A prepreg content detection method and detection device

Abstract

The present application belongs to the technical field of composite material detection, and particularly relates to a prepreg impregnation degree detection method and a detection device. The device comprises two conductive probes inserted into the prepreg in parallel, an adjusting mechanism, and a circuit module connected with the conductive probes to form an on-off indicating circuit. The two conductive probes are located on the same side of the prepreg, or are arranged on opposite sides of the prepreg. The depth of the conductive probes is adjusted so that the ends of the two conductive probes are at the same level at the required detection depth. The circuit module and the conductive probes are connected to obtain the on-off state of the on-off indicating circuit at this time, and the on-off state of the on-off indicating circuit at the detection depth is obtained. The depth from which the upper and lower sides of the prepreg are switched from off to on is recorded as the impregnation depth of the side, and the impregnation degree of the prepreg is obtained. The difference in electrical characteristics between carbon fiber conductivity and epoxy insulation is used to convert the impregnation degree into a quantifiable electrical signal.

Description

Technical Field

[0001] This invention belongs to the field of composite material testing technology, and particularly relates to a method and device for detecting the impregnation content of prepregs. Background Technology

[0002] Prepreg is a core intermediate material in carbon fiber reinforced composites, and its quality directly determines the mechanical properties of the final product. Among these, impregnation content (the degree to which the resin wets the interior of the fiber bundle) is a key indicator for evaluating prepreg quality. Low impregnation content can lead to defects such as dry spots and porosity in the product, severely reducing the strength and modulus of the composite material.

[0003] Currently, the main methods for detecting the impregnation content of prepregs in industry are as follows: Microscopic observation: This method requires complex sample preparation processes such as sampling, grinding, and polishing of the prepreg before the cross-section can be observed under a microscope. This process takes more than an hour, is inefficient, and is a destructive test, making it impossible to achieve rapid online feedback.

[0004] Ultrasonic testing: This method utilizes the reflection and attenuation characteristics of ultrasonic waves in materials to assess internal quality. However, ultrasonic testing equipment is expensive, complex to operate, requires professional personnel to analyze and interpret the echo images, and the test results are subject to lag.

[0005] Tape tearing method: This method involves attaching tape to both sides of a prepreg sample, then tearing it off, and observing the exposed fibers inside the prepreg to determine the impregnation content. This method is highly subjective and subject to significant human intervention; results obtained by different operators vary greatly, leading to large testing errors and making it difficult to quantify.

[0006] In summary, existing technologies lack a rapid, low-cost, simple-to-operate method for detecting the impregnation content of prepregs suitable for large-scale industrial production. Therefore, there is an urgent need to develop a simple, easily applicable detection method and device. Summary of the Invention

[0007] This invention addresses the shortcomings of time-consuming and destructive microscopy, high cost and complex operation of ultrasonic methods, and subjective and unquantifiable tape methods. It utilizes the difference in electrical properties between carbon fiber (conductive) and epoxy resin (insulating) to achieve impregnation detection. 1) For conductive probes arranged in parallel on the same side: When the resin fully impregnates and completely wraps the carbon fiber monofilament, the insulating resin forms an electrical isolation layer between the two conductive probes, and the circuit is in an open circuit state; when the resin does not impregnate / completely wrap the carbon fiber, the exposed carbon fiber forms a conductive path between the two probes, and the circuit is conductive.

[0008] 2) For conductive probes placed on both sides of the prepreg and with the insertion end on the same horizontal plane: Two probes are arranged across the thickness direction of the prepreg. When the resin is fully impregnated and completely wraps the carbon fiber, the insulating resin forms an integral insulating isolation layer between the two probes, and the circuit is in an open circuit state; when there is an unimpregnated area of ​​resin and the carbon fiber is exposed, the conductive fiber connects the two probes to form a conductive path, and the circuit is conductive.

[0009] By controlling the probe insertion depth and detecting the circuit continuity, the unwetted area in the thickness direction of the prepreg can be accurately located, and the abstract impregnation degree can be converted into a quantifiable electrical signal to achieve layered and standardized detection.

[0010] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, a prepreg impregnation content detection device includes: Two conductive probes are inserted in parallel into the prepreg. An adjustment mechanism for adjusting the insertion depth of the conductive probe into the prepreg; The circuit module is connected to the conductive probe to form a continuity indication circuit; The power-on indicator circuit includes: DC power supply; An indicator unit, connected in series in the circuit, is used to reflect the on / off state of the circuit. A current-limiting resistor is connected in series in the circuit; Power switch; The two conductive probes are connected to the positive and negative terminals of the DC power supply, respectively.

[0011] Optionally, the two conductive probes are located on the same side of the prepreg and run parallel to each other; or, the two conductive probes are arranged on opposite sides of the prepreg.

[0012] Optionally, the two conductive probes are controlled by the same adjustment mechanism; or, the two conductive probes are controlled independently by two separate adjustment mechanisms.

[0013] Optionally, when the two conductive probes are located on the same side of the prepreg, the adjustment mechanism is used to control the conductive probes to rise and fall synchronously to ensure consistent insertion depth; When the two conductive probes are respectively arranged on opposite sides of the prepreg, the adjustment mechanism is used to control the two conductive probes to move in opposite directions so that the insertion ends of the two probes are at the same horizontal plane.

[0014] Specifically, the upper and lower conductive probes are equipped with independent adjustment mechanisms. By reading the feed scales of the two sets of graduated knobs, the lifting and lowering displacement values ​​of the upper and lower probes are manually matched so that the sum of the insertion depths of the two probes is equal to the material thickness, that is, to maintain them on the same detection level.

[0015] Optionally, the spacing between the two conductive probes is greater than the diameter of the carbon fiber monofilament.

[0016] Optionally, the conductive probe is made of conductive metal and has a pointed tip. And / or, the diameter of the conductive probe is 0.1-0.3 mm.

[0017] Optionally, the indicating unit is an LED light or a microammeter; and / or, the voltage of the DC power supply is not higher than 5V.

[0018] Optionally, it also includes: The main support frame and the platform for holding the prepreg samples; The conductive probe is connected to the main support via a probe holder, and the main support provides mounting points for the wires in the continuity indicator circuit.

[0019] Optionally, the conductive probe is configured as multiple probe arrays, each probe array containing a pair of conductive probes. Multiple sets of conductive probes are arranged perpendicular to the axis of the prepreg. The adjustment mechanism is a linkage or independent structure, adapted to the depth adjustment of multiple probe arrays; the circuit module is a multi-channel on / off indicator circuit, with each probe array corresponding to an independent on / off indicator branch.

[0020] In a second aspect, the present invention provides a method for detecting the impregnation content of a prepreg, wherein the prepreg comprises conductive fibers and insulating resin, and based on the prepreg impregnation content detection device described in the first aspect, the method includes the following steps: Adjust the insertion depth of the conductive probes so that the insertion ends of the two conductive probes are at the same horizontal plane at the required detection depth. Connect the circuit module and the conductive probes to obtain the on / off state of the on / off indicator circuit at this time. The on / off state of the on / off indicator circuit at this detection depth can be obtained. The on / off status of the on / off indicator circuit is obtained when the prepreg is inserted at different depths from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the upper side of the prepreg are compared. The final disconnection depth of the circuit from off to on is the upper impregnation depth h1. The on / off status of the on / off indicator circuit is obtained when the prepreg is inserted at different depths from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the lower side of the prepreg are compared. The final disconnection depth at which the circuit changes from off to on can be the lower impregnation depth h2. Prepreg impregnation percentage = (h1 + h2) / prepreg thickness × 100%.

[0021] Optionally, if the two conductive probes are located on the same side of the prepreg, when adjusting the detection depth from the top of the prepreg to the bottom, both conductive probes are inserted from the top of the prepreg; when adjusting the detection depth from the bottom of the prepreg to the bottom, both conductive probes are inserted from the bottom of the prepreg. When two conductive probes are placed on both sides of the prepreg, one probe is inserted from the top side of the prepreg and the other from the bottom side.

[0022] When adjusting the detection depth from shallow to deep, the range of adjustment can be adjusted according to the required accuracy. Alternatively, a coarse adjustment can be made first to obtain the detection depth of the nearest short-circuit state and the detection depth of the pass state, and then the position between the two detection depths can be finely adjusted to increase the accuracy of the detection results.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects: This invention transforms the abstract impregnation degree into a specific, quantifiable electrical signal by controlling the probe insertion depth and combining it with circuit on / off states. This allows for the assessment of the impregnation status of prepreg at different thicknesses, achieving standardized judgment of impregnation degree levels, eliminating the human subjectivity in traditional methods, and significantly improving detection efficiency.

[0024] This device is simple to operate, requires no complex sample preparation, has a short testing cycle, and is suitable for industrial online testing. It can provide real-time feedback for adjusting prepreg production processes, avoiding excessive damage to samples. Furthermore, the device has a simple structure and requires no professional personnel for operation and maintenance.

[0025] The device has a simple structure, low processing and assembly costs, and can be used to flexibly test prepregs of different thicknesses. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a prepreg impregnation detection device according to an embodiment of the present invention (the conductive probes are located on the same side of the prepreg); Figure 2 This is a schematic diagram of another prepreg impregnation detection device in an embodiment of the present invention (conductive probes are placed on both sides of the prepreg). In the diagram: 1. Main support; 2. Current limiting resistor; 3. Wire; 4. Indicator unit; 5. DC power supply; 6. Power switch; 7. Probe support; 8. Lifting threaded rod; 9. Knob with scale; 10. Rolling bearing; 11. Conductive probe; 12. Placement platform; 13. Sliding slot. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings: Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings. Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods; all reagents and materials used are commercially available; experiments involving quantitative detection are all performed at least three times, and the results are averaged.

[0029] Example 1

[0030] This embodiment provides a device for detecting the impregnation content of prepreg, including: Two parallel conductive probes 11 are inserted into the prepreg. An adjustment mechanism for adjusting the insertion depth of the conductive probe 11 into the prepreg; The circuit module is connected to the conductive probe 11 to form a continuity indicator circuit; The power-on indicator circuit includes: DC power supply 5; Indicator unit 4, connected in series in the circuit, is used to reflect the on / off state of the circuit through its status; Current-limiting resistor 2 is connected in series in the circuit; Power switch 6; Two conductive probes 11 are connected to the positive and negative terminals of the DC power supply 5, respectively. The indicating unit 4 is an LED light or a microammeter; in this embodiment, an LED light is used. The voltage of the DC power supply 5 is no higher than 5V, and a 3-5V lithium battery can be used.

[0031] Specifically, the two conductive probes 11 can be arranged in the following two ways: (a) The two conductive probes 11 are located on the same side of the prepreg and are parallel to each other, such as Figure 1 As shown (method one is used in this embodiment); in this embodiment, the two conductive probes 11 are controlled by the same adjustment mechanism; and the adjustment mechanism is used to control the conductive probes 11 to rise and fall synchronously to ensure consistent insertion depth.

[0032] In this embodiment, the adjustment mechanism includes: a probe bracket 7 and a lifting threaded rod 8; the lifting threaded rod 8 and the probe bracket 7 are connected by a threaded rotation, a lifting slider is provided below the lifting threaded rod 8, and a rolling bearing 10 is arranged between the lifting slider and the lifting threaded rod 8; a sliding groove 13 is provided on one side of the probe bracket 7, one end of the lifting slider is engaged in the sliding groove 13 and slides up and down along the sliding groove 13; a conductive probe 11 is fixed on the lifting slider. The adjustment mechanism also includes a graduated knob 9, which is connected to the lifting threaded rod 8. The graduated knob 9 is used to drive the lifting threaded rod 8 to move up and down relative to the probe holder 7 and to indicate the depth of the conductive probe 11 inserted into the prepreg. For example, the graduated knob 9 has a scale line every 5 degrees. The thread pitch of the threaded rod is 3.6 mm. At this time, every 5 degrees of rotation of the graduated knob, the probe moves 0.05 mm, that is, the probe movement accuracy is 0.05 mm. The adjustment mechanism also includes a limiting block, which is arranged at the top of the lifting threaded rod 8 and slidably connected to the limiting cavity of the probe holder 7. It is used to guide the lifting direction of the lifting threaded rod 8.

[0033] (ii) Two conductive probes 11 are respectively arranged on opposite sides of the prepreg, such as Figure 2 As shown, the two conductive probes 11 can be independently controlled by two adjusting mechanisms. In this case, the two adjusting mechanisms need to cooperate to control the two conductive probes 11 to move in opposite directions so that their insertion ends are on the same horizontal plane (this can be controlled so that the sum of the insertion depths of the two probes is equal to the material thickness, i.e., maintaining the same detection horizontal plane). At this time, the conductive probes can be directly connected to the center of the bottom end of the lifting threaded rod 8 via the roller bearing.

[0034] In this embodiment, the distance between the two conductive probes 11 is greater than the diameter of the carbon fiber monofilament, which avoids the two probes being inserted into the same filament, thus preventing the circuit from being blocked and affecting the accuracy of the test.

[0035] The conductive probe 11 is made of conductive metal, and its tip is pointed to reduce damage to the prepreg and facilitate insertion. The diameter of the conductive probe 11 is 0.1-0.3 mm. When the diameter of the conductive probe 11 is <0.1 mm, the hardness may be insufficient and the probe diameter may be smaller than the width of the fiber or fabric gap, resulting in a circuit break and affecting the test results. When the diameter of the conductive probe 11 is >0.3 mm, the diameter is too large and may easily damage the internal structure of the prepreg.

[0036] The prepreg impregnation content detection device in this embodiment also includes: The main support 1 and the placement platform 12 for holding the prepreg sample are perpendicular to the conductive probe 11. The probe holder 7 and the placement platform 12 are both connected to the main support 1. The placement platform 12 is provided with a through hole for the conductive probe 11 located below to extend out. The main support 1 also provides mounting points for the wire 3 in the continuity indicator circuit.

[0037] In one possible embodiment, the conductive probes can also be configured as multiple probe arrays, each containing a pair of conductive probes 11; the multiple sets of conductive probes 11 are arranged perpendicular to the prepreg axis; the adjustment mechanism is a linkage or independent structure, adapted to the depth adjustment of multiple probe arrays; the circuit module is a multi-channel on / off indicator circuit, with each probe array corresponding to an independent on / off indicator branch. By arranging multiple probes, the detection efficiency can be improved.

[0038] By controlling the probe insertion depth and combining it with circuit on / off states, the abstract impregnation degree is transformed into a specific, quantifiable electrical signal. If the insertion point of the conductive probe 11 is not wetted with insulating resin, the two conductive probes 11 are connected through the carbon fiber phase, forming a conductive path and generating an electrical signal. If the insertion point of the conductive probe 11 is wetted with insulating resin, the insulating resin blocks the two conductive probes 11, and no electrical signal is generated. This allows for the evaluation of the impregnation status of the prepreg at different thicknesses, achieving standardized judgment of the impregnation degree level.

[0039] Example 2

[0040] A method for detecting the impregnation content of prepreg, wherein the prepreg comprises conductive fibers and insulating resin, based on the prepreg impregnation content detection device in Example 1, the method includes the following steps: Adjust the insertion depth of the conductive probes 11 so that the insertion ends of the two conductive probes 11 are at the same horizontal plane at the required detection depth. Connect the circuit module and the conductive probes 11 to obtain the on / off state of the on / off indicator circuit at this time. The on / off state of the on / off indicator circuit at this detection depth can be obtained. Both conductive probes 11 are inserted from the top of the prepreg to obtain the on / off state of the on / off indicator circuit when the insertion depth on the top of the prepreg is different from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the upper side of the prepreg are compared. The final disconnection depth of the circuit from off to on is the upper impregnation depth h1. Both conductive probes 11 are inserted from the underside (other side) of the prepreg (the probes can be kept still and the prepreg can be flipped over) to obtain the on / off state of the on / off indicator circuit when the insertion depth of the prepreg is different from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the lower side of the prepreg are compared. The final disconnection depth at which the circuit changes from off to on can be the lower impregnation depth h2. Prepreg impregnation percentage = (h1 + h2) / prepreg thickness × 100%.

[0041] The prepreg sample tested in this embodiment is a T700 carbon fiber / epoxy resin unidirectional prepreg with a thickness of 0.4 mm, an intact resin layer on the surface, and local unwetted areas inside.

[0042] Testing steps: 1) Place the sample flat on the platform 12, with the two conductive probes 11 positioned on the same side of the sample's upper surface (e.g., ...). Figure 1 Maintain a spacing of 1mm; 2) Coarse positioning: Each insertion depth is 25% of the sample thickness (0.1mm), and the sample is inserted simultaneously to 0.1mm, 0.2mm, 0.3mm, and 0.4mm. The circuit is found to be open at 0.1mm and 0.2mm, and open at 0.3mm and 0.4mm. The open circuit range is determined to be 0.2mm–0.3mm. The insertion depth was gradually increased from 0.2 mm from the top surface, with each increase being 5% of the sample thickness (0.02 mm). The upper critical depth (depth in the final open circuit state) at which the circuit switched from open to closed was measured to be 0.22 mm. 3) Turn the prepreg sample over and insert the conductive probe 11 (since the conductive probe 11 is not moving and the prepreg sample is turned over, the insertion surface at this time is the lower side opposite to the insertion surface in step 2). Following the same method as in step 2, measure the depth of the circuit on this side when it changes from open to closed to the final short circuit state as 0.12 mm. 4) Calculation of impregnation: Impregnation = (0.22 + 0.12) / 0.4 × 100% = 85%.

[0043] Test results: There was a 15% unwetted area inside the sample, the overall impregnation was 85%, the single sample test time was ≤1 minute, and there was no structural damage to the sample.

[0044] Microscopic observation (500x): The prepreg was cut open with a utility knife to observe the resin impregnation inside the prepreg. The resin completely wrapped the carbon fiber bundles within 0.22mm on the upper side and 0.12mm on the lower side, while the fibers were exposed in the area between them. The results were consistent with the test results of this embodiment.

[0045] Example 3

[0046] In this embodiment, two conductive probes 11 are placed on opposite sides of the prepreg (e.g., Figure 2 As shown), the insertion depth of the conductive probe 11 is adjusted so that the ends of the probes are on the same horizontal plane. At this time, the depth of the horizontal plane relative to the upper side of the prepreg is the detection depth of the upper side of the prepreg; the depth of the horizontal plane relative to the lower side of the prepreg is the detection depth of the lower side of the prepreg.

[0047] During operation, the tips are kept at the same level by matching the scale values. Specific operating steps are as follows: Sample zero-point calibration: After measuring the thickness of the prepreg, place the prepreg on the platform and rotate the upper and lower probes until the probes lightly touch the upper and lower surfaces of the sample, respectively. Record the reference scale of the upper and lower knobs at this time.

[0048] Adjusting the detection depth: Record the insertion depth of the two probes when raising and lowering the probes. Ensure that the sum of the insertion depths of the upper and lower probes is equal to the material thickness, so that the tips of the two probes are on the same horizontal plane.

[0049] Impregnation measurement: The upper and lower probes can be independently controlled to control the insertion depth. The tips are inserted into different thicknesses of the prepreg, and the circuit signals are recorded and converted into impregnation information.

[0050] Prepreg sample: The same T700 carbon fiber / epoxy resin unidirectional prepreg as in Example 2 was used, with a thickness of 0.4 mm, an intact resin layer on the surface, and some unimpregnated areas inside.

[0051] Test results: There is a 15% unwetted area inside the sample, the overall impregnation is 85%, the single sample test time is ≤1 minute, and there is no structural damage to the sample; the double-sided opposing structure does not require flipping, which can reduce the risk of misjudgment.

[0052] Based on the quality control of the prepreg industry, the calculated impregnation content can be divided into 11 levels, enabling rapid grading and determination.

[0053] Table 1: Classification of Immersion Content 10 100% 9 More than 90% (excluding 100%) 8 80%~90% (excluding 90%) 7 70%~80% (excluding 80%) 6 60%~70% (excluding 70%) 5 50%~60% (excluding 60%) 4 40%~50% (excluding 50%) 3 30%~40% (excluding 40%) 2 20%~30% (excluding 30%) 1 10%~20% (excluding 20%) 0 Less than 10% (excluding 10%) Note: Table 1 is only for rapid grading. To verify the accuracy and practicality of the method of the present invention, three groups of typical prepreg samples were selected, and the present invention was compared with existing microscopic observation method, ultrasonic detection method, and tape tearing method for parallel verification.

[0054] Microscopic observation method: The absence of exposed fibers is used as the criterion for determining infiltration; this method involves complex sample preparation, takes more than 20 minutes, and is a destructive test.

[0055] Ultrasonic testing: High structural accuracy; however, the equipment is expensive, requires professional analysis, and takes about 10 minutes.

[0056] Tape tearing method: The absence of lint indicates wetting, but the judgment is highly subjective, cannot be quantified, and is prone to human error.

[0057] This invention utilizes the difference in conductivity between carbon fiber and resin to determine the impregnation content of prepregs through electrical on / off switching, enabling rapid, accurate, and quantitative detection. Compared to existing methods, it offers advantages such as speed, quantification, low cost, ease of operation, and minimal damage. The detection results are consistent with microscopic standards, allowing for layered detection in the thickness direction and precise determination of impregnation content, making it suitable for rapid online industrial testing.

Claims

1. A device for detecting the impregnation content of prepreg, characterized in that, include: Two conductive probes are inserted in parallel into the prepreg. An adjustment mechanism for adjusting the insertion depth of the conductive probe into the prepreg; The circuit module is connected to the conductive probe to form a continuity indication circuit; The power-on indicator circuit includes: DC power supply; An indicator unit, connected in series in the circuit, is used to reflect the on / off state of the circuit. A current-limiting resistor is connected in series in the circuit; Power switch; The two conductive probes are connected to the positive and negative terminals of the DC power supply, respectively.

2. The prepreg impregnation detection device according to claim 1, characterized in that, The two conductive probes are located on the same side of the prepreg and are parallel to each other; or, the two conductive probes are respectively arranged on opposite sides of the prepreg.

3. The prepreg impregnation content detection device according to claim 2, characterized in that, The two conductive probes are controlled by the same adjustment mechanism; or, the two conductive probes are controlled independently by two separate adjustment mechanisms.

4. The prepreg impregnation detection device according to claim 3, characterized in that, When the two conductive probes are located on the same side of the prepreg, the adjustment mechanism is used to control the conductive probes to rise and fall synchronously to ensure consistent insertion depth. When the two conductive probes are respectively arranged on opposite sides of the prepreg, the adjustment mechanism is used to control the two conductive probes to move in opposite directions so that the insertion ends of the two probes are at the same horizontal plane.

5. The prepreg impregnation content detection device according to claim 1, characterized in that, The distance between the two conductive probes is greater than the diameter of the carbon fiber monofilament.

6. The prepreg impregnation content detection device according to claim 1, characterized in that, The indicating unit is an LED light or a microammeter; and / or, the voltage of the DC power supply is not higher than 5V.

7. The prepreg impregnation detection device according to claim 1, characterized in that, Also includes: The main support frame and the platform for holding the prepreg samples; The conductive probe is connected to the main support via a probe holder, and the main support provides mounting points for the wires in the continuity indicator circuit.

8. The prepreg impregnation content detection device according to claim 1, characterized in that, The conductive probe is configured as multiple probe arrays, and each probe array contains a pair of conductive probes. Multiple sets of conductive probes are arranged perpendicular to the axis of the prepreg. The adjustment mechanism is a linkage or independent structure, adapted to the depth adjustment of multiple probe arrays; the circuit module is a multi-channel on / off indicator circuit, with each probe array corresponding to an independent on / off indicator branch.

9. A method for detecting the impregnation content of a prepreg, wherein the prepreg comprises conductive fibers and insulating resin, characterized in that, Based on the prepreg impregnation content detection device according to any one of claims 1-8, the method includes the following steps: Adjust the insertion depth of the conductive probes so that the insertion ends of the two conductive probes are at the same horizontal plane at the required detection depth. Connect the circuit module and the conductive probes to obtain the on / off state of the on / off indicator circuit at this time. The on / off state of the on / off indicator circuit at this detection depth can be obtained. The on / off status of the on / off indicator circuit is obtained when the prepreg is inserted at different depths from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the upper side of the prepreg are compared. The final disconnection depth of the circuit from off to on is the upper impregnation depth h1. The on / off status of the on / off indicator circuit is obtained when the prepreg is inserted at different depths from shallow to deep. The on / off states of the on / off indicator circuit at different detection depths on the lower side of the prepreg are compared. The final disconnection depth at which the circuit changes from off to on can be the lower impregnation depth h2. Prepreg impregnation percentage = (h1 + h2) / prepreg thickness × 100%.

10. The method for detecting the impregnation content of prepreg according to claim 9, characterized in that, If the two conductive probes are located on the same side of the prepreg, when adjusting the detection depth from the top of the prepreg to the bottom, both conductive probes are inserted from the top of the prepreg; when adjusting the detection depth from the bottom of the prepreg to the bottom, both conductive probes are inserted from the bottom of the prepreg. When two conductive probes are placed on both sides of the prepreg, one probe is inserted from the top side of the prepreg and the other from the bottom side.

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