Continuous carbon fiber reinforced thermoplastic t-stiffened and method of making same

Abstract

The application provides a continuous carbon fiber reinforced thermoplastic T-shaped rib and a preparation method thereof, and belongs to the technical field of hot forming. The application controls the temperature of stamping forming of the plate to ensure that the stamped plate is sufficiently softened and the size precision of the L-shaped rib is ensured; the temperature of hot melting and pressure welding is controlled to ensure the welding strength; the L-shaped rib, the twisted bar and the bottom plate are all made of the same material, and can be combined into an integral whole after welding, so that the mechanical properties and structural stability of the product are ensured; at the same time, transverse pressure and longitudinal pressure are applied, so that displacement during welding can be avoided, and the machining precision is affected. The results of the examples show that the tensile strength of the continuous carbon fiber reinforced thermoplastic T-shaped rib provided by the application reaches more than 850 MPa, and the impact strength reaches more than 142 MPa.

Description

Technical Field

[0001] This invention belongs to the field of thermoforming technology, specifically relating to a continuous carbon fiber reinforced thermoplastic T-shaped stiffener and its preparation method. Background Technology

[0002] Composite material stiffened structures are widely used in the main load-bearing components of aircraft due to their excellent bending and shear resistance and good load-bearing capacity. Among them, the T-shaped stiffened structure is a typical component of composite material stiffened structures, and also the prototype for U-shaped, I-shaped, and J-shaped stiffened structures. They are widely used in structures such as wing webs, spars, fuselage panels, and horizontal stabilizing beams.

[0003] Continuous carbon fiber reinforced materials (CFRTSCs) are a type of composite material using continuous carbon fiber as reinforcement and plastic as the matrix, and are the main material for stiffened structures. Currently, aerospace stiffened structures are processed and assembled using carbon fiber reinforced thermosetting composites (CFRTSCs). CFRTSCs possess excellent mechanical stability, ensuring flight safety. Because CFRTSCs cannot be refluxed after curing, they cannot be processed using hot welding. Currently, through integrated molding processes such as co-curing and co-bonding, T-stiffeners can form strong chemical bonds with the skin, resulting in extremely high bonding strength and a reinforced structure with excellent structural integrity. Moreover, CFRTSCs exhibit almost no deformation after curing, ensuring the positional accuracy of the T-stiffeners and guaranteeing the aerodynamic performance of the wing.

[0004] However, CFRTSCs are difficult to recycle and repair, and are highly brittle, easily broken, and have poor corrosion and water resistance. Carbon fiber reinforced thermoplastic composites overcome these problems, being easily recyclable, weldable, repairable, water-resistant, corrosion-resistant, and heat-resistant. The raw materials do not require cold chain transportation and storage, and they possess high toughness, low density, and short molding cycles, making them strong competitors for next-generation aerospace materials. Unfortunately, currently, carbon fiber reinforced thermoplastic composites are only used in composite panels, and there is no technology yet for preparing complex T-shaped stiffeners. Summary of the Invention

[0005] The purpose of this invention is to provide a continuous carbon fiber reinforced thermoplastic T-shaped stiffener and its preparation method. The preparation method provided by this invention can produce complex T-shaped stiffeners with performance that meets the requirements for aerospace applications.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, comprising the following steps: The sheet is heated to temperature T1 and stamped to obtain an L-shaped rib; the material of the sheet is a continuous carbon fiber reinforced thermoplastic composite material; T1 satisfies T0-20℃≤T1≤T0+20℃, and T0 is the melting point of the thermoplastic plastic in the continuous carbon fiber reinforced thermoplastic composite material; After assembling the L-shaped ribs with the twist strips and the base plate, hot melt pressing and welding are performed to obtain continuous carbon fiber reinforced thermoplastic T-shaped ribs. The base plate and the tumbler strip are made of the same material as the plate. The hot melt pressure welding includes: assembling the L-shaped ribs, twill strips and the fusion surface of the base plate by heating to temperature T2, and then simultaneously applying transverse pressure and longitudinal pressure; T2 satisfies T0+10℃≤T2≤T0+50℃.

[0007] Preferably, the transverse pressure in the hot melt pressure welding is 1~10MPa and the longitudinal pressure is 1~15MPa.

[0008] Preferably, the holding time in the hot melt pressure welding is 30~120s.

[0009] Preferably, the hot melt pressing welding uses a mold to apply pressure, the mold including: an upper mold, a lower mold, a welding left mold and a welding right mold; the welding left mold and the welding right mold contact the L-shaped rib and apply lateral pressure; the upper mold contacts the top of the L-shaped rib and the top of the welding left mold and the welding right mold, the lower mold contacts the base plate, and the upper mold and the lower mold apply longitudinal pressure.

[0010] Preferably, the temperature of the die during the stamping process is 120~220℃.

[0011] Preferably, the pressing time during the stamping process is 5 to 30 seconds.

[0012] Preferably, the twisted strip is prepared by a triangular twisted strip pultrusion process, wherein the temperature of the die in the triangular twisted strip pultrusion process is T3, wherein T3 satisfies T0+20℃≤T3≤T0+60℃, and the traction rate is 0.1~2m / min.

[0013] Preferably, the thickness of the L-shaped rib and the base plate is independently 1~5mm.

[0014] Preferably, the thermoplastic in the continuous carbon fiber reinforced thermoplastic composite material includes polyaryletherketone or polyphenylene sulfide, with a mass content of 30-60%.

[0015] The present invention provides a continuous carbon fiber reinforced thermoplastic T-shaped stiffener prepared by the preparation method described in the above technical solution.

[0016] This invention provides a method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners. The method involves stamping a sheet material, controlling the stamping temperature to ensure sufficient softening of the sheet and dimensional accuracy of the L-shaped stiffeners; controlling the temperature of the hot-melt pressing welding to ensure welding strength; and using the same material for the L-shaped stiffeners, twist strips, and base plate, which can be welded together as a whole, ensuring the mechanical properties and structural stability of the part. Simultaneous application of transverse and longitudinal pressure prevents displacement during welding, thus avoiding impact on processing accuracy. Results from the embodiments show that the continuous carbon fiber 0° / 90° reinforced thermoplastic T-shaped stiffeners provided by this invention achieve a tensile strength of over 850 MPa and an impact strength of over 142 MPa. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the die used in the stamping process in an embodiment of the present invention; Figure 2 These are cross-sectional views and left views of the hot melt press welding in an embodiment of the present invention; Figure 3 These are the front view and left view of the welding left mold in the hot melt pressing welding embodiment of the present invention; Figure 4 These are the front and left views of the right mold in the hot melt pressing welding process in this embodiment of the invention; Figure 5 This is a schematic diagram of continuous carbon fiber reinforced thermoplastic T-shaped stiffener in an embodiment of the present invention. Detailed Implementation

[0018] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0019] This invention provides a method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, comprising the following steps: The sheet is heated to temperature T1 and stamped to obtain an L-shaped rib; the material of the sheet is a continuous carbon fiber reinforced thermoplastic composite material; T1 satisfies T0-20℃≤T1≤T0+20℃, and T0 is the melting point of the thermoplastic plastic in the continuous carbon fiber reinforced thermoplastic composite material; After assembling the L-shaped ribs with the twist strips and the base plate, hot melt pressing and welding are performed to obtain continuous carbon fiber reinforced thermoplastic T-shaped ribs. The base plate and the tumbler strip are made of the same material as the plate. The hot melt pressure welding includes: assembling the L-shaped ribs, twill strips and the fusion surface of the base plate by heating to temperature T2, and then simultaneously applying transverse pressure and longitudinal pressure; T2 satisfies T0+10℃≤T2≤T0+50℃.

[0020] The present invention heats the sheet material to a temperature T1 and then stamps it to obtain an L-shaped rib.

[0021] In this invention, the material of the plate is a continuous carbon fiber reinforced thermoplastic composite material.

[0022] In this invention, the thermoplastic in the continuous carbon fiber reinforced thermoplastic composite preferably includes polyaryletherketone (PEEK) or polyphenylene sulfide (PPS). As one embodiment of this invention, the PEEK can be polyetheretherketone (PEEK) or polyetherketoneketone (PEKK), or low-melting-point PEEK (LMPAEK). These materials are all common special engineering plastics with excellent mechanical properties and corrosion resistance.

[0023] In this invention, the mass content of thermoplastic plastic in the continuous carbon fiber reinforced thermoplastic composite material is preferably 30-60%, more preferably 40-50%. As one embodiment of this invention, the mass content of thermoplastic plastic in the continuous carbon fiber reinforced thermoplastic composite material can be 35%, 40%, 45%, 50%, 55%, 60%, or 65%. The mass content of thermoplastic plastic in the continuous carbon fiber reinforced thermoplastic composite material within the above range can ensure the mechanical properties and processing performance of the T-shaped reinforcement.

[0024] In one embodiment of the present invention, the thickness of the sheet material is preferably 1-5 mm, specifically 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. Sheet material within this thickness range exhibits high strength and good processability.

[0025] In one embodiment of the present invention, the sheet is formed by hot pressing continuous carbon fiber reinforced thermoplastic material unidirectional prepreg tapes laid in an alternating pattern of 0° and 90°.

[0026] In this invention, T1 satisfies T0-20℃≤T1≤T0+20℃, where T0 is the melting point of the thermoplastic in the continuous carbon fiber reinforced thermoplastic composite. This invention utilizes a stamping process to rapidly and efficiently prepare L-shaped ribs; by limiting the stamping temperature, the dimensional stability of the L-shaped ribs can be ensured.

[0027] In this invention, the temperature of the die during stamping is preferably 120~220℃, more preferably 150~180℃; as one embodiment of this invention, the temperature of the die during stamping can be 140℃, 160℃, 180℃, 200℃, or 210℃. A die temperature within the above range during stamping is beneficial for the formation of L-shaped ribs.

[0028] In this invention, the pressing time during stamping is preferably 5-30 seconds, more preferably 10-20 seconds; as one embodiment of this invention, the pressing time during stamping can be 6 seconds, 8 seconds, 10 seconds, 15 seconds, 20 seconds, or 25 seconds. A pressing time within the above range is beneficial for the formation of L-shaped ribs.

[0029] As one embodiment of the present invention, the sheet metal can be cut according to the size of the L-shaped rib before stamping; after stamping, the resulting part can be cut with a water jet to obtain the L-shaped rib.

[0030] In an embodiment of the present invention, the cross-sectional view of the die used in the stamping process is shown below. Figure 1 As shown, 1 is the upper die, 2 is the lower die, and 3 is a T-shaped rib; the lower die is convex, and the upper die is concave; the height of the protruding part of the lower die is 50mm and the width is 152mm, the depth of the concave part of the upper die is 50mm and the width is 156mm, and the corners of the protruding part of the lower die and the concave part of the upper die are all provided with a radius of 5mm; four L-shaped ribs can be stamped in one go between the upper die and the lower die (the yellow and blue parts in the figure are L-shaped ribs, and the green part is excess material).

[0031] In this invention, the thickness of the L-shaped stiffener is preferably 1-5 mm, more preferably 2-4 mm. A thickness within the above range is beneficial for improving the mechanical properties of the T-shaped stiffener.

[0032] After obtaining the L-shaped rib, the present invention assembles the L-shaped rib with the twist strip and the base plate and then performs hot melt pressing welding to obtain a continuous carbon fiber reinforced thermoplastic T-shaped rib.

[0033] In this invention, the base plate and the tack strip are made of the same material as the plate. The L-shaped stiffener, the tack strip, and the base plate are all made of the same material, allowing them to form a single unit after welding, thus ensuring the mechanical properties and structural stability of the T-shaped stiffener.

[0034] In this invention, the thickness of the base plate is preferably 1-5 mm, more preferably 2-4 mm. A thickness within this range is beneficial for improving the mechanical properties of the T-shaped stiffener.

[0035] In this invention, the twisted strip is preferably prepared using a triangular twisted strip pultrusion process. The die temperature in the triangular twisted strip pultrusion process is preferably T3, where T3 satisfies T0+20℃≤T3≤T0+60℃, and the traction rate is preferably 0.1~2m / min. The triangular twisted strip pultrusion process is a conventional process for preparing twisted strips; process parameters within the above range are beneficial for improving the uniformity of the twisted strip and further enhancing the mechanical properties of the T-shaped reinforcement.

[0036] As one embodiment of the present invention, the raw material for the triangular twisted strip pultrusion process can be a continuous carbon fiber reinforced thermoplastic composite prepreg tape with a width of 6.35~12.7mm.

[0037] In an embodiment of the present invention, the two sides of the twisted strip are rounded with a radius of 7 mm.

[0038] In this invention, the hot melt pressure welding includes: assembling the L-shaped ribs, twill strips and the fusion surface of the base plate by heating to a temperature T2, and then simultaneously applying transverse pressure and longitudinal pressure; wherein T2 satisfies T0+10℃≤T2≤T0+50℃.

[0039] In this invention, the hot-melt pressing welding preferably uses a mold to apply pressure. The mold preferably includes: an upper mold, a lower mold, a left welding mold, and a right welding mold. The left and right welding molds contact the L-shaped ribs, applying lateral pressure. The upper mold contacts the top of the L-shaped ribs and the tops of the left and right welding molds. The lower mold contacts the base plate. The upper and lower molds apply longitudinal pressure. The mold has independent lateral and longitudinal pressure systems, which can improve the mechanical properties and processing accuracy of the T-shaped stiffener.

[0040] In an embodiment of the present invention, the cross-sectional view and left view of the hot melt press welding are as follows: Figure 2 As shown, the left image is a cross-sectional view, and the right image is a left view. From Figure 2 It can be seen that the two L-shaped ribs and the base plate fix the tack strip at the connection point of the three; the height of the welding left mold and the welding right mold is 76mm, the width is 23mm, and the length is 560mm; the width of the base plate is 50mm; the length of the L-shaped ribs and the base plate is 500mm, the welding left mold and the welding right mold are in contact with the L-shaped ribs, and the welding left mold and the welding right mold are provided with grooves with a length of 502mm to restrict the short side of the L-shaped ribs and the base plate.

[0041] In an embodiment of the present invention, the front view and left view of the welding left mold are as follows: Figure 3 As shown, the front view and left view of the welding right mold are as follows: Figure 4 As shown, the left image is the front view, and the right image is the left view. From Figure 3 , Figure 4 It can be seen that the surface roughness of the surfaces of the left and right welding molds that contact the L-shaped rib is 0.8μm; the edges of the left and right welding molds that contact the corners of the L-shaped rib are provided with rounded corners with a radius of 5mm; the surfaces of the left and right welding molds that contact the short sides of the L-shaped rib are provided with grooves with a depth of 4mm; and both the left and right welding molds are provided with 4 bolt holes with a diameter of 16mm.

[0042] In this invention, the transverse pressure during the hot-melt pressure welding is preferably 1~10 MPa, more preferably 3~6 MPa; as one embodiment of this invention, the transverse pressure during the hot-melt pressure welding can be 2 MPa, 4 MPa, 6 MPa, 8 MPa, or 10 MPa. A transverse pressure within the above range is beneficial for the connection of L-shaped ribs.

[0043] In this invention, the longitudinal pressure during the hot-melt pressure welding is preferably 1~15MPa, more preferably 5~10MPa; as one embodiment of this invention, the longitudinal pressure during the hot-melt pressure welding can be 3MPa, 4MPa, 6MPa, 8MPa, 10MPa, 12MPa, or 14MPa. A longitudinal pressure within the above range is beneficial for the connection between the L-shaped rib and the base plate.

[0044] In this invention, the holding time in the hot-melt pressure welding is preferably 30-120s, more preferably 50-100s; as one embodiment of this invention, the holding time in the hot-melt pressure welding can be 40s, 50s, 60s, 70s, 80s, 90s, 100s, or 110s. Holding times within the above ranges in the hot-melt pressure welding are beneficial for the connection between the L-shaped ribs, the tack strips, and the base plate.

[0045] This invention utilizes a stamping process to form sheet metal, controlling the stamping temperature to ensure sufficient softening of the sheet metal and dimensional accuracy of the L-shaped ribs. It also controls the temperature of the hot-melt pressing welding to guarantee weld strength. The L-shaped ribs, twill strips, and base plate are all made of the same material, allowing them to be welded together as a single unit, ensuring the mechanical properties and structural stability of the part. Simultaneous application of transverse and longitudinal pressure prevents displacement during welding, thus avoiding impact on processing accuracy. The manufacturing method provided by this invention offers fast processing speed, high efficiency, and significantly reduced manufacturing costs. Raw materials are easy to store and do not require low-temperature preservation.

[0046] The present invention provides a continuous carbon fiber reinforced thermoplastic T-shaped stiffener prepared by the preparation method described in the above technical solution.

[0047] This invention uses high-strength thermoplastic as a matrix, which ensures the processing accuracy and mechanical properties of the T-shaped reinforcement; the thermoplastic also gives the T-shaped reinforcement the effect of being recyclable and repairable, and improves its corrosion resistance and water resistance.

[0048] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] Example 1 A method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, comprising the following steps: The continuous carbon fiber reinforced PEEK composite material (PEEK melting point 343℃, mass content 50%) was cut into 500×130×2mm sheets; Heat the cut board to T1=345℃, then place it in... Figure 1 The surface of the lower die for stamping (preheated to 150℃) is shown. The upper die is pressed and held for 10 seconds. The sample is then removed and cut with a water jet into an L-shaped rib with a long side length of 71mm, a short side length of 20mm, and a corner radius of 5mm. The continuous carbon fiber reinforced PEEK composite prepreg tape was cut into 7mm narrow strips and twisted strips were prepared on a triangular twisted strip pultrusion production line. The die temperature T3=380℃ and the traction speed was 0.5m / min. The continuous carbon fiber reinforced PEEK composite material sheet was cut into 500×50×2mm pieces to serve as the base plate; Heat the weld surfaces of the two L-shaped reinforcing bars, the twist strip, and the base plate to T2=360℃, then proceed according to... Figure 2 As shown, the assembly was performed, with a transverse pressure of 5 MPa and a longitudinal pressure of 8 MPa. Hot melt pressure welding was carried out, and the pressure was held for 50 seconds. The mold was then removed to obtain a continuous carbon fiber reinforced thermoplastic T-shaped stiffener. A schematic diagram of the fabricated continuous carbon fiber reinforced thermoplastic T-stiffener is shown below. Figure 5 As shown, the left image is the main view, and the right image is the left view.

[0050] Example 2 A method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, the steps are the same as in Example 1, except that the raw material is continuous carbon fiber reinforced LMPAEK composite material (LMPAEK melting point is 305℃, content is 50%), T1=255℃, T2=320℃, T3=335℃.

[0051] Example 3 A method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, the steps are the same as in Example 1, except that the raw material is continuous carbon fiber reinforced PPS composite material (PPS melting point is 280℃, content is 50%), T1=250℃, T2=300℃, T3=310℃.

[0052] Test Example 1 The performance of the continuous carbon fiber reinforced thermoplastic T-shaped stiffeners prepared in Examples 1-3 was tested, and the test results are recorded in Table 1.

[0053] Table 1. Forming process parameters and performance test records for different T-shaped stiffeners.

[0054] As can be seen from Table 1, the continuous carbon fiber reinforced thermoplastic T-shaped stiffener provided by this invention meets the processing accuracy requirements, with a tensile strength exceeding 850 MPa and an impact strength reaching 142 kJ / m². 2 above.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing continuous carbon fiber reinforced thermoplastic T-shaped stiffeners, characterized in that, Includes the following steps: The sheet material is heated to temperature T1 and stamped to obtain L-shaped ribs; the sheet material is a continuous carbon fiber reinforced thermoplastic composite material. The T1 satisfies T0-20℃≤T1≤T0+20℃, where T0 is the melting point of the thermoplastic in the continuous carbon fiber reinforced thermoplastic composite. After assembling the L-shaped ribs with the twist strips and the base plate, hot melt pressing and welding are performed to obtain continuous carbon fiber reinforced thermoplastic T-shaped ribs. The base plate and the tumbler strip are made of the same material as the plate. The hot melt pressure welding includes: assembling the L-shaped ribs, twill strips and the fusion surface of the base plate by heating to temperature T2, and then simultaneously applying transverse pressure and longitudinal pressure; T2 satisfies T0+10℃≤T2≤T0+50℃.

2. The preparation method according to claim 1, characterized in that, The transverse pressure in the hot melt pressure welding is 1~10MPa, and the longitudinal pressure is 1~15MPa.

3. The preparation method according to claim 2, characterized in that, The holding time in the hot melt pressure welding is 30~120s.

4. The preparation method according to claim 1, characterized in that, The hot melt pressing welding uses a mold to apply pressure. The mold includes an upper mold, a lower mold, a welding left mold, and a welding right mold. The welding left mold and the welding right mold contact the L-shaped rib and apply lateral pressure. The upper mold contacts the top of the L-shaped rib and the top of the welding left mold and the welding right mold. The lower mold contacts the base plate. The upper mold and the lower mold apply longitudinal pressure.

5. The preparation method according to claim 1, characterized in that, The temperature of the die during the stamping process is 120~220℃.

6. The preparation method according to claim 5, characterized in that, The pressing time during the stamping process is 5~30s.

7. The preparation method according to claim 1, characterized in that, The twisted strip is prepared by a triangular twisted strip pultrusion process. The temperature of the die in the triangular twisted strip pultrusion process is T3, which satisfies T0+20℃≤T3≤T0+60℃, and the traction rate is 0.1~2m / min.

8. The preparation method according to claim 1, characterized in that, The thickness of the L-shaped ribs and the base plate is independently 1~5mm.

9. The preparation method according to claim 1, characterized in that, The thermoplastic in the continuous carbon fiber reinforced thermoplastic composite material includes polyaryletherketone or polyphenylene sulfide, with a mass content of 30-60%.

10. The continuous carbon fiber reinforced thermoplastic T-shaped stiffener prepared by the preparation method according to any one of claims 1 to 9.

Images