Fiber-reinforced composite with damage-assisted positioning and method of manufacture and detection

Abstract

The application discloses a kind of fiber reinforced composite with damage auxiliary positioning and preparation method and detection method, including reinforcing fiber, resin matrix, and microcapsule indicating system dispersed in the resin matrix, the microcapsule indicating system includes the microcapsule with wall thickness of 3-15 μm, and the microcapsule is encapsulated with indicator substance, when the composite produces the crack of width ≥0.05mm, microcapsule on crack path breaks, releases indicator substance, interface performance is relatively poor, solve the problem that existing fiber reinforced composite is damaged, and the problem of not timely, intuitive, remote discovery is solved, provide a kind of damage self-indication composite material which does not depend on external energy, environmental adaptability is strong, signal is durable, and preparation method thereof, significantly improve the safety and service life of key structural components.

Description

Technical Field

[0001] This invention belongs to the field of materials science and engineering, specifically a fiber-reinforced composite material with damage self-indication function and its preparation method. Background Technology

[0002] Fiber-reinforced composite materials, with their high specific strength, high specific modulus, and excellent design flexibility, have been widely applied in many key areas of the national economy and defense construction, covering wind power equipment, aerospace, power transmission, and transportation, becoming one of the core materials driving the upgrading of high-end manufacturing. However, during long-term service, these composite materials are susceptible to internal damage such as matrix cracking, fiber-matrix interface debonding, and interlayer delamination due to multiple factors including load and environmental erosion. This damage is initially difficult to detect and will continue to expand over time, seriously threatening structural safety and service life.

[0003] Traditional nondestructive testing (NDT) techniques have significant shortcomings when dealing with such hidden damage. Not only are the testing equipment expensive and the operation procedures complex, requiring a high level of professional expertise from the testing personnel, but they also struggle to achieve in-situ real-time monitoring during service, failing to capture the dynamic process of damage initiation and expansion in a timely manner, which can easily lead to safety hazards.

[0004] Existing self-indicating composite material technologies have certain limitations: US Patent US20150361288A1 discloses a dye-containing microcapsule composite material, but the dye is prone to diffusion and the signal decays rapidly; Chinese Patent CN107815068A describes a self-indicating epoxy resin containing fluorescent substances, but it does not solve the problem of environmental stability; European Patent EP3214123B1 proposes a pH-sensitive dye system, but the response speed is slow and it is easily affected by environmental interference. Especially under long-term outdoor use conditions, existing technologies cannot simultaneously meet the requirements of high sensitivity, environmental tolerance, and long lifespan. Therefore, there is an urgent need to develop a damage self-indicating technology that is applicable to various fiber-reinforced composite material systems and has stable and reliable performance. Summary of the Invention

[0005] This invention aims to solve the problem of the difficulty in timely, intuitive and remote detection of damage in existing fiber-reinforced composite materials, and provides a damage self-indicating composite material and its preparation method that does not rely on external energy, has strong environmental adaptability and persistent signal, which significantly improves the safety and service life of key structural components.

[0006] The specific technical solution of this invention is as follows:

[0007] A fiber-reinforced composite material with selective modal damage self-indication function includes reinforcing fibers, a resin matrix, and a microcapsule indication system dispersed in the resin matrix;

[0008] The microcapsule indicator system comprises microcapsules with a wall thickness of 3-15 μm, and the microcapsules encapsulate an indicator substance.

[0009] When a crack with a width ≥ 0.05 mm is generated in the composite material, the microcapsules along the crack path rupture and release an indicator substance.

[0010] Damage location can be identified by one or more detection modalities selected from the following group: visual observation of optical signals, ultraviolet light source excitation fluorescence detection, laser excitation upconversion fluorescence detection, portable gas sensor detection, and handheld electromagnetic detector detection.

[0011] Preferably, the microcapsule indication system is any one of the following microcapsule types: (a) gas-releasing microcapsule containing a tracer gas detected by a gas sensor; (b) optically indicating microcapsule containing a fluorescent color-changing substance that generates a visible signal when excited by light; (c) electromagnetically responsive microcapsule containing a metallic substance that is identified by an electromagnetic detection device.

[0012] Preferably, the gas-emitting microcapsule contains 3 parts sulfur hexafluoride, 4 parts methane and 3 parts perfluorocarbon compound. The gas-emitting microcapsule has a double-wall structure, with the inner layer being a brittle polymer and the outer layer being an elastic polymer. It can be detected by infrared absorption spectroscopy, laser spectroscopy or a specific gas sensor.

[0013] Preferably, the optical indicator microcapsule contains a long-afterglow fluorescent material with the chemical formula SrAl2O4:Eu 2+ ,Dy 3 + The particle size is 0.3-3μm, the afterglow time is ≥10 hours, and the detection is performed by visual observation, ultraviolet light source, laser excitation or infrared thermal imaging.

[0014] Preferably, the optical indicator microcapsule contains an upconversion fluorescent material with the chemical formula NaYF4:Yb 3+ Er 3+ Or NaYF4:Yb 3+ ,Tm 3+ The surface is coated with SiO2, with a shell thickness of 10-30nm; it can be detected by visual observation, ultraviolet light source, laser excitation or infrared thermal imaging.

[0015] Preferably, the electromagnetically responsive microcapsule contains Fe3O4@SiO2 core-shell nanoparticles and silver nanowires;

[0016] The Fe3O4@SiO2 nanoparticles have a diameter of 10-30 nm and a saturation magnetization of ≥60 emu / g;

[0017] The silver nanowires have a length of 5-15 μm and a diameter of 50-150 nm; they can be detected by low-frequency electromagnetic detection, high-frequency electromagnetic detection, or X-ray fluorescence analysis.

[0018] Preferably, the indicator substance comprises 3-15 wt% hydrophobic polymer, 0.2-1.0 wt% UV stabilizer and 0.1-0.5 wt% antioxidant to improve environmental stability and signal duration.

[0019] Preferably, the outer layer of the microcapsule wall material contains a pH-sensitive polymer selected from poly(dimethylaminoethyl methacrylate), polyacrylic acid, and chitosan derivatives, with a thickness of 0.2-0.5 μm, which swells and accelerates the release of contents upon contact with rainwater or moisture.

[0020] Preferably, the microcapsules are distributed in a gradient within the resin matrix, with a density of 1.5-2.5 × 10⁻⁶ in the high-stress region. 4 pcs / mm 3 The density in the low-stress region is 0.3-0.8×10⁻⁶. 4 pcs / mm 3 ;

[0021] The various types of microcapsules have differentiated spatial distributions in the composite material and are customized according to the risk areas of different damage modes.

[0022] Preferably, the reinforcing fiber is selected from one of carbon fiber, glass fiber, aramid fiber, and ultra-high molecular weight polyethylene fiber;

[0023] The resin matrix is ​​selected from one of epoxy resin, unsaturated polyester resin, vinyl ester resin, bismaleimide resin and polyimide resin.

[0024] A method for preparing a fiber-reinforced composite material includes the following steps: Step 1: Select the appropriate microcapsules according to the application requirements and perform surface functionalization treatment;

[0025] Step 2: Disperse the microcapsules in the resin solution at a ratio of 0.3%-2.0% of the total weight of the resin matrix;

[0026] Step 3: Impregnate the reinforcing fibers with a resin system containing microcapsules;

[0027] Step 4: Molding is achieved through pultrusion, compression molding, winding, hand lay-up, and vacuum-assisted resin infusion automated placement processes;

[0028] Step 5: Curing is carried out according to the curing process of the corresponding resin system.

[0029] A damage detection method for fiber-reinforced composite materials includes the following selected detection strategies: (a) damage identification using only a single detection mode; (b) cross-validation using two different detection modes; (c) data fusion analysis using three or more detection modes; wherein the single detection mode is selected from any of the following:

[0030] Observe optical signals with the naked eye;

[0031] ① Ultraviolet light source excitation for fluorescence detection;

[0032] ②Laser-excited upconversion fluorescence detection;

[0033] ③ Detection using portable gas sensors;

[0034] ④ Handheld electromagnetic detector detection; the combination of the two different detection modes is selected from any one of the following groups:

[0035] ① Combination of optical detection and gas detection;

[0036] ② Combination of optical and electromagnetic detection;

[0037] ③ Combination of gas detection and electromagnetic detection: Select the optimal combination of detection modes based on the actual application scenario, environmental conditions, equipment usability, and detection accuracy requirements.

[0038] The fiber-reinforced composite material can be used in any of the following fields: wind turbine blades, carbon fiber reinforcement in civil engineering, aerospace structural components, automotive parts, overhead conductor core rods, sports equipment, power facilities, rail transit, shipbuilding or offshore platforms, with appropriate test mode combinations selected according to the specific application scenario.

[0039] A method for damage-assisted localization of fiber-reinforced composite materials includes the following steps:

[0040] Step 1: When suspected damage occurs in fiber-reinforced composite materials, wipe the surface of the composite material with fluorescent sensor paper or use a portable IMS detector to sample the surface of the composite material by aspiration.

[0041] Step 2: Observe whether the fluorescence sensor test strip undergoes fluorescence quenching or color change, or read the detection signal from the portable IMS detector; if a characteristic signal appears, it is determined that there is damage in the area, thus achieving auxiliary damage localization; the characteristic signal is the fluorescence sensor test strip showing a preset color change and the portable IMS detector detecting the characteristic peak of the corresponding volatile marker.

[0042] The fiber-reinforced composite material is the core rod of the carbon fiber composite core conductor. After the composite material is damaged, the volatile markers released diffuse through the strand gaps of the outer aluminum strands of the conductor to the surface of the conductor, thus completing the damage-assisted localization without peeling off the outer aluminum strands.

[0043] Compared with the prior art, the technical effects and advantages of the present invention are:

[0044] 1. Wide range of applications, suitable for various reinforcement systems such as carbon fiber, glass fiber, and aramid fiber, and can be combined with different resin matrices to meet the application needs of multiple fields such as aerospace, wind power, and automobiles.

[0045] 2. It has strong environmental adaptability. The indicator material has undergone special surface modification, and the signal retention time is ≥72 hours under rain washout. Combined with ultraviolet stabilizers and antioxidants, it meets the needs of long-term outdoor use.

[0046] 3. No external energy is required. It adopts a rare earth fluorescence system to achieve energy storage during the day and self-luminescence at night, reducing detection costs and adapting to in-situ monitoring in scenarios without power supply.

[0047] 4. High detection sensitivity: The microcapsule wall material adopts a pH-responsive design, which automatically accelerates the release of indicator substances when exposed to rainwater, capturing microcracks with a width of ≥0.05mm and accurately identifying early damage.

[0048] 5. Does not affect the core properties of the material; the volume resistivity of the indicator material is >10. 14 The microcapsule content is controlled within the range of 0.3-2.0 wt%, which does not affect the electrical properties of the composite material. The impact of microcapsule addition on the mechanical properties of the composite material is less than 5%, meeting the requirements for structural components.

[0049] 6. Supports remote detection, enabling remote identification within a distance of 200 meters via handheld devices or drones, improving detection efficiency and reducing the difficulty of detection in complex scenarios such as high altitudes.

[0050] 7. Adaptable to extreme environments, the indicator system operates in a temperature range of -60℃ to +180℃, enabling it to cope with extreme high and low temperature conditions and expand its application scenarios. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of damage to glass fiber composite materials;

[0052] Figure 2 This is a schematic diagram of laser-excited fluorescence due to delamination damage in the carbon fiber / epoxy composite material in Example 2;

[0053] Figure 3 This is a schematic diagram of the microcapsule structure;

[0054] Figure 4 This is a schematic diagram of the layered structure of the composite material.

[0055] Explanation of reference numerals in the attached diagram: 1-wall material, 2-indicator substance, 3-pH-sensitive outer layer, 4-reinforcing fiber layer, 5-microcapsule-containing resin matrix layer. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Example 1: Application of gas-release microcapsules

[0059] Test object: Glass fiber reinforced epoxy resin composite material for wind turbine blades. Positioning method: Gas-release microcapsules are used as damage indicator units. The microcapsules contain a composite tracer gas of sulfur hexafluoride, methane, and perfluorocarbons, with a double-wall structure (inner layer of brittle polymer, outer layer of elastic polymer) and a wall thickness of 8 μm. When the composite material develops a crack ≥0.05 mm, the microcapsule ruptures, releasing the tracer gas.

[0060] Detection method: Using a portable gas sensor and laser spectrometer, gas is drawn from the surface of the composite material to sample and identify characteristic gas signals.

[0061] Test results: The cracked area can show obvious gas characteristic peaks within 10 seconds, with a positioning accuracy of ≤5mm. It can achieve in-situ rapid detection without excavation or disassembly, and the signal duration is ≥2h, which meets the requirements of high-altitude inspection of wind turbine blades.

[0062] Example 2: Application of optical indicator microcapsules (containing long-afterglow fluorescent materials)

[0063] Test object: Carbon fiber reinforced composite material for building and civil engineering

[0064] Positioning method: Optically indicating microcapsules containing long-afterglow fluorescent material SrAl2O4:Eu were used. 2+ ,Dy 3+ The particles have a diameter of 0.3-3 μm and a afterglow time of ≥10 h. Fluorescent substances are released after the microcapsules rupture, exhibiting significant fluorescence under natural / ultraviolet light.

[0065] Detection method: Excitation by ultraviolet lamp (365nm) irradiation, and observation of the luminescent area by naked eye or fluorescence camera to achieve damage localization.

[0066] Test results: The microcrack area showed a bright yellow-green fluorescence, and the crack outline was clearly visible. No continuous power supply was required, and it could still be observed at night. The afterglow lasted for more than 12 hours, which can be used for long-term non-destructive monitoring of building structures.

[0067] Example 3: Application of optical indicator microcapsules (containing upconversion fluorescent materials)

[0068] Test object: Carbon fiber / epoxy laminate composite material for aerospace applications

[0069] Positioning method: Optically indicating microcapsules containing the upconversion fluorescent material NaYF4:Yb were used. 3+ Er 3+ @SiO2, with a shell thickness of 10-30nm. Excitation with a 980nm near-infrared laser produces visible fluorescence, accurately indicating the location of delamination and cracks.

[0070] Detection method: 980nm infrared laser excitation, signal acquisition by upconversion fluorescence imaging system.

[0071] Test results: Internal delamination damage immediately shows a green fluorescent area under laser irradiation, with a positioning resolution of ≤2mm. It can penetrate the surface of composite materials to identify hidden internal damage and is suitable for high-precision inspection of aerospace components.

[0072] Example 4: Application of Electromagnetically Responsive Microcapsules

[0073] Test subject: Carbon fiber / aramid hybrid composite material for automotive bumpers

[0074] Positioning method: Electromagnetically responsive microcapsules containing Fe3O4@SiO2 core-shell nanoparticles (diameter 10-30nm, saturation magnetization ≥60emu / g) and silver nanowires are used. After being stressed and broken, magnetic and conductive substances are released, changing the local electromagnetic properties.

[0075] Detection methods: handheld electromagnetic detector, low-frequency electromagnetic scanning or X-ray fluorescence analysis.

[0076] Test results: The electromagnetic signal in the damaged area changed significantly, which can quickly identify the collision crack and deformation area. The detection response time is less than 3 seconds. It can be used for rapid damage assessment after a car collision and is not affected by environmental factors such as oil and dust.

[0077] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fiber-reinforced composite material with selective modal damage self-indication function, characterized in that, It includes reinforcing fibers, a resin matrix, and a microcapsule indicating system dispersed in the resin matrix; The microcapsule indicator system comprises microcapsules with a wall thickness of 3-15 μm, and the microcapsules encapsulate an indicator substance. When a crack with a width ≥ 0.05 mm is generated in the composite material, the microcapsules along the crack path rupture and release an indicator substance.

2. The fiber-reinforced composite material according to claim 1, characterized in that, The microcapsule indication system is one of the following microcapsule types: (a) Gas-releasing microcapsules containing tracer gas detected by a gas sensor; (b) Optical indicator microcapsules containing a fluorescent color-changing substance that generates a visible signal when excited by light; (c) Electromagnetically responsive microcapsules containing metallic substances that can be detected by electromagnetic detection devices.

3. The fiber-reinforced composite material according to claim 2, characterized in that, The gas-emitting microcapsule contains 3 parts sulfur hexafluoride, 4 parts methane and 3 parts perfluorocarbon compound. The gas-emitting microcapsule has a double-wall structure, with the inner layer being a brittle polymer and the outer layer being an elastic polymer.

4. The fiber-reinforced composite material according to claim 2, characterized in that, The optical indicator microcapsule contains a long-afterglow fluorescent material with the chemical formula SrAl2O4:Eu. 2+ ,Dy 3+ The particle size is 0.3-3μm, and the afterglow time is ≥10 hours.

5. The fiber-reinforced composite material according to claim 2, characterized in that, The optical indicator microcapsule contains an upconversion fluorescent material with the chemical formula NaYF4:Yb. 3+ Er 3+ Or NaYF4:Yb 3+ ,Tm 3+ The surface is coated with SiO2, and the shell thickness is 10-30nm.

6. The fiber-reinforced composite material according to claim 2, characterized in that, The electromagnetically responsive microcapsules contain Fe3O4@SiO2 core-shell nanoparticles and silver nanowires. The Fe3O4@SiO2 nanoparticles have a diameter of 10-30 nm and a saturation magnetization of ≥60 emu / g; The silver nanowires have a length of 5-15 μm and a diameter of 50-150 nm.

7. The fiber-reinforced composite material according to claim 1, characterized in that, The indicator contains 3-15 wt% hydrophobic polymer, 0.2-1.0 wt% UV stabilizer and 0.1-0.5 wt% antioxidant to improve environmental stability and signal duration.

8. The fiber-reinforced composite material according to claim 2, characterized in that, The outer layer of the microcapsule wall material contains a pH-sensitive polymer selected from poly(dimethylaminoethyl methacrylate), polyacrylic acid, and chitosan derivatives, with a thickness of 0.2-0.5 μm. It swells and accelerates the release of contents when exposed to rain or moisture.

9. The fiber-reinforced composite material according to claim 2, characterized in that, The microcapsules are distributed in a gradient within the resin matrix, with a density of 1.5-2.5 × 10⁻⁶ in high-stress regions. 4 pcs / mm 3 The density in the low-stress region is 0.3-0.8×10⁻⁶. 4 pcs / mm 3 .

10. The fiber-reinforced composite material according to claim 1, characterized in that, The reinforcing fiber is selected from one of carbon fiber, glass fiber, aramid fiber and ultra-high molecular weight polyethylene fiber; The resin matrix is ​​selected from one of epoxy resin, unsaturated polyester resin, vinyl ester resin, bismaleimide resin and polyimide resin.

11. A method for preparing a fiber-reinforced composite material, characterized in that, Includes the following steps: Step 1: Select the appropriate microcapsules according to the application requirements and perform surface functionalization treatment; Step 2: Disperse the microcapsules in the resin solution at a ratio of 0.3%-2.0% of the total weight of the resin matrix; Step 3: Impregnate the reinforcing fibers with a resin system containing microcapsules; Step 4: Molding is achieved through pultrusion, compression molding, winding, hand lay-up, and vacuum-assisted resin infusion automated placement processes; Step 5: Curing is carried out according to the curing process of the corresponding resin system.

12. A method for damage-assisted localization of fiber-reinforced composite materials, comprising the following steps: Step 1: When suspected damage occurs in fiber-reinforced composite materials, wipe the surface of the composite material with fluorescent sensor paper or use a portable IMS detector to sample the surface of the composite material by aspiration. Step 2: Observe whether the fluorescence sensor test strip undergoes fluorescence quenching or color change, or read the detection signal from the portable IMS detector; if a characteristic signal appears, it is determined that there is damage in the area, thus achieving auxiliary damage localization; the characteristic signal is the fluorescence sensor test strip showing a preset color change or the portable IMS detector detecting the characteristic peak of the corresponding volatile marker. The fiber-reinforced composite material is the core rod of the carbon fiber composite core conductor. After the composite material is damaged, the volatile markers released diffuse through the strand gaps of the outer aluminum strands of the conductor to the surface of the conductor, thus completing the damage-assisted localization without peeling off the outer aluminum strands.

13. The application of the fiber-reinforced composite material according to any one of claims 1-11 in any of the following fields: wind turbine blades, carbon fiber reinforcement in civil engineering, aerospace structural components, automotive parts, overhead conductor core rods, sports equipment, power facilities, rail transportation, shipbuilding or offshore platforms.

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