Carbon fiber composite material layered precise curing method based on near-infrared laser

Abstract

The invention belongs to the technical field of composite material manufacturing, and particularly relates to a carbon fiber composite material layered precise curing method based on near-infrared laser. The method comprises the following steps: S1, static curing behavior modeling; s2, optimizing a dynamic scanning process; s3, adaptively curing the paving layer structure; and S4, curing the target component. According to the method, a quantitative model of the laser curing CFRP key process is established, so that the process design is changed from experience driving to model and data driving; the mechanism that dynamic parameters influence the curing uniformity is defined, a clear optimization process window and a parameter matching principle are given, and the uniformity control problem of scanning curing is effectively solved; through the adaptation research of the laying layer structure, an optimal laying layer scheme and a corresponding process adjustment strategy for different laying layers are provided; and the universality and reliability of the method are enhanced.

Description

Technical Field

[0001] This invention belongs to the field of composite material manufacturing technology, and in particular relates to a method for precise curing of carbon fiber composite materials in layers based on near-infrared laser. Background Technology

[0002] Carbon fiber reinforced resin matrix composites (CFRPs) are widely used in high-end fields such as aerospace, rail transportation, and new energy due to their excellent specific strength, specific modulus, and designability. The traditional mainstream curing process for CFRPs is autoclave curing. While this process ensures product quality, it suffers from drawbacks such as long cycle time, high energy consumption, large equipment investment, and limitations in molding large or complex components. Laser curing technology, as a non-contact, high-energy-density curing method, offers potential advantages such as fast heating rate, good spatial selectivity, and ease of automation integration, providing a new approach for the rapid manufacturing and repair of composite materials.

[0003] However, applying lasers to CFRP curing is a complex photo-thermal-chemical coupling process that faces many challenges: I. Unclear Process Mechanism and Blind Process Design: Laser energy is absorbed by carbon fibers and converted into heat, which is then conducted to the resin to initiate curing. This process is influenced by laser parameters (power, spot size, scanning method), material properties (anisotropic thermal conductivity), and layup structure, resulting in complex interactions. Current research largely focuses on observation or limited-parameter experiments, lacking a deep understanding of the quantitative relationship between "parameter input - thermal history - curing result," leading to inefficient process development that relies on trial and error.

[0004] II. Challenges in Controlling Uniformity of Dynamic Scanning Curing: Laser scanning is commonly used for actual curing. Even minute changes in scanning rate and inter-row step displacement can significantly alter the spatiotemporal distribution of energy input, triggering "heat accumulation" and "thermal field superposition" effects. This can easily lead to surface overheating and ablation or insufficient internal curing, making it difficult to achieve uniform curing quality. Currently, there is a lack of clear parameter matching criteria.

[0005] Third, poor adaptability to different layup structures: The layup sequence of CFRP determines its internal heat conduction path. The thermal behavior of unidirectional and multidirectional layups under laser irradiation differs significantly. Existing laser curing processes often ignore this difference and use fixed parameters, resulting in poor curing quality for certain layup structures.

[0006] IV. Lack of quality assessment and prediction methods: It is difficult to monitor the internal curing state in real time during the curing process, and there is also a lack of rapid quality assessment methods based on macroscopic characteristics after curing, which is not conducive to process stability control and product quality assurance.

[0007] Therefore, developing a laser curing method based on solid mechanistic research, capable of quantitatively guiding process design, and adaptable to different material structures has become an urgent problem to be solved. Summary of the Invention

[0008] The main objective of this invention is to provide a method for precise curing of carbon fiber composite materials in layers based on near-infrared lasers, so as to overcome the shortcomings of the prior art.

[0009] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: According to a first aspect of the present invention, a method for precise layering and curing of carbon fiber composite materials based on near-infrared laser is provided, comprising the following steps: S1. Static curing behavior modeling: Static laser irradiation was performed on unidirectional lay-up carbon fiber composite prepreg to obtain surface temperature rise curves, layered curing profiles and corresponding degrees of curing under different laser powers and lay-up thicknesses. A quantitative prediction model for curing temperature field distribution, curing morphology and degree of curing was established. S2. Dynamic scanning process optimization: Based on the quantitative prediction model, the unidirectional ply carbon fiber composite prepreg is subjected to S-shaped path laser scanning curing to determine the optimized process parameter window of laser scanning rate and longitudinal step displacement in order to obtain uniform curing quality. S3. Curing for Adaptability of Layup Structure: Select multiple layup structures, apply the optimized process parameter window for curing, evaluate the curing quality under different layups, and determine the preferred layup scheme and corresponding process adjustment strategy suitable for laser curing; S4. Target component curing implementation: Based on the layup structure type and thickness of the component to be cured, the preferred layup scheme and corresponding process adjustment strategy are invoked; the corresponding laser process parameters are selected and laser curing is implemented.

[0010] Furthermore, the quantitative prediction model established in step S1 includes: Quantitative prediction model for curing temperature field distribution: T(w, t, h) = k(w, h) t n (w0(h)+w) m(h) , Where n is a constant, k, w0, and m are functions related to w and h; T is the static irradiation center temperature, w is the laser power, t is the irradiation time, and h is the layer thickness. Quantitative prediction model for solidification morphology: Under a given laser power w, the solidification profile at the l-th layer depth is described by an ellipse equation: x² / a²(w, l)+y² / b²(w, l) =1, Where the major axis a and minor axis b of the ellipse are functions of w and l; Quantitative prediction model for degree of curing: Under constant laser power w, the degree of curing α of a single layer is linearly positively correlated with the cured area s of that layer. α = u(w) + v(w) s, Where u(w) and v(w) are coefficients related to laser power.

[0011] Furthermore, in the quantitative prediction model: k(w, h) = -1392.5e -0.97h +625.2e -0.92h w w0(h) = 0.58 + 0.225h, m(h) = 1.64 + 0.425h n=0.15; a(w, l)=[0.15+(w-2.91) 0.43 ](3.81-e 1.51l ), b(w, l)=[-83.19+(w+28.67) 1.31 ](1.15-e 0.14l ); u(w) = 0.018w² + 3.024 / w² v(w)=e -0.81w .

[0012] Furthermore, in step S2, the optimized process parameter window is: laser power 4-6W, scanning rate 15-25mm / min, and longitudinal step displacement 1.5-2.5mm.

[0013] Furthermore, in step S2, the scanning rate determines the spot overlap rate, which affects the thermal accumulation effect; the longitudinal step displacement determines the line overlap rate, which affects the thermal field superposition effect; and the optimized process parameters make the spot and the scanning line reach a moderate tangent state.

[0014] Furthermore, in step S3, the preferred layup scheme suitable for laser curing is determined to be a symmetrical alternating layup of 45° / -45° / -45° / 45°.

[0015] Furthermore, in step S3, for unidirectional layup structures, the process adjustment strategies suitable for laser curing include: using alternating double-sided irradiation to compensate for insufficient curing in the thickness direction, or reducing the scanning rate to enhance heat transfer to the interior.

[0016] According to a second aspect of the present invention, a carbon fiber composite material component is provided, the component being cured and formed by the method described above.

[0017] Furthermore, for components using 45° / -45° / -45° / 45° layup and cured by the method described above, the tensile strength of the component is not less than 1800 MPa.

[0018] According to a third aspect of the present invention, an application of any of the above-described carbon fiber composite material components is provided in high-performance aerospace structural components, lightweight rail transit components, or load-bearing components for new energy equipment.

[0019] Compared with the prior art, the advantages of the present invention include: This invention provides a method for precise layered curing of carbon fiber composites based on near-infrared laser. This method establishes a quantitative model of the key processes in laser-cured CFRP, shifting process design from experience-driven to model- and data-driven approaches. It clarifies the mechanism by which dynamic parameters affect curing uniformity, providing a clear optimization process window and parameter matching principles, effectively solving the problem of uniformity control in scanning curing. Through layup adaptability studies, it provides optimal layup schemes and corresponding process adjustment strategies for different layups, enhancing the method's universality and reliability. The established model allows for rapid evaluation of the internal curing degree through easily observable curing morphology (such as area), providing a convenient means for quality monitoring. Using this method, especially in conjunction with optimized layups, composite material components with mechanical properties approaching those of traditional autoclave processes can be prepared, demonstrating significant application potential. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a simplified three-dimensional schematic diagram of the CFRP static curing layer outline in Embodiment 1 of the present invention; Figure 2 This is a simplified infrared thermographic comparison of the surface temperature field distribution of CFRP at different scanning rates in Embodiment 2 of the present invention. Figure 3 This is a bar chart showing the curing degree of CFRP with five different layup structures in Embodiment 3 of the present invention; Figure 4 This is a bar chart showing the tensile strength of CFRP after curing for five different layup structures in Embodiment 3 of the present invention. Detailed Implementation

[0021] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0022] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0023] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials used in the following embodiments are commercially available.

[0024] This invention provides a method for precise layered curing of carbon fiber composite materials based on near-infrared laser, following a technical route of "mechanism research - model construction - process optimization - application adaptation" to delve deeper layer by layer.

[0025] Layer 1: Fundamental Laws and Model Construction of Static Curing. First, using unidirectional 0° layup CFRP prepreg as the object, a systematic near-infrared laser static fixed-point irradiation experiment was conducted. By precisely controlling the laser power (e.g., 3W, 4W, 5W) and material layup thickness (e.g., 0.25, 0.5, 1.0, 2.0 mm), and comprehensively utilizing infrared thermography, layer-by-layer dissection observation, and differential scanning calorimetry, the experiment quantitatively revealed for the first time that the temperature at the static irradiation center point increases exponentially with time, and its specific functional relationship is modulated by both laser power and layup thickness. Due to the significant difference in axial and radial thermal conductivity of carbon fibers, the cured zone on the material surface is elliptical, with a conical energy attenuation distribution along the thickness direction; the curing profile of each layer can be described by an elliptical equation. Under the same power, the degree of curing of a single layer is significantly positively correlated with its cured area. Based on extensive experimental data, three core quantitative prediction models were established: a quantitative prediction model for the curing temperature field distribution, a quantitative prediction model for the curing morphology, and a quantitative prediction model for the degree of curing. These models link key process inputs (power, time, thickness) with observable curing characteristics (temperature, shape, area) and final performance indicators (degree of curing), providing a theoretical basis and computational tools for process design.

[0026] The second layer focuses on the optimization and mechanism elucidation of dynamic scanning technology. Building upon the static research, this study investigates more practical dynamic scanning methods. S-shaped path scanning curing was performed on unidirectional layup CFRP, with a particular emphasis on the coupling effect of two dynamic parameters: scanning rate (V) and longitudinal step displacement (D). The study found that the scanning rate (V) determines the spot overlap rate, influencing the heat accumulation effect. Too slow a rate leads to excessive local heat accumulation, causing surface resin degradation; too fast a rate results in insufficient heat input, hindering internal curing. The longitudinal step displacement (D) determines the line overlap rate, affecting the thermal field superposition effect. Too small a displacement leads to intense heat superposition between adjacent scan rows, easily causing resin "bursting" in the overlapping area; too large a displacement results in uncured gaps between rows. Through systematic experiments, the mechanism by which these effects lead to defects was clarified, and an optimized process parameter window (e.g., 5W power, 20 mm / min speed, 2mm step) was determined to balance heat accumulation and superposition, achieving a uniformly cured layer. Within this optimized process parameter window, energy is reasonably distributed in both time and space.

[0027] The third layer: Layup structure adaptation and performance verification. Recognizing that layup structure is one of the fundamental factors affecting curing behavior, this invention further applies the optimized process to various typical layup structures, including unidirectional layups (all 0°, all 90°) and alternating layups ([0° / 90° / 90° / 0°], [90° / 0° / 0° / 90°], [45° / -45° / -45° / 45°]). Comparative studies revealed that unidirectional layups, due to their single heat transfer path, exhibit a distinctly elliptical temperature field, large temperature differences between upper and lower layers, and are prone to localized overheating, resulting in poor curing uniformity. Alternating layups, especially [45° / -45° / -45° / 45°] layups, utilize the multidirectional nature of the fiber direction to achieve a more uniform heat distribution and a near-circular temperature field, forming a complete and continuous cured layer with a significantly higher average degree of cure than unidirectional layups. For unidirectional layups that are difficult to cure, compensation can be achieved through process strategies such as alternating double-sided irradiation. Performance tests show that the tensile strength of the [45° / -45° / -45° / 45°] layup sample cured using the method of this invention can reach 1865 MPa, verifying that this method can obtain high-performance products.

[0028] The fourth layer: Integration of layered precision curing methods. Finally, by integrating the research results from the above three layers, this invention forms the layered precision curing method for carbon fiber composites based on near-infrared lasers. The core of this method lies in: firstly, predicting the thermal behavior and curing characteristics of the target CFRP component based on a static model, considering the specific layup and thickness; then selecting matching scanning parameters from the optimized process parameter window; and for special layups (such as unidirectional layups), initiating corresponding adaptive process strategies. The entire process achieves forward design and precise control from material properties to process parameters and quality expectations.

[0029] To better understand the technical solution of the present invention, the following detailed discussion is provided in conjunction with specific embodiments.

[0030] Example 1: Static Solidification Modeling This example demonstrates the process of establishing and verifying a statically solidified model.

[0031] Materials and equipment used: A USN150A unidirectional 0° carbon fiber / epoxy resin prepreg laser, an 808nm near-infrared laser, with a spot diameter of 2mm, was used. Surface temperature was monitored using an infrared thermal imager.

[0032] Prepreg was cut and laid to prepare samples with thicknesses of 0.25 mm (2 layers), 0.5 mm (4 layers), 1 mm (8 layers), and 2 mm (16 layers). For each thickness, samples were irradiated at specific points using lasers with powers of 3 W, 4 W, and 5 W for 60 seconds. The temperature change curve at the irradiation center point over time was recorded. After curing, the laminate was carefully peeled off in layers, and the contour (approximately elliptical) of the cured area of ​​each layer was observed and measured using a digital microscope. The lengths of the major axis (2a) and minor axis (2b) were recorded. A sample was taken from the center of the cured area of ​​each layer for DSC testing to obtain the degree of curing (α) of that layer.

[0033] The obtained temperature-time data were fitted to derive the specific equation for T(w, t, h). The elliptic parameters a and b measured for each layer were fitted with the layer depth l and laser power w to obtain expressions for a(w, l) and b(w, l). Linear regression analysis was performed on the degree of curing α measured for each layer and the corresponding cured area s (s=πab) to obtain the relationship α=u(w)+v(w)s and the functional forms of u(w) and v(w). The final model showed good agreement with the experimental data. Figure 1 A simplified 3D schematic diagram of the CFRP static curing layer profile is shown. When the laser power is 5W, the predicted 3D morphology of the layer curing profile is compared with the experimentally observed morphology. At this time, the curing zone depth is the largest and the curing area is the largest under the same depth conditions, thus proving the reliability of the morphology prediction model.

[0034] Example 2: Optimization of Dynamic Scanning Process This embodiment is used to determine the optimal process parameters for dynamic S-shaped scanning.

[0035] A 1mm thick CFRP prepreg sample with unidirectional 0° layup was used. The laser power was fixed at 5W. Two sets of experiments were designed: Group A: Fixed longitudinal step displacement D=3mm, varying scan rate V: 10, 20, 30mm / min.

[0036] Group B: Fixed scanning rate V = 20 mm / min, varying longitudinal step displacement D: 1, 2, 3 mm.

[0037] Laser at 20mm An S-shaped reciprocating scan was performed within a 20mm area. The surface temperature field distribution during the scanning process was recorded using an infrared thermal imager. After curing, the macroscopic state of the sample surface was observed (whether there was charring, cracks, or uncured bands), and samples were taken to test the overall degree of curing in the central area.

[0038] Figure 2 The typical surface temperature field at different scanning rates in Group A is shown. It can be seen that at V=10 mm / min, the heat-affected zone is wide with obvious localized high temperatures; at V=30 mm / min, the heat-affected zone is narrow with lower temperatures; and at V=20 mm / min, the temperature field distribution is relatively uniform. In Group B, at D=1 mm, obvious traces of excessive resin reaction (bursting polymerization) are visible in the overlapping areas of the scanning lines; at D=3 mm, clear uncured dark bands exist between the lines; and at D=2 mm, the surface is uniform with smooth transitions between lines.

[0039] To clarify the advantages of the optimized parameters, comparative experimental data under non-optimized parameters were added, as shown in Table 1.

[0040] Table 1

[0041] Comprehensive comparison revealed that when using the optimized parameter combination (V=20mm / min, D=2mm), the sample surface was uniform and defect-free. The microstructure showed that the resin was uniformly and tightly adhered to the carbon fiber, with a central region curing degree of 49.8% and optimal overall uniformity. Under these parameters, the spot overlap rate and line overlap rate were moderate, effectively balancing heat input and heat dissipation, avoiding local overheating and uncured defects, and achieving uniform energy distribution in space and time. This verified the effectiveness and necessity of the determined optimized process parameter window.

[0042] Example 3: Verification of the adaptability and performance of the ply structure This embodiment is used to verify the adaptability of the method to different layups and to evaluate the final performance.

[0043] Materials and Layups: Five 1 mm thick CFRP prepreg samples with different layup structures were prepared: full 0°, full 90°, [0° / 90° / 90° / 0°], [90° / 0° / 0° / 90°], and [45° / -45° / -45° / 45°]. Curing Process: All samples were cured using the optimized parameters (5W, 20 mm / min, 2 mm) determined in Example 2. After curing, the full 0° and full 90° layups showed obvious heating traces and local color differences along the fiber direction; while the three alternating layups, especially [45° / -45° / -45° / 45°], showed a uniform surface color without significant traces.

[0044] Curing Degree Analysis: After DSC testing, the residual heat of reaction of prepregs with various layup structures was significantly lower than that of uncured samples. Furthermore, the residual heat of reaction for alternating layup structures was significantly lower than that for unidirectional layup structures. Except for uncured samples, the [45° / -45° / -45° / 45°] layup had the lowest residual heat of reaction, while the full 0° and full 90° layups had the highest. The magnitude of the residual heat of reaction determines the degree of curing of the material; the lower the residual heat of reaction, the more resin undergoes cross-linking and curing reactions, resulting in a higher degree of curing. Figure 3 The [45° / -45° / -45° / 45°] layup had the highest average degree of cure, reaching 81.8%; the full 90° layup had the lowest, at 42.7%. Alternating layups were generally superior to unidirectional layups. Mechanical property testing: To obtain fully cured mechanical specimens, the five layup specimens were subjected to double-sided laser curing (with identical parameters on each side and doubled cumulative time). They were then processed into standard tensile specimens for testing. Performance results: Figure 4 The tensile strength of five types of specimens was demonstrated. The tensile strength of the laser-cured specimen with a [45° / -45° / -45° / 45°] layup reached 1865 MPa, which was the best among the five layup structures. This strength value reached 98% of the level of the autoclave-cured specimen (approximately 1900 MPa) of the same batch of material, fully demonstrating that the laser curing process of this invention can obtain high-performance products. Although the tensile strength of the full 90° layup structure is very close to that of the [45° / -45° / -45° / 45°] layup structure, due to its unidirectional layup, its transverse tensile strength is very weak, and it does not possess excellent tensile properties in all directions.

[0045] The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for precise layered curing of carbon fiber composite materials based on near-infrared laser, characterized in that, Includes the following steps: S1. Static curing behavior modeling: Static laser irradiation was performed on unidirectional lay-up carbon fiber composite prepreg to obtain surface temperature rise curves, layered curing profiles and corresponding degrees of curing under different laser powers and lay-up thicknesses. A quantitative prediction model for curing temperature field distribution, curing morphology and degree of curing was established. S2. Dynamic scanning process optimization: Based on the quantitative prediction model, the unidirectional ply carbon fiber composite prepreg is subjected to S-shaped path laser scanning curing to determine the optimized process parameter window of laser scanning rate and longitudinal step displacement in order to obtain uniform curing quality. S3. Curing for Adaptability of Layup Structure: Select multiple layup structures, apply the optimized process parameter window for curing, evaluate the curing quality under different layups, and determine the preferred layup scheme and corresponding process adjustment strategy suitable for laser curing; S4. Implementation of curing the target component: Based on the layup structure type and thickness of the component to be cured, the preferred layup scheme and corresponding process adjustment strategy are invoked; Select the appropriate laser process parameters and implement laser curing.

2. The method for precise curing of carbon fiber composite materials in layers according to claim 1, characterized in that, The quantitative prediction model established in step S1 includes: Quantitative prediction model for curing temperature field distribution: T(w, t, h)=k(w, h) t n (w0(h)+w) m(h) , Where n is a constant, k, w0, and m are functions related to w and h; T is the static irradiation center temperature, w is the laser power, t is the irradiation time, and h is the ply thickness. Quantitative prediction model for solidification morphology: Under a given laser power w, the solidification profile at the l-th layer depth is described by an ellipse equation: x² / a²(w, l)+y² / b²(w, l) =1, Where the major axis a and minor axis b of the ellipse are functions of w and l; Quantitative prediction model for degree of curing: Under constant laser power w, the degree of curing α of a single layer is linearly positively correlated with the cured area s of that layer. α = u(w) + v(w) s, Where u(w) and v(w) are coefficients related to laser power.

3. The method for precise curing of carbon fiber composite materials in layers according to claim 2, characterized in that, In the quantitative prediction model: k(w, h)=-1392.5e -0.97h +625.2e -0.92h w, w0(h) = 0.58 + 0.225h, m(h)= 1.64+0.425h, n=0.15； a(w, l)=[0.15+ (w-2.91) 0.43 ](3.81-e 1.51l ), b(w, l)=[-83.19+ (w+28.67) 1.31 ](1.15-e 0.14l ); u(w) = 0.018w² + 3.024 / w² v(w)=e -0.81w 。 。 4. The method for precise curing of carbon fiber composite materials in layers according to claim 1, characterized in that, In step S2, the optimized process parameter window is: laser power 4-6W, scanning rate 15-25 mm / min, and longitudinal step displacement 1.5-2.5mm.

5. The method for precise curing of carbon fiber composite materials in layers according to claim 4, characterized in that: In step S2, the scanning rate determines the spot overlap rate, which affects the heat accumulation effect; the longitudinal step displacement determines the line overlap rate, which affects the thermal field superposition effect; and the optimized process parameters make the spot and the scanning line reach a moderate tangent state.

6. The method for precise curing of carbon fiber composite materials in layers according to claim 1, characterized in that: In step S3, the preferred layup scheme suitable for laser curing is determined to be 45° / -45° / -45° / 45° symmetrical alternating layup.

7. The method for precise curing of carbon fiber composite materials in layers according to claim 1, characterized in that, In step S3, for unidirectional layup structures, the process adjustment strategies suitable for laser curing include: using alternating double-sided irradiation to compensate for insufficient curing in the thickness direction, or reducing the scanning rate to enhance heat transfer to the interior.

8. A carbon fiber composite material component, characterized in that, The component is cured and formed by the method of any one of claims 1-7.

9. The carbon fiber composite component according to claim 8, characterized in that, For a component using a 45° / -45° / -45° / 45° layup and cured by the method described above, the tensile strength of the component shall not be less than 1800 MPa.

10. The application of a carbon fiber composite component as described in claim 8 or 9 in high-performance aerospace structural components, lightweight rail transit components, or load-bearing components for new energy equipment.

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