Continuous forming method suitable for prepreg composite structural member

Abstract

The invention relates to the technical field of composite material continuous forming, in particular to a continuous forming method suitable for a prepreg composite material structural member, and the method comprises the following steps: according to the layering design requirement, a prepreg coiled material is unfolded and layered; heating and mould pressing are carried out on the laid prepreg, so that the prepreg is preformed; the pre-formed prepreg sequentially passes through at least two heating and pressurizing areas with the temperature and the pressure capable of being independently regulated and controlled to be cured; the cured prepreg is subjected to post-curing in a mold at the temperature of 150 DEG C to 170 DEG C and the pressure of 0 MPa to 3 MPa; and pulling the post-cured product to move forwards in a stepping motion mode to obtain the prepreg composite material structural member. The continuous production of the prepreg from laying, preforming and curing to finished products is realized, the size limitation of the traditional autoclave is broken through, and the integrated forming of the super-long structural member becomes possible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of continuous forming of composite materials, and particularly to a continuous forming method suitable for a pre-impregnated composite material structural member. BACKGROUND

[0002] With the increasing demand for high-performance lightweight structures in the fields of aerospace, low-altitude economy, military industry, etc., the application scale of carbon fiber composite materials continues to expand due to their excellent specific strength, specific stiffness and designability, and the market demand is showing a rapid growth trend.

[0003] Currently, the mainstream process for manufacturing composite material structural members such as aviation stiffeners, longerons, beams, etc. in the above-mentioned fields mainly relies on hot die pressing forming and autoclave forming technology of pre-impregnated materials. Although these traditional processes can better ensure the forming stability and final mechanical properties of the parts, they still face the following problems in actual mass production: first, the energy consumption of the forming process is high, and the auxiliary material consumption is large, resulting in high cost of single piece manufacturing; second, the process flow includes multiple steps of mold loading, heating, curing, cooling and demolding, and the overall forming cycle is long, limiting the production efficiency, which is difficult to match the rhythm and capacity demand of the market rapid development; third, due to the physical size limitation of the autoclave equipment and the matching mold, it is difficult to realize the integrated and continuous forming of super-long size structural members, which often needs to be manufactured in segments and then connected, which not only increases the process complexity and weight, but also may introduce additional connection weak areas.

[0004] The information disclosed in this BACKGROUND section is only intended to enhance the understanding of the general background of the present disclosure and is not intended to be recognized or implied in any form that this information constitutes prior art well known to those skilled in the art. SUMMARY

[0005] The present application provides a continuous forming method suitable for a pre-impregnated composite material structural member, which effectively solves the problems in the background art.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is: A continuous forming method suitable for a pre-impregnated composite material structural member, the method comprising: S1, according to the requirements of the layer design, the pre-impregnated material roll is unfolded and layered; this step unfolds the pre-impregnated material roll and stacks it according to the set layering sequence, providing a continuous material strip with a predetermined layer structure for the subsequent steps, which is the basis for the forming of the composite material structural member.

[0007] S2, heating and molding the layered pre-impregnated material to make it preform; this step heats the layered material strip and simultaneously applies a molding action, so that the shape of the material changes from the initial flat layer to a continuous blank similar to the cross section of the final component.

[0008] S3 sequentially guides the preformed prepreg through at least two heating and pressurizing zones with independently controllable temperature and pressure, for curing; this step guides the preformed prepreg through at least two heating and pressurizing zones with independently controllable temperature and pressure, and the heating and pressurizing zones are arranged to allow the material to be subjected to sequential temperature and pressure conditions to drive and control the resin matrix to complete the main curing reaction.

[0009] S4 post-cures the cured prepreg at a temperature of 150-170 DEG C and a pressure of 0-3 MPa in a mold; this step allows the pre-cured prepreg to continue to be subjected to an independent heat treatment stage with a specific temperature and pressure in the mold, further improving the crosslinking density of the prepreg, and allowing the material properties to reach the design value.

[0010] S5 moves the post-cured product forward in a step-by-step manner, to obtain a prepreg composite structural member; this step periodically removes the product that has completed the heat treatment from the mold, cooperates with the pressure cycle of the mold, removes the completed part at the same time, and provides space for the new material to enter the mold, thereby realizing the continuity of the molding process.

[0011] The continuous molding method of the present application replaces multiple independent molding with continuous feeding of a roll material, cooperates with continuous heating and pressurizing in the mold, reduces auxiliary material consumption and equipment idle energy consumption, thereby reducing the cost of a single piece; during the entire process, the material moves forward, eliminating the independent temperature rising and demolding steps required in the traditional process, shortening the molding cycle and improving the production efficiency; step-by-step traction allows the product to be continuously removed from the mold after curing, while new material is continuously supplied, thereby realizing the integrated molding of a super-long size structural member and avoiding the weight increase and structural weak area caused by segmented manufacturing and connection.

[0012] Further, in S1, the laying material is corrected and positioned during laying to control the laying position and dimensional accuracy of the laying material.

[0013] Specifically, during laying, for the fabric prepreg, the fibers are in an interwoven or multi-axial stable state, which can be directly expanded and conveyed by a winding device to form a required layup; for unidirectional prepreg, in order to realize accurate laying of different direction fiber layers in the layup structure, an automatic tape layering machine is required, which cuts, lays and compacts the unidirectional prepreg tape at a predetermined angle according to a preset program, thereby constructing a unidirectional layup sequence that meets the complex design requirements.

[0014] Specifically, the layup operation is performed in a layup workstation with an integrated deviation correction and positioning control function; along the conveying path of the prepreg coil, online detection units based on vision sensing or edge sensing are set at key workstations to capture the side position or specific marker point position of the material during operation in real time. The detection unit transmits the collected position signals to the motion controller in real time, and a theoretical reference path of the material corresponding to the layup design drawing is preset in the motion controller. By comparing the real-time position signals with the theoretical reference path, the motion controller calculates the lateral position deviation value and longitudinal cumulative error of the material; Based on the deviation value, the motion controller generates corresponding correction instructions and drives the actuator to act; for the preliminary deviation correction in the coil unwinding stage, it can be achieved by adjusting the lateral fine-tuning motor of the unwinding rack; for the precise alignment during the layup process, it is completed by controlling the lateral translation device of the layup head or guide roller. The entire deviation correction process constitutes a closed-loop feedback control system, and its control objective is to continuously and stably control the laying position deviation of the material within the allowable tolerance range, for example, the lateral position deviation ≤ ±1.0 mm, and the longitudinal cumulative error ≤ ±1.5 mm.

[0015] Furthermore, the prepreg after preforming layup is completed by a cooperating female die and male die; the profiles of the female die and male die continuously change gradually from the feeding end to the discharging end. The profile at the feeding end is adapted to the input shape of the prepreg after layup, and the profile at the discharging end corresponds to the cross-sectional shape of the prepreg composite structure member.

[0016] More specifically, the continuous and gradually changing profile is formed by the cooperation of the above-mentioned female die and male die, providing a smooth and controlled deformation path for the transformation of the layup material from a two-dimensional planar state to a three-dimensional complex cross-sectional shape. Through the continuous and progressive guidance and restraint exerted on the material by the die profile, the multi-layer prepreg can undergo coordinated interlayer slip and overall deformation in the heat-softened state, effectively dispersing the local stress during the deformation process, thereby suppressing defects such as fiber wrinkling, local resin enrichment, or interlayer separation caused by uncoordinated deformation.

[0017] More specifically, referring to Figure 2 , taking the preparation of a hat-shaped stringer member with a "channel" cross-section as an example, the profiles of the female die and male die in the feeding end area are a gentle open structure adapted to the flat prepreg tape after layup. As the profile extends towards the discharging end, the cavity depth of the female die and the protrusion height of the male die increase synchronously, continuously, and uniformly. The profile contours on both sides gradually converge inward and finally form vertical sidewalls with a specific corner radius; at the discharging end, the cross-section of the cavity formed after the complete closure of the female die and male die completely matches the "channel" cross-sectional shape and dimensions of the hat-shaped stringer member; along the entire path from the feeding to the discharging end, there is no sudden change in the geometric shape or curvature of the die profile.

[0018] Further, from the moving direction of the prepreg, the heating and pressing zone is three, the first zone temperature is 100~140℃, the pressure is 0~1MPa; the second zone temperature is 140~180℃, the pressure is 0.5~2MPa; the third zone temperature is 160~190℃, the pressure is 0.5~3MPa.

[0019] More specifically, the first zone is a preheating and initial gelation zone. The temperature is controlled between 100~140℃, while applying a pressure of 0~1MPa. Under this temperature and pressure condition, the resin viscosity decreases, the flowability moderately increases, which is conducive to the further infiltration of fibers and the removal of residual gas between layers; at the same time, the resin begins to undergo preliminary crosslinking reaction, and enters the gelation starting point, providing the necessary initial structural strength for the subsequent stage.

[0020] The second zone is a pressure curing main reaction zone, the temperature is increased to 140~180℃, and the pressure is simultaneously increased to 0.5~2MPa. The higher temperature accelerates the crosslinking reaction rate of the resin, while the increased pressure effectively compacts the material, further expels the micro-bubbles, promotes the uniform distribution and sufficient infiltration of the resin between the fibers, and controls the fiber volume content of the product. This stage is the main stage of resin curing exothermic and viscosity growth.

[0021] The third zone is a curing completion and sizing zone, the temperature is maintained at 160~190℃, and the pressure range is 0.5~3MPa. In this section, the crosslinking reaction of the resin tends to be complete, and the molecular network is fully formed; the maintained temperature ensures the reaction to be thorough, while the higher optional pressure is used for final sizing to inhibit the deformation caused by resin shrinkage or internal stress, ensuring the stability of the cross-sectional size of the product.

[0022] The above process can obtain a composite product with low internal porosity, uniform fiber infiltration, sufficient curing degree and stable size. The specific temperature and pressure setting values of each zone are determined by experiments according to the differential scanning calorimetry data, rheological properties of the specific prepreg resin system used and the performance requirements of the target component.

[0023] Further, the pulling speed of the step motion in S5 is 0.1~0.4m / min.

[0024] Specifically, the step-by-step pulling operation in S5 is performed by a set of hydraulic clamping pulling devices, the pulling speed of which is controlled and maintained within the range of 0.1-0.4 m / min, and a slower pulling speed is adopted to minimize the mechanical disturbance to the internal structure of the material during the pulling process and improve the consistency of the product performance along the length direction. The clamping pulling device comprises one or more pairs of hydraulic clamping jaws that can act synchronously. After the product in the mold completes a solidification cycle, the control system first instructs the mold to perform a pressure release program to reduce the mold clamping pressure to a predetermined low level. Subsequently, the hydraulic clamping jaws are closed under the instruction of the control system, and the clamping surface thereof matches the outer shape of the product that has completed solidification and is located at the outlet end of the mold, thereby firmly clamping the product segment.

[0025] After the clamping operation is completed, the hydraulic driving unit is started to pull the clamped product to move along the production line direction at a controlled constant speed. The set value of the pulling speed is determined by the solidification reaction time of the resin system, the effective length of the mold heating zone, and the target production cycle. After the preset displacement of the pulling operation is performed, the hydraulic clamping jaws are released and reset. At the same time, the control mold is closed and restored to the set solidification pressure. The pulled-out product enters the subsequent process, and the remaining partially solidified material in the mold continues its solidification process under the new round of pressurization and heating.

[0026] Further, after the product is solidified and formed in the mold, the mold pressure is first reduced, and then the pulling operation is performed; after the pulling is completed, the mold is pressurized to the set pressure again.

[0027] Specifically, the mold pressure is reduced to eliminate the clamping effect of the mold clamping force on the product, thereby greatly reducing the frictional resistance in the pulling process and avoiding damage to the surface of the product and overloading of the pulling mechanism; after the pulling is completed, the mold is restored to the set pressure, so that the subsequent material can immediately obtain the necessary compaction and heat transfer conditions when entering the mold, maintaining the continuity and stability of the solidification reaction.

[0028] Further, in the step-by-step movement, the single pulling distance is controlled so that there is always a product in the solidification region of the mold that is in the solidification process from the gel region to the glass transition.

[0029] Specifically, by the above method of controlling the single pulling distance, the cold interface between the new and old material segments caused by the complete removal of the material in the solidification region is avoided, thereby eliminating the possible weak area of interlayer bonding strength and ensuring that the formed product has uniform and consistent mechanical properties along its length direction.

[0030] Further, the method further comprises a post-processing step, specifically: the pulled-out product is subjected to appearance and internal quality detection, and is cut and trimmed according to the set length.

[0031] Specifically, the appearance inspection is completed by an industrial vision system erected above and beside the product, which collects high-resolution images of the product surface and automatically compares them with pre-set standard image templates of qualified products to identify and record appearance defects such as surface scratches, wrinkles, pits, glue particle foreign matters and color unevenness. The internal non-destructive inspection is performed at the following station, and according to the material and structural characteristics of the product, a penetrating ultrasonic testing (UT) device or an industrial computed tomography (CT) device can be selected. The UT inspection obtains and analyzes the ultrasonic wave propagation signals in the material interior through the coupling of the probe and the product to determine whether there are internal defects such as delamination, porosity and poor resin infiltration; the CT inspection reconstructs the three-dimensional structure of the product interior by collecting X-ray projection images at different angles, which is suitable for detecting more complex internal abnormalities.

[0032] Further, the temperature in S2 is 80-140℃.

[0033] Specifically, the temperature application in the preforming process is realized by electric heating elements or hot oil circulation channels integrated in the preforming mold. Thermocouple temperature sensors are arranged at key positions of the mold profile to monitor the actual temperature of the measurement points in real time.

[0034] For the prepreg with high initial resin viscosity, a temperature close to the upper limit of the range is selected for preforming to effectively reduce the resin viscosity and increase its flowability; for the prepreg with low initial viscosity, a temperature close to the lower limit of the range can be selected.

[0035] Further, the prepreg in S1 is selected from carbon fiber prepreg or glass fiber prepreg, and is a fabric prepreg or a unidirectional prepreg, and the impregnation degree of the prepreg is ≥80%; the resin content of the fabric prepreg is 28-32%, and the resin content of the unidirectional prepreg is 26-30%.

[0036] Specifically, the impregnation degree of the prepreg is not less than 80%, so that the fibers are fully wrapped by the resin before entering the forming process, effectively reducing the probability of pore formation due to the presence of dry fibers in the subsequent heating and pressing process, and providing a good initial bonding interface between the layers. The resin content of the fabric prepreg is controlled to be 28-32%, and the resin content of the unidirectional prepreg is controlled to be 26-30%, which aims to reserve an optimized resin flow and distribution window for the curing stage, so that it can fully impregnate the fibers and fill the interlayer voids, and also form a proper fiber volume fraction after curing, so as to ensure that the product obtains the designed expected stiffness, strength and controls its weight.

[0037] The technical scheme of the present application can realize the following technical effects: the present application uses continuous feeding of a roll material to replace multiple independent mold loading, and cooperates with continuous heating and pressurization in the mold to reduce auxiliary material consumption and equipment idle energy consumption, thereby reducing the cost of a single piece; during the whole process, the material moves forward, and the independent temperature rising and demolding link required in each batch in the traditional process is omitted, the forming cycle is shortened, and the production efficiency is improved; the step-by-step traction enables the product to be continuously moved out of the mold after solidification, and new material is continuously supplemented, thereby realizing integrated forming of a structure piece with an ultra-long size, and avoiding the weight increase and structural weak area caused by segmented manufacturing and connection. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical schemes in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings described below are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0039] Figure 1 Flowchart of a continuous forming method suitable for a prepreg composite structure piece; Figure 2 Structure diagram of the left and right sides of the upper punch in Example 1. DETAILED DESCRIPTION

[0040] The technical schemes in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0042] The above description is only a summary of the technical schemes of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described.

[0043] Example 1: The present application provides a continuous forming method suitable for a prepreg composite structure piece, and the present embodiment selects T700 grade carbon fiber / epoxy resin unidirectional prepreg as a raw material, and the performance parameters are as follows: the fiber surface density is 190 g / m2 The resin content is 28%, and the wetting degree of the prepreg is ≥85%. The prepreg is supplied in roll form with a roll width of 300mm; the specific steps are as follows: S1 unfolds and lays up the prepreg roll according to the layup design requirements; Specifically, the layup process takes place in a layup workstation integrating an Automatic Tape Laying (ATL) machine and a vision correction system. Following the stringer layup design sequence of 0° / 90° / 0°, the ATL machine unfolds the unidirectional prepreg roll and conveys it with a constant tension of 10N. It then performs angled cutting (0° layers are laid directly, while 90° layers are laid after the tape is rotated) and compaction, forming a continuous strip-shaped laminate with a total thickness of approximately 2.1 mm. Simultaneously, the vision correction system monitors the tape edge position in real time and, by controlling the lateral fine-tuning of the guide rollers, continuously controls the layup position deviation within a tolerance range of ±0.8 mm laterally and ±1.2 mm cumulatively longitudinally.

[0044] S2 heats and molds the prepreg after layup to preform it; Specifically, the laid-up strip-shaped laminate then enters the preforming mold. (Refer to...) Figure 2 The mold consists of an upper punch and a lower die, with its surface gradually changing from the feed end to the discharge end. The feed end has a gently sloping 12mm high opening to accommodate a 2.1mm thick flat strip, while the discharge end is a fully closed "U"-shaped cavity with a cross-sectional dimension of 50mm (width) × 30mm (height). The mold is heated and stabilized at 120℃ by a built-in hot oil circulation system. Under the molding pressure of 0.8MPa, the laminated body is progressively guided and deformed into a continuous "U"-shaped cross-section preform within 20 seconds through an 800mm long mold.

[0045] S3 involves passing the pre-formed prepreg through at least two independently adjustable heating and pressurizing zones for curing; Specifically, the preform immediately enters the curing mold, which consists of three independent temperature and pressure control zones.

[0046] Zone 1: Mold temperature is 125℃, pressure is 0.5MPa; Zone 2: Mold temperature is 165℃, pressure rises to 1.2MPa; Zone 3: Mold temperature is 175℃, pressure is maintained at 2.0MPa.

[0047] S4 involves post-curing the cured prepreg in a mold at a temperature of 150~170℃ and a pressure of 0~3MPa. Specifically, the profile cured at S3 then enters an independent post-curing mold. The post-curing mold has a temperature of 160°C, a pressure of 1.5 MPa, and a length of 3 m. The profile continues to travel in the post-curing mold for about 40 minutes, so that the glass transition temperature of the resin is raised and stabilized above 180°C, reaching the final performance index.

[0048] S5 pulls the post-cured product forward in a step-by-step manner, i.e., the prepreg composite structure is obtained; Specifically, when the system detects that the product has completed the curing cycle, the post-curing mold pressure is reduced from 2.0 MPa to 0.2 MPa within 5 seconds, the hydraulic clamps at the outlet end of the post-curing mold are closed to hold the product, and then the product is pulled forward at a constant speed of 0.25 m / min for 300 mm. This pulling action takes 72 seconds; then the clamps are released and reset, and at the same time the post-curing mold is restored to a set pressure of 2.0 MPa within 10 seconds, and the total pulling cycle takes about 87 seconds; by controlling the single pulling distance to be much smaller than the total length of the curing area in the mold, it is ensured that there is always a section of material in the transition zone from gel to glass transition in the mold, avoiding the problem of curing interface.

[0049] S6 detects the appearance and internal quality of the pulled-out product, and cuts and edges according to the set length; Specifically, 100% online detection is performed by an industrial vision system to identify surface defects; multi-channel penetrating ultrasonic equipment is used for segment-by-segment scanning to detect internal porosity and delamination; according to the encoder signal, when the cumulative length of the profile reaches 2000 mm, the flying saw cutting system is started to cut it into fixed-length workpieces. Then, the workpieces are trimmed to within a tolerance of ±0.5 mm by a profiling edge milling device.

[0050] Example 2 The present application provides a continuous forming method suitable for prepreg composite structural parts, and in this embodiment, carbon fiber satin fabric prepreg is selected as the raw material, and the performance parameters are: resin content is 30%, and the impregnation degree of the prepreg is ≥82%. The prepreg is supplied in the form of a roll with a width of 400 mm; the specific steps are as follows: S1 according to the requirements of the layer design, the prepreg roll is unfolded and layered; Specifically, the layering is carried out in a layering workstation integrated with a winding device and a vision correction system. According to the design sequence 0° / 45°, two layers of fabric prepreg roll are unfolded in turn, and the winding device delivers the material with a micro-tension of ≤10 N, and the vision correction system monitors the edge position of the material belt in real time and corrects it, so that the position deviation of the layering is continuously controlled within a tolerance range of ±1.0 mm in the transverse direction, forming a continuous strip-shaped laminated body with a total thickness of about 2.4 mm.

[0051] S2 heats and molds the prepreg after layup to preform it; Specifically, the laid-up strip-shaped laminate then enters the preforming mold. This mold consists of an upper punch and a lower die, with its surface continuously tapering from the infeed end to the outlet end. The infeed end has a gently sloping 15mm high opening to accommodate the 2.4mm thick flat strip, while the outlet end is a fully closed "U"-shaped cavity with a cross-sectional dimension of 60mm (width) × 35mm (height). The mold is heated and stabilized at 110℃ by a built-in heating system. Under a molding pressure of 0.6MPa, the laminate is progressively guided and deformed into a continuous "U"-shaped cross-section preform through the 800mm long mold.

[0052] S3 involves passing the pre-formed prepreg through at least two independently adjustable heating and pressurizing zones for curing; Specifically, the preformed parison immediately enters a curing mold consisting of three independent temperature- and pressure-controlled zones. The parison remains in each zone for approximately 40 minutes. Zone 1: Mold temperature is 111℃, pressure is 0.3MPa; Zone 2: Mold temperature is 150℃, pressure is increased to 0.8MPa; Zone 3: Mold temperature is 170℃, and pressure is maintained at 1.5MPa.

[0053] S4 involves post-curing the cured prepreg in a mold at a temperature of 150~170℃ and a pressure of 0~3MPa. Specifically, the profiles cured in S3 then enter a separate post-curing mold. The temperature of the post-curing mold is 155℃, and the pressure is 1.0MPa. The profiles continue to travel within the post-curing mold for approximately 40 minutes to achieve their final performance specifications.

[0054] S5 uses a stepping motion to pull the post-cured product forward, thus obtaining the prepreg composite structural component; Specifically, after the product is cured and formed in the mold, the mold pressure is first reduced, and then the clamping device located at the mold outlet clamps the cured product and performs a traction action. The traction speed is 0.2m / min and the single traction distance is 300mm. After the traction is completed, the mold is pressurized again to the set pressure. By controlling the single traction distance, it is ensured that there is always a product in the curing process of transitioning from the gel region to the vitrification region within the curing area of ​​the mold.

[0055] S6 performs appearance and internal quality inspection on the pulled-out products, and cuts and trims them according to the set length; Specifically, the process involves: visual inspection using video imaging equipment; non-destructive testing of the internal components using ultrasonic testing equipment; and cutting the product to the required length while simultaneously trimming the edges.

[0056] Example 3 The present application provides a continuous forming method suitable for prepreg composite structural parts. In this embodiment, carbon fiber twill fabric prepreg is selected as the raw material, and the performance parameters are as follows: resin content is 31%, and the degree of impregnation of the prepreg is ≥83%. The prepreg is supplied in the form of a roll, and the roll width is 300 mm. The specific steps are as follows: S1. According to the requirements of the layer design, the prepreg roll is unfolded and layered. Specifically, the layering is carried out in a layering workstation integrated with a unwinding device and a visual correction system. According to the design sequence, two layers of fabric prepreg roll are unfolded in turn, and the unwinding device transports the material with a micro-tension of ≤10 N. The visual correction system monitors the edge position of the material belt in real time and corrects it, continuously controls the position deviation of the layer within the tolerance range of ±1.1 mm in the transverse direction, and forms a continuous strip-shaped laminated body.

[0057] S2. The layered prepreg is heated and molded to form a preform. Specifically, the strip-shaped laminated body after layering immediately enters the preforming mold. The mold is composed of an upper convex mold and a lower concave mold, and the profile surface is continuously variable from the feeding end to the discharging end. The feeding end profile is a gentle opening suitable for the thickness of the layer, and the discharging end profile is a "C" shaped groove cavity with a cross-sectional size of 65 mm (width) x 50 mm (height) formed after complete closure. The mold is heated and stabilized at 115℃ by the built-in heating system. Under the action of 0.7 MPa mold pressure, the laminated body is gradually guided to deform into a "C" shaped groove cross-section continuous profile by the mold.

[0058] S3. The preformed prepreg is sequentially passed through at least two heating and pressurizing zones with independent temperature and pressure control for curing. Specifically, the preformed profile immediately enters the curing mold composed of three independent temperature and pressure control zones.

[0059] The first zone: the mold temperature is 115℃, and the pressure is 0.4 MPa; The second zone: the mold temperature is 155℃, and the pressure is 1.0 MPa; The third zone: the mold temperature is 180℃, and the pressure is 2.0 MPa.

[0060] S4. The cured prepreg is subjected to post-curing in the mold at a temperature of 150-170℃ and a pressure of 0-3 MPa. Specifically, the profile after S3 curing then enters the independent post-curing mold. The post-curing mold temperature is 165℃, and the pressure is 1.8 MPa. The profile continues to travel in the post-curing mold to achieve the final performance index.

[0061] S5 pulls the post-cured product forward in a step-by-motion manner, i.e. the prepreg composite structure is obtained; Specifically, after the product is cured and formed in the mold, the mold pressure is first reduced, and then the clamping device located at the outlet end of the mold clamps the cured product to perform a pulling action, the pulling speed is 0.3 m / min, and the single pulling distance is 400 mm; after the pulling is completed, the mold is pressurized again to the set pressure; by controlling the single pulling distance, it is ensured that there is always a product in the curing area of the mold in the curing process from the gel area to the glass transition.

[0062] S6 performs appearance and internal quality detection on the pulled product, and cuts and edges according to the set length; Specifically, appearance detection is performed by video imaging equipment; non-destructive testing is performed on the inside by using ultrasonic detection equipment; according to the length requirement of the product, the product is cut to a fixed length, and the edges are trimmed.

[0063] Comparative Example 1: The prepreg layers in Example 1 were placed in a mold and then placed in a hot press tank as a whole by using a traditional hot press tank process, and after experiencing a single heating, pressurizing, curing and cooling cycle, the product was demolded to obtain a single product.

[0064] Comparative Example 2: The prepreg layers in Example 2 were placed in a mold and then placed in a hot press tank as a whole by using a traditional hot press tank process, and after experiencing a single heating, pressurizing, curing and cooling cycle, the product was demolded to obtain a single product.

[0065] Comparative Example 3: The prepreg layers in Example 3 were placed in a mold and then placed in a hot press tank as a whole by using a traditional hot press tank process, and after experiencing a single heating, pressurizing, curing and cooling cycle, the product was demolded to obtain a single product.

[0066] The products prepared in the examples and comparative examples were tested for performance comparison, and in terms of core performance indicators such as interlaminar shear strength (according to ASTM D2344), tensile strength and modulus (according to ASTM D3039), bending strength and modulus (according to ASTM D790), glass transition temperature (measured by DSC), fiber volume content and porosity, and cross-sectional size consistency, the test data of the products prepared by the continuous molding method in each example were at the same level as the products prepared by the traditional hot press tank process in the comparative examples, and there was no significant difference.

[0067] Although the present application has been described in connection with certain specific features and embodiments thereof, it is to be understood that it is provided as an example to the best of the applicant's knowledge and that various modifications and combinations will occur to those skilled in the art. Accordingly, all modifications, combinations and equivalents that fall within the scope of the application are intended to be included herein. It is evident that those skilled in the art can, without departing from the scope of the application, make various changes and modifications of the application to adapt it to various usages and conditions. Thus, such changes and modifications are intended to be included within the scope of the application as defined in the appended claims.

Claims

1. A continuous forming process suitable for use in the manufacture of a prepreg composite structure, characterised in that, The method comprises: S1. According to the requirements of the layer design, the prepreg roll is unfolded and layered; S2. The layered prepreg is heated and molded to be preformed; S3. The preformed prepreg is sequentially passed through at least two heating and pressing zones with independently controllable temperature and pressure for curing; S4. The cured prepreg is post-cured in a mold at a temperature of 150-170 DEG C and a pressure of 0-3 MPa; S5. The post-cured product is moved forward in a step motion, and the prepreg composite structural member is obtained.

2. The continuous forming process for a prepreg composite structure according to claim 1, wherein In S1, the laying material is corrected and positioned to control the laying position and dimensional accuracy of the laying material.

3. The continuous forming process for a prepreg composite structure according to claim 1, wherein In S2, the preformed layered prepreg is completed by the concave die and the convex die; the profile of the concave die and the convex die is continuously changed from the feeding end to the discharging end, the profile of the feeding end is adapted to the input shape of the layered prepreg, and the profile of the discharging end corresponds to the cross-sectional shape of the prepreg composite structural member.

4. The continuous forming process for a prepreg composite structure according to claim 1, wherein From the moving direction of the prepreg, the heating and pressing zone is three, the first zone temperature is 100-140 DEG C, the pressure is 0-1 MPa; the second zone temperature is 140-180 DEG C, the pressure is 0.5-2 MPa; the third zone temperature is 160-190 DEG C, the pressure is 0.5-3 MPa.

5. The continuous forming process for a prepreg composite structure according to claim 1, wherein The traction speed of the step motion in S5 is 0.1-0.4 m / min.

6. The continuous forming process for a prepreg composite structure according to claim 5, wherein After the product is cured and formed in the mold, the mold pressure is first reduced, and then the traction action is performed; after the traction is completed, the mold is again pressurized to the set pressure.

7. The continuous forming process for a prepreg composite structure according to claim 5, wherein In the step motion, the single traction distance is controlled so that there is always a product in the curing area of the mold in the curing process from the gel area to the glass transition.

8. The continuous forming process for a prepreg composite structure according to claim 1, wherein The method further comprises a post-processing step, specifically: the appearance and internal quality of the pulled-out product are detected, and the product is cut and trimmed according to the set length.

9. The continuous forming process for a prepreg composite structure according to claim 1, wherein The temperature in S2 is 80-140 DEG C.

10. The continuous forming process for a prepreg composite structure according to claim 1, wherein The prepreg in S1 is selected from carbon fiber prepreg or glass fiber prepreg, and is a fabric prepreg or a unidirectional prepreg, the impregnation degree of the prepreg is greater than or equal to 80%; the resin content of the fabric prepreg is 28-32%, and the resin content of the unidirectional prepreg is 26-30%.

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