System and method for measuring conductivity of fiber reinforced composite material under lightning current based on six-electrode method

Abstract

The device comprises a clamp, an excitation source, a measuring device, a silver paste layer and a copper foil which are respectively positioned on two opposite side surfaces of a to-be-measured fiber reinforced composite material test piece, each copper foil is provided with a current exciting electrode and two voltage measuring electrodes; wherein the current excitation electrode located on one copper foil is connected to an excitation source, the two voltage measurement electrodes are both connected to a measurement device, and the electrodes located on the other copper foil are both grounded; the two voltage measuring electrodes on the same copper foil are located on the same side of the current excitation electrode and are arranged in a centering mode. Compared with the prior art, the device can measure the real voltage of the test sample during excitation application.

Description

Technical Field

[0001] The invention relates to the field of material performance measurement, and in particular to a system and method for measuring the conductivity of a fiber-reinforced composite material under lightning current based on a six-electrode method. Background Art

[0002] Lightning is a high-intensity electromagnetic pulse discharge phenomenon that occurs frequently in nature. It is inevitable that lightning-sensitive systems such as aircraft will be struck by lightning. According to statistics, a single civil airliner will be struck by lightning once every 10 months during its service. Carbon fiber reinforced composite (CFRP) is lighter than traditional metal materials, which helps to reduce the overall weight of the aircraft, improve fuel efficiency and flight performance. At the same time, it can still provide excellent strength and stiffness. These advantages make CFRP a widely used material in the aviation field.

[0003] Traditional metal aircraft have great advantages in dissipating lightning current due to the high conductivity of their materials. However, when the metal frames and skins of aircraft are gradually replaced by CFRP, the anisotropic low conductivity of CFRP will become a disadvantage in lightning protection. A large amount of arc heat carried by lightning impulses is directly applied to the surface of CFRP. At the same time, due to the large resistance of CFRP, the current applied to the surface by the impulse cannot be quickly discharged, resulting in a large amount of Joule heat. The combined action of arc heat and Joule heat causes resin pyrolysis and carbon fiber debonding. Intense high temperatures will also cause carbon fiber vaporization and sublimation, and composite materials will fail. In the thermoelectric coupling model that studies the numerical simulation and prediction of CFRP when it is directly struck by lightning, conductivity will affect the numerical simulation and prediction of CFRP damage results and temperature rise, and is a key factor in the simulation. In other words, it is necessary to improve the accuracy of material conductivity parameters in the simulation model.

[0004] In traditional CFRP conductivity measurement methods, the excitation source is mostly a DC excitation source, and the measurement method is mostly a two-electrode method or a four-electrode method. However, there are significant differences between lightning current pulses and low-amplitude DC in frequency domain, duration and intensity. The two-electrode measurement method is easily affected by contact resistance and wire resistance, and the four-electrode measurement method is affected by the distance between electrodes and cannot accurately measure the voltage at the excitation application point. Summary of the invention

[0005] The purpose of the present invention is to provide a system and method for measuring the conductivity of fiber reinforced composite materials under lightning current based on a six-electrode method.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A six-electrode method-based conductivity measurement system for fiber-reinforced composite materials under lightning current, comprising:

[0008] A fixture, an excitation source and a measuring device, wherein the fixture is an insulating part used to clamp the fiber reinforced composite material specimen to be tested;

[0009] There are two silver paste layers, which are respectively located on two opposite sides of the fiber reinforced composite material specimen to be tested;

[0010] There are two copper foils, which are respectively located outside the two silver paste layers, and the projection area of ​​the copper foil on the side where the copper foil is located is completely located in the projection area of ​​the corresponding silver paste layer on the same side, and each copper foil is provided with a current excitation electrode and two voltage measurement electrodes;

[0011] The current excitation electrode on one of the copper foils is connected to an excitation source, the two voltage measurement electrodes are connected to a measurement device, and the current excitation electrode and the two voltage measurement electrodes on the other copper foil are grounded;

[0012] The two voltage measuring electrodes on the same copper foil are located on the same side of the current excitation electrode, and the line connecting the current excitation electrodes on the two copper foils coincides with the symmetry axis of the fiber reinforced composite material specimen to be tested. The two voltage measuring electrodes on one copper foil are paired with the two voltage measuring electrodes on the other copper foil respectively, and the line connecting any voltage measuring electrode and its paired voltage measuring electrode is parallel to the symmetry axis.

[0013] The three electrodes on the same copper foil are distributed at equal intervals.

[0014] The area of ​​the projection region of the silver paste layer on the side where the silver paste layer is located overlaps with the side.

[0015] The thickness of the silver paste layer is 0.125 mm.

[0016] The distance between two adjacent electrodes on the same copper foil is:

[0017] d≥0.1b

[0018] Wherein: d is the distance between any two adjacent electrodes, and b is the length of the side of the copper foil along the electrode arrangement direction.

[0019] The fiber reinforced composite material specimen to be tested is a plate with the bottom surface in the positive direction.

[0020] All electrodes are connected to the copper foil by means of lead wires.

[0021] The fixture comprises:

[0022] A fixture base, comprising a base frame and a slideway, a first baffle and a hole seat arranged on the base frame, wherein the first baffle and the hole seat are respectively arranged at two ends of the upper surface of the base frame, the slideway is arranged in the base frame and distributed along the direction from the first baffle to the hole seat, and the hole seat is provided with a first through hole;

[0023] A top pad seat, comprising a second baffle and a slider matched with the slideway, wherein the second baffle is arranged on the slider, a second through hole is arranged on the second baffle, the axes of the second through hole and the first through hole are in a straight line, and at least one of the second through hole and the second through hole is a screw hole, and the overlap rate of the projection area of ​​the second baffle and the first baffle on the vertical plane of the second through hole exceeds 90%, and is used for clamping the fiber reinforced composite material test piece to be tested;

[0024] A threaded rod, passing through the first through hole and the second through hole respectively, connected to the second baffle plate to adjust the position of the second baffle plate along the slideway direction;

[0025] Two pads, one of which is arranged on a side of the first baffle plate close to the second baffle plate, and the other pad is arranged on a side of the second baffle plate close to the first baffle plate.

[0026] A horizontal block is arranged on the first baffle plate. The horizontal block is arranged on a side of the second baffle plate away from the first baffle plate and supported on the bottom frame.

[0027] A method based on the above measurement system comprises:

[0028] Step S1: an excitation source applies excitation through a current excitation electrode;

[0029] Step S2: The measuring device obtains voltages corresponding to horizontal coordinates through two pairs of voltage measuring electrodes, wherein the horizontal coordinates are coordinates corresponding to the arrangement direction of the electrodes;

[0030] Step S3: fitting the voltage values ​​measured by the two pairs of voltage measuring electrodes to obtain a fitting function of the voltage value with respect to the lateral position;

[0031] Step S4, obtaining the voltage at the current excitation electrode based on the fitting function.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The fiber reinforced composite material conductivity measurement system under lightning current based on the six-electrode method generates lightning current excitation by applying a multi-waveform multi-pulse actual lightning current simulation test system, combined with a fiber reinforced composite material fixture, and adopts a six-electrode measurement method to improve the accuracy of existing fiber reinforced composite material conductivity measurements. It can also perform measurements under different size specimens and different excitation source waveform parameters, providing more reliable and efficient technical support for related research and experiments.

[0034] 2. Current equalization is performed based on silver paste of sufficient size to improve the linearity of voltage change with distance from the excitation application position, thereby improving the accuracy of fitting.

[0035] 3. The three electrodes are distributed at equal intervals to improve the accuracy of fitting.

[0036] 4. Setting the spacing large enough can reduce the error.

[0037] 5. Specially designed fixtures can stably fix specimens of various sizes, as follows:

[0038] High overlap rate design: the overlap rate of the projected area of ​​the first baffle and the second baffle on the vertical plane of the second through hole exceeds 90%. This design ensures that the specimen is subjected to uniform pressure during the clamping process, avoids deformation or damage of the specimen due to uneven pressure during the measurement, and thus improves the accuracy and stability of the measurement.

[0039] The adjustable threaded rod passes through the first through hole and the second through hole to connect the second baffle. The position of the second baffle along the slideway can be precisely controlled by adjusting the threaded rod. This design enables the fixture to adapt to specimens of different sizes, ensuring that the specimen is always in the best position during the measurement process, thereby improving the flexibility and applicability of the measurement.

[0040] The cooperation between the slideway and the slider makes the second baffle move freely on the slideway. This design not only facilitates the installation and disassembly of the specimen, but also ensures that the specimen will not shift during the clamping process, thereby improving the measurement accuracy and reliability.

[0041] Pad settings:

[0042] Advantages: The two pads are respectively arranged on the first baffle and the second baffle. This design can effectively disperse the clamping force and prevent the specimen from being damaged due to excessive local force. At the same time, the pads can also provide additional support to ensure that the specimen remains flat during the measurement process, thereby improving the stability of the measurement.

[0043] The support of the horizontal block is arranged on the side of the second baffle away from the first baffle and supported on the base frame. This design ensures the overall stability of the fixture and prevents tilting or shaking due to the weight of the specimen or external force during the measurement process, thereby improving the accuracy and safety of the measurement.

[0044] The design of the through hole and the screw hole is that the axes of the second through hole and the first through hole are in a straight line, and at least one of them is a screw hole. This design not only facilitates the installation and disassembly of the threaded rod, but also ensures the firmness and stability of the fixture during use, and improves the reliability and durability of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 The A / B / C / D waveforms are generated by the multi-waveform multi-pulse actual lightning current simulation test system of the present invention;

[0046] Figure 2 It is a schematic diagram of the principle of the present invention;

[0047] Figure 3 It is a schematic diagram of the arrangement of electrodes, copper foil and silver paste of the present invention;

[0048] Figure 4 A combination diagram of a fixture model designed for the present invention;

[0049] Figure 5 A parts drawing for designing a fixture model for the present invention;

[0050] Figure 6 It is a structural schematic diagram of the clamp base of the present invention;

[0051] Figure 7 A schematic diagram showing a perspective of a top pad seat;

[0052] Figure 8 A schematic diagram of the top pad seat from another perspective;

[0053] Fig. 9 A diagram showing the relationship between the potential difference on the excitation application side and the coordinates in the verification model of the present invention;

[0054] Fig.10 The error curve diagrams of the six-point method and the four-point method are designed for the present invention;

[0055] Wherein: 1. fixture, 2. excitation source, 3. measuring device, 4. copper foil, 5. silver paste layer, 6. test piece, 7. current excitation electrode, 8. voltage measuring electrode, 1-1. top pad seat, 1-2. fixture base, 1-3. pad, 1-4. threaded rod, 1-5. fixing sleeve, 1-6. base fixing plate, 1-7. thin rod, 1-8. nut, 1-9. fixing ball, 1-1-1. second baffle, 1-1-2. slider, 1-2-1. base frame, 1-2-2. first baffle, 1-2-3. hole seat, 1-1-1-1. second through hole, 1-1-1-2. nut seat, 1-2-3-1. first through hole. DETAILED DESCRIPTION

[0056] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0057] The measurement system provided in this application is used to generate multi-waveform multi-pulse actual lightning currents with different waveforms that meet the requirements of multiple international standards such as SAE, APL, IEC, etc., and conduct simulation tests. It can be applied to sample plates of different sizes and shapes, can be adjusted and customized according to specific needs, and has a fiber-reinforced composite fixture that will not have any effect on the conductivity measurement results during the clamping process. It also applies a six-electrode measurement method that can solve the effects of factors such as contact resistance, wire resistance, and distance between electrodes on the measurement results. The specific implementation method includes the following steps:

[0058] Figure 1 The waveform diagram of the A / B / C / D components of the lightning current generated by the multi-waveform multi-pulse actual lightning current simulation test system used to generate different waveform lightning currents that meet the requirements of multiple international standards such as SAE, APL, and IEC is shown. The multi-waveform multi-pulse actual lightning current simulation test system is used to generate lightning current pulses in various forms to simulate various discharge processes in real lightning activities. The amplitude and occurrence order of the A / B / C / D waveforms in the system are adjustable and controllable, and users can freely set different parameters according to actual needs. The output of the multi-waveform multi-pulse actual lightning current simulation test system is connected to the current excitation electrode in the six-electrode method as an excitation to carry out subsequent measurements.

[0059] A six-electrode method based conductivity measurement system for fiber reinforced composite materials under lightning current, such as Figure 2 As shown, including:

[0060] A fixture 1, an excitation source 2 and a measuring device 3, wherein the fixture 1 is an insulating part and is used to clamp a fiber reinforced composite material specimen 6 to be tested;

[0061] Silver paste layer 5, there are two, such as Figure 3 As shown, they are respectively located on two opposite sides of the fiber reinforced composite material specimen 6 to be tested;

[0062] There are two copper foils 4, which are respectively located outside the two silver paste layers 5, and the projection area of ​​the copper foil 4 on the side where it is located is completely located in the projection area of ​​the corresponding silver paste layer 5 on the same side, and each copper foil 4 is provided with a current excitation electrode 7 and two voltage measurement electrodes 8;

[0063] The current excitation electrode 7 on one of the copper foils 4 is connected to the excitation source 2, the two voltage measurement electrodes 8 are connected to the measurement device 3, and the current excitation electrode 7 and the two voltage measurement electrodes 8 on the other copper foil 4 are grounded;

[0064] The two voltage measuring electrodes 8 on the same copper foil 4 are located on the same side of the current excitation electrode 7, and the line connecting the current excitation electrodes 7 on the two copper foils 4 coincides with the symmetry axis of the fiber reinforced composite material specimen 6 to be tested. The two voltage measuring electrodes 8 on one copper foil 4 are paired with the two voltage measuring electrodes 8 on the other copper foil 4, respectively, and the line connecting any voltage measuring electrode 8 and its paired voltage measuring electrode 8 is parallel to the symmetry axis.

[0065] The fiber reinforced composite material conductivity measurement system under lightning current based on the six-electrode method generates lightning current excitation by applying a multi-waveform multi-pulse actual lightning current simulation test system, combined with a fiber reinforced composite material fixture 1, and adopts a six-electrode measurement method to improve the accuracy of existing fiber reinforced composite material conductivity measurement. It can also perform measurements under different size specimens and different excitation source 2 waveform parameters, providing more reliable and efficient technical support for related research and experiments.

[0066] In this embodiment, the three electrodes on the same copper foil 4 are distributed at equal intervals, so that the accuracy of fitting can be improved.

[0067] Moreover, in this embodiment, the area of ​​the projection region of the silver paste layer 5 on the side where it is located overlaps with the side, and current is evenly distributed based on the silver paste of sufficient size, thereby improving the linearity of the voltage changing with the distance from the excitation application position, thereby improving the accuracy of the fitting.

[0068] In this embodiment, the thickness of the silver paste layer 5 is 0.125 mm. Of course, in other embodiments, it can also be determined according to actual conditions.

[0069] Generally, the distance between two adjacent electrodes on the same copper foil 4 is:

[0070] d≥0.1b

[0071] Wherein: d is the distance between any two adjacent electrodes, b is the length of the side surface where the copper foil 4 is located along the electrode arrangement direction, and the distance is set large enough to reduce the error.

[0072] In this embodiment, the fiber reinforced composite material specimen 6 to be tested is a plate with the bottom surface in the positive direction.

[0073] In actual measurement, all electrodes are connected to the copper foil 4 by means of lead wires, so that wiring can be conveniently performed.

[0074] like Figure 4 and Figure 5 As shown, the fixture 1 comprises:

[0075] Fixture base 1-2, such as Figure 6As shown, it includes a base frame 1-2-1 and a slideway arranged on the base frame 1-2-1, a first baffle 1-2-2 and a hole seat 1-2-3, the first baffle 1-2-2 and the hole seat 1-2-3 are respectively arranged at two ends of the upper surface of the base frame 1-2-1, the slideway is arranged in the base frame 1-2-1 and distributed along the direction from the first baffle 1-2-2 to the hole seat 1-2-3, and the hole seat 1-2-3 is provided with a first through hole 1-2-3-1;

[0076] Top plate 1-3 seat 9, such as Figure 7 and Figure 8 As shown, it includes a second baffle 1-1-1 and a slider 1-1-2 matched with a slideway, the second baffle 1-1-1 is arranged on the slider 1-1-2, the second baffle 1-1-1 is provided with a second through hole 1-1-1-1, the axes of the second through hole 1-1-1-1 and the first through hole 1-2-3-1 are in a straight line, and at least one of the second through hole 1-1-1-1 and the second through hole 1-1-1-1 is a screw hole, and the overlap rate of the projection area of ​​the second baffle 1-1-1 and the first baffle 1-2-2 on the vertical plane of the second through hole 1-1-1-1 exceeds 90%, and is used to clamp the fiber reinforced composite material specimen 6 to be tested;

[0077] The threaded rod 1-4 passes through the first through hole 1-2-3-1 and the second through hole 1-1-1-1 respectively to connect the second baffle 1-1-1 to adjust the position of the second baffle 1-1-1 along the slide direction;

[0078] There are two pads 1-3, one of which is arranged on a side of the first baffle 1-2-2 close to the second baffle 1-1-1, and the other pad 1-3 is arranged on a side of the second baffle 1-1-1 close to the first baffle 1-2-2.

[0079] A horizontal block is provided on the first baffle 1-2-2. The horizontal block is provided on a side of the second baffle 1-1-1 away from the first baffle 1-2-2 and supported on the base frame 1-2-1.

[0080] The top pad 1-3 seat 9 can slide along the slideway through the cooperation of the slider 1-1-2 and the slideway, so as to adjust the distance between the second baffle 1-1-1 and the first baffle 1-2-2. In this embodiment, a part of the second through hole 1-1-1-1 is a screw hole. Specifically, a part of the second through hole 1-1-1-1 is a round hole, and the other part forms a nut seat 1-1-1-2. A nut 1-8 is arranged in the nut seat 1-1-1-2, so that a part of the second through hole 1-1-1-1 is a screw hole. In addition, a thin rod 1-7 is arranged vertically and crosswise with the threaded rod 1-4, and fixing balls 1-9 are arranged at both ends of the thin rod 1-7 for easy gripping.

[0081] The fixture 1 as a whole is suitable for sample plates of different sizes and shapes, and can be adjusted and customized according to specific needs. The main material of the fixture 1 is insulating resin, and the clamping process will not have any effect on the conductivity measurement results. The fixture base 1-2 and the base fixing plate 1-6 are combined to fix the overall fixture 1 to improve the stability of the clamping.

[0082] A method based on the above measurement system comprises:

[0083] Step S1: the excitation source 2 applies excitation through the current excitation electrode 7;

[0084] Step S2: the measuring device 3 obtains the voltage corresponding to the horizontal coordinate through two pairs of voltage measuring electrodes 8, wherein the horizontal coordinate is the coordinate corresponding to the arrangement direction of the electrodes;

[0085] Step S3: fitting the voltage values ​​measured by the two pairs of voltage measuring electrodes 8 to obtain a fitting function of the voltage value with respect to the lateral position;

[0086] Step S4, obtaining the voltage at the current excitation electrode 7 based on the fitting function.

[0087] In this embodiment, Figure 3 As shown, a silver paste layer 5 and a copper foil 4 are laid on the opposite side of the test piece 6 in the measuring direction, so as to achieve a uniform distribution of the current density, wherein the copper foil can also completely cover the silver paste layer.

[0088] The following is a sample with dimensions of 50×50×1mm (a×b×c) and ply ratio of [45° / -45° / 0° / 90°] s The advantages of the six-point method are verified in the model and the measurement process of the six-point method is introduced. A current of 2.0372E9A / m is applied to one of the current excitation electrodes 7. 2 of the surface current (used to simulate a current input of 400A), while the other current excitation electrode 7 is grounded. Fig. 9 The relationship between the potential difference and the coordinates on the excitation application side is shown. It can be seen that the potential difference reaches its maximum value at the excitation application point.

[0089] When measuring resistance using the four-point method, the position of the current measurement electrode is set at y = 25mm. Due to practical limitations, the potential difference cannot be measured directly at the current electrode, which causes the four-point measurement result to be affected by the electrode spacing. By selecting y = 25mm as the reference point for the potential difference, and considering that the potential difference changes almost linearly with the coordinates near it, the potential difference at y = 15mm and y = 20mm can be measured and used to extrapolate the potential difference at y = 25mm. This extrapolated value is used to calculate the impedance, which is the measurement method of the six-point method. Fig.10The impedance error values ​​obtained using the six-point method (with one pair of current electrodes and two pairs of voltage measurement points) are compared with the impedance error values ​​obtained using the four-point method at different coordinates of the voltage measurement points. Due to practical limitations, the voltage measurement points in the four-point resistance measurement method need to be kept at a certain distance from the current electrodes. This results in a significantly larger measurement error in the four-point method than in the six-point method. Therefore, the six-point method is recommended for measuring the impedance of the specimen.

[0090] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

Claims

1. A six-electrode method based conductivity measurement system for fiber reinforced composite materials under lightning current, comprising: A fixture, an excitation source and a measuring device, wherein the fixture is an insulating part used to clamp the fiber reinforced composite material specimen to be tested; It is characterized by further comprising: There are two silver paste layers, which are respectively located on two opposite sides of the fiber reinforced composite material specimen to be tested; There are two copper foils, which are respectively located outside the two silver paste layers, and the projection area of ​​the copper foil on the side where the copper foil is located is completely located in the projection area of ​​the corresponding silver paste layer on the same side, and each copper foil is provided with a current excitation electrode and two voltage measurement electrodes; The current excitation electrode on one of the copper foils is connected to an excitation source, the two voltage measurement electrodes are connected to a measurement device, and the current excitation electrode and the two voltage measurement electrodes on the other copper foil are grounded; The two voltage measuring electrodes on the same copper foil are located on the same side of the current excitation electrode, and the line connecting the current excitation electrodes on the two copper foils coincides with the symmetry axis of the fiber reinforced composite material specimen to be tested. The two voltage measuring electrodes on one copper foil are paired with the two voltage measuring electrodes on the other copper foil respectively, and the line connecting any voltage measuring electrode and its paired voltage measuring electrode is parallel to the symmetry axis.

2. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The three electrodes on the same copper foil are distributed at equal intervals.

3. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The area of ​​the projection region of the silver paste layer on the side where the silver paste layer is located overlaps with the side.

4. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The thickness of the silver paste layer is 0.125 mm.

5. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The distance between two adjacent electrodes on the same copper foil is: d≥0.1b Wherein: d is the distance between any two adjacent electrodes, and b is the length of the side of the copper foil along the electrode arrangement direction.

6. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The fiber reinforced composite material specimen to be tested is a plate with the bottom surface in the positive direction.

7. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: All electrodes are connected to the copper foil by means of lead wires.

8. The conductivity measurement system of fiber reinforced composite materials under lightning current based on the six-electrode method according to claim 1 is characterized in that: The fixture comprises: A fixture base, comprising a base frame and a slideway, a first baffle and a hole seat arranged on the base frame, wherein the first baffle and the hole seat are respectively arranged at two ends of the upper surface of the base frame, the slideway is arranged in the base frame and distributed along the direction from the first baffle to the hole seat, and the hole seat is provided with a first through hole; A top pad seat, comprising a second baffle and a slider matched with the slideway, wherein the second baffle is arranged on the slider, a second through hole is arranged on the second baffle, the axes of the second through hole and the first through hole are in a straight line, and at least one of the second through hole and the second through hole is a screw hole, and the overlap rate of the projection area of ​​the second baffle and the first baffle on the vertical plane of the second through hole exceeds 90%, and is used for clamping the fiber reinforced composite material test piece to be tested; A threaded rod, passing through the first through hole and the second through hole respectively, connected to the second baffle plate to adjust the position of the second baffle plate along the slideway direction; Two pads, one of which is arranged on a side of the first baffle plate close to the second baffle plate, and the other pad is arranged on a side of the second baffle plate close to the first baffle plate.

9. The six-electrode method-based conductivity measurement system for fiber-reinforced composite materials under lightning current according to claim 8, characterized in that: A horizontal block is arranged on the first baffle plate. The horizontal block is arranged on a side of the second baffle plate away from the first baffle plate and supported on the bottom frame.

10. A method based on the measurement system according to any one of claims 1 to 9, characterized in that: include: Step S1: an excitation source applies excitation through a current excitation electrode; Step S2: The measuring device obtains voltages corresponding to horizontal coordinates through two pairs of voltage measuring electrodes, wherein the horizontal coordinates are coordinates corresponding to the arrangement direction of the electrodes; Step S3: fitting the voltage values ​​measured by the two pairs of voltage measuring electrodes to obtain a fitting function of the voltage value with respect to the lateral position; Step S4, obtaining the voltage at the current excitation electrode based on the fitting function.

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