Depth-controllable needling method for regulating and controlling pore structure of PAN-based pre-oxidized fibrofelt

Abstract

The invention relates to the technical field of carbon fiber product processing, and solves the problems of uniform parameters, no real-time density feedback, low needling precision, lack of dynamic regulation and control, lack of vibration and thermal management, poor process stability, single needling needle design and limited pore regulation and control dimension of a traditional process. The depth-controllable needling method for regulating and controlling the PAN-based pre-oxidized fibrofelt pore structure comprises the following steps which are executed in sequence: pretreating a fibrofelt, and performing real-time scanning through a beta-ray density instrument to obtain a density distribution diagram; regional needling parameter matching: a plurality of groups of needling assemblies are automatically divided according to a density distribution diagram; executing dynamic needling, and synchronously introducing into a water-based cooling system; and performing closed-loop depth calibration, and updating the density-acupuncture depth mapping model based on the resistance data. According to the method, dynamic, accurate and self-adaptive adjustment of acupuncture parameters is achieved, the consistency, uniformity and controllability of pore structure regulation and control are remarkably improved, and the multi-layer pore structure is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber product processing, and in particular to a depth-controllable needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt. Background Art

[0002] The production process of oxidized fiber felt includes pre-oxidation, adhesive coating, felting, heat treatment and other steps. Needle punching, as a key process in felting, can effectively integrate the fiber network, provide a structural basis for subsequent heat treatment, and ensure the stable performance of the final product; pre-oxidized fiber felt is made of pre-oxidized fibers, which are treated with high temperature and oxygen and have heat resistance and flame retardancy, but the bonding force between fibers is weak. The needling process uses the puncture action of the needle to entangle the fibers with each other to form a three-dimensional network structure, thereby significantly improving the mechanical properties of the material, such as tensile strength and tear resistance; the needling process can also optimize the structural stability of the pre-oxidized fiber felt. During the needling process, the fibers are rearranged and compressed, reducing the porosity inside the material and making the structure tighter. This structural improvement helps to improve the dimensional stability and deformation resistance of the material, especially in high temperature or corrosive environments.

[0003] Traditional processes rely on manual sampling or offline detection of fiber felt density, and are unable to obtain the global density distribution in real time, resulting in a mismatch between the needle insertion force and depth and the local density, which can easily lead to fiber damage or insufficient entanglement, and poor uniformity of the fiber felt pore structure; relying on mechanical drive, it has slow response speed and low positioning accuracy (difficult to achieve at the micron level), and lacks real-time monitoring and closed-loop feedback of key parameters such as needle insertion resistance and needle body position; mechanical vibration is not effectively suppressed during high-speed needling, which affects the needle body inclination angle and insertion position accuracy, and the heat generated by the friction between the needle rod and the fiber causes the needle tip to soften and deform, and there is a lack of active cooling mechanism; using a single type of needle (such as only cone barbs or groove barbs), the barb structure is fixed, and it is impossible to synergistically optimize deep entanglement and surface combing. Summary of the Invention

[0004] In order to solve the problems of uniform parameters in the above-mentioned traditional processes, no real-time density feedback, low needling accuracy, lack of dynamic control, lack of vibration and thermal management, poor process stability, single needle design, and limited pore control dimension, the present invention provides a depth-controllable needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt.

[0005] To solve the above technical problems, the present invention provides a technical solution: a depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt, comprising the following steps performed sequentially:

[0006] S1: Fiber mat pretreatment: The pre-oxidized fiber mat is placed on the work station and a density distribution map is obtained by real-time scanning with a β-ray density meter;

[0007] Among them, the β-ray density meter realizes non-contact, real-time, and high-precision density distribution measurement, providing objective and quantitative basic data for subsequent precise zoning control.

[0008] S2: Regional acupuncture parameter matching: Several groups of acupuncture components are automatically divided according to the density distribution map:

[0009] Marginal area: set the inclination angle to 58°±2° and the needling frequency to 300-500 punctures / minute;

[0010] Central area (≤40 mm from the center): set the inclination angle to 90°±2° and the needling frequency to 200-400 punctures / minute;

[0011] The acupuncture assembly uses a combination of alternating triangular pyramid needles and spiral groove needles, with the front group of needles (triangular pyramid needles) and the rear group of needles (spiral groove needles) staggered along the direction of travel;

[0012] Among them, the areas are dynamically divided according to the actual density distribution, and the optimal needling parameters (inclination angle, frequency) are customized according to the characteristics of different areas (such as fiber orientation and density) to improve the uniformity and efficiency of the overall needling effect; the combination of triangular pyramid needles and spiral groove needles can simultaneously achieve deep fiber entanglement and surface fiber refinement / connection, synergistically optimize the pore structure, and staggered settings along the direction of travel can effectively disperse the needling stress, reduce instantaneous excessive damage to the fibers, and may enable the fibers to form a more uniform network structure in three-dimensional space.

[0013] S3: Dynamic needling execution: Multiple needling assemblies arranged in front and behind are driven by a piezoelectric ceramic actuator array (stroke 0-8mm); needling is initiated based on density parameters and a water-based cooling system is simultaneously introduced;

[0014] Among them, the piezoelectric ceramic driver array has fast response and high precision, and can accurately control the depth and speed of acupuncture. It is the key hardware to achieve "depth controllable". Water-based cooling can effectively suppress friction heat during the acupuncture process, prevent fiber thermal damage, needle tip softening and deformation, and process parameter drift, ensuring process stability and the service life of the needle.

[0015] S4: Closed-loop depth calibration: Executed after every N acupuncture cycles (N=50): Real-time acupuncture resistance data is collected via the piezoresistive force sensor; the density-acupuncture depth mapping model is updated based on the resistance data; when the real-time density deviation δ>3%, the feedforward-feedback composite controller is triggered:

[0016] Q1: Feedforward compensation module: predicts acupuncture depth offset based on density gradient, with hysteresis compensation ≤8ms;

[0017] Q2: Feedback adjustment module: Dynamically correct the acupuncture depth according to the formula ΔD = kpδ + ki∫δdt (kp, ki are PID coefficients);

[0018] The piezoresistive force sensor provides direct, real-time feedback on the acupuncture process. Dynamic model updates the "density-needle depth mapping model" based on real-time resistance data, enabling the model to adapt to disturbances such as material batch differences and equipment status changes, maintaining long-term accuracy. Feedforward compensation predicts offset based on the density gradient and compensates in advance, quickly responding to system changes and reducing initial deviations. Feedback regulation utilizes classic PID control (proportional-integral) to continuously correct residual deviations and ensure ultimate control accuracy. The combination of these two significantly improves the system's dynamic response performance and steady-state accuracy.

[0019] Furthermore, in step S3, a vibration suppression strategy is set:

[0020] (a) The needle tilt deviation is monitored by a piezoelectric gyroscope array (sampling frequency ≥ 500 Hz);

[0021] (b) When the inclination angle deviation is greater than 0.8° for 0.2s, the servo motor correction mechanism is activated (response time ≤ 0.4s);

[0022] (c) Using a two-stage adaptive filter:

[0023] The first-stage filter suppresses 50-200Hz mechanical vibration;

[0024] The secondary filter suppresses 200-500Hz piezoelectric harmonics;

[0025] Among them, the high-sampling-rate piezoelectric gyroscope array accurately captures the tiny tilt deviation of the needle body, sets a clear deviation threshold and a rapid response mechanism, promptly corrects the needle body posture, ensures the accuracy of the insertion angle, and suppresses the high-frequency harmonics of the piezoelectric driver itself. This hierarchical processing significantly improves the overall stability of the system and reduces the impact of vibration on acupuncture accuracy and needle life.

[0026] Furthermore, the triangular pyramid needle is provided with a plurality of main barbs, and the spiral groove needle is provided with a plurality of auxiliary barbs, the main barbs are 0.12-0.18 mm deep and 0.8 mm apart, and the auxiliary barbs are 0.06-0.10 mm deep and 0.4 mm apart;

[0027] Among them, the hook depth and spacing are differentiated: the main barb is responsible for deep, strong grabbing and entanglement of fibers; the secondary barb is responsible for shallow, finer fiber combing and hooking, which synergistically optimizes the pore structure formation of the fiber felt from the surface to the deep layer, avoiding excessive damage or insufficient entanglement that may be caused by a single hook type.

[0028] Furthermore, the density-depth mapping model in step S4 is constructed by the following steps:

[0029] (1) Offline training phase: Fiber mats of different densities (0.15-0.35 g / cm 3 ) acupuncture response data;

[0030] (2) Online update stage: using an incremental learning algorithm, the model parameters are automatically updated every 100 acupuncture cycles;

[0031] (3) Anomaly detection mechanism: When the prediction error is greater than 8%, the model reset procedure is triggered.

[0032] Furthermore, a hybrid drive of piezoelectric ceramics and voice coil motors is used. The piezoelectric ceramics are responsible for micron-level fine adjustment (0-2mm stroke), and the voice coil motor is responsible for millimeter-level displacement (0-6mm stroke), achieving a resolution of 0.1μm within a 0-8mm stroke. A fiber Bragg grating displacement sensor (resolution 0.05μm) and a piezoresistive force sensor are added to form dual-mode redundant detection.

[0033] Among them, by combining the advantages of both piezoelectric ceramics and voice coil motors, an ultra-high resolution of 0.1μm is achieved within a 0-8mm stroke, which is better than the performance of a single driver. The redundant design verifies each other, improves the reliability and fault tolerance of the measurement data, and provides double protection for high-precision control.

[0034] Furthermore, the triangular pyramid needle and spiral groove needle are both provided with dual cooling channels, which suppress the thermal deformation of the needle rod through low-temperature coolant, and the dual cooling channels are connected to the pipeline of the water-based cooling system;

[0035] Among them, low-temperature coolant can strongly suppress the thermal deformation of the needle rod, and can maintain the geometric accuracy and mechanical properties of the needle even under high-speed and high-frequency needling. It is a key detail to maintain long-term process stability and high precision.

[0036] The advantages of the present invention are:

[0037] 1. Dynamic, precise, and adaptive adjustment of acupuncture parameters has been achieved, significantly improving the consistency, uniformity, and controllability of pore structure regulation. Beta-ray density scanning, piezoresistive force sensing, and piezoelectric gyroscopes are used to sense the fiber mat state and the acupuncture process in real time. Based on a dynamically updated "density-depth mapping model," a feedforward-feedback composite control strategy is adopted.

[0038] 2. Intelligent zoning is performed based on the actual density distribution of the fiber mat, and the optimal inclination angle, frequency and needle combination are matched for different areas (edge / center), effectively solving the problem of regional performance differences caused by traditional uniform needling;

[0039] 3. The alternating staggered arrangement of triangular pyramid needles (deep main barbs) and spiral groove needles (shallow secondary barbs), combined with differentiated hook depth / spacing design, synergistically achieves multi-level pore structure optimization from deep strong entanglement to surface fine combing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a process flow diagram of the present invention.

[0041] Figure 2 It is a schematic structural diagram of the acupuncture assembly of the present invention.

[0042] Figure 3 It is a schematic structural diagram of the triangular pyramid needle and the spiral groove needle of the present invention.

[0043] Figure 4 It is a schematic diagram of the dual cooling channel structure of the present invention.

[0044] As shown in the figure: 10, acupuncture assembly; 11, triangular pyramid needle; 12, spiral groove needle; 110, main barb; 120, auxiliary barb; 13, double cooling channel. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Combined with attachment Figure 1-4 A depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber mats, step S1: fiber mat pretreatment

[0047] The PAN-based pre-oxidized fiber felt was spread flat on a horizontal workbench, and the surface of the felt was scanned along the XY directions using a β-ray density meter.

[0048] The scanning resolution is set to ≤5mm, and a 2D density distribution cloud map is generated in real time. The density data is uploaded to a controller (such as an industrial PLC or embedded industrial computer).

[0049] Step S2: Acupuncture parameter matching by region

[0050] The central controller divides the dynamic area according to the density cloud map:

[0051] Edge area: density ≥0.25g / cm 3 The parameters were set as follows: needle inclination angle: 58°±2° (relative to normal), acupuncture frequency: 300–500 punctures / min;

[0052] Central area: ≤40mm from the geometric center and density <0.25g / cm 3 The parameters were set as follows: needle inclination angle: 90°±2° (vertical insertion), acupuncture frequency: 200–400 punctures / min;

[0053] Needle combination configuration: The acupuncture assembly 10 is composed of alternating triangular pyramid needles 11 and spiral groove needles 12; Needle layout: Along the direction of travel, the front group of triangular pyramid needles 11 and the rear group of spiral groove needles 12 are staggered by 20mm to avoid stress overlap.

[0054] Step S3: Dynamic acupuncture execution

[0055] Drive control: The acupuncture assembly 10 is driven by a piezoelectric ceramic driver array with a total stroke of 0–8 mm. The start command is generated based on the density parameter of S1, and the high-density area is executed first;

[0056] Cooling system:

[0057] Synchronously start the water-based cooling system (flow rate 5–10 L / min), and the coolant temperature is ≤15°C.

[0058] Vibration suppression strategy: The needle body inclination angle is monitored in real time through a piezoelectric gyroscope array (sampling frequency 500Hz). When the inclination angle deviation is greater than 0.8° and persists for 0.2s, the servo motor correction mechanism is triggered (response time ≤ 0.4s).

[0059] Using a two-stage adaptive filter:

[0060] A first-stage filter (FIR structure) suppresses 50–200 Hz mechanical vibrations;

[0061] A second-stage filter (IIR structure) suppresses the 200–500 Hz piezoelectric harmonics.

[0062] Step S4: Closed-loop depth calibration

[0063] Data collection: After every 50 acupuncture cycles, real-time acupuncture resistance (range 0–200 N, accuracy ±0.5%) was collected using a piezoresistive force sensor (e.g., Kistler 9017B).

[0064] Model Update:

[0065] The resistance data are input into the density-needle penetration depth mapping model, and the model parameters are updated online.

[0066] Compound control trigger conditions:

[0067] When the real-time density deviation δ>3% (δ = measured density - target density), start the controller:

[0068] Q1 feedforward compensation: predicts depth offset based on density gradient, with lag compensation time ≤8ms;

[0069] Q2 Feedback adjustment: Dynamically correct the acupuncture depth according to the formula ΔD=kpδ+ki∫δdt, where:

[0070] kp=0.35mm / %, ki=0.02mm / (%·s) (obtained through PID tuning).

[0071] Density-depth mapping model construction

[0072] Offline training: Collect 500 sets of different densities (0.15–0.35 g / cm 3 ) Needle punching data of fiber felt (resistance-depth relationship) to train BP neural network model;

[0073] Online update: Using incremental learning algorithms (such as Online RandomForest), the weights are updated every 100 acupuncture cycles;

[0074] Abnormal handling: When the model prediction error is greater than 8%, it will automatically reset to the initial offline version and issue an alarm.

[0075] Hybrid drive and detection:

[0076] Driver: piezoelectric ceramic (stroke 0–2 mm, resolution 0.1 μm) superimposed voice coil motor (stroke 0–6 mm, resolution 1 μm);

[0077] Dual-mode detection: A fiber Bragg grating displacement sensor (resolution 0.05 μm) monitors the actual penetration depth; a piezoresistive force sensor monitors the penetration force, and the data from the two are fused and fed back to the controller.

[0078] Needle cooling channel:

[0079] The triangular pyramid needle 11 and the spiral groove needle 12 are provided with double cooling channels 13 inside, into which -10°C ethylene glycol aqueous solution (flow rate 0.5 L / min) is introduced and connected to the water-based cooling system through a quick connector.

[0080] The present invention and its embodiments are described above. This description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs structures and embodiments similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt, characterized by: It includes the following steps, which are performed in sequence: S1: Fiber mat pretreatment: The pre-oxidized fiber mat is placed on the work station and a density distribution map is obtained by real-time scanning with a β-ray density meter; S2: Acupuncture parameter matching by region: Several groups of acupuncture components (10) are automatically divided according to the density distribution map: Marginal area: set the inclination angle to 58°±2° and the needling frequency to 300-500 punctures / minute; Central area (≤40 mm from the center): set the inclination angle to 90°±2° and the needling frequency to 200-400 punctures / minute; The acupuncture assembly (10) is composed of alternatingly arranged triangular pyramid needles (11) and spiral groove needles (12), wherein the front group of needles (triangular pyramid needles (11)) and the rear group of needles (spiral groove needles (12)) are staggered along the direction of travel; S3: Dynamic acupuncture execution: a plurality of acupuncture components (10) arranged in front and back are driven by a piezoelectric ceramic driver array (stroke 0-8 mm); acupuncture is started based on density parameters and a water-based cooling system is simultaneously introduced; S4: Closed-loop depth calibration: Executed after every N acupuncture cycles (N=50): Real-time acupuncture resistance data is collected via the piezoresistive force sensor; the density-acupuncture depth mapping model is updated based on the resistance data; when the real-time density deviation δ>3%, the feedforward-feedback composite controller is triggered: Q1: Feedforward compensation module: predicts acupuncture depth offset based on density gradient, with hysteresis compensation ≤8ms; Q2: Feedback adjustment module: Dynamically correct the acupuncture depth according to the formula ΔD = kp*δ + ki∫δdt (where kp and ki are PID coefficients).

2. The depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt according to claim 1, characterized in that: In step S3, the vibration suppression strategy is set: (a) The needle tilt deviation is monitored by a piezoelectric gyroscope array (sampling frequency ≥ 500 Hz); (b) When the inclination angle deviation is greater than 0.8° for 0.2s, the servo motor correction mechanism is activated (response time ≤ 0.4s); (c) Using a two-stage adaptive filter: The first-stage filter suppresses 50-200Hz mechanical vibration; The second-stage filter suppresses the 200-500Hz piezoelectric harmonics.

3. The depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt according to claim 1, characterized in that: The triangular pyramid needle (11) is provided with a plurality of main barbs (110), and the spiral groove needle (12) is provided with a plurality of secondary barbs (120). The main barbs (110) have a depth of 0.12-0.18 mm and a spacing of 0.8 mm, and the secondary barbs (120) have a depth of 0.06-0.10 mm and a spacing of 0.4 mm.

4. The depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt according to claim 1, characterized in that: The density-depth mapping model in step S4 is constructed by the following steps: (1) Offline training phase: Fiber mats of different densities (0.15-0.35 g / cm 3 ) acupuncture response data; (2) Online update stage: using an incremental learning algorithm, the model parameters are automatically updated every 100 acupuncture cycles; (3) Anomaly detection mechanism: When the prediction error is greater than 8%, the model reset procedure is triggered.

5. The depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt according to claim 1, characterized in that: A hybrid driver of piezoelectric ceramics and voice coil motors is used. The piezoelectric ceramics are responsible for micron-level fine-tuning (0-2mm stroke), and the voice coil motor is responsible for millimeter-level displacement (0-6mm stroke), achieving a resolution of 0.1μm within a 0-8mm stroke. Fiber Bragg grating displacement sensors (resolution 0.05μm) and piezoresistive force sensors are added to form dual-mode redundant detection.

6. The depth-controlled needling method for regulating the pore structure of PAN-based pre-oxidized fiber felt according to claim 1, characterized in that: The triangular pyramid needle (11) and the spiral groove needle (12) are both provided with double cooling channels (13) to suppress the thermal deformation of the needle rod through low-temperature cooling liquid. The double cooling channels (13) are connected to the pipeline of the water-based cooling system.

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