System and method for detecting thickness and fiber direction of carbon fiber material

Abstract

The invention discloses a system and a method for detecting the thickness and the fiber direction of a carbon fiber material, and the system is characterized in that the long sides of three rectangular receiving coils are respectively close to the three sides of a right triangle excitation coil, and the right triangle excitation coil and the three rectangular receiving coils are respectively led out and are connected with a multi-channel eddy current instrument; the eddy current sensor is placed on the carbon fiber material plate; the multi-channel eddy current instrument is used for introducing alternating current into the right triangle excitation coil to generate an excitation magnetic field, analyzing measurement signals generated by the three rectangular receiving coils to obtain three groups of measurement values, and transmitting the three groups of measurement values to the computer; the computer is used for filtering each group of measured values, extracting signal amplitudes and comparing and analyzing the signal amplitudes to obtain the thickness and the fiber direction of the carbon fiber material plate, and the number of layers and the direction of the carbon fibers can be inverted by analyzing the measured signals from the three rectangular receiving coils, so that the measurement accuracy is improved. And synchronous measurement of the layer number and direction of the carbon fiber is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing of carbon fiber materials, and more particularly to a system and method for testing the thickness and fiber direction of carbon fiber materials. Background Art

[0002] Carbon fiber composites (CFRP) are widely used in various fields such as aerospace, automotive industry, shipbuilding, civil engineering and electronics due to their high strength, light weight, good thermal insulation and electrical insulation. However, their excellent performance depends on the precise arrangement of carbon fibers; therefore, reliable non-destructive testing methods are essential to ensure the quality of carbon fiber materials during the manufacturing process.

[0003] Eddy current testing (ECT) is a nondestructive testing method based on the principle of electromagnetic induction. Compared with ultrasonic testing, X-ray and infrared thermal imaging, it can achieve non-contact rapid detection of carbon fiber materials. The eddy current testing method has been widely used in direction detection and defect detection of carbon fiber.

[0004] A study proposed a multi-coil eddy current sensor, which is composed of eight coils. It uses two groups of coils (four coils in each group) to alternately excite and receive to generate an axial rotating magnetic field to measure the direction of the CFRP sheet pile, which can replace the sensor of the mechanical rotation system. Some scholars have also proposed a multi-element sensor to evaluate carbon fiber materials. Each unit is square in shape and consists of four triangular coils that are jointly excited and received. The entire array contains multiple units, which can also achieve the effect of reducing mechanical rotation. However, the above sensors have high requirements for resources and instrument channels, and the workmanship is relatively complex, making them difficult to manufacture and apply in actual industry.

[0005] In the prior art, a new type of eddy current probe without lift-off interference is proposed for the material defect detection process to detect defects in carbon fiber materials. The process consists of an '8'-shaped excitation coil and a ring-shaped receiving coil, so that the total excitation magnetic field passing through the receiving coil is zero, which helps to prevent the influence of the lift-off effect. However, when the probe is tilted, the material defect detection process loses the effectiveness of preventing the lift-off effect and the accuracy of detection.

[0006] The thickness and orientation of carbon fiber have a very important impact on the performance and quality of manufactured products. However, in the existing carbon fiber eddy current detection technology, most sensors are relatively difficult to manufacture, and require a lot of resources and sufficient safety precautions to reduce errors, making it difficult to achieve high-precision measurement of thickness or orientation at the same time. Summary of the invention

[0007] The purpose of the present invention is to provide a detection system and method for the thickness and fiber direction of carbon fiber materials, which realizes the synchronous measurement of the thickness and fiber direction of carbon fiber materials by analyzing the measurement signals of three rectangular receiving coils.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A detection system for the thickness and fiber direction of a carbon fiber material, comprising: a carbon fiber material plate, an eddy current sensor, a multi-channel eddy current instrument and a computer;

[0010] The eddy current sensor comprises: a right-angled triangle excitation coil and three rectangular receiving coils;

[0011] The long sides of the three rectangular receiving coils are respectively placed close to the three sides of the right-angled triangle excitation coil, and the right-angled triangle excitation coil and the three rectangular receiving coils are respectively led out and connected to the multi-channel eddy current instrument;

[0012] The eddy current sensor is placed on the carbon fiber material plate;

[0013] The multi-channel eddy current instrument is used to pass alternating current into the right-angled triangle excitation coil to generate an excitation magnetic field, and analyze the measurement signals generated by the three rectangular receiving coils to obtain three groups of measurement values, which are transmitted to the computer;

[0014] The computer is used to perform filtering processing on the three groups of measurement values ​​respectively, extract signal amplitudes, and compare and analyze the signal amplitudes to obtain the fiber thickness and fiber direction of the carbon fiber material plate.

[0015] Furthermore, the right-angled triangle excitation coil is supplied with alternating current to generate an excitation signal, and the measurement signals generated by the three rectangular receiving coils are analyzed to obtain three groups of measurement values, specifically:

[0016] The carbon fiber material plate induces eddy currents under the action of the excitation magnetic field of the right-angled triangle excitation coil, and the eddy currents generate secondary magnetic fields. The three rectangular receiving coils generate corresponding measurement signals under the action of the excitation magnetic field and the secondary magnetic field.

[0017] The multi-channel eddy current instrument collects measurement signals generated by three rectangular receiving coils respectively, performs IQ demodulation and parameter configuration, and obtains three groups of induced voltages.

[0018] Furthermore, the computer is used to perform filtering processing on the three groups of measurement values ​​respectively, specifically:

[0019] The filtering algorithm is used to calculate the average of the three measured values, and the average value is subtracted from the three groups of measured values ​​to obtain the processed filtered signal.

[0020] Furthermore, the right-angled triangle excitation coil has 200 turns, the three rectangular receiving coils have 100 turns respectively, and the wire diameters of the right-angled triangle excitation coil and the three rectangular receiving coils are all 0.2 mm.

[0021] The present invention also provides a method for detecting the thickness and fiber direction of a carbon fiber material, comprising the following steps:

[0022] S1. Place the long sides of the three rectangular receiving coils close to the three sides of the right-angled triangle excitation coil to form an eddy current sensor, and lead out the right-angled triangle excitation coil and the three rectangular receiving coils respectively and connect them to the multi-channel eddy current instrument;

[0023] S2, passing alternating current through the right-angled triangle excitation coil through a multi-channel eddy current instrument to generate an excitation magnetic field;

[0024] S3. During detection, the eddy current sensor is placed above the carbon fiber material and perpendicular to the surface of the carbon fiber material plate, the eddy current sensor is rotated, the detection point is changed, and the amplitude of the measurement signal at different positions is recorded to obtain the fiber direction and thickness of the carbon fiber material plate.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The arrangement of the eddy current sensors in the present invention has high sensitivity to different directions of carbon fiber materials; by analyzing the measurement signals from three rectangular receiving coils, the number of carbon fiber layers and directions can be inverted, thereby achieving synchronous measurement of the number of carbon fiber layers and directions.

[0027] Through the design of the present invention, the difficulty of manufacturing the sensor and the resource requirements are reduced, while the detection accuracy of the eddy current sensor is improved, thereby contributing to the research and application in the field of carbon fiber material detection.

[0028] The present invention also ensures that the measurement signals of each rectangular receiving coil are different in different directions by designing three rectangular receiving sensors in different directions. The direction and thickness of the carbon fiber can be accurately determined by the combination of three different measurement signals. Compared with the existing detection technology, the thickness and direction of the carbon fiber can be detected at the same time, and the operation is simple, the cost is low, and the detection speed is fast, so that quality assurance can be provided for large-scale carbon fiber production processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] The following is a further description of the carbon fiber material thickness and fiber direction detection system and method of the present invention in conjunction with the accompanying drawings;

[0031] Figure 1 It is a schematic diagram of the structure of an eddy current sensor in a carbon fiber material thickness and fiber direction detection system provided by the present invention;

[0032] Figure 2 It is a working principle diagram of the carbon fiber material thickness and fiber direction detection system provided by the present invention;

[0033] Figure 3 The present invention provides a fiber direction and thickness detection process in a carbon fiber material thickness and fiber direction detection system;

[0034] Figure 4 It is a flow chart of filtering processing in the detection system of carbon fiber material thickness and fiber direction provided by the present invention;

[0035] Figure 5 It is a carbon fiber material used for detection in the test process of the carbon fiber material thickness and fiber direction detection system provided by the present invention;

[0036] Figure 6 It is a curve diagram of the number of carbon fiber layers and the voltage amplitude during the test process of the carbon fiber material thickness and fiber direction detection system provided by the present invention;

[0037] Figure 7 It is the experimental measurement signal result of different carbon fiber layer thicknesses and fiber directions during the test process of the carbon fiber material thickness and fiber direction detection system provided by the present invention.

[0038] In the figure: 1. Right-angled triangle excitation coil; 2. Rectangular receiving coil. DETAILED DESCRIPTION

[0039] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0040] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0041] like Figure 1 and Figure 2 As shown, a detection system for the thickness and fiber direction of a carbon fiber material comprises: a carbon fiber material plate, an eddy current sensor, a multi-channel eddy current instrument and a computer;

[0042] The eddy current sensor comprises: a right-angled triangular excitation coil 1 and three rectangular receiving coils 2;

[0043] The long sides of the three rectangular receiving coils 2 are respectively placed close to the three sides of the right-angled triangle excitation coil 1, and the right-angled triangle excitation coil 1 and the three rectangular receiving coils 2 are respectively led out and connected to the multi-channel eddy current instrument;

[0044] The eddy current sensor is placed on the carbon fiber material plate;

[0045] The multi-channel eddy current instrument is used to pass alternating current into the right-angled triangle excitation coil 1 to generate an excitation magnetic field, and analyze the measurement signals generated by the three rectangular receiving coils 2 to obtain three groups of measurement values, which are transmitted to the computer;

[0046] The computer is used to perform filtering processing on the three groups of measurement values ​​respectively, extract the signal amplitude, and compare and analyze the signal amplitude to obtain the carbon fiber thickness and fiber direction.

[0047] The measurement signals generated by the three rectangular receiving coils are analyzed to obtain three groups of measurement values, specifically:

[0048] The carbon fiber material plate induces eddy currents under the action of the excitation magnetic field of the right-angled triangle excitation coil 1, and the eddy currents generate secondary magnetic fields. The three rectangular receiving coils 2 generate corresponding measurement signals under the action of the excitation magnetic field and the secondary magnetic field.

[0049] like Figure 3 As shown, the multi-channel eddy current instrument collects measurement signals generated by three rectangular receiving coils 2 respectively, performs IQ demodulation and parameter configuration, and obtains three groups of induced voltages.

[0050] The computer is used to perform filtering processing on the three groups of measurement values ​​respectively, specifically:

[0051] like Figure 4 As shown, the filtering algorithm is used to calculate the average values ​​of the three measured values, and the average values ​​are subtracted from the three groups of measured values ​​to obtain the processed filtered signals.

[0052] The right-angled triangle excitation coil 1 has 200 turns, and the three rectangular receiving coils 2 have 100 turns respectively. The wire diameters of the right-angled triangle excitation coil 1 and the three rectangular receiving coils 2 are all 0.2 mm.

[0053] The present invention provides a detection method using a detection system for the thickness and fiber direction of a carbon fiber material, comprising the following steps:

[0054] S1, place the long sides of the three rectangular receiving coils 2 close to the three sides of the right-angled triangle excitation coil 1 to form an eddy current sensor, and lead out the right-angled triangle excitation coil 1 and the three rectangular receiving coils 2 respectively, and connect them to the multi-channel eddy current instrument;

[0055] S2, passing alternating current into the right-angled triangle excitation coil 1 through a multi-channel eddy current instrument to generate an excitation magnetic field;

[0056] S3. During detection, the eddy current sensor is placed above the carbon fiber material and perpendicular to the surface of the carbon fiber material plate, and the amplitude of the measurement signal is recorded to obtain the fiber direction and fiber thickness of the carbon fiber material plate.

[0057] It should be noted that: when the present application detects the thickness of the carbon fiber layer, due to the principle of electromagnetic induction, the sensor will induce a stronger induction signal on a thicker carbon fiber plate; Figure 5 and Figure 6 As shown in the figure, when the carbon fiber direction is 0°, the voltage amplitude increases with the increase of the number of carbon fiber layers, and the induced voltage in the three rectangular receiving coils 2 of the array sensor will increase. Therefore, by rotating the array sensor 180° on the carbon fiber material, it is possible to collect signals at different carbon fiber angles. By selecting the maximum voltage value of the right-angled triangle excitation coil during the 180° rotation process, the number of carbon fiber layers can be accurately obtained. The relationship between the voltage amplitude of the right-angled triangle excitation coil 1 and the number of carbon fiber layers is shown in Figure 6 shown.

[0058] The induced voltage signals measured by the three rectangular receiving coils 2 are as follows: Figure 7 As shown in the figure, when the coil rotates 180°, the maximum voltage is 0.612V. Figure 6 It can be seen that the number of carbon fiber layers is 4. When the number of carbon fiber layers has been measured, the voltage amplitudes of the initial rotation angles of the three coils in the three rectangular receiving coils 2 are observed and compared with the voltage amplitudes corresponding to the known 4 layers of carbon fiber. It can be measured that the angle of the carbon fiber is 90°.

[0059] Example 1

[0060] like Figure 1 As shown, the eddy current sensor of the present invention is composed of a right-angled triangle excitation coil and three rectangular receiving coils surrounding and parallel to the right-angled triangle coil. The three rectangular receiving coils in the sensor are of the same size, and the right-angled triangle excitation coil has 200 turns, the rectangular receiving coil has 100 turns, and the wire diameter is 0.2mm. Figure 2As shown, the right-angled triangle excitation coil and the three rectangular receiving coils are respectively led out and connected to the multi-channel eddy current instrument to realize the transmission of the measurement signal. Specifically, the multi-channel eddy current instrument passes alternating current into the right-angled triangle excitation coil to generate an excitation signal, and the three rectangular receiving coils are respectively used as induction coils. The multi-channel eddy current instrument performs IQ demodulation and parameter configuration on the measurement signal to obtain the induced voltage value, which is transmitted to the computer for subsequent carbon fiber thickness detection and fiber direction identification.

[0061] At an excitation frequency of 5 MHz, the eddy current sensor array is placed on the carbon fiber material to be tested, the measurement values ​​of all coils are extracted, and the collected signals are processed using an average value filtering algorithm on a computer. Figure 3 As shown, the present invention is tested on 1-7 layers of carbon fiber boards respectively; Figure 4 As shown, the average values ​​of the three measurement signals are calculated respectively, and the average values ​​are subtracted from the collected signals; Figure 5 The carbon fiber test materials with different thicknesses and different orientations are shown; e.g. Figure 6 As shown, when detecting carbon fiber materials of different thicknesses and different directions, it can be found that the three sensor signals are different, where the greater the amplitude of the signal, the thicker the thickness of the carbon fiber material. In addition, the combination of the three sensor signals is also different in different carbon fiber directions. In general, for each carbon fiber material, the thickness and direction of the carbon fiber material can be detected simultaneously by intuitively analyzing the amplitude of the signals of the three sensors and their combination.

[0062] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A carbon fiber material thickness and fiber direction detection system, characterized in that: include: Carbon fiber material plates, eddy current sensors, multi-channel eddy current instruments and computers; The eddy current sensor comprises: a right-angled triangle excitation coil (1) and three rectangular receiving coils (2); The long sides of the three rectangular receiving coils (2) are respectively placed close to the three sides of the right-angled triangle excitation coil (1), and the right-angled triangle excitation coil (1) and the three rectangular receiving coils (2) are respectively led out and connected to the multi-channel eddy current instrument; The eddy current sensor is placed on the carbon fiber material plate; The multi-channel eddy current instrument is used to pass alternating current through the right-angled triangle excitation coil (1) to generate an excitation magnetic field, and to analyze the measurement signals generated by the three rectangular receiving coils (2) to obtain three groups of measurement values, which are then transmitted to a computer; The computer is used to filter the three groups of measurement values ​​respectively, extract the signal amplitude, and compare and analyze the signal amplitude to obtain the thickness and fiber direction of the carbon fiber material plate.

2. The carbon fiber material thickness and fiber direction detection system according to claim 1, characterized in that: The measurement signals generated by the three rectangular receiving coils are analyzed to obtain three groups of measurement values, specifically: The carbon fiber material plate induces eddy currents under the action of the excitation magnetic field of the right-angled triangle excitation coil (1), and the eddy currents generate secondary magnetic fields. The three rectangular receiving coils (2) generate corresponding measurement signals under the action of the excitation magnetic field and the secondary magnetic field. The multi-channel eddy current instrument respectively collects measurement signals generated by three rectangular receiving coils (2), performs IQ demodulation and parameter configuration, and obtains three groups of induced voltages.

3. The carbon fiber material thickness and fiber direction detection system according to claim 2, characterized in that: The computer is used to perform filtering processing on the three groups of measurement values ​​respectively, specifically: The filtering algorithm is used to calculate the average values ​​of the three groups of induced voltages respectively, and the average values ​​of the induced voltages are subtracted from the three groups of induced voltages to obtain filtered signals.

4. The carbon fiber material thickness and fiber direction detection system according to claim 1, characterized in that: The right-angled triangle excitation coil (1) has 200 turns, the three rectangular receiving coils (2) have 100 turns respectively, and the wire diameters of the right-angled triangle excitation coil (1) and the three rectangular receiving coils (2) are all 0.2 mm.

5. A method for detecting the thickness and fiber direction of a carbon fiber material, applied to the detection system for the thickness and fiber direction of a carbon fiber material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, placing the long sides of the three rectangular receiving coils (2) close to the three sides of the right-angled triangle excitation coil (1) to form an eddy current sensor, and leading out the right-angled triangle excitation coil (1) and the three rectangular receiving coils (2) respectively, and connecting them to a multi-channel eddy current instrument; S2, passing alternating current through the right-angled triangle excitation coil (1) through a multi-channel eddy current instrument to generate an excitation magnetic field; S3. During detection, the eddy current sensor is placed above the carbon fiber material and perpendicular to the surface of the carbon fiber material plate, and the amplitude of the measurement signal is recorded to obtain the fiber direction and fiber thickness of the carbon fiber material plate.

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