Method for monitoring the pressure of a fibre prepreg layup using nanosensors

Abstract

The application provides a kind of nanometer sensor monitoring method of fiber prepreg layer pressure, and relates to composite manufacturing process control technical field.The composite fiber prepreg interlayer pressure monitoring method provided by the application uses flexible pressure sensor with high elastic modulus multidimensional nanometer material, prepares monitoring unit according to the size and shape of composite fiber prepreg, uses monitoring unit to collect pressure data of each monitoring position between composite fiber prepreg layers and calculates the pressure value between composite fiber prepreg layers;According to the pressure value between composite fiber prepreg layers, the pressure distribution between composite fiber prepreg layers is monitored, the dynamic change of pressure field is accurately identified, the abnormal point data is captured in time, whether defect is caused in automatic layer loading process is confirmed, and the purpose of guiding process optimization is achieved.

Description

Technical Field

[0001] This invention relates to the field of composite material manufacturing process control technology, specifically to a nanosensor monitoring method for fiber prepreg layup pressure. Background Technology

[0002] Fiber-reinforced composites possess extremely high specific stiffness and specific strength, and are widely used in aerospace, automotive, and rail transportation industries. During the preparation of composite materials, the layup quality of the fiber prepreg is one of the key factors affecting the performance of the final product. Regardless of the process method used, such as vacuum bag molding, compression molding, or autoclave molding, strict requirements are placed on the density of the prepreg layup. A tight prepreg layup effectively reduces the formation of porosity and internal cavities, which is crucial for ensuring the quality of future molding. In vacuum bag molding, the vacuum pressure forces the prepreg to adhere tightly, expelling air and reducing porosity. Compression molding relies on the pressure of the mold to ensure a tight layup of the prepreg within the mold, avoiding the formation of internal cavities. Autoclave molding requires a high-temperature, high-pressure environment to ensure the prepreg adheres tightly during the layup process to achieve the ideal molding effect. If the prepreg layup is not tight, the presence of porosity and internal cavities will lead to a decrease in the mechanical properties of the composite material, affecting its key performance indicators such as strength, stiffness, and durability, and consequently impacting the product's service life and reliability. Therefore, ensuring that the prepreg is tightly laid up and the pressure field is uniform, and reducing pores and internal cavities, is an indispensable and important step in the preparation process of various composite materials, and is of decisive significance for improving the molding quality of composite materials.

[0003] To ensure tight interlayer pressure distribution and optimal process parameters in fiber prepreg, real-time monitoring of interlayer pressure using sensors is necessary. Currently available pressure monitoring methods include fiber optic grating sensors, MEMS sensors, and capacitive pressure sensors. These methods are applicable to their respective fields, and the sensors possess unique shapes, suitable installation methods, and sensing performance. Therefore, when considering interlayer pressure monitoring in fiber prepreg, it is crucial to ensure that the sensor's size, shape, installation method, and performance meet the monitoring requirements. Due to the limited space between fiber prepreg layers and the variable monitoring locations, rigid sensors are difficult to install effectively, and their microscopic structural changes impose stringent requirements on sensing performance, thus limiting the application of the aforementioned sensors in interlayer pressure monitoring.

[0004] Existing testing methods, such as fiber Bragg grating sensors, MEMS sensors, and capacitive pressure sensors, suffer from insufficient sensor monitoring range. The main reasons include: the low elastic modulus of the sensor materials limits the monitoring range; and insufficient sensor sensitivity directly affects monitoring accuracy. Therefore, in practical applications, they often fail to achieve the expected monitoring results. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of existing technologies. It proposes a method for monitoring interlayer pressure in composite fiber prepregs. This method involves designing a carbon nanotube sensor array to monitor interlayer pressure during the automated composite material layup process, guiding the optimization of the composite material preparation process, and achieving quality control of the workpiece to reduce the product defect rate. The key lies in using carbon nanotubes to construct a piezoresistive sensing network, which can change shape in response to pressure applied by an external elastic indenter, thereby enabling in-situ monitoring of the interlayer pressure distribution.

[0006] The present invention provides a method for monitoring interlayer pressure in composite fiber prepregs, comprising the following steps:

[0007] Monitoring units are prepared based on the size and shape of the composite fiber prepreg, and monitoring units are deployed between the composite fiber prepreg layers.

[0008] The pressure data at various monitoring locations between the composite fiber prepreg layers were collected using the monitoring unit, and the pressure values ​​between the composite fiber prepreg layers were calculated.

[0009] The pressure distribution between the fiber prepreg layers of the composite material is monitored based on the pressure value between the layers, and the molding quality of the composite material is evaluated in combination with different process pressure parameters.

[0010] Furthermore, the composite fiber prepreg includes any one or more of thermoplastic or thermosetting carbon fiber prepreg, glass fiber prepreg, and aramid fiber prepreg.

[0011] Furthermore, the monitoring unit includes a sensor unit and a multimeter. The sensor unit includes one or more nanosensors and a flexible printed circuit. The nanosensors include a sensing layer.

[0012] Furthermore, the sensing layer is prepared by one or more nanomaterials with one or more of the following morphologies: two-dimensional nanosheets, one-dimensional nanowires, and zero-dimensional nanodots, through one or more of the following processes: 3D printing, vacuum filtration, and screen printing.

[0013] Furthermore, a monitoring unit is prepared based on the size and shape of the composite fiber prepreg, including:

[0014] The nanosensor and flexible printed circuit are cut according to the size and shape of the composite fiber prepreg. The nanosensor is arranged in an array and the nanosensor and flexible printed circuit are bonded together. Then, the nanosensor is encapsulated with any one of the insulating materials, such as polyimide, polydimethylsiloxane, or polyurethane film, to obtain the sensor unit.

[0015] Connect the sensor unit to the multimeter to obtain the monitoring unit.

[0016] Furthermore, pressure data at various monitoring locations between floors are collected using monitoring units. The specific method is as follows:

[0017] The monitoring unit collects interlayer pressure data of the composite prepreg. Multiple nanosensors arranged in an array in the monitoring unit collect pressure values ​​at corresponding monitoring locations and convert them into digital signals. A multimeter is used to record the pressure values ​​collected by the multiple nanosensors at corresponding monitoring locations to obtain pressure data at each monitoring location in the interlayer of the composite prepreg.

[0018] Furthermore, the pressure value between the fiber prepreg layers of the composite material is calculated using the following formula:

[0019]

[0020] in, M This is the set of response values ​​for a nanosensor array. P The pressure values ​​at the corresponding monitoring locations are collected by the nanosensors. ξ The pressure coefficient of the nanosensor. This represents the correction coefficient for the nanosensor. R i For the first i Real-time resistance value of a nanosensor m This represents the total number of nanosensors. R 0i The initial resistance value acquired by the nanosensor, ( Ri - R 0i ) / R 0i The resistance change rate of the nanosensor.

[0021] Furthermore, the pressure distribution between the fiber prepreg layers of the composite material was monitored using the following method:

[0022] A pressure distribution cloud map of the interlayer of fiber prepreg is generated based on the pressure value between the layers of the composite fiber prepreg, and the response value set of the nanosensor array is used as a basis. M The variance of the pressure values ​​collected by each nanosensor at the corresponding monitoring location is used to determine whether the pressure field is uniform and whether there are abnormal pressure points.

[0023] Furthermore, the molding quality of composite materials is evaluated by combining different process pressure parameters. The specific method is as follows:

[0024] Different process parameters were determined based on the interlayer pressure distribution of the fiber prepreg to prepare the finished composite material.

[0025] By verifying the strength of composite materials prepared using different process parameters and identifying the composite material with the best strength, the optimal process scheme for preparing the composite material can be determined.

[0026] The beneficial effects of adopting the above technical solution are as follows: The nanosensor monitoring method for fiber prepreg layup pressure provided by this invention monitors the interlayer pressure distribution of composite fiber prepreg by embedding a carbon nanotube sensor array. It employs a self-assembled porous sensing network structure of high-elastic-modulus multidimensional carbon nanomaterials, allowing resin impregnation and fixing the carbon nanotube network architecture, presenting a three-dimensional arrangement, achieving relatively uniform and stable conductive path distribution. The resin material provides the necessary mechanical support for the conductive network, achieving the purpose of in-situ pressure monitoring and ensuring a wide service range and stability of the carbon nanotube sensor.

[0027] In the nanosensor prepared by the method of the present invention, two-dimensional carbon nanomaterials, one-dimensional carbon nanomaterials and zero-dimensional nanodots jointly construct a multi-path sensing network, which synergistically improves the sensor sensitivity.

[0028] This invention employs an array of nanosensors arranged between different layups of a composite fiber prepreg. This array accurately identifies dynamic changes in the pressure field, promptly captures abnormal data, and confirms whether defects have occurred during the automatic layup loading process. The sensor array can also monitor pressure changes in real time, thereby guiding process optimization.

[0029] The method of this invention has high flexibility and freedom. It can select different proportions of carbon nanomaterials according to different application scenarios to prepare "nanosensors" suitable for different application scenarios. Moreover, the preparation method is simple, has a high success rate, is safe and environmentally friendly, has low preparation cost, saves materials, and the finished product has a wide range of applications. It has high operability and practicality and is worthy of widespread promotion and application. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the microstructure of the nanosensor provided in Embodiment 1 of the present invention;

[0031] Figure 2 This is a pressure field change cloud map of the nanosensor array provided in Embodiment 1 of the present invention during the pressure monitoring process between fiber layups in composite prepregs.

[0032] Figure 3 This is a schematic diagram of the resistance change rate versus pressure provided in Embodiment 1 of the present invention;

[0033] Figure 4 This is a schematic diagram of a pressure distribution abnormality sensing unit provided in Embodiment 2 of the present invention. Detailed Implementation

[0034] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0035] Example 1

[0036] This embodiment describes a nanosensor-based method for monitoring the layup pressure of fiber prepregs. The microstructure of the nanosensor is as follows: Figure 1 As shown, a monitoring unit using nanosensors collects interlayer pressure data of the composite fiber prepreg, obtains the pressure distribution between the fiber prepreg layers, and evaluates the molding quality of the composite material under different process pressure parameters to guide process optimization. The process includes the following steps:

[0037] Monitoring units are prepared based on the size and shape of the composite fiber prepreg, and monitoring units are deployed between the composite fiber prepreg layers.

[0038] The pressure data at various monitoring locations between the composite fiber prepreg layers were collected using the monitoring unit, and the pressure values ​​between the composite fiber prepreg layers were calculated.

[0039] The pressure distribution between the fiber prepreg layers of the composite material is monitored based on the pressure value between the layers, and the molding quality of the composite material is evaluated in combination with different process pressure parameters.

[0040] Composite fiber prepregs include any one or more of thermoplastic or thermosetting carbon fiber prepregs, glass fiber prepregs, and aramid fiber prepregs.

[0041] The monitoring unit includes a sensor unit and a multimeter. The sensor unit includes one or more nanosensors and a flexible printed circuit. The nanosensors include a sensing layer.

[0042] The sensing layer is made of one or more nanomaterials with one or more of the following morphologies: two-dimensional nanosheets, one-dimensional nanowires, and zero-dimensional nanodots, through one or more of the following processes: 3D printing, vacuum filtration, and screen printing.

[0043] In this embodiment, the sensing layer of the nanosensor uses an MXene / CNT sensor. The MXene / CNT sensor is prepared based on the preparation method in patent application CN201911336931.8, "A method for preparing a sensor for monitoring liquid molding processes of composite materials," and includes the following steps:

[0044] (1) A certain amount of MXene powder was added to a certain amount of deionized water and ultrasonically exfoliated to obtain a monodisperse aqueous solution of MXene sheets; wherein the mass-volume ratio of MXene powder to deionized water was 1:2.67.

[0045] (2) Using a high-pressure spray gun, the monodisperse aqueous solution of MXene sheets is sprayed onto the treated polyurethane (PU) film, and vacuum dried to obtain an MXene matrix film with a thickness of a; wherein, the vacuum degree of the vacuum drying oven is -0.06MPa, the drying temperature is 80~100℃, and the drying time is 1~2h; the PU film is treated by repeatedly washing with acetone, ethanol, and deionized water 3~5 times;

[0046] (3) The prepared CNT monodisperse aqueous solution was sprayed onto the obtained MXene matrix film using a high-pressure spray gun, and vacuum dried to obtain an MXene-CNT composite matrix film with a thickness of b; wherein, the vacuum degree of the vacuum drying oven was -0.06MPa, the drying temperature was 80~100℃, and the drying time was 1~2h;

[0047] (4) The MXene sheet monodisperse aqueous solution was sprayed onto the obtained MXene-CNT composite matrix film again using a high-pressure spray gun, and vacuum dried to obtain an MXene-CNT-MXene sandwich structure film with a thickness of c; wherein, the vacuum degree of the vacuum drying oven was -0.06MPa, the drying temperature was 80~100℃, and the drying time was 1~2h;

[0048] (5) Peel the MXene-CNT-MXene sandwich structure film from the PU film and cut it into a circle with a diameter of 2 to 10 mm. Set electrodes at both ends of the circular film diameter to obtain the MXene / CNT sensor.

[0049] Nanosensors and flexible printed circuits are cut according to the size and shape of the composite fiber prepreg, the nanosensors are arranged in an array, the nanosensors and flexible printed circuits are bonded together, and then polyimide is used to encapsulate the nanosensor array to obtain the sensor unit.

[0050] Connect the sensor unit to the multimeter to obtain the monitoring unit.

[0051] The monitoring unit collects interlayer pressure data of the composite prepreg. Multiple nanosensors arranged in an array in the monitoring unit collect pressure values ​​at corresponding monitoring locations and convert them into digital signals. A multimeter is used to record the pressure values ​​collected by the multiple nanosensors at corresponding monitoring locations to obtain pressure data at each monitoring location in the interlayer of the composite prepreg.

[0052] The pressure value between the fiber prepreg layers of the composite material is calculated using the following formula:

[0053]

[0054] Where M is the set of response values ​​of the nanosensor array, P is the pressure value at the corresponding monitoring location collected by the nanosensor, and ξ is the pressure coefficient of the nanosensor. R is the correction factor for the nanosensor. i R is the real-time resistance value of the i-th nanosensor, m is the total number of nanosensors, and R 0i The initial resistance value acquired by the nanosensor, (Ri-R) 0i ) / R 0i The resistance change rate of the nanosensor.

[0055] The pressure distribution between the fiber prepreg layers of the composite material was monitored using the following method:

[0056] A pressure distribution cloud map of the interlayer of fiber prepreg is generated based on the pressure value between the layers of the composite fiber prepreg, and the response value set of the nanosensor array is used as a basis. M The variance of the pressure values ​​collected by each nanosensor at the corresponding monitoring location is used to determine whether the pressure field is uniform and whether there are abnormal pressure points.

[0057] Based on the pressure values ​​at each monitoring location between layers, the following is generated: Figure 2 The pressure distribution cloud map of the fiber prepreg shown illustrates the placement of sensors between the fiber prepreg layers. A press was then used to apply cyclic pressure to the fiber prepreg, and the resistance change of the sensors during the stretching process was measured using a multimeter. Ri - R 0i ) / R 0i The calculated rate of change of resistance under pressure is shown in the diagram below. Figure 3 As shown.

[0058] When a nanosensor is subjected to pressure, its resistance increases with increasing strain; conversely, upon pressure recovery, the resistance decreases with decreasing strain. This is because when pressure is applied between the fiber prepreg layers, the nanosensor's conductive network narrows due to the compression effect, causing its resistance to increase with pressure. Conversely, upon recovery, the conductive network recovers, and the resistance returns to its original level. Therefore, the resistance of the nanosensor changes differently depending on the magnitude of the pressure applied between the fiber prepreg layers. Based on these resistance changes, the pressure values ​​at different locations within the fiber prepreg layers can be calculated using the above formula. P Size, based on the nanosensor array combined with the set of response values M Pressure values ​​collected by each nanosensor at the corresponding monitoring location P The variance is used to determine whether the pressure field is uniform and whether there are abnormal pressure points.

[0059] Different process parameters were determined based on the interlayer pressure distribution of the fiber prepreg to prepare the finished composite material.

[0060] By verifying the strength of composite materials prepared using different process parameters and identifying the composite material with the best strength, the optimal process scheme for preparing the composite material can be determined.

[0061] Example 2

[0062] This embodiment of a nanosensor-based method for monitoring fiber prepreg layup pressure includes the following steps:

[0063] Monitoring units are prepared based on the size and shape of the composite fiber prepreg, and monitoring units are deployed between the composite fiber prepreg layers.

[0064] The pressure data at various monitoring locations between the composite fiber prepreg layers were collected using the monitoring unit, and the pressure values ​​between the composite fiber prepreg layers were calculated.

[0065] The pressure distribution between the fiber prepreg layers of the composite material is monitored based on the pressure value between the layers, and the molding quality of the composite material is evaluated in combination with different process pressure parameters.

[0066] The monitoring unit includes a sensor unit and a multimeter. The sensor unit includes one or more nanosensors and a flexible printed circuit. The nanosensors include a sensing layer.

[0067] The sensing layer is made of one or more nanomaterials with one or more of the following morphologies: two-dimensional nanosheets, one-dimensional nanowires, and zero-dimensional nanodots, through one or more of the following processes: 3D printing, vacuum filtration, and screen printing.

[0068] In this embodiment, the sensing layer of the nanosensor uses an MXene / CNT sensor, which is prepared using the same preparation method as in Example 1.

[0069] Nanosensors and flexible printed circuits are cut according to the size and shape of the composite fiber prepreg. The nanosensors are arranged in an array. The micro-nano sensor array and the flexible printed circuit are bonded together. Then, the micro-nano sensor array is encapsulated with an insulating layer of polydimethylsiloxane to obtain the sensor unit.

[0070] The encapsulated sensor unit array is arranged between the fiber prepreg layers and connected to a multimeter to obtain the monitoring unit.

[0071] The monitoring unit collects interlayer pressure data of the composite prepreg. Multiple nanosensors arranged in an array in the monitoring unit collect pressure values ​​at corresponding monitoring locations and convert them into digital signals. A multimeter is used to record the pressure values ​​collected by the multiple nanosensors at corresponding monitoring locations to obtain pressure data at each monitoring location in the interlayer of the composite prepreg.

[0072] The pressure value between the fiber prepreg layers of the composite material is calculated using the following formula:

[0073] ;

[0074] Where M is the set of response values ​​of the nanosensor array, P is the pressure value at the corresponding monitoring location collected by the nanosensor, and ξ is the pressure coefficient of the nanosensor. R is the correction factor for the nanosensor. i R is the real-time resistance value of the i-th nanosensor, m is the total number of nanosensors, and R 0i The initial resistance value acquired by the nanosensor, (Ri-R) 0i ) / R 0i The resistance change rate of the nanosensor.

[0075] The interlayer pressure of composite fiber prepreg is monitored, and the presence of abnormal pressure points is determined based on the pressure distribution. It is confirmed that there are no abnormal points in the sensor array.

[0076] Different process parameters are determined based on the interlayer pressure distribution of the fiber prepreg to prepare the finished composite material; when there are conditions such as... in the sensor array Figure 4 The sensor unit showing abnormal pressure values ​​indicates that a pressure value higher than other sensor unit monitoring points indicates significant stress concentration in that area, causing resin extrusion and overflow; a pressure value lower than other sensor unit monitoring points indicates lower pressure in that area, leading to defects in the finished composite material. Strength verification is performed on composite materials prepared using different process parameters to identify the composite material with the optimal strength, guiding process optimization and determining the optimal process scheme for preparing this composite material.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the present invention.

Claims

1. A nanosensor-based method for monitoring the layup pressure of fiber prepregs, characterized in that, Includes the following steps: Monitoring units are prepared based on the size and shape of the composite fiber prepreg, and monitoring units are deployed between the composite fiber prepreg layers. The pressure data at various monitoring locations between the composite fiber prepreg layers were collected using the monitoring unit, and the pressure values ​​between the composite fiber prepreg layers were calculated. The pressure distribution between the fiber prepreg layers of the composite material is monitored based on the pressure value between the layers, and the molding quality of the composite material is evaluated in combination with different process pressure parameters. The monitoring unit is fabricated based on the size and shape of the composite fiber prepreg, including: The nanosensor and flexible printed circuit are cut according to the size and shape of the composite fiber prepreg. The nanosensor is arranged in an array and the nanosensor and flexible printed circuit are bonded together. Then, the nanosensor is encapsulated with any one of the insulating materials, such as polyimide, polydimethylsiloxane, or polyurethane film, to obtain the sensor unit. Connect the sensor unit to the multimeter to obtain the monitoring unit; Pressure data at various monitoring locations between floors is collected using a monitoring unit. The specific method is as follows: The monitoring unit collects pressure data between the layers of the composite prepreg. Multiple nanosensors arranged in an array in the monitoring unit collect pressure values ​​at corresponding monitoring locations and convert them into digital signals. A multimeter is used to record the pressure values ​​collected by the multiple nanosensors at corresponding monitoring locations to obtain pressure data at each monitoring location between the layers of the composite prepreg. The pressure value between the fiber prepreg layers of the composite material is calculated using the following formula: Where M is the set of response values ​​of the nanosensor array, P is the pressure value at the corresponding monitoring location collected by the nanosensor, and ξ is the pressure coefficient of the nanosensor. R is the correction factor for the nanosensor. i R is the real-time resistance value of the i-th nanosensor, m is the total number of nanosensors, and R 0i The initial resistance value acquired by the nanosensor, (R) i -R 0i ) / R 0i The resistance change rate of the nanosensor.

2. The nanosensor monitoring method for fiber prepreg layup pressure according to claim 1, characterized in that, The composite fiber prepreg includes any one or more of thermoplastic or thermosetting carbon fiber prepreg, glass fiber prepreg, and aramid fiber prepreg.

3. The nanosensor monitoring method for fiber prepreg layup pressure according to claim 2, characterized in that, The monitoring unit includes a sensor unit and a multimeter. The sensor unit includes one or more nanosensors and a flexible printed circuit. The nanosensors include a sensing layer.

4. The nanosensor monitoring method for fiber prepreg layup pressure according to claim 3, characterized in that, The sensing layer is made of nanomaterials with one or more of the following morphologies: two-dimensional nanosheets, one-dimensional nanowires, and zero-dimensional nanodots, through one or more processes such as 3D printing, vacuum filtration, and screen printing.

5. The nanosensor monitoring method for fiber prepreg layup pressure according to claim 1, characterized in that, The pressure distribution between the fiber prepreg layers of the composite material was monitored using the following method: A pressure distribution cloud map of the fiber prepreg is generated based on the pressure value between the fiber prepreg layers of the composite material. The variance of the pressure value at the corresponding monitoring position collected by each nanosensor in the nanosensor array response value set M is used to determine whether the pressure field is uniform and whether there are abnormal pressure points.

6. The nanosensor monitoring method for fiber prepreg layup pressure according to claim 1, characterized in that, The method for evaluating the molding quality of composite materials by combining different process pressure parameters is as follows: Different process parameters were determined based on the interlayer pressure distribution of the fiber prepreg to prepare the finished composite material. The strength of composite materials prepared using different process parameters was checked to identify the composite material with the best strength and determine the optimal process scheme for preparing the composite material.

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