Process of Nanosecond Pulsed Laser Paint Removal

Simulation Study of the Mechanism of Action in the Process of Nanosecond Pulsed Laser Paint Removal

Simulation and Experimental Study of Nanosecond Pulse Laser Removal of Epoxy Paint on 6061 Aluminum Alloy Surface

Laser paint removal is a new cleaning technology that mainly removes paint through thermal ablation and mechanical stripping mechanisms. This paper established a thermal-mechanical coupling laser removal model of paint based on the heat conduction equation, Newton’s second law, and Fabbro’s theory. The removal process of epoxy resin paint film on an aluminum alloy surface via a nanosecond pulsed laser was studied using finite element simulations and experimental measurements. The simulation and experimental results show that the nanosecond pulse laser’s primary paint removal mechanism is the mechanical stripping caused by thermal stress and plasma shock. The laser paint removal threshold is 1.4 J/cm2. In addition, due to the different generation times of plasma shock and thermal stress, the mutual superposition of stress waves occurs in the material. This results in a discrepancy between the actual and thermal stress differences. Moreover, the thermal stress difference causes the maximum actual stress difference to fluctuate. The simulation model established in this paper can provide a reference for studying the thermal-mechanical coupling process of laser paint removal.

Effect of scanning speed on laser cleaning of composite paint layer on aluminum alloy

To explore the effect of varying scanning speeds on laser cleaning of the composite paint layer on the surface of civil aircraft skin, the paint removal transient process by laser ablation was simulated, and laser paint removal experiments of the acrylic polyurethane composite paint layer on the aluminium alloy surface were conducted using nanosecond pulse laser-cleaning equipment at three scanning speeds (v = 900 mm/s, 720 mm/s and 540 mm/s). The experiments show that the topcoat is entirely removed and the primer is partially removed when the scanning speed is 900 mm/s, and the actual paint removal depth is significantly less than the simulation result. The residual primer thickness is further reduced, and the partial oxide film is damaged when the scanning speed is 720 mm/s. The composite paint layer is removed, and part of the aluminium alloy substrate is slightly melted when the scanning speed is 540 mm/s. This study indicates that the ablation behaviour triggers three action mechanisms: plasma shielding, plasma shock-wave and thermal stress paint removal during laser paint removal. With the gradual decrease in scanning speed, the behaviour of ablation paint removal progressively strengthens, the effect of plasma action gradually weakens and the impact of thermal stress remains constant.

Process and mechanism of paint stripping on CFRP by UV nanosecond laser

Laser cleaning shows exciting promise for removing paint from aircraft skins. This paper focuses on the application of a 355 nm (UV) nanosecond pulsed laser for paint removal from aircraft skin composites. First, the effects of process parameters on laser paint removal are analyzed, and mapping relationships between these parameters and the depth and roughness of paint removal are established. After that, the micromorphology and dynamic behavior of the samples are observed and characterized with the help of SEM, EDS and high-speed photography. Finally, the paint cleaning mechanism and damage mechanism of the 355 nm laser are discussed. The results show that the removal of paint is a combined result of photothermal and photochemical effects, while the damage of carbon fiber is caused by thermo-mechanical forces. When the laser repetition frequency is 50 kHz, the scanning speed is 1100 mm/s, and three cleanings are performed, the paint on the CFRP surface can be completely removed while maintaining the integrity of the carbon fiber.

Shape evolution and characteristics of carbon fiber reinforced polymer surface in laser ablation

Carbon fiber reinforced polymer (CFRP) has been far-ranging used for structural components in structural engineering. Laser paint removal is promising in the repair and maintenance of CFRP structural components. However, there are still many unknowns relating to laser paint removal, and the existing theory and practice are insufficient to guide the industrial application of laser paint removal from CFRP laminate. This paper uses nanosecond laser cleaning experiments on the paint of CFRP laminate surface to study the cleaning mechanism and cleaning effect of different process parameters for removing the paint. The surface morphology and three-dimension morphology of laser-cleaned samples are observed to reveal the cleaning quality. In addition, after laser paint removal, the nanostructures are generated on the carbon fibers (CFs) surface. The thermodynamic behavior of CFRP laminate during laser paint removal is discussed by the combination of experimental results and theoretical analysis. The contact angle measurements and single lap joints experiments demonstrate laser-cleaned surfaces present better wettability and higher tensile shear strength than other cleaning methods. This study provides a theoretical and experimental basis for the application of laser paint removal from CFRP laminate.

Evolution and interpretation of LIBS signals based on laser selective layered paint removal from aircraft composite tail

The reliability and controllability of laser selective layered paint removal depend on effective online monitoring technology. In the process of laser cleaning the surface paint layer of the aircraft composite tail, this paper studied the evolution and interpretation of laser induced breakdown spectroscopy (LIBS) signals. The laser power is adjusted to achieve different depths of the laser cleaned composite surface paint layer to compare the Pearson linear correlation between the LIBS online spectrum and the reference spectrum and decode the characteristic peak signal of the LIBS spectrum. The linear correlation of the LIBS spectra and the evolution of the characteristic peaks of the LIBS spectra are mutually verified to establish the intrinsic correlation between the controllability of layered paint removal and the variation of the LIBS spectra, which demonstrates the feasibility of the LIBS technology for online monitoring and feedback of laser paint removal. The results show that the Pearson correlation coefficient r was 0.87–0.89 for the laser cleaning depth range of 44.79–51.50 μm, the layered boundary of laser cleaning the topcoat without damaging the primer is reached, it is proved that the Pearson correlation coefficient r can determine the laser paint removal process. This research compared the different LIBS spectra with cleaning depths at 44.79 and 51.50 μm. It was found that the characteristic peak of strontium element Sr I at wavelength 460.66 nm could characterize the delamination boundary of laser paint removal from aircraft composite tail.

Investigation on dynamic behavior of laser paint removal based on high-speed shadow imaging technology

Investigation on dynamic behavior of laser paint removal based on high-speed shadow imaging technology

Mechanism of paint removal by nanosecond pulsed laser plasma shock: simulation and experiment.

This paper establishes a new theoretical paint removal model of plasma shock based on Fabbro's model and Newton's second law. A two-dimensional axisymmetric finite element model is established to calculate the theoretical model. By comparing the theoretical and experimental results, it is found that the theoretical model can accurately predict the threshold of laser paint removal. It is indicated that plasma shock is an essential mechanism in laser paint removal. The threshold for laser paint removal is approximately 1.73J/c m 2. The experiments show that, with the increase of the laser fluence, the effect of laser paint removal first increases and then decreases. With the increase of the laser fluence, the paint removal effect is improved due to the increase of the paint removal mechanism. The competition between the plastic fracture and pyrolysis leads to a reduction in paint effectiveness. In summary, this study can provide a theoretical reference for studying the paint removal mechanism of plasma shock.

Optimization of Laser Paint Removal Process for Carbon Fiber Composite Substrate Based on Response Surface Analysis

Optimization of Laser Paint Removal Process for Carbon Fiber Composite Substrate Based on Response Surface Analysis

Current status and prospect of engineering application of laser paint removal technology for aircraft skin (invited)

Current status and prospect of engineering application of laser paint removal technology for aircraft skin (invited)

Effect of Laser Paint Removal of Aircraft Skin on Surface Integrity of Substrate

Effect of Laser Paint Removal of Aircraft Skin on Surface Integrity of Substrate

Pulsed and continuous-wave laser paint removal on glass fiber-reinforced polymer composites (invited)

Pulsed and continuous-wave laser paint removal on glass fiber-reinforced polymer composites (invited)

Simulation Analysis and Verification of Single Pulse Laser Paint Removal Morphology with Multi Physics Field

Simulation Analysis and Verification of Single Pulse Laser Paint Removal Morphology with Multi Physics Field