Method for detecting stress in polymer composite material curing process

Abstract

The invention discloses a method for detecting stress in a curing process of a polymer composite material. The method comprises the following steps: preparing a standard tensile sample strip of the polymer composite material; acquiring the Raman spectrum change of the Raman spectrum stress indication peak of the standard tensile spline while changing the stress of the standard tensile spline; establishing a relationship between the Raman spectrum and the stress according to the plurality of stresses and the Raman spectrum corresponding to each stress so as to calibrate a stress frequency shift factor; and carrying out stress detection in the polymer composite material curing process according to the calibrated stress frequency shift factor so as to calculate the stress of the polymer composite material. After the polymer composite material sample is prepared, the stress frequency shift factor is calibrated through the Raman spectrum change of the standard tensile sample strip, and the relationship between the Raman spectrum and the stress is established. By utilizing the stress frequency shift factor, stress detection is carried out in the material curing process, the stress value is accurately calculated, and in-situ nondestructive detection of the stress state of the material is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and in particular relates to a method for detecting stress during the curing process of a polymer composite material. Background Art

[0002] Polymer composites are a class of engineering materials composed of a polymer matrix combined with a variety of reinforcing and functional materials. The matrix material is typically a plastic or resin, such as epoxy, polyester, or polyurethane, which primarily provides the material with shape and toughness. Reinforcements, such as fibers (such as glass fiber and carbon fiber) and particles, primarily contribute to the composite's strength and stiffness. Polymer composites can also contain additives such as inorganic fillers, curing agents, and toughening agents. Inorganic fillers contribute to the material's dimensional stability and thermal performance; curing agents facilitate the chemical curing of the matrix; and toughening agents enhance the material's impact resistance and durability. Polymers are high-molecular-weight compounds composed of repeating monomer molecules linked by chemical bonds. They are widely used in a variety of applications, including packaging, textiles, medical devices, and construction materials. Based on this foundation, polymer composites combine a polymer matrix with various reinforcing materials (such as fibers and particles) and functional additives (such as inorganic fillers, curing agents, and toughening agents), resulting in a class of engineering materials with superior performance. These composite materials have been widely used in aerospace, automotive industry, construction and electronics due to their lightweight, high strength, heat resistance and corrosion resistance.

[0003] The curing process of polymer composites is a critical step in their formation. Through chemical reactions, the liquid resin matrix is transformed into a solid polymer network structure, which determines the material's ultimate properties, including mechanical properties, chemical resistance, and thermal stability. Common curing methods include thermal curing, light curing, and moisture curing, each of which can result in different internal stress distributions. These stresses can cause problems such as cracking and delamination in the material, affecting its reliability and service life.

[0004] In engineering and materials science, stress testing is crucial for polymer composites because it directly impacts the reliability and durability of the materials in practical applications. Stress testing can promptly identify structural deformation, crack propagation, or stress concentration that may occur during processing or use. Traditional testing methods typically include mechanical testing, dynamic mechanical analysis, thermomechanical analysis, thermogravimetric analysis, and photoelastic analysis. However, these existing testing methods require complex testing equipment and are often destructive to the object being tested. Summary of the Invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, an embodiment of the present invention provides a method for detecting stress during the curing process of a polymer composite material.

[0006] The method for detecting stress during the curing process of a polymer composite material provided in an embodiment of the present invention comprises the following steps:

[0007] (1) Prepare standard tensile specimens of polymer composite materials;

[0008] (2) obtaining Raman spectrum changes of the stress indicator peak of the Raman spectrum of the standard tensile spline while changing the stress of the standard tensile spline;

[0009] (3) establishing a relationship between Raman spectra and stress based on multiple stresses and the Raman spectra corresponding to each stress, so as to calibrate the stress frequency shift factor;

[0010] (4) Performing stress detection during the curing process of the polymer composite material according to the calibrated stress frequency shift factor to calculate the stress of the polymer composite material.

[0011] In an example of the detection method provided in the above aspect, the stress is linearly related to the Raman spectrum.

[0012] In an example of the detection method provided in the above aspect, the relationship between the stress and the Raman spectrum is expressed by the following formula:

[0013] Y=A+K*X

[0014] Wherein, Y represents the stress, X represents the Raman spectrum, K represents the stress frequency shift factor, and A represents a constant.

[0015] In an example of the detection method provided in the above aspect, in step (2), the method of changing the stress of the standard tensile spline includes: stretching the standard tensile spline using a stretching table to change the stress of the standard tensile spline;

[0016] The process of stretching the standard tensile spline using the stretching table is achieved by adjusting any one of a stretching rate, a changing a loading direction, a temperature control, and a humidity control.

[0017] In an example of the detection method provided in the above aspect, in step (2), the Raman spectrum change of the stress indication peak in the standard tensile spline obtained includes at least one of the intensity change, displacement change, intensity ratio change and morphological change of the characteristic peak.

[0018] In an example of the detection method provided in the above aspect, in step (2), when the standard tensile spline is subjected to Raman spectroscopy testing, the laser wavelength of the laser irradiating the standard tensile spline includes at least one of 266nm, 325nm, 488nm, 514nm, 532nm, 633nm, 785nm, 830nm, and 1064nm, the power of the laser is 1mW to 50mW, and the integration time is 1s to 1000s.

[0019] It should be noted that the shorter the laser wavelength, the higher the energy and the stronger the Raman signal, but it is easy to damage the sample. It is necessary to select the appropriate wavelength according to the different types of polymer composite materials. In addition, by controlling the laser power within a specific range, a clear signal is obtained without damaging the sample. If the laser power is too low, it is difficult to obtain a clear signal; if the laser power is too high, it is easy to damage the sample. Furthermore, by controlling the integration time within a specific range, a clear signal is obtained without damaging the sample. If the integration time is too low, it is difficult to obtain a clear signal; if the integration time is too high, the signal overflow is easy.

[0020] Furthermore, the integration time needs to be set according to the power. Generally, the greater the power, the shorter the integration time.

[0021] In an example of the detection method provided in the above aspect, in step (3), the method of establishing the relationship between Raman spectrum and stress includes any one of linear regression modeling, machine learning, variable statistical analysis and comparative testing.

[0022] In an example of the detection method provided in the above aspect, in step (4), the curing process of the polymer composite material includes a process of increasing the temperature from room temperature to a curing temperature and then cooling it back to room temperature; wherein the curing temperature ranges from 80°C to 300°C.

[0023] In an example of the detection method provided in the above aspect, step (1) specifically includes: mixing raw materials such as epoxy resin, filler, curing agent and toughening agent to prepare a polymer composite material sample; and preparing a standard tensile specimen of the polymer composite material by filling, defoaming, curing and polishing the polymer composite material sample.

[0024] In an example of the detection method provided in the above aspect, based on the mass percentage of the prepared polymer composite material being 100%, the mass percentage of the epoxy resin is 5%-99%, for example, 30%.

[0025] In an example of the detection method provided in the above aspect, based on the mass percentage of the prepared polymer composite material being 100%, the mass percentage of the filler is 5%-99%, for example, 60%.

[0026] In an example of the detection method provided in the above aspect, based on the mass percentage of the prepared polymer composite material being 100%, the mass percentage of the curing agent is 5%-99%, for example, 9%.

[0027] In an example of the detection method provided in the above aspect, based on the mass percentage of the prepared polymer composite material being 100%, the mass percentage of the toughening agent is 1%-99%, for example, 1%.

[0028] In an example of the detection method provided in the above aspect, the raw material further includes at least one of a catalyst, a diluent, a coupling agent and a pigment.

[0029] In an example of the detection method provided in the above aspect, the method for preparing the polymer composite material by mixing includes any one of high-speed mixing, melt blending, solution blending and in-situ polymerization.

[0030] It should be noted that when mixing to prepare polymer composite materials, the materials need to be mixed as evenly as possible.

[0031] In an example of the detection method provided in the above aspect, the polymer composite material includes any one of an underfill, an epoxy resin molding compound, and a thermal interface material.

[0032] In an example of the detection method provided in the above aspect, a method for preparing a standard tensile specimen of the sample includes steps such as filling, defoaming, curing and polishing.

[0033] Beneficial Effects: After preparing a polymer composite material sample according to an embodiment of the present invention, the stress frequency shift factor is calibrated by the Raman spectrum change of a standard tensile spline, and the relationship between the Raman spectrum and stress is established. Utilizing this stress frequency shift factor, stress detection is performed during the material curing process, and the stress value is accurately calculated, enabling in-situ non-destructive testing of the material stress state, providing guidance for performance optimization and failure analysis. Furthermore, according to an embodiment of the present invention, utilizing the stress frequency shift factor, information on stress changes in the polymer composite material during the curing process can be indirectly and accurately obtained, facilitating the evaluation of stress characterization and the determination of failure analysis. Furthermore, the stress changes can be detected in real time in conjunction with microscopic observation, allowing for non-destructive acquisition of stress information of the sample.

[0034] Therefore, according to embodiments of the present invention, Raman spectroscopy is used to perform real-time, non-destructive stress detection during the curing process of polymer composites. With its unique advantages of high spatial resolution, non-contact nature, and non-destructive testing, Raman spectroscopy can accurately capture changes in the stress state within a material, providing comprehensive characterization information. This can optimize the curing process, improve the overall performance and quality of the material, and enable efficient detection and monitoring of polymer stress states. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and other aspects, features and advantages of the embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0036] Figure 1 is a schematic flow chart of a method for detecting stress during the curing process of a polymer composite material according to an embodiment of the present invention;

[0037] Figure 2 1 is a schematic diagram of a preparation process of a standard tensile specimen of a polymer composite material according to an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of the change in Raman shift of the stress indication peak of the Raman spectrum during the stretching process of a standard tensile spline of a polymer composite material according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of the linear regression fitting results of the Raman shift of the stress indicator peak of the Raman spectrum during the stretching process of the standard tensile spline of the polymer composite material according to an embodiment of the present invention;

[0040] Figure 5 is a schematic diagram of changes in Raman spectra at different temperatures during the curing process of the polymer composite material according to an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the change of the Raman shift of the stress indication peak of the Raman spectrum during the curing process of the polymer composite material according to an embodiment of the present invention;

[0042] Figure 7 3 is a schematic diagram of stress changes calculated based on the stress frequency shift factor during the curing process of the polymer composite material according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0044] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0045] Figure 1 4 is a flow chart of a method for detecting stress during the curing process of a polymer composite material according to an embodiment of the present invention.

[0046] Reference Figure 1 In step S110 , a standard tensile specimen of the polymer composite material is prepared.

[0047] Specifically, in step S110, first, bisphenol A epoxy resin, nano-silica particles, dimethyl toluene diamine, toughening agent and other raw materials are mixed to prepare a polymer composite material sample; secondly, a standard tensile specimen of the polymer composite material is prepared by filling, defoaming, curing and polishing, wherein the operation process of filling, defoaming, curing and polishing is as follows: Figure 2 shown.

[0048] Furthermore, the curing process in operation is to set the program oven to increase the temperature from room temperature to 100°C at a heating rate of 2.34°C / min, keep it at this temperature for 1 hour, then increase the temperature from 100°C to 150°C at a heating rate of 3.33°C / min, keep it at this temperature for 2 hours, and finally cool it down from 150°C to room temperature at a cooling rate of 4°C / min.

[0049] In step S120 , a Raman spectrum change of a stress indication peak of the standard tensile spline is obtained while changing the stress of the standard tensile spline.

[0050] Specifically, the stretching process is carried out in a temperature-controlled stretching table. The standard tensile spline is fixed in the temperature-controlled stretching table with a clamp and stretched. Raman detection is performed on the surface of the standard tensile spline every time the tensile force increases by 1N. The Raman shift change of the stress indicator peak during the stretching process (such as Figure 3 In the Raman spectrum detection process, the Raman laser wavelength was set to 532 nm, the laser power was set to 25 mW, and the integration time was set to 15 s.

[0051] In step S130 , a relationship between the Raman spectrum and the stress is established based on the multiple stresses and the Raman spectrum corresponding to each stress, so as to calibrate the stress frequency shift factor.

[0052] Specifically, a linear regression fitting was performed on multiple stresses (i.e., each increase of 1N of tension) and the Raman spectra corresponding to each stress (i.e., Raman shift) to establish a negative linear relationship between the Raman spectrum and stress, thereby calibrating the stress frequency shift factor of the standard tensile spline to -0.6995 cm -1 / N(such as Figure 4 As shown, where Y = A + K * X, Y represents Raman shift, X represents stress, and K represents stress frequency shift factor, i.e. K = -0.6995 cm -1 / N, A represents a constant, i.e. A=3068.7368cm -1 ). In addition, the unit conversion can be performed based on the cross-sectional area of the standard tensile spline, and the converted stress frequency shift factor is -0.175cm -1 / Mpa.

[0053] In step S140 , stress detection is performed during the curing process of the polymer composite material according to the calibrated stress frequency shift factor to calculate the stress of the polymer composite material.

[0054] Specifically, in step S140, the condition parameters of the curing process of the polymer composite material are the same as the condition parameters of the curing process of the standard tensile spline in step S110; the parameter conditions when collecting the Raman spectrum of the polymer composite material are the same as the parameter conditions for the Raman spectrum test of the standard tensile spline in step S120.

[0055] In addition, Raman spectroscopy stress tests were performed at different times during the curing process of polymer composite materials, and the obtained Raman spectroscopy images were as follows: Figure 5 As shown in the figure, the Raman shift of the stress-indicating peak changes as shown in the figure. Figure 6 As shown, the displacement change of the stress indicator peak is calculated by the stress frequency shift factor, and the stress value of the polymer composite material during the curing process is obtained as follows Figure 7 shown.

[0056] In summary, after preparing polymer composite samples according to embodiments of the present invention, the stress frequency shift factor is calibrated by the Raman spectrum changes of a standard tensile spline, and the relationship between the Raman spectrum and stress is established. Utilizing this stress frequency shift factor, stress detection is performed during the material curing process, and the stress value is accurately calculated, enabling in-situ non-destructive testing of the material's stress state, providing guidance for performance optimization and failure analysis. Furthermore, according to embodiments of the present invention, utilizing the stress frequency shift factor can indirectly and accurately obtain information on stress changes in polymer composites during the curing process, facilitating the evaluation of stress characterization and the determination of failure analysis. Furthermore, the stress frequency shift factor can be used in conjunction with microscopic observation to detect stress changes in real time, allowing for non-destructive acquisition of stress information from the sample.

[0057] Therefore, according to embodiments of the present invention, Raman spectroscopy is used to perform real-time, non-destructive stress detection during the curing process of polymer composites. With its unique advantages of high spatial resolution, non-contact nature, and non-destructive testing, Raman spectroscopy can accurately capture changes in the stress state within a material, providing comprehensive characterization information. This can optimize the curing process, improve the overall performance and quality of the material, and enable efficient detection and monitoring of polymer stress states.

[0058] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Equivalent structures or equivalent process changes made by utilizing the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for detecting stress during the curing process of a polymer composite material, characterized in that: The detection method comprises the following steps: (1) Prepare standard tensile specimens of polymer composite materials; (2) obtaining Raman spectrum changes of the stress indicator peak of the Raman spectrum of the standard tensile spline while changing the stress of the standard tensile spline; (3) establishing a relationship between Raman spectra and stress based on multiple stresses and the Raman spectra corresponding to each stress, so as to calibrate the stress frequency shift factor; (4) Performing stress detection during the curing process of the polymer composite material according to the calibrated stress frequency shift factor to calculate the stress of the polymer composite material.

2. The detection method according to claim 1, wherein The stress is linearly related to the Raman spectrum.

3. The detection method according to claim 2, characterized in that The relationship between the stress and the Raman spectrum is expressed by the following formula, Y=A+K*X Wherein, Y represents the stress, X represents the Raman spectrum, K represents the stress frequency shift factor, and A represents a constant.

4. The detection method according to claim 1, wherein In step (2), the method for changing the stress of the standard tensile spline includes: stretching the standard tensile spline using a stretching table to change the stress of the standard tensile spline; The process of stretching the standard tensile spline using the stretching table is achieved by adjusting any one of a stretching rate, a changing a loading direction, a temperature control, and a humidity control.

5. The detection method according to claim 1, wherein In step (2), the Raman spectrum change of the stress indication peak in the standard tensile spline is obtained, including at least one of the intensity change, displacement change, intensity ratio change and morphology change of the characteristic peak.

6. The detection method according to claim 1, characterized in that In step (2), when the Raman spectroscopy test is performed on the standard tensile spline, the laser wavelength of the laser irradiated on the standard tensile spline includes at least one of 266nm, 325nm, 488nm, 514nm, 532nm, 633nm, 785nm, 830nm, and 1064nm, the power of the laser is 1mW to 50mW, and the integration time is 1s to 1000s.

7. The detection method according to claim 1, characterized in that In step (3), the method of establishing the relationship between Raman spectrum and stress includes any one of linear regression modeling, machine learning, variable statistical analysis and comparative experiment.

8. The detection method according to claim 1, wherein In step (4), the curing process of the polymer composite material includes a process of heating from room temperature to a curing temperature and then cooling to room temperature; wherein the curing temperature ranges from 80°C to 300°C.

9. The detection method according to claim 1, wherein The step (1) specifically includes: The epoxy resin, filler, curing agent and toughening agent are mixed to prepare a polymer composite material sample; Standard tensile specimens of polymer composites are prepared by filling, defoaming, curing and grinding the polymer composite samples.

10. The detection method according to claim 9, characterized in that: The epoxy resin includes any one of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin or glycidyl ether epoxy resin; and / or, the filler comprises at least one of silicon dioxide, diamond, aluminum oxide, graphene or boron nitride; and / or, the curing agent comprises any one of an amine curing agent, an acid anhydride curing agent or a phenolic curing agent; And / or, the toughening agent includes any one of carboxyl-terminated nitrile butadiene rubber, hydroxyl-terminated nitrile butadiene rubber, amine-terminated nitrile butadiene rubber or acrylic rubber.

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