A forming method for the physical consolidation of fibrous materials

Abstract

The present application relates to the technical field of plastic forming processing, and discloses a forming method for physical consolidation of fiber materials, which comprises the following steps: feeding a multi-component fiber mixed felt into a forming channel and heating and melting in a front section temperature zone; applying static stress and superimposing alternating normal pulse stress in a forming temperature zone; when a real-time transient pressure value exceeds a standard, keeping a temperature gradient constant and increasing a pulse frequency, and synchronously reducing the static stress to adjust a flow resistance mass transfer state; and linearly reducing the temperature in a cooling temperature zone to make the melt phase change and solidify. The present application introduces asymmetric pulse stress to control the non-equilibrium disentanglement of macromolecular segments, overcome the wetting resistance of phase interfaces, and drive the melt to deeply penetrate into the wall holes of plant fibers to construct space locking and anchoring under low base static pressure, so as to solve the opposite problems of mass transfer penetration of porous materials and high-temperature thermal degradation of heat-sensitive polymers.

Description

Technical Field

[0001] This invention relates to a molding method for the physical consolidation of fiber materials, belonging to the field of plastic molding and processing technology. Background Technology

[0002] Currently, in the thermoforming manufacturing process of fully biodegradable covering materials, the use of thermoplastic plastics and porous plant fiber materials to construct glue-free interlocking structures is a common processing method. Conventional processing usually uses a fixed molding temperature and constant static extrusion pressure to melt the thermoplastic polymer fibers and flow into the interwoven network of plant fibers. The two-phase material is solidified by the rheological penetration of the melt into the fiber gaps and subsequent cooling and solidification. However, with the increasing requirements for the connection strength and weather resistance of parts in large-scale continuous industrial production, this constant temperature and pressure processing approach has encountered physical constraints. Thermoplastic biopolymer materials have a narrow processing temperature window. When the processing channel is kept at a constant high temperature for a long time, it causes molecular chain breakage, resulting in embrittlement of the matrix material. At the same time, plant fibers have a heterogeneous porous cellular structure. The continuous normal static high pressure causes irreversible pressure collapse of the porous skeleton structure, sealing the cellular channels inside the fibers. This causes a sharp rise in capillary reverse back pressure at the interface, which hinders the melt from penetrating into the cellular cavity. As a result, the final composite board is prone to delamination and failure.

[0003] To address the aforementioned mass transfer and degradation challenges, linear solutions such as extending the hot-pressing cycle or further increasing the hot-pressing temperature cannot provide effective solutions. This is because increasing the temperature accelerates the thermal decomposition of thermosensitive polymers, while extending the cycle leads to a significant reduction in production efficiency. Increasing the static pressure also fails due to exacerbating the structural damage to the fiber cavities. Existing molding and processing systems cannot reconcile the conflicting relationship between the rheological wetting resistance of thermoplastic melts and solid boundary collapse. In terms of process parameter control and material modification, existing technologies attempt to introduce auxiliary solvents or improve the slurry system to optimize interfacial bonding. For example, Chinese invention patent application CN118893683A discloses a fiber without external adhesives. The present invention relates to a biomass board and its preparation method, which utilizes the eutectic solvent DES to dissolve plant powder and disrupt fiber hydrogen bonds, releasing cellulose and lignin as biomass adhesives. However, this improvement logic based on the dissolution of chemical components faces challenges in continuous production: the introduction and subsequent removal of DES are complex, requiring high washing intensity and easily causing swelling damage to the fiber matrix; the solution relies on chemical recombination of components, which cannot solve the dynamic penetration problem of polymer melts into the deep micron-level cellular lumen under non-ideal conditions while maintaining the intrinsic mechanical strength of the fiber; and for heterogeneous porous fibers with complex hierarchical structures, simple component modification is difficult to achieve cross-interface topological mechanical locking, and the finished product is at risk of interfacial delamination failure under mechanical conditions.

[0004] Therefore, how to control the multi-segment temperature distribution and dynamic pressure field timing during the molding process, and drive the polymer melt to achieve deep rheological wetting while keeping the plant fiber cell cavity channels from irreversibly collapsing, and construct a stable heterogeneous phase physical interlocking interface, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems in the background art, the technical solution of the present invention is as follows: A molding method for the physical consolidation of fiber materials, comprising the following steps:

[0006] Step S1: The mixed felt containing thermoplastic polymer fibers and porous plant fibers is continuously fed into the molding channel. An increasing temperature gradient is established in the first and second stages of the molding channel. Heating causes the thermoplastic polymer fibers to melt and impregnate the porous plant fibers.

[0007] Step S2: In the third stage of the forming channel, while applying static stress to the molten mixed felt, an alternating normal pulse stress is applied by a pulse mechanism located on the outer wall of the forming channel, and the real-time transient pressure value of the mixed felt passing through is collected by a pressure sensor located on the inner wall of the outlet end of the forming channel.

[0008] Step S3: When the real-time transient pressure value exceeds the safety threshold pressure determined by the sum of the reference pressure and the fluctuation deviation, keep the temperature gradient between the first stage and the second stage constant, increase the frequency of the alternating normal pulse stress from 3Hz to 5.5Hz, and simultaneously control the static pressure drive mechanism to reduce the static stress by 15% and increase the local flow velocity at the immersion point.

[0009] Step S4: The mixed felt body with reduced static stress is continuously introduced into the fourth stage cooling temperature zone. The molding channel is controlled to implement a linear cooling rate of 1.5℃ / s to 2.5℃ / s for primary cooling, so that the internal center temperature of the mixed felt body is reduced to the range of 20℃ to 60℃.

[0010] Preferably, step S4 includes: step S41, maintaining constant temperature and pressure for 45s to 60s when the temperature drops to 115°C to 105°C; step S42, keeping the local deviation of the surface anchoring depth of the two-phase interface within the range of 0% to 8%.

[0011] Preferably, the thermoplastic polymer fiber is polylactic acid fiber, and the porous plant fiber is jute fiber with a basis weight of 600 g / m² to 1200 g / m²; the temperature in the first stage of step S1 is 175°C to 185°C, and the temperature in the second stage is 190°C to 200°C.

[0012] Preferably, step S2 includes: step S21, using the pressure sensor on the inner wall to collect the extrusion resistance signal and convert it into an electrical signal; step S22, using the signal conditioning unit to filter and extract the characteristic difference of the electrical signal and convert it into a real-time transient pressure value.

[0013] Preferably, step S3 includes: step S31, controlling the initial frequency of the alternating normal pulse stress to 3Hz; step S32, adjusting the frequency to 5.5Hz when the pressure exceeds the limit, and simultaneously controlling the static pressure drive mechanism to reduce the static stress by 15%.

[0014] Preferably, step S41 includes step S411, reducing the heating power of the molding channel and stopping the heating of the first stage and the second stage, while stopping the conveying of the mixed felt and keeping the mixed felt resting at constant temperature and pressure.

[0015] Preferably, step S4 includes step S43, where after the local deviation stabilizes, the material enters the secondary cooling zone and is cooled to below 40°C at a rate of 3.0°C / s to 4.5°C / s, and the formed sheet is discharged from the forming channel.

[0016] Preferably, the method further includes the following steps: Step S5, collecting the initial material temperature when the mixed felt is fed into the first stage by a temperature sensor configured at the front end; Step S6, increasing the heating power of the first stage when the initial material temperature is below 50°C.

[0017] Preferably, the method further includes the following steps: Step S7, real-time acquisition of the pressure limit gap change value between the upper mold and the lower mold using a displacement sensor; Step S8, when the pressure limit gap change value exceeds 1.5 mm for 3 seconds, stopping heating and stopping the conveying of the mixed felt.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. In the physical consolidation molding of fiber materials, by controlling the temperature in the first stage, the moisture content of the mixed felt is reduced to below 1.2% through contact heat conduction preheating, eliminating the cause of high-temperature hydrolysis. Combined with limiting the material residence time to 15s to 25s in the third stage temperature zone, the fully molten thermoplastic biopolymer fiber is stably maintained in the flow window. The two mechanisms work together to cut off the thermal degradation path of the polymer chain in the viscous flow state. While protecting the molecular weight and intrinsic mechanical toughness of the heat-sensitive polymer, the melt has a stable isotropic flow state that penetrates the porous structure of the heterogeneous interface. This solves the contradiction between the mass transfer and penetration of porous materials and the high-temperature thermal degradation of heat-sensitive polymers in conventional isothermal and constant-pressure extrusion molding.

[0020] 2. By setting a low base static pressure, the cell cavity skeleton of plant fibers is in an elastic recovery state under load without yielding. Periodic nonlinear shear pulse waves are superimposed simultaneously. Taking advantage of the timing characteristics that the stress loading duration of the pulse wave is shorter than the intrinsic rheological relaxation time of polymer chain segments (45ms to 60ms), a transient high shear rate is generated at the cell wall pore section, inducing non-equilibrium disentanglement and orientation slip of the melt. This drives the polymer melt in the high viscosity window to overcome the wetting resistance caused by surface tension and penetrate into the cell wall pores, eliminating the phenomenon of a sharp increase in capillary reverse back pressure caused by the mechanical closure of fiber pores in traditional high-pressure extrusion molding.

[0021] 3. Utilizing the temporal structure where the stress release duration in a single pulse wave is significantly longer than the intrinsic rheological relaxation time of molecular chain segments, the molecular chain segments penetrating into the pores of the channel are given sufficient time to re-entangle randomly and relax their conformation. Before solidification, a blocking interface is generated to prevent the melt from flowing backward. Combined with the linear cooling of the molding channel within the four-stage cooling temperature zone, the polymer melt at the inner wall of the pore is induced to undergo volumetric crystallization shrinkage. This generates continuous normal stress on the pore wall at the interlacing sites to lock the internal plugs, achieving glue-free integrated solidification of two-phase heterogeneous materials and protection against delamination failure. Attached Figure Description

[0022] Figure 1 This is a flowchart of the physical consolidation molding process for fiber materials according to the present invention;

[0023] Figure 2 This is a diagram showing the signal acquisition and closed-loop control of the physical consolidation molding equipment of the present invention.

[0024] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0026] A molding method for the physical consolidation of fiber materials includes the following steps:

[0027] Step S1: The mixed felt containing thermoplastic polymer fibers and porous plant fibers is continuously fed into the molding channel. An increasing temperature gradient is established in the first and second stages of the molding channel. Heating causes the thermoplastic polymer fibers to melt and impregnate the porous plant fibers.

[0028] Step S2: In the third stage of the forming channel, while applying static stress to the molten mixed felt, an alternating normal pulse stress is applied by a pulse mechanism located on the outer wall of the forming channel, and the real-time transient pressure value of the mixed felt passing through is collected by a pressure sensor located on the inner wall of the outlet end of the forming channel.

[0029] Step S3: When the real-time transient pressure value exceeds the safety threshold pressure determined by the sum of the reference pressure and the fluctuation deviation, keep the temperature gradient between the first stage and the second stage constant, increase the frequency of the alternating normal pulse stress from 3Hz to 5.5Hz, and simultaneously control the static pressure drive mechanism to reduce the static stress by 15% and increase the local flow velocity at the immersion point.

[0030] Step S4: The mixed felt body with reduced static stress is continuously introduced into the fourth stage cooling temperature zone. The molding channel is controlled to implement a linear cooling rate of 1.5℃ / s to 2.5℃ / s for primary cooling, so that the internal center temperature of the mixed felt body is reduced to the range of 20℃ to 60℃.

[0031] Preferably, step S4 includes: step S41, maintaining constant temperature and pressure for 45s to 60s when the temperature drops to 115°C to 105°C; step S42, keeping the local deviation of the surface anchoring depth of the two-phase interface within the range of 0% to 8%.

[0032] Preferably, the thermoplastic polymer fiber is polylactic acid fiber, and the porous plant fiber is jute fiber with a basis weight of 600 g / m² to 1200 g / m²; the temperature in the first stage of step S1 is 175°C to 185°C, and the temperature in the second stage is 190°C to 200°C.

[0033] Preferably, step S2 includes: step S21, using the pressure sensor on the inner wall to collect the extrusion resistance signal and convert it into an electrical signal; step S22, using the signal conditioning unit to filter and extract the characteristic difference of the electrical signal and convert it into a real-time transient pressure value.

[0034] Preferably, step S3 includes: step S31, controlling the initial frequency of the alternating normal pulse stress to 3Hz; step S32, adjusting the frequency to 5.5Hz when the pressure exceeds the limit, and simultaneously controlling the static pressure drive mechanism to reduce the static stress by 15%.

[0035] Preferably, step S41 includes step S411, reducing the heating power of the molding channel and stopping the heating of the first stage and the second stage, while stopping the conveying of the mixed felt and keeping the mixed felt resting at constant temperature and pressure.

[0036] Preferably, step S4 includes step S43, where after the local deviation stabilizes, the material enters the secondary cooling zone and is cooled to below 40°C at a rate of 3.0°C / s to 4.5°C / s, and the formed sheet is discharged from the forming channel.

[0037] Preferably, the method further includes the following steps: Step S5, collecting the initial material temperature when the mixed felt is fed into the first stage by a temperature sensor configured at the front end; Step S6, increasing the heating power of the first stage when the initial material temperature is below 50°C.

[0038] Preferably, the method further includes the following steps: Step S7, real-time acquisition of the pressure limit gap change value between the upper mold and the lower mold using a displacement sensor; Step S8, when the pressure limit gap change value exceeds 1.5 mm for 3 seconds, stopping heating and stopping the conveying of the mixed felt.

[0039] Example 1: In the continuous hot-pressing mass production of fully biodegradable ecological covering materials, a mixed felt composed of jute fiber and polylactic acid fiber is continuously fed into the molding channel. Due to the heterogeneous fluctuations in the local basis weight and bulk density of jute fiber in the molding area, a porous cellular structure and transverse pore network with dense fluid resistance are generated inside the system. Furthermore, the porous cell walls generate flow wetting resistance due to surface tension polarity mismatch during the continuous extrusion molding stage. Simultaneously, if the high molecular weight polylactic acid melt is kept at a fixed high temperature for a long time, thermal shearing degradation of the polymer chain segments leads to deterioration of apparent viscosity and matrix embrittlement. The two heterogeneous materials... The consolidation interface only forms a shallow layer of mechanical accumulation, leading to delamination and cracking at the consolidation interface when the finished cover board is subjected to high-moisture swelling deformation or alternating shear load service cycles. To eliminate the performance degradation factors of the aforementioned heat-sensitive polymer plastics during the viscous flow molding process and to establish an initial interlocking topology, the mixed felt is preheated by contact heat conduction at a temperature range of 85°C to 95°C in the first-stage temperature zone, with the material residence time stabilized in the range of 35s to 45s. This reduces the overall mass moisture content of the mixed felt to below 1.2%, thereby cutting off the physical degradation path of polylactic acid molecular chains caused by the high-temperature hydrolysis reaction. The material then continuously enters the second-stage molding channel. In the temperature zone, the temperature is maintained between 135°C and 145°C for 25 to 35 seconds. In this zone, the amorphous polymer chains, located between the glass transition temperature and melting temperature of polylactic acid (PLA), thaw and gain high elasticity and slip capability. The softened PLA fibers undergo spatial deformation at the two-phase interlocking points and encapsulate adjacent jute fibers, constructing an initial spatial geometric topological interlocking structure. The material then enters the three-stage viscous flow molding temperature zone, where the internal molding temperature is maintained at 172°C to 182°C to induce PLA melting. The residence time of the material within this temperature zone in the molding channel is limited to 15 to 25 seconds to maintain the PLA melt. Within a flow window with a static apparent viscosity ranging from 140 Pa·s to 220 Pa·s, the pressure-applying component of the forming channel applies a normal asymmetric relaxation resonant pulse stress sequence to the molten mixed felt. This stress sequence is composed of a constant base static stress stable in the range of 0.15 MPa to 0.25 MPa, combined with superimposed periodic nonlinear shear pulse waves. Under the constraint of this base static stress, the elastic deformation of the jute fiber cellular skeleton under load is lower than its plastic yield limit, in order to maintain the adaptive open state of the pore cell walls. The maximum pulse peak stress of the periodic nonlinear shear pulse wave is between 1.2 MPa and 1.Within a pressure range of 6 MPa, the characteristic frequency of the pulse wave is controlled within the range of 3 Hz to 5 Hz, and the stress loading phase of a single pulse waveform is controlled within the range of 15 ms to 25 ms. Since this stress loading duration is shorter than the intrinsic rheological relaxation time of the polylactic acid (PLA) macromolecular chain segments in the current viscous flow state (45 ms to 60 ms), the high-frequency, intense extrusion shear wave generates a transient high shear rate at the pore cross-section of the porous cell wall of jute fiber. This causes the PLA melt molecular chains to undergo non-equilibrium disentanglement and align parallel to the flow direction, resulting in a rapid, stepwise drop in dynamic apparent viscosity and overcoming surface tension wetting resistance. Under low substrate stress load, the polymer melt forcibly penetrates the transverse wall pores and longitudinal cell cavities of jute fiber to a depth of 22 μm to 38 μm to construct a three-dimensional network permeation structure.

[0040] In the subsequent stress release phase, the stress release duration of a single pulse waveform is controlled within the range of 180ms to 220ms. This duration is greater than the intrinsic rheological relaxation time of the polylactic acid (PLA) macromolecular chain segments, allowing the normal stress to fall back to the static stress level of the substrate. Within this time window without an external shear field, the PLA macromolecular chain segments injected into the pores of the jute fiber wall gain sufficient time to recover their conformational entropy. Through spontaneous relaxation of disorder, the macromolecular chain segments rebuild a spatial entanglement network, and the non-oriented recombination of the molecular chains drives the interior of the pores. The intrinsic viscosity of the polylactic acid melt undergoes a spontaneous rheological rebound, constructing a backflow-blocking interface within the wall pores before solidification, preventing reverse flow of the melt. It should be noted that, to establish accurate correspondence between equipment control and process stages, the molding channel employs multiple independent temperature-controlled heaters in its actual structural layout for zoned temperature control. This is achieved by establishing an increasing temperature gradient within the aforementioned sub-zones: the first sub-zone is controlled between 175℃ and 185℃, and the second sub-zone between 190℃ and 200℃, ensuring the polylactic acid... The fiber achieves uniform melt impregnation before contacting the high-frequency pulsed shear field. Simultaneously, regarding the timing control of the asymmetric relaxation resonant pulse stress sequence, under normal operating conditions with a reference frequency of 3Hz to 5Hz, since the full cycle time of a single pulse has a margin of 200ms to 333.3ms, the sum of the stress loading phase (15ms to 25ms) and the stress release phase (180ms to 220ms) of the single pulse waveform can be precisely nested within the current cycle, while the static stress of the substrate is automatically maintained during the remaining periods. When the system performs adaptive adjustment to progressively increase the characteristic frequency to 5.5Hz, the frequency conversion control loop within the control unit will, according to the period proportional scaling rule, automatically compress and adjust the stress loading phase of the single pulse waveform to the range of 10ms to 12ms, and automatically compress and adjust the stress release phase to the range of 110ms to 125ms, so that the sum of the two phase durations is controlled between 120ms and 137ms, strictly less than 181ms corresponding to the 5.5Hz frequency.The 8ms single pulse full-cycle upper limit ensures that the core physical mechanism of fast loading and slow release of the asymmetric shear pulse wave remains unchanged, achieving full closed-loop self-consistency of the timing control trajectory under overall high-frequency operation. To clarify the complex temperature field architecture within the stage temperature zone, from shallow dehydration to microscopic melting, this invention implements nested gradient partition control in the spatial layout of this stage. The preheating peripheral section near the foremost feed lip of the forming channel has its actual temperature control core limited to a contact-type low-temperature range of 85℃ to 95℃, specifically designed for efficient physical evaporation and dehydration when the material is first fed in. Immediately following the feed lip, the core section of the first sub-section of the forming channel features a heater with forcibly increased power and independently controlled temperature within a melting high-temperature range of 175°C to 185°C. This allows the polylactic acid fibers, whose moisture content has been reduced to below the safe threshold after preheating and dehydration, to melt instantly within this high-temperature sub-section. This spatial zoning gradient not only eliminates the numerical conflict between the high-temperature boundary defined in the claims and the low-temperature window surface of preheating and dehydration, but also achieves highly efficient causal synergy between pre-dehydration and uniform melting at the process physics level, avoiding the engineering risk of polylactic acid molecular chain hydrolysis and degradation caused by free water at high temperatures.

[0041] To combat sudden changes in mass transfer resistance caused by localized weight fluctuations in jute fiber felt during continuous mass production, a reverse extrusion pressure sensor is installed at the outlet of the forming channel to collect real-time resistance fluctuation data. When the local bulk density of jute fibers increases, causing the real-time transient pressure value collected by the reverse extrusion pressure sensor to exceed the safety threshold pressure determined by the sum of the reference pressure and the fluctuation deviation, the control unit issues an adaptive adjustment command to maintain a constant temperature gradient between the first and second stage temperature zones. The stress timing characteristic frequency of the third stage temperature zone is increased from 3Hz to 5.5Hz in a stepwise manner, and the static stress of the substrate is simultaneously reduced by 15% through the hydrostatic drive mechanism. The shear thinning depth induced by high-frequency pulses at the cell wall pores is used to compensate for this. Local fiber layers are used to compensate for the mass transfer resistance of these layers, ensuring that the local deviation of the physical interlocking anchoring depth at the two-phase interface is stably controlled below 8% across the entire width. Specifically, the local deviation of the surface anchoring depth at the two-phase interface is not directly obtained through online microscopic measurement, but rather based on the extrusion flow dynamics mechanism of polymer melt in heterogeneous porous media. This is achieved through indirect mapping and dead zone control by controlling the uniformity of the overall back-extrusion pressure fluctuation. Since the surface penetration depth of the melt within the plant fiber cell lumen channel is negatively correlated with the local mass transfer resistance of the channel, and the heterogeneous fluctuation of the local mass transfer resistance directly and linearly feeds back to the transient deviation of the back-extrusion pressure at the channel outlet, the control unit adjusts the pulse in a stepwise manner. By adjusting the characteristic frequency and synchronously lowering the static stress of the substrate, and locking the real-time transient pressure value at the outlet end within the preset safety threshold pressure, the difference in the advancing speed of the melt flow front caused by the flow resistance difference at various points along the width of the sheet is compensated in real time by the dynamic shear thinning effect of the high-frequency pulse. This eliminates the surface non-uniformity of the interlocking depth at the two-phase interface, and makes the local deviation of the surface anchoring depth at each measuring point of the final phase interface converge deterministically to the closed-loop process target range of 0% to 8%. During the stagnation time window of isothermal and atmospheric pressure residence and stopping upstream delivery, in order to prevent the polylactic acid melt remaining in the third stage viscous flow forming temperature zone from undergoing thermal shear chain breakage due to prolonged residence time, the control unit simultaneously triggers the resting residence and moves to the third stage. The independent temperature-controlled heater of the section sends a temperature correction command, controlling the internal molding temperature of the molding temperature zone to be instantaneously reduced by 15°C to 20°C from the flow window of 172°C to 182°C. This causes the temperature of the melt in this section to drop rapidly to the low-temperature metastable viscous flow window of 155°C to 160°C. By utilizing the kinetic passivation effect brought about by the reduction in temperature field, the thermal decomposition reaction rate of the polymer backbone is significantly suppressed. Thus, without affecting the directional crystallization of the fourth stage, the local thermal degradation conflict during the sequential evolution and switching process of the continuous extrusion process is eliminated. This ensures that the intrinsic mechanical toughness of the polymer material in the upstream stagnant state does not deteriorate. The continuous cooling of the material causes the polylactic acid to solidify and undergo a phase transformation, producing a volume percentage of 4.5% to 5%.A 5% micro-shrinkage in spatial crystallization induces normal stress on the inner wall of the jute fiber pores, locking the internally cured plastic plugs. This achieves integrated physical consolidation and molding of the fully biodegradable covering material without the addition of chemical adhesives. Furthermore, the finished material retains over 88% of its wet interface bond strength under continuous service conditions in high-humidity soils.

[0042] Example 2: When the system faces a verification condition where the interfacial bonding performance of heterogeneous materials is uncertain, a mixed felt containing jute fiber and polylactic acid fiber is continuously fed into the molding channel. A composite physical thermo-pressure field is established using multiple independent temperature-controlled heaters and a hydraulic hydrostatic drive mechanism installed in the molding channel. The extrusion resistance signal of the material passing through is collected by a reverse extrusion pressure sensor configured on the inner wall of the outlet end of the molding channel. The reverse extrusion pressure sensor has a resistance of not less than 0.With a measurement accuracy of 0.01 MPa and a signal sampling frequency of no less than 100 Hz, the extrusion resistance signal is filtered by a signal conditioning unit to extract characteristic differences and convert them into real-time transient pressure values. These values ​​serve as a process characterization indicator for monitoring the evolution trend of interface flow wetting resistance. Specifically, the signal conditioning unit integrates a two-stage digital filtering architecture and a difference extraction operator to remove mechanical vibration interference from the equipment itself and extract characteristic differences from the original extrusion resistance signal. In the actual signal processing flow, the original voltage signal output by the back-extrusion pressure sensor is filtered by a fourth-order Butterworth low-pass filter with a cutoff frequency set to 30 Hz to remove high-frequency Gaussian noise introduced by the high-frequency impact of the pulse mechanism on the outer wall of the forming channel and the hydraulic pump source. The filtered smooth signal is then synchronized... The data is fed into a moving average operator with a time-domain width of 50 sampling points to calculate the background moving average value representing the current extrusion base resistance of the flow channel. The microprocessor of the control unit subtracts the background moving average value from the real-time resistance signal value after Butterworth low-pass filtering to calculate the transient fluctuation characteristic difference after removing the static base load. This difference is then multiplied by the sensor's sensitivity calibration coefficient to accurately convert it into a real-time transient pressure value representing the variation of mass transfer resistance at the surface of the heterogeneous interface. When determining the internal molding temperature of the three-stage molding temperature zone of the molding channel, its parameter setting is subject to the interaction between the shear thinning behavior of polylactic acid melt and the thermal shear chain breakage decomposition rate. When the internal molding temperature increases, the melting rate of polylactic acid fibers increases, leading to the surface of the liquefied melt... While a monotonic decrease in viscosity facilitates penetration, when the processing temperature exceeds the thermal degradation boundary of the polylactic acid (PLA) molecular chain, the thermoplastic polymer backbone undergoes main-chain thermal decomposition, leading to matrix embrittlement. This results in a precipitous drop in the flexural toughness of the finished sheet. To establish a stable window between fluid wetting mass transfer efficiency and high molecular weight retention in the matrix, an offline high-pressure capillary rheometer was used to calibrate the flow characteristic curves of PLA melt apparent viscosity as a function of shear rate and temperature. Using the apparent viscosity of the melt maintained between 140 Pa·s and 220 Pa·s in the flow characteristic curves as the criterion, inverse mapping determined the internal molding temperature control range of the three-stage molding temperature zone to be 172℃ to 182℃. This was to verify the rationality and boundary of the rheological characteristic window within the phase change melting region. To ensure certainty, physical consolidation tests were conducted on multiple combinations of different process parameter configurations within a molding channel test platform of the same specifications. The first invention sample group adopted a scalar combination of the lower limit of the process parameter range, with the jute fiber mass percentage determined to be 80% and the basis weight 600 g / m², and the polylactic acid fiber mass percentage determined to be 20%. The hot pressing temperature of the first-stage temperature zone of the molding channel was controlled at 85℃ and the material residence time was 35 s; the hot pressing temperature of the second-stage temperature zone was controlled at 135℃ and the material residence time was 25 s; and the internal molding temperature of the third-stage core molding temperature zone was set at 172℃ and the material residence time was 15 s. The static stress of the substrate was controlled at 0.15 MPa, and the maximum pulse peak stress of the superimposed periodic nonlinear shear pulse wave was 1.The pressure was 2 MPa and the pulse frequency was 3 Hz. The stress loading stage of the single pulse waveform lasted 15 ms and the stress release stage lasted 180 ms. After going through four cooling temperature zones, the first cooling stage was carried out at a linear cooling rate of 1.5 ℃ / s. When the internal core temperature dropped to 105 ℃, the static pressure drive mechanism was controlled to maintain a normal pressure state and allow the material to rest for 45 s. Then, it entered the secondary cooling temperature zone and cooled to below 40 ℃ at a rate of 3.0 ℃ / s before being discharged from the test channel. The measured local penetration depth of the plastic plug into the jute fiber cell cavity was 22.6 μm, and the volume crystallization shrinkage rate was 4.54%. The wet interface bond strength retention rate of the board after undergoing service cycles in high-humidity soil remained stable at 8%. 8.2%; The second invention sample group adopted a median scalar combination of process parameters. The jute fiber mass percentage was determined to be 70% with a basis weight of 900 g / m², and the polylactic acid fiber mass percentage was determined to be 30%. The corresponding hot-pressing temperature settings for the first-stage, second-stage, and third-stage core molding temperature zones were 90℃, 140℃, and 177℃, respectively. The material residence times were set to 40s, 30s, and 20s, respectively. The static stress of the substrate was controlled at 0.20 MPa, the maximum pulse peak stress was 1.4 MPa, and the pulse frequency was 4 Hz. The stress loading stage duration and stress release stage duration were set to 20ms and 200ms, respectively. During the cooling stage, the temperature was controlled at 2.0... The temperature was linearly reduced at a rate of ℃ / s and an isothermal residence step was triggered at 110℃ for 52 seconds. It then entered a secondary cooling zone and was cooled to below 40℃ at a rate of 3.8℃ / s before being discharged from the test channel. The measured interfacial penetration depth reached 30.7μm, the volume crystallization shrinkage rate was 4.93%, and the wet interfacial bonding strength retention rate reached 91.4%. The third invention sample group used the upper limit scalar combination of process parameters. The jute fiber mass percentage was determined to be 60% with a basis weight of 1200g / m², and the polylactic acid fiber mass percentage was determined to be 40%. The corresponding hot-pressing temperature settings for the first to third stages were 95℃, 145℃, and 182℃, respectively, and the material residence time was set accordingly. The stress loading and release phases were set to 45 s, 35 s, and 25 s, with a controlled static stress of 0.25 MPa, a maximum pulse peak stress of 1.6 MPa, and a pulse frequency of 5 Hz. The stress loading and release phases were set to 25 ms and 220 ms respectively. During the cooling phase, the material was linearly cooled at a rate of 2.5 °C / s and held isothermally at 115 °C for 60 s. It then entered a secondary cooling zone and cooled to below 40 °C at a rate of 4.5 °C / s before being discharged from the test channel. The measured local penetration depth at the phase interface reached 37.4 μm, the volumetric crystallization shrinkage rate was 5.42%, and the wet interface bond strength retention rate of the plate consolidation interface under alternating soil humidity conditions reached 88.6%.

[0043] To empirically demonstrate the nonlinear physical response characteristics defined by the process parameter boundaries, multiple out-of-range control groups were introduced within the same test channel as a multidimensional boundary comparison. The first control group lowered the internal molding temperature setting of the three-stage core molding temperature zone to 168℃, while keeping all other process conditions identical to the second invention sample group. Because the temperature was below the critical field strength for the rheological slip of the polylactic acid long-chain segments, the static apparent viscosity of the polymer melt in the fully molten state was high, resulting in significant isotropic flow mass transfer resistance. The measured interfacial penetration depth drastically decreased to only 5.2 μm. The finished board rapidly peeled off when subjected to alternating stress caused by high-humidity swelling of the soil, and its wet interfacial bonding strength retention rate significantly decreased to 32.3%. The second control group increased the internal molding temperature setting of the three-stage core molding temperature zone to 188℃, while keeping all other process parameters identical to the second invention sample group. Due to the irreversible thermal shear chain scission reaction of the main chain of the thermosensitive biodegradable polymer induced by the strong processing thermal field, its weight-average molecular weight retention rate decreased from 9... The percentage of brittle fracture material dropped sharply from over 2% to 63.8%, leading to embrittlement of the internal phase structure of the cooled matrix material. Under external impact, large-area brittle crack propagation occurred at the phase interface, causing the wet interface bonding strength retention rate to degrade to 26.5%. The third control group, subjected to a constant overall static high pressure of 2.0 MPa within the molding temperature range while eliminating periodic nonlinear shear pulse waves, lacked non-equilibrium disentanglement orientation induction behavior within a short time window shorter than the intrinsic rheological relaxation time. Furthermore, the continuously applied static stress exceeded the plastic yielding capacity of the jute fiber cell cavity skeleton. The irreversible compaction and collapse of the porous framework structure caused by the limit of yielding leads to the physical closure of pore channels and a sharp increase in capillary back pressure at the two-phase contact surface. The measured penetration depth of the plastic melt is less than 3.0 μm, and the surface of the finished product shows a simple shallow mechanical stacking. The wet interface bonding strength retention rate is only 18.3%. The defect performance trends of the above three groups of out-of-range control groups confirm that the temperature range and pulse pressure field parameters determined by this process belong to the optimal working window that can synergistically maintain the porous morphology and achieve low-resistance penetration.

[0044] To further elucidate the causal synergistic mechanism between different control nodes of the present invention, a reverse evidence tracing of the physical consolidation effect was constructed using a partially missing control group. In the fourth control group, after the mixed felt was continuously fed into the molding channel, the contact-type heat conduction preheating and dehydration process in the first-stage temperature zone was directly canceled, allowing it to directly enter the high-temperature molding zone in an initial material state containing ambient humidity. Due to the violent high-temperature hydrolysis and thermal decomposition behavior induced by the residual free water in the system under the liquefaction and melting thermal field above 172°C, the weight-average molecular weight retention rate of the polymer chain segments deteriorated, and the bending strength of the finished plate after consolidation and molding decreased by 55.6% compared with the second invention sample group. In the fifth control group, the material was controlled from 170°C in the first-stage cooling program of the fourth stage. Continuing with linear cooling to room temperature and directly crossing the specific temperature range of 115°C to 105°C, the isothermal and atmospheric pressure resting stage within this efficient crystallization temperature window was eliminated. Due to the lack of sufficient residence time to drive high-density anisotropic crystallization reconstruction of the polymer chains, a hydrophobic layer restricting the spatial freedom of water molecule penetration failed to grow directionally around the jute fiber cell wall. This resulted in an overall degradation of the phase interface's resistance to reverse water degradation under alternating soil humidity conditions. The wet interface bonding strength retention rate plummeted from 91.4% to 41.5%, thus confirming the active counteracting degradation synergistic causal chain between the one-stage dehydration mechanism and the four-stage directional crystallization mechanism. Here, the phase interface's resistance to reverse water degradation specifically refers to the non-chemically bonded consolidation of the two phases. The mechanical structural stability of the interface under alternating shear stress from external moisture penetration and swelling of heterogeneous materials is quantitatively characterized at the process level by the aforementioned wet-state interface bonding strength retention rate. The specific test procedure is as follows: the consolidated plate sample is completely immersed in deionized water at a set temperature of 23°C for 48 hours, then removed and air-dried in an environment with a relative humidity of 50% for 24 hours to constitute a complete wet-heat alternating service cycle. After 10 consecutive cycles, the interfacial shear strength is measured using a universal testing machine, and the percentage of this strength value relative to the original dry-state interfacial shear strength before the cycle is calculated. This eliminates the ambiguity in the overall qualitative description of the surface interface, directly converting the abstract anti-degradation performance into... To achieve a deterministic and measurable overall mechanical retention rate index, and to assess the adaptability of the molding method to resist external heterogeneous disturbances during continuous mass production, a problem intensity gradient control system was established. Under fluctuating conditions where the basis weight of jute fiber increased from 600 g / m² to 1200 g / m², and the initial material temperature at the first stage was determined by a front-end temperature sensor, the increase in fiber bulk density caused the real-time transient pressure value collected by the reverse extrusion pressure sensor to exceed the preset safety threshold pressure. The control unit sent adaptive adjustment commands to the pressure application components and heater to maintain a constant temperature gradient between the first and second stages, and adjusted the alternating normal pulse stress frequency of the third stage from 3 Hz to 5 Hz.At 5Hz, and simultaneously reduced by 15% of the static stress of the substrate through a hydrostatic driving mechanism, experimental measurement data show that, under various weight gradients, the shear thinning behavior induced at the orifice section by increasing the characteristic frequency can offset the influence of local high mass transfer resistance. The local deviation of the surface anchoring depth of the two-phase interface is stably controlled within the range of 5.2% to 7.7% across the entire width, and the final wet interface bonding strength retention rate of the plate is maintained above 88.1%. Thus, through the above-mentioned complete data gradient and reverse comparison system, the final empirical demonstration of the high creative value and practical industrial applicability of the molding method of this invention has been completed. The control unit, based on the original displacement data collected by the displacement sensor, The displacement signal extracts the pressure limit gap change value. When the forming channel is empty and unloaded, the driving pulse mechanism applies sweeping mechanical impacts to the upper and lower molds within the 3Hz to 5.5Hz frequency band. The reference vibration amplitude generated by the isotropic elastic deformation of the mold steel is measured. A digital low-pass filter algorithm with a cutoff frequency of 1.0Hz is introduced into the control operation to process the original displacement signal, filtering out the periodic peak alternating displacement corresponding to the alternating normal pulse stress frequency, and extracting the static gap slip component caused by material accumulation. When the static gap slip component exceeds 1.5mm within a continuous 3s time period, the control signal is converted into a stop command to cut off the heating power supply and shut down the material conveying motor.

[0045] Example 3: When the system faces the technical problem of sudden changes in mass transfer and wetting resistance caused by local weight fluctuations in jute fibers in fully biodegradable ecological covering materials, leading to lag in the transmission of thermal and compressive stress, a reverse extrusion pressure sensor configured on the inner wall of the continuous forming channel outlet collects real-time pressure fluctuation signals as the material passes through. The control unit calls the controller with an integrated pressure discrete alignment program to calculate the real-time transient pressure value based on the melt pressure change captured by the reverse extrusion pressure sensor at the forming channel outlet with a length-to-diameter ratio of 40:1. The real-time transient pressure value is then mathematically compared with the safety threshold pressure to ensure safety. The threshold pressure is determined through an offline normal operating condition calibration program. The safe threshold pressure is composed of the reference pressure of the constant feedback pressure of the corresponding homogeneous jute fiber under normal flow resistance and the flow deviation of the allowable background noise signal amplitude of the corresponding reverse extrusion pressure sensor. When the local bulk density of the jute fiber increases, causing the real-time transient pressure value to exceed the safe threshold pressure, the control unit activates the parameter calibration loop, converting the collected physical deviation into a characteristic frequency up-adjustment step value. Specifically, the characteristic frequency up-adjustment step value of the alternating normal pulse stress sequence in the three-stage temperature zone of the forming channel is calculated according to the following formula: ,in, To increase the step value of the characteristic frequency, This is the frequency adjustment gain coefficient, with a value of 25Hz / MPa; The real-time transient pressure value is collected by the reverse extrusion pressure sensor. The preset safety threshold pressure.

[0046] In an industrial application where the forming channel operates continuously, the system's preset reference pressure is 0.20 MPa, and the background noise flow deviation, calibrated offline, is 0.05 MPa. The calculated safe threshold pressure... The pressure is kept constant at 0.25 MPa; the real-time transient pressure value measured by the back extrusion pressure sensor when the local high-density jute fiber felt passes through the outlet end of the forming channel. When the pressure is changed to 0.35 MPa, the pressure deviation value is... The calculated pressure is 0.10 MPa; substituting the pressure deviation value into the above formula, the pressure deviation value of 0.10 MPa and the frequency adjustment gain coefficient are calculated. The product is used to calculate the step value of the characteristic frequency upregulation. The frequency is 2.5Hz. Correspondingly, the control unit sends a frequency conversion control command to the pulse mechanism based on this calculation result, driving the characteristic frequency of the alternating normal pulse stress sequence to be progressively increased from the basic 3Hz to 5.5Hz. Simultaneously, the control unit synchronously adjusts the hydraulic hydrostatic drive mechanism to reduce the static stress of the substrate by 15% from the initial 0.20MPa to 0.17MPa. This utilizes the shear thinning effect induced at the orifice section by the alternating normal pulse stress sequence to locally compensate for the flow mass transfer resistance generated by the jute fiber layer, keeping the local deviation of the physical interlocking penetration depth of the two-phase solidified phase interface below 8% across the entire width. The control unit adjusts the alternating normal pulse stress frequency and static stress based on the real-time transient pressure value collected by the reverse extrusion pressure sensor, according to the relationship... Calculate the fluid transport delay, where, For fluid transport time delay scalar, The distance is the axial distance from the midpoint of the pulse mechanism to the mounting point of the reverse extrusion pressure sensor. The linear velocity of the mixed felt body within the forming channel is used, and the real-time pressure deviation signal output by the reverse extrusion pressure sensor is imported into the Smith predictive compensation control program to shift the time reference, thus retrospectively adjusting the current pressure feedback in the time domain. The frequency up-adjustment and static stress down-adjustment actions are dynamically aligned to the actual axial position of the mixed felt body that is currently causing pressure fluctuations. This eliminates the fluid flow transmission lag caused by the aspect ratio of the molding channel and maintains the stability of the pressure adaptive feedback control loop. In the specific physical control process, because the molten polymer and fiber interwoven network in the molding channel form a continuous viscous fluid column with high viscosity, the sudden change in flow resistance caused by local high-density fibers will not only directly increase the back extrusion pressure at the outlet end, but also, because the mixed felt body has the continuity and spatial correlation of overall physical properties along the axial feeding direction, its basis weight fluctuation usually exhibits a continuous gradual change characteristic on the scale of several meters. The Smith predictive compensation control program introduces fluid delivery delay. The essence of time-domain backtracking and translation is to eliminate the phase lag in feedback control actions caused by the time required for material to move from the third stage to the outlet. This ensures that the current adaptive adjustment of the upstream high-frequency pulse mechanism and the hydrostatic drive mechanism can be accurately applied to the continuous felt section that immediately follows into the third stage and has the same weight fluctuation trend as the material at the current outlet. This achieves dynamic phase balance in the continuous extrusion process within the high aspect ratio channel, avoiding overshoot and divergence in the control system caused by feedback blind spots. It is also effective in extreme cases where the linear velocity drops sharply to 0 due to the execution of a stop conveying action during process changes. The control unit integrates a speed dead-zone protection latch circuit. When the online speed sensor detects that the linear velocity is below the preset static threshold of 0.01 mm / s, this protection latch circuit immediately activates and forcibly cuts off the real-time denominator update of the Smith predictive compensation control program. Simultaneously, it automatically locks the fluid delivery delay to the valid historical value of the last transient cycle before delivery stopped. This causes the gain and time parameters of the entire feedback control loop to enter a temporary frozen mode during the stoppage phase, until material delivery resumes and the linear velocity crosses the static threshold again. Only then does the dynamic flow of the reference time axis restart, thereby eliminating the dead zone. Besides preventing computational overflow and control system crashes caused by a zero denominator, ensuring the full-cycle robustness of the continuous extrusion process during dynamic modal transitions, after the aforementioned mass transfer and impregnation process, the mixed felt is continuously introduced into a four-stage cooling zone. The forming channel controls the cooling temperature to decrease at a rate of 1.5℃ / s to 2.5℃ / s. When the internal core temperature drops to the polylactic acid crystallization temperature range of 115℃ to 105℃, the heating power of the forming channel is reduced and the conveying of the mixed felt is stopped. The mixed felt is then kept at atmospheric pressure for 45s to 60s, allowing the polylactic acid molecular chain segments impregnated within the jute fiber pores to generate... High-density anisotropic nucleation and the formation of a crystalline network structure around the fiber cell wall result in a polylactic acid crystallinity of 42% to 48%, restricting the freedom of water molecule penetration. Controlled continuous cooling and solidification phase transition of the material leads to a crystallization volume shrinkage of 4.5% to 5.5% by volume. This crystallization volume shrinkage generates normal stress on the inner wall of the jute fiber pores, securing the solidified polylactic acid plastic plugs. This process achieves integrated molding of a fully biodegradable covering material without the addition of chemical adhesives. The solidified board retains a wet interface bond strength of at least 88% under alternating high humidity soil conditions.

[0047] Example 4: When the system faces the situation of changing production batches of jute fiber and polylactic acid fiber in the molding channel, the hydraulic hydrostatic drive mechanism and the high-frequency pulse mechanism are calibrated before mass production. The control unit adjusts the static pressure stress to increase from 0.10MPa to 0.30MPa in 0.05MPa increments. The critical static pressure for jute fiber cell collapse is collected using a reverse extrusion pressure sensor. At the same time, the high-frequency pulse mechanism is adjusted to apply a shear pulse wave with a maximum pulse peak stress of 1.4MPa and a frequency increasing from 1Hz to 5Hz under a base stress of 0.20MPa. The transient pressure drop of the polylactic acid melt at different frequencies is collected by the reverse extrusion pressure sensor. The frequency adjustment gain coefficient in the aforementioned formula is calculated based on the ratio of the frequency variation to the transient pressure drop. The control unit will adjust the gain coefficient based on the determined frequency. The system is integrated into the control loop. When flow resistance changes due to increased jute fiber bulk density during subsequent mass production, the system adjusts the gain coefficient based on the frequency. The characteristic frequency of the alternating normal pulse stress sequence is calculated and increased. The shear pulse wave induces orientation and viscosity reduction at the micropore section within a loading duration shorter than the rheological relaxation time. Under material batch interference conditions, the local deviation of the physical interlocking anchoring depth of the solidified phase interface in the molding channel is limited to less than 8%. The network permeation structure inside the finished product forms a uniform physical distribution under the condition of no chemical adhesive. Moreover, the normal stress generated by the shrinkage of the crystal volume maintains the wet interface bonding strength retention rate of the finished product at more than 88% under the alternating high humidity service conditions of the soil.

[0048] Example 5: When the production batch of fully biodegradable ecological covering material with different nominal thicknesses is changed in the forming channel, the mixed felt body cools linearly with the thermal field temperature in the four-stage cooling temperature zone of the forming channel. Due to the heat conduction and heat transfer delay in the thickness direction of the sheet, a temperature difference occurs between the core layer and the surface layer of the part, and the distribution of phase transformation shrinkage stress is uneven. This causes local gradient variation in the crystal density at the interface of the two-phase material interweaving and consolidation phases, and uneven release of thermal stress, which causes the sheet to warp or crack during forming. Before the material enters the four-stage cooling temperature zone, the control unit retrieves the nominal thickness value of the sheet collected by the online thickness sensor, and determines the isothermal and atmospheric pressure resting residence time in the cooling channel based on the nominal thickness value of the sheet. The formula for calculating the isothermal and atmospheric pressure resting residence time is as follows: ,in, The isothermal and atmospheric pressure resting residence time, This is the heat transfer delay correction factor, with a value of 5.0 s / mm; The nominal thickness of the fully biodegradable covering material sheet. The constant value of the spontaneous relaxation base for polylactic acid macromolecular chain segment crystallization is 25.0 s. The linear calculation method of the isothermal and atmospheric pressure resting residence time is an equivalent expression obtained by engineering linearization fitting of the Fourier law of unsteady heat conduction within a specific industrial mass production range of 2.0 mm to 8.0 mm nominal thickness of the sheet material as defined in this invention. Within this specific thickness range, the nonlinear quadratic heat transfer delay term caused by the actual transverse thermal resistance between the core layer and the surface layer of the sheet material is actively offset and canceled by the adaptive nonlinear enhancement adjustment of the contact cooling rate by the cooling jacket on the outer wall of the molding channel. Thus, in terms of macroscopic control timing, the overall temperature regulation delay is forcibly constrained to a linear relationship proportional to the nominal thickness, ensuring the efficient convergence and stable operation of the control algorithm in continuous production processes.

[0049] According to the above calculation formula, when the nominal thickness of the current batch of fully biodegradable covering material collected by the online thickness sensor is... When the thickness is 5.0 mm, the heat transfer delay correction factor is used. With the nominal thickness of the plate The product of these factors determines the heat transfer compensation time delay of the fluid core layer to be 25.0 s, superimposed with a constant base value for the spontaneous relaxation of the main chain structure crystallization. After 25.0 s, the isothermal and atmospheric pressure resting residence time was calculated. For 50.0s, when the center temperature of the material drops to the polylactic acid crystallization region within the range of 112℃, the hydrostatic drive mechanism stops conveying the mixed felt according to the control command of the control unit, and keeps the mixed felt isothermally and atmospherically stationary for 50.0s within the molding temperature range of 115℃ to 105℃. During the fourth stage cooling temperature zone, when the molding channel controls the cooling of the mixed felt, based on the low thermal conductivity of polylactic acid fibers and jute fibers, the transverse thermal resistance in the thickness direction of the sheet is determined by the control unit according to the formula... Calculate the isothermal and atmospheric pressure resting residence time, where, The isothermal and atmospheric pressure resting residence time, This is the heat transfer delay correction factor, with a value of 5.0 s / mm. The nominal thickness of the fully biodegradable covering material sheet is... The constant value of the spontaneous relaxation base for polylactic acid macromolecular chain segment crystallization is 25.0 s. The cooling jacket arranged on the outer wall of the molding channel is controlled to adjust the contact cooling rate of the outer wall, offsetting the temperature gradient deviation between the core layer and the surface layer of the part caused by the transverse thermal resistance. The contact cooling rate of the outer wall is set to be 1.5℃ / s to 2.5℃ / s greater than the target linear cooling rate inside the center of the mixed felt. The cooling load of the outer wall is used to compensate for the time delay of heat transfer to the core layer of the part, and the entire cross section of the mixed felt is controlled to enter the isothermal resting phase simultaneously, suppressing the warping defects of the sheet caused by uneven release of thermal stress. Within the set time, the macromolecular chain segments reduce the non-equilibrium strain residue caused by the previous alternating method to the pulse stress sequence, and flow and penetrate into the fiber voids. The internal polylactic acid melt directionally precipitates and coats the outer periphery of jute fiber cell walls with embedded crystals. The measured crystallinity across the entire cross-section is 45.2%, and the volumetric shrinkage rate is 4.88%. Phase transformation shrinkage generates normal stress on the inner wall of the jute fiber pores to secure the polymer plugs. The local deviation of the bonding depth at the two-phase consolidation interface is maintained at 5.3%, eliminating deformation caused by stress concentration. The final product maintains a wet interface bonding strength retention rate of 91.2% under alternating high-humidity soil conditions. The integrated consolidation molding of the fully biodegradable covering material is achieved without the introduction of external chemical adhesives. To ensure the objectivity and certainty of the above control parameters and calculation formulas in engineering applications, the frequency adjustment gain coefficient... Heat transfer delay correction factor and the constant value of the spontaneous relaxation base of crystallization The specific values ​​are all derived and calibrated based on the intrinsic physicochemical properties of the materials and the physical laws of heat conduction of this invention; specifically, the frequency adjustment gain coefficient By measuring the capillary rheological nonlinear curves of polylactic acid melt in a viscous flow state from 172℃ to 182℃, the derivative of the flow viscosity with respect to the shear rate was calculated. This allowed for the inverse mapping of the characteristic frequency variation corresponding to the shear thinning depth required to compensate for a transient back pressure increase of 0.1 MPa at the outlet due to increased flow resistance, which was found to be exactly 2.5 Hz. The heat transfer delay correction coefficient in the formula... This is calculated based on Fourier's law of heat conduction, combined with the measured values ​​of the anisotropic low thermal conductivity of jute fiber and polylactic acid mixed felt in a dense state, ranging from 0.045 W / mK to 0.065 W / mK. It represents a 1 mm increase in the nominal thickness of the representative board, resulting in a 5.0 s delay in transverse thermal resistance heat transfer required to compensate for the core layer's temperature drop to the crystallization temperature zone. This corresponds to the minimum induction period required for the spontaneous relaxation of the intrinsic homogeneous / heterogeneous nucleation spatial conformation of polylactic acid macromolecular chain segments within the efficient crystallization window of 105℃ to 115℃. Below this time limit, the directional growth of high-density anisotropic crystal nuclei cannot be triggered. Through the physical meaning and calibration process determined above, the arbitrariness of parameter selection is eliminated, ensuring the theoretical self-consistency of the fully closed-loop control system.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A forming process for the physical consolidation of fibrous materials, characterized in that, Includes the following steps: Step S1: The mixed felt containing thermoplastic polymer fibers and porous plant fibers is continuously fed into the molding channel. An increasing temperature gradient is established in the first and second stages of the molding channel. Heating causes the thermoplastic polymer fibers to melt and impregnate the porous plant fibers. Step S2: In the third stage of the forming channel, while applying static stress to the molten mixed felt, an alternating normal pulse stress is applied by a pulse mechanism located on the outer wall of the forming channel, and the real-time transient pressure value of the mixed felt passing through is collected by a pressure sensor located on the inner wall of the outlet end of the forming channel. Step S3: When the real-time transient pressure value exceeds the safety threshold pressure determined by the sum of the reference pressure and the fluctuation deviation, keep the temperature gradient between the first stage and the second stage constant, increase the frequency of the alternating normal pulse stress from 3Hz to 5.5Hz, and simultaneously control the static pressure drive mechanism to reduce the static stress by 15% and increase the local flow velocity at the immersion point. Step S4: The mixed felt body with reduced static stress is continuously introduced into the fourth stage cooling temperature zone. The molding channel is controlled to implement a linear cooling rate of 1.5℃ / s to 2.5℃ / s for primary cooling, so that the internal center temperature of the mixed felt body is reduced to the range of 20℃ to 60℃.

2. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, Step S4 includes: Step S41, maintaining constant temperature and pressure for 45s to 60s when the temperature drops to 115℃ to 105℃; Step S42, keeping the local deviation of the surface anchoring depth of the two-phase interface within the range of 0% to 8%.

3. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, The thermoplastic polymer fiber is polylactic acid fiber, and the porous plant fiber is jute fiber with a basis weight of 600 g / m² to 1200 g / m²; the temperature in the first stage of step S1 is 175°C to 185°C, and the temperature in the second stage is 190°C to 200°C.

4. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, Step S2 includes: Step S21, using the pressure sensor on the inner wall to collect the extrusion resistance signal and convert it into an electrical signal; Step S22, using the signal conditioning unit to filter and extract the characteristic difference of the electrical signal and convert it into a real-time transient pressure value.

5. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, Step S3 includes: Step S31, controlling the initial frequency of the alternating normal pulse stress to 3Hz; Step S32, adjusting the frequency to 5.5Hz when the pressure exceeds the limit, and simultaneously controlling the static pressure drive mechanism to reduce the static stress by 15%.

6. A forming process for the physical consolidation of fibrous materials according to claim 2, characterized in that, Step S41 includes step S411, which involves reducing the heating power of the molding channel and stopping the heating of the first and second stages, while stopping the conveying of the mixed felt and keeping the mixed felt resting at constant temperature and pressure.

7. A forming process for the physical consolidation of fibrous materials according to claim 2, characterized in that, Step S4 includes step S43, where after the local deviation stabilizes, the material enters the secondary cooling zone and is cooled to below 40°C at a rate of 3.0°C / s to 4.5°C / s, and the formed sheet is discharged from the forming channel.

8. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, It also includes the following steps: Step S5: Collect the initial material temperature when the mixed felt is fed into the first stage using a temperature sensor configured at the front end; Step S6: When the initial material temperature is below 50°C, increase the heating power of the first stage.

9. A forming process for the physical consolidation of fibrous materials according to claim 1, characterized in that, It also includes the following steps: Step S7: The pressure limit gap change value between the upper mold and the lower mold is collected in real time by the displacement sensor; Step S8: When the pressure limit gap change value exceeds 1.5mm for 3 seconds, heating is stopped and the conveying of the mixed felt is stopped.

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