An adaptive pultrusion system for a composite material pultruder and a method of controlling the same

Abstract

The present application relates to the field of composite material pultrusion machine, and particularly relates to a self-adaptive pultrusion system of a composite material pultrusion machine and a control method thereof, the self-adaptive pultrusion system comprising: a pultrusion die, a drawing device, and an ultrasonic detection module and a control module, the ultrasonic detection module being used for emitting ultrasonic waves and receiving ultrasonic signals after penetrating through the composite material, so as to obtain an acoustic parameter related to the curing degree of the composite material; the control module is configured to: calculate the current curing degree of the composite material based on the acoustic parameter, compare the current curing degree with a preset target curing degree, and according to the comparison result, adjust the drawing speed of the drawing device in real time, so as to perform closed-loop feedback control on the curing process of the composite material. The embodiment of the present application utilizes ultrasonic technology to detect the curing degree of the composite material on-line and non-destructively, and performs closed-loop feedback control on the drawing speed based on the detection result, so as to realize the synchronous optimization of production efficiency and product quality.

Description

Technical Field

[0001] The invention relates to the field of composite material pultrusion machines, and in particular to an adaptive pultrusion system of a composite material pultrusion machine.

[0002] The present invention also relates to a control method applied to an adaptive pultrusion system. Background Art

[0003] Pultrusion is an efficient, continuous production process for manufacturing composite profiles with a constant cross-section. The drawing speed of the production process is preset and maintained constant based on the operator's experience. This static control strategy cannot respond in real time to dynamic changes in the production process, such as fluctuations in the performance of raw materials between batches and changes in ambient temperature and humidity. This is especially true when producing wood wrapped in fiber cloth, where performance fluctuations between raw material batches far exceed the operator's experience.

[0004] When processing raw materials with unstable properties, if the drawing speed is set too fast, it may lead to incomplete solidification inside the profile, seriously affecting product quality and mechanical properties, and causing a large amount of waste. To ensure complete solidification of the product, operators tend to adopt a conservative, slower drawing speed, but this reduces production efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide an adaptive pultrusion system and a control method for a composite material pultruder, which aims to automatically control the pulling speed in real time when processing raw materials with unstable performance, so that the material can be fully solidified to ensure high efficiency and high quality.

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] An adaptive pultrusion system for a composite material pultruder comprises: a pultrusion die for heating, curing and forming a composite material; a drawing device for drawing the composite material through the pultrusion die at an adjustable speed; an ultrasonic detection module, disposed on the pultrusion die, for emitting ultrasonic waves and receiving ultrasonic signals after penetrating the composite material, so as to obtain acoustic parameters related to the degree of curing of the composite material; and a control module, electrically connected to the ultrasonic detection module and the drawing device; wherein the control module is configured to: calculate the current degree of curing of the composite material based on the acoustic parameters, compare the current degree of curing with a preset target degree of curing, and adjust the drawing speed of the drawing device in real time according to the comparison result, so as to perform closed-loop feedback control on the curing process of the composite material.

[0008] Further, the ultrasonic detection module comprises at least one pair of ultrasonic sensors, the ultrasonic sensors are acoustically coupled with the inner cavity of the pultrusion die through a waveguide rod, one end of the waveguide rod is connected with the ultrasonic sensor, and the other end is used for transmitting ultrasonic waves to the composite material.

[0009] Further, a blind hole is arranged on the pultrusion die, a 1-2mm-thick die body material is reserved between the extension end of the blind hole and the surface of the inner cavity of the pultrusion die as an acoustic thin wall for transmitting ultrasonic waves, and the other end of the waveguide rod is in contact with the side surface of the acoustic thin wall facing the outside of the die.

[0010] Further, a pressure self-adaptive compensation mechanism is further included for applying a supporting pressure to the acoustic thin wall to offset the stress caused by the process pressure of the composite material in the pultrusion die to the acoustic thin wall; the pressure self-adaptive compensation mechanism comprises: a sensing side assembly for sensing the process pressure in real time; an execution side assembly for applying a pushing force to the waveguide rod, and further generating the supporting pressure to the acoustic thin wall through the waveguide rod; and a hydraulic transmission system connected with the sensing side assembly and the execution side assembly for transmitting the pressure sensed by the sensing side assembly to the execution side assembly; wherein the sensing side assembly and the execution side assembly are configured to make the supporting pressure equal to the process pressure in real time.

[0011] Further, the execution side assembly comprises a hydraulic cylinder driven by the hydraulic transmission system, the hydraulic cylinder is fixedly connected to the pultrusion die, and the pushing force generated by the hydraulic cylinder acts on the waveguide rod; the sensing side assembly comprises a sensing piston, the front end surface of the sensing piston is flush with the inner cavity of the pultrusion die, and is used for directly contacting the composite material to sense the process pressure, and the rear end surface of the sensing piston transmits the process pressure to the hydraulic cylinder through the hydraulic transmission system.

[0012] Further, a countersunk hole is formed on the pultrusion die, the countersunk hole is closed by a sealing cover, and the sensing piston is installed inside the countersunk hole; the sensing piston comprises a coaxial piston rod and a positioning shoulder, the front end surface of the piston rod forms a sensing surface flush with the inner wall of the die for sensing the process pressure, and the upper surface of the positioning shoulder constitutes a hydraulic force receiving surface; the sealing cover, the inner peripheral wall of the countersunk hole and the hydraulic force receiving surface jointly form a hydraulic chamber for accommodating hydraulic oil, and the hydraulic transmission system comprises a hydraulic pipeline connected with the hydraulic chamber.

[0013] Further, the execution side assembly comprises a guide section formed on the waveguide rod, the guide section forms a thrust step towards the end face of the rear end of the waveguide rod; a water-cooled guide sleeve fixedly connected to the pultrusion die and slidingly connected to the guide section, for providing axial guidance and water-cooled cooling for the guide section; a hydraulic cylinder having one end connected to the hydraulic pipeline to receive input pressure and the other end provided with an axially movable main pressure piston; a loading bracket having a structure for avoiding the ultrasonic sensor, one end of the loading bracket in contact with the thrust step and the other end in contact with the main pressure piston, for transmitting the thrust generated by the hydraulic cylinder to the waveguide rod.

[0014] Further, the ultrasonic detection module further comprises a reset spring, one end of the reset spring connected to the water-cooled guide sleeve and the other end connected to the guide section, the reset spring used to provide a pullback force to the waveguide rod away from the acoustic thin wall, so that the waveguide rod is separated from the acoustic thin wall when there is no composite material in the pultrusion die.

[0015] A control method of an adaptive pultrusion system, comprising the following steps: step one, a pulling device pulls the composite material through the pultrusion die; step two, an ultrasonic detection module obtains the acoustic parameters of the ultrasonic wave penetrating the composite material; step three, the current curing degree of the composite material is calculated based on the acoustic parameters; step four, the current curing degree is compared with the preset target curing degree, and a control signal for adjusting the pulling speed is calculated according to the deviation of the comparison; step five, the control signal is sent to the pulling device to adjust the pulling speed in real time.

[0016] Further, in step two, the following substep is further included: real-time monitoring of the process pressure generated by the composite material in the pultrusion die, and applying a support pressure equal in size and opposite in direction to the acoustic thin wall to eliminate the interference of process pressure fluctuation on acoustic parameter measurement.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The embodiments of the present application utilize ultrasonic technology to detect the curing degree of the composite material on-line and non-destructively, and perform closed-loop feedback control on the pulling speed based on the detection result, so as to realize the synchronous optimization of production efficiency and product quality. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are only exemplary and, for those ordinarily skilled in the art, other drawings can be obtained from the provided drawings without any creative effort.

[0020] Figure 1 is a front view of an embodiment of the present application;

[0021] Figure 2 is a sectional view along the A-A direction of Figure 1

[0022] Figure 3 is an enlarged view of B of Figure 2

[0023] Figure 4 is a perspective view of Figure 3

[0024] The reference signs in the drawings represent the following respectively:

[0025] 1-pultrusion die; 11-blind hole; 12-acoustic thin wall; 13-countersunk through hole; 2-ultrasonic detection module; 21-ultrasonic sensor; 22-waveguide rod; 24-guiding section; 25-thrust step; 23-connection sleeve; 3-induction side assembly; 31-piston rod; 32-positioning shoulder; 33-sealing cover; 34-hydraulic chamber; 4-execution side assembly; 41-water-cooled guide sleeve; 42-loading bracket; 43-hydraulic cylinder; 44-main pressure piston; 5-hydraulic pipeline; 6-return spring. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those ordinarily skilled in the art without any creative effort belong to the scope of protection of the present application.

[0027] The present application aims to provide a self-adaptive pultrusion system of a composite material pultrusion machine and a control method thereof, which aims to control the drawing speed in real time and automatically when processing raw materials with unstable performance, so that the material can be fully solidified, ensuring high efficiency and high quality.

[0028] ​​​The adaptive pultrusion system operates based on the following principle: as the resin matrix in a composite material transforms from liquid to solid, its physical properties, such as density and elastic modulus, undergo dramatic changes. This directly leads to significant and regular changes in the speed and attenuation of sound waves propagating through it. Therefore, by detecting the speed and attenuation of sound waves in the composite material, the degree of curing and curing speed of the resin matrix in the composite material can be obtained.

[0029] refer to Figure 1 and Figure 2 The adaptive pultrusion system includes an ultrasonic detection module 2, a control module and a pulling device. Its core technical means is to use ultrasonic technology to perform online and non-destructive detection of the curing degree of the composite material, and to perform closed-loop feedback control of the pulling speed based on the detection results, thereby achieving simultaneous optimization of production efficiency and product quality.

[0030] The control module and the extraction device are not shown in the figure.

[0031] The ultrasonic detection module 2 is arranged at the end of the curing molding section of the pultrusion die 1, that is, the position where the composite material is about to complete curing and leave the main heat source. The ultrasonic detection module 2 includes at least one pair of ultrasonic sensors 21 arranged on one or more opposite sides of the die (such as the top and bottom), wherein one ultrasonic sensor 21 serves as a transmitting end and the other ultrasonic sensor 21 serves as a receiving end. The ultrasonic wave is propagated through the composite material in the pultrusion die 1 as a medium.

[0032] The control module receives the electrical signal from the receiving end of the ultrasonic sensor 21, calculates the flight time and signal attenuation of the ultrasonic wave penetrating the composite material, and compares it with the pre-established reference database stored in the controller to obtain the minimum degree of cure on the current cross section of the composite material. The calculated minimum degree of cure is then compared with the pre-established target degree of cure stored in the controller, and the remaining cure time is calculated based on the deviation between the two. The pulling speed of the composite material is then adjusted based on the remaining cure time.

[0033] The pulling device can be a crawler or roller traction machine. When the controller detects that the curing is insufficient, the pulling device can smoothly reduce the pulling speed so that the material can stay in the heating zone for a longer time. Conversely, when the controller detects that the curing meets the standard, the pulling device can gradually increase the pulling speed and dynamically approach the set maximum production efficiency.

[0034] Furthermore, since the high temperature inside the mold will damage the ultrasonic sensor 21, in order to solve this problem, refer to Figure 3 and Figure 4In this embodiment, a waveguide rod 22 is provided inside the mold, and the waveguide rod 22 is connected to the ultrasonic sensor 21 on the outside of the mold, so that ultrasonic waves are indirectly transmitted and received through the waveguide rod 22.

[0035] The waveguide rod 22 is a metal rod with high strength and excellent acoustic performance, and its front end is precisely polished.

[0036] The waveguide rod 22 and the ultrasonic sensor 21 are installed as follows:

[0037] The rear end of the waveguide rod 22 is processed with an external thread, and the working end of the ultrasonic sensor 21 also has an external thread, and its spiral direction is opposite to the spiral direction of the thread at the rear end of the waveguide rod 22. The two are tightened and fixed by a connecting sleeve 23 with an internal thread to ensure that they will not loosen under vibration conditions. Acoustic coupling agent is coated between the working end face of the ultrasonic sensor 21 and the rear end face of the waveguide rod 22.

[0038] The waveguide rod 22 and the pultrusion die 1 are installed as follows:

[0039] A blind hole 11 is processed on the pultrusion die 1 to form an acoustic thin wall 12. The blind hole 11 is located on one or more opposite sides of the die (such as the upper and lower sides), and extends from the outer wall of the die toward the inner surface in contact with the composite material. A 1 to 2 mm thick die body material (acoustic thin wall 12) is retained between the extension end point of the blind hole 11 and the inner cavity surface of the die.

[0040] A waveguide rod 22 is arranged in each blind hole 11. One end of the waveguide rod 22 is tightly coupled with the ultrasonic sensor 21 installed in the normal temperature zone outside the mold, and the other end is in contact with the acoustic thin wall 12. A high-temperature acoustic coupling agent is coated between the two.

[0041] The acoustic thin wall 12 is used to serve as a transmission window for ultrasonic waves while maintaining the structural integrity of the mold, transmitting vibrations between the waveguide rod 22 and the composite material.

[0042] Furthermore, in order to eliminate the interference of resin pressure fluctuations in the pultrusion die 1 on acoustic measurement and ensure the stability of acoustic coupling and the accuracy of measurement results, it is also necessary to provide the waveguide rod 22 and the acoustic thin wall 12 with a suitable working environment. The goal is: when the pultrusion die 1 is unloaded, ensure that the sensor coupling surface (acoustic thin wall 12) is not subjected to any external stress, or is only subjected to low stress that does not affect its structural strength; when the pultrusion die 1 is loaded and the material generates pressure, the system automatically applies a precise and dynamic support pressure to the acoustic thin wall 12. The magnitude of this support pressure is equal to the process pressure generated by the material inside the pultrusion die 1 in real time, so that the pressures on the inside and outside of the acoustic thin wall 12 offset each other, making it in an ideal measurement state of approximately zero stress.

[0043] The following article proposes a pressure adaptive compensation mechanism for achieving the above-mentioned goal, which includes: a sensing side component 3, an execution side component 4 and a hydraulic transmission system. The sensing side component 3 is used to monitor the process pressure generated by the material inside the pultrusion die 1 in real time, and the hydraulic transmission system transmits the pressure equivalent to the process pressure to the execution side component 4, so that the execution side component 4 applies pressure to the waveguide rod 22 in real time, and the pressure of the waveguide rod 22 acting on the acoustic wall is equal to the process pressure generated by the material inside the pultrusion die 1.

[0044] The sensing side component 3 includes: a sensing piston and a sealing cover 33 .

[0045] The induction piston comprises a coaxial slender piston rod 31 and a short positioning shoulder 32 . The induction piston is installed in a precise countersunk through hole 13 on the pultrusion die 1 . The countersunk through hole 13 is adjacent to the blind hole 11 and is located upstream of the blind hole 11 .

[0046] The front end surface of the piston rod 31 is precisely polished to form a sensing surface, which is flush with the inner wall of the mold after installation and is used to directly sense the process pressure generated by the material in the mold cavity. The lower surface of the positioning shoulder 32 is the positioning surface, which is used to achieve precise positioning in the countersunk hole of the mold, and the positioning shoulder 32 structure prevents the piston from falling into the mold cavity.

[0047] The sealing cover 33 is connected to the pultrusion die 1 through threads or flanges and closes the outside of the countersunk hole. A hydraulic pipe 5 connected to the hydraulic transmission system is provided at one end of the sealing cover 33 away from the countersunk hole.

[0048] Hydraulic oil is injected into the interior of the countersunk hole, and the sealing cover 33, the countersunk hole and the hydraulic force surface of the sensing piston together form a sealed hydraulic chamber 34. The upper surface of the positioning shoulder 32 constitutes a hydraulic force surface, which is used to contact with the hydraulic oil and convert the material pressure into the pressure in the hydraulic pipeline 5.

[0049] The execution side assembly 4 includes: a guide section 24 , a water-cooled guide sleeve 41 , a loading bracket 42 and a hydraulic cylinder 43 .

[0050] The guide section 24 is coaxially formed between the front and rear ends of the waveguide rod 22 and is annular in shape with a diameter larger than that of the waveguide rod 22 . A thrust step 25 is formed on the end surface of the guide section 24 facing the rear end of the waveguide rod 22 .

[0051] The water-cooled guide sleeve 41 is a metal sleeve with a flange, which has an inner layer for cooling water to flow into. Its inner hole forms a sliding fit with the outer diameter of the guide section 24, providing precise axial motion guidance and water cooling for the waveguide rod 22. Its flange surface is used for fixed connection to the mold or external mounting bracket.

[0052] The loading bracket 42 is a sturdy metal bracket with a structure having slots to avoid the ultrasonic sensor 21 unit and its cable. Its front end contacts the thrust step 25 of the waveguide rod 22, and its rear end presses against the main pressure piston 44 of the hydraulic cylinder 43, serving as a rigid bridge for transmitting thrust.

[0053] A main pressure piston 44 is installed at the front end of the hydraulic cylinder 43, and the rear end is connected to the hydraulic pipeline 5. The countersunk hole, the hydraulic pipeline 5 and the interior of the hydraulic cylinder 43 are filled with high-temperature hydraulic oil.

[0054] The front end of the main pressure piston 44 pushes the loading bracket 42 , and the rear end of the main pressure piston 44 contacts the hydraulic oil and is driven by the hydraulic pressure.

[0055] It should be noted that the area of ​​the sensing surface where the sensing piston is in direct contact with the material is equal to the area of ​​the contact surface where the front end of the waveguide rod 22 is in contact with the acoustic thin wall 12; the effective force-bearing area where the positioning shoulder 32 of the sensing piston is in contact with the hydraulic oil is equal to the effective force-bearing area where the main pressure piston 44 is in contact with the hydraulic oil.

[0056] In addition to the hydraulic pipeline 5, the hydraulic transmission system also includes an oil filling port and an exhaust port connected to the hydraulic pipeline 5 to achieve the purpose of filling oil into the hydraulic pipeline 5 and discharging internal bubbles. The oil filling port and exhaust port are not shown in the figure.

[0057] Furthermore, the pressure adaptive compensation mechanism also includes a reset spring 6, one end of which is connected to the fixed water-cooled guide sleeve 41, and the other end is connected to the guide section 24 of the waveguide rod 22. Its function is to provide a weak pullback force when the system is unloaded (there is no composite material inside the pultrusion die 1), so that the waveguide rod 22 automatically breaks away from contact with the acoustic thin wall 12, thereby protecting the acoustic thin wall 12.

[0058] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the spirit and scope of protection of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the scope of protection of the embodiments of the present invention.

Claims

1. An adaptive pultrusion system for a composite material pultrusion machine, characterized in that: include: A pultrusion die (1) for heating, curing and shaping the composite material; A pulling device for pulling the composite material through the pultrusion die (1) at an adjustable speed; An ultrasonic detection module (2) is provided on the pultrusion die (1) and is used for emitting ultrasonic waves and receiving ultrasonic signals after penetrating the composite material, so as to obtain acoustic parameters related to the degree of curing of the composite material; A control module electrically connected to the ultrasonic detection module (2) and the pulling device; The control module is configured to calculate a current degree of curing of the composite material based on the acoustic parameters, compare the current degree of curing with a preset target degree of curing, and adjust the pulling speed of the pulling device in real time according to the comparison result, so as to perform closed-loop feedback control on the curing process of the composite material; The ultrasonic detection module (2) comprises at least one pair of ultrasonic sensors (21), wherein the ultrasonic sensors (21) are acoustically coupled to the inner cavity of the pultrusion die (1) via a waveguide rod (22), one end of the waveguide rod (22) is connected to the ultrasonic sensor (21), and the other end is used to transmit ultrasonic waves to the composite material; The pultrusion die (1) is provided with a blind hole (11), and a die body material with a thickness of 1 to 2 mm is retained between the extension end of the blind hole (11) and the inner cavity surface of the pultrusion die (1), serving as an acoustic thin wall (12) for transmitting ultrasonic waves, and the other end of the waveguide rod (22) is in contact with a side surface of the acoustic thin wall (12) facing the outside of the die; It also includes a pressure adaptive compensation mechanism for applying a supporting pressure to the acoustic thin wall (12) to offset the stress on the acoustic thin wall (12) caused by the process pressure generated by the composite material in the pultrusion die (1); The pressure adaptive compensation mechanism includes: A sensing side component (3) for sensing the process pressure in real time; An execution side component (4) is used to apply a thrust to the waveguide rod (22), thereby generating the supporting pressure on the acoustic thin wall (12) through the waveguide rod (22); a hydraulic transmission system, connecting the sensing side component (3) and the execution side component (4), and used to transmit the pressure sensed by the sensing side component (3) to the execution side component (4); The sensing side component (3) and the execution side component (4) are configured to make the support pressure and the process pressure equal in magnitude in real time.

2. The adaptive pultrusion system according to claim 1, characterized in that The execution side component (4) includes a hydraulic cylinder (43) driven by the hydraulic transmission system, the hydraulic cylinder (43) is fixedly connected to the pultrusion die (1), and the thrust generated by the hydraulic cylinder (43) acts on the waveguide rod (22); The sensing side component (3) includes a sensing piston, the front end face of the sensing piston is flush with the inner cavity of the pultrusion die (1), and is used to directly contact the composite material to sense the process pressure, and the rear end face of the sensing piston transmits the process pressure to the hydraulic cylinder (43) through the hydraulic transmission system.

3. The adaptive pultrusion system according to claim 2, characterized in that A countersunk through hole (13) is formed on the pultrusion die (1), the countersunk through hole (13) is sealed by a sealing cover (33), and the sensing piston is installed inside the countersunk through hole (13); The sensing piston comprises a coaxial piston rod (31) and a positioning shoulder (32), the front end surface of the piston rod (31) forming a sensing surface flush with the inner wall of the mold for sensing the process pressure, and the upper surface of the positioning shoulder (32) forming a hydraulic pressure surface; The sealing cover (33), the inner peripheral wall of the countersunk through hole (13) and the hydraulic force surface together form a hydraulic chamber (34) for accommodating hydraulic oil, and the hydraulic transmission system includes a hydraulic pipeline (5) connected to the hydraulic chamber (34).

4. The adaptive pultrusion system according to claim 3, characterized in that The execution side component (4) includes: A guide section (24) is formed on the waveguide rod (22), wherein the end surface of the guide section (24) toward the rear end of the waveguide rod (22) forms a thrust step (25); A water-cooling guide sleeve (41) is fixedly connected to the pultrusion die (1) and slidably connected to the guide section (24), and is used to provide axial guidance and water cooling for the guide section (24); A hydraulic cylinder (43), one end of which is connected to the hydraulic pipe (5) to receive input pressure, and the other end of which is provided with a main pressure piston (44) capable of axial movement; The loading bracket (42) has a structure for avoiding the ultrasonic sensor (21), one end of which contacts the thrust step (25) and the other end contacts the main pressure piston (44), and is used to transmit the thrust generated by the hydraulic cylinder (43) to the waveguide rod (22).

5. The adaptive pultrusion system according to claim 4, characterized in that The ultrasonic detection module (2) further includes a return spring (6), one end of the return spring (6) being connected to the water-cooling guide sleeve (41), and the other end being connected to the guide section (24), and the return spring (6) being used to provide a pulling force to the waveguide rod (22) to move it away from the acoustic thin wall (12), thereby separating the waveguide rod (22) from the acoustic thin wall (12) when there is no composite material in the pultrusion die (1).

6. A control method for the adaptive pultrusion system according to claim 1, It is characterized by: The following steps are involved: Step 1: a drawing device pulls the composite material through the pultrusion die (1); Step 2: obtaining acoustic parameters of the ultrasonic wave penetrating the composite material through the ultrasonic detection module (2); Step 3: calculating the current curing degree of the composite material based on the acoustic parameters; Step 4: comparing the current curing degree with a preset target curing degree, and calculating a control signal for adjusting the drawing speed based on a deviation from the comparison; Step five: sending the control signal to the drawing device to adjust the drawing speed in real time.

7. The control method according to claim 6, characterized in that: In step 2, the following sub-steps are also included: The process pressure generated by the composite material in the pultrusion die (1) is monitored in real time, and a supporting pressure of equal magnitude and opposite direction is applied to the acoustic thin wall (12) to eliminate the interference of process pressure fluctuations on acoustic parameter measurement.

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