Additive manufacturing method based on local reinforcement of double continuous fiber braiding

Abstract

The present invention provides an additive manufacturing method based on local reinforcement of double continuous fiber weaving, which adopts a molten deposition additive manufacturing process, uses high-strength and high-cost continuous fibers and general-strength and low-cost continuous fibers for coordinated deposition, greatly reducing manufacturing costs, and through the design of a weaving structure and a local reinforcement structure, the molded parts are transferred to the fibers through resin after being loaded, and are transferred to between layers at the junction of the fibers. While enhancing the bonding strength between layers, the problem of fracture caused by stress concentration at the opening of the parts is avoided, ensuring that the mechanical properties of the final parts meet the use requirements, and can be suitable for UAV frames.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing of resin-based continuous fiber composite materials, and in particular to an additive manufacturing method based on local reinforcement of double continuous fiber weaving. Background Art

[0002] A drone is an unmanned aircraft controlled by a radio remote control device and a self-contained program control device. It has the advantages of low ground security requirements and a small safety risk factor. It is widely used in military and civilian fields. Due to the huge market demand, the large-scale production of drones is a development trend, which requires us to reduce production costs. At the same time, in order to adapt to various applications in different fields, excellent performance is also essential.

[0003] Traditional UAV materials are generally metal materials such as alloy steel and aluminum alloy. Such materials have a short service life and are prone to breakage. At the same time, as the flight speed requirements of UAVs become higher and higher and the application size becomes larger and larger, traditional materials are increasingly unable to meet the use requirements of new UAVs.

[0004] Resin-based composite materials have the advantages of light weight, high specific strength, high specific modulus, strong fatigue resistance and strong earthquake resistance. At the same time, according to different processing techniques, it has anisotropic characteristics and is inherently designable. Without changing the weight of the structure, it can be optimized according to the strength and stiffness requirements of the aircraft. The corrosion resistance of resin-based composite materials can meet the special requirements of long storage life of drones in harsh environments and reduce the life cycle cost of use and maintenance.

[0005] Adding continuous fibers to the resin matrix can improve the mechanical properties of parts, such as adding continuous carbon fibers or continuous glass fibers to thermoplastic resins to improve their mechanical properties. However, if high-strength continuous fibers such as continuous carbon fibers are used exclusively, the cost is extremely high, limiting large-scale production, while the use of cheap, low-strength continuous fibers will result in insufficient mechanical properties and will be difficult to meet the actual use environment. Summary of the invention

[0006] The purpose of the present invention is to address the shortcomings of the prior art and provide an additive manufacturing method based on double continuous fiber weaving and local reinforcement. The method adopts molten deposition additive manufacturing technology, utilizes two continuous fiber prepreg wires of different strengths for deposition, and designs the weaving structure and the local reinforcement structure. Under the premise of maintaining the mechanical properties to meet the requirements, the printing cost is reduced to meet the needs of the UAV frame.

[0007] The first aspect of the present invention relates to an additive manufacturing method based on double continuous fiber braiding local reinforcement, comprising:

[0008] S11, Raw material silk making

[0009] Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber;

[0010] S21, Fused Deposition Modeling

[0011] The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows:

[0012] S211, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain an outer frame structure of the printed part;

[0013] S212, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range;

[0014] S213, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range;

[0015] S214, the first print head continues to deposit the third deposition layer in a single pass, wherein in the third deposition layer, the single deposition layer passes through the overlapping point of the first deposition layer and the second deposition layer, and both ends overlap with the outer frame structure;

[0016] S215, the first print head continues to deposit the fourth deposition layer between the gaps of each adjacent single-pass deposition layer in the first deposition layer, and then the second print head deposits the fifth deposition layer between the gaps of each adjacent single-pass deposition layer in the second deposition layer;

[0017] S216, the second print head continues to deposit the sixth deposition layer in a single pass, wherein in the sixth deposition layer, the single deposition layer passes through the overlapping point of the fourth deposition layer and the fifth deposition layer, and both ends overlap with the outer frame structure;

[0018] S217. Repeat steps S211, S212, S213, S214, S215 and S216, accumulating layer by layer until deposition is completed to obtain a printed part.

[0019] The second aspect of the present invention relates to an additive manufacturing method based on double continuous fiber braiding local reinforcement, comprising:

[0020] S12, Raw material silk making

[0021] Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber;

[0022] S22, Fused Deposition Modeling

[0023] The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows:

[0024] S221, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain an outer frame structure of the printed part;

[0025] S222, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range;

[0026] S223, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range;

[0027] S224, the first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the first deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the second deposition layer;

[0028] The first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the second deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the first deposition layer;

[0029] S225, the first print head continues to deposit between the gaps of each adjacent single-track deposition layer in the first deposition layer, and the single-track deposition layer overlaps the rectangular structure;

[0030] The second print head deposits between the gaps between each adjacent single-track deposition layer in the second deposition layer, and the single-track deposition layer overlaps the rectangular structure;

[0031] S226. Repeat steps S221, S222, S223, S224 and S225, accumulating layer by layer until deposition is completed to obtain a printed part.

[0032] In an optional embodiment, the first continuous fiber includes a mixture of one or more of carbon fiber, carbon nanotube fiber, aramid fiber, ceramic fiber, and titanium fiber.

[0033] In an optional embodiment, the second continuous fibers include a mixture of one or more of glass fibers, basalt fibers, boron fibers, copper fibers, and aluminum fibers.

[0034] In an optional embodiment, the resin substrate includes a mixture of one or more of PLA material, ABS resin material, PEEK material, PEKK material, nylon material, PEI material, PAEK material, polycarbonate material, and polyimide material.

[0035] In an optional embodiment, the first spacing is greater than or equal to a width of a deposition path of the first deposition layer; and the second spacing is greater than or equal to a width of a deposition path of the second deposition layer.

[0036] In an optional embodiment, specific parameters of the first print head include:

[0037] The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

[0038] In an optional embodiment, specific parameters of the second print head include:

[0039] The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

[0040] The third aspect of the present invention relates to an unmanned aerial vehicle frame, which is prepared by the additive manufacturing method based on double continuous fiber weaving local reinforcement involved in the first aspect.

[0041] The fourth aspect of the present invention relates to an unmanned aerial vehicle frame, which is prepared by the additive manufacturing method based on double continuous fiber weaving local reinforcement involved in the second aspect.

[0042] In summary, the additive manufacturing method based on double continuous fiber braiding local reinforcement proposed in the present invention has the following advantages:

[0043] The present invention adopts a molten deposition additive manufacturing process, utilizes two continuous fiber prepreg wires of different strengths to deposit and weave a grid structure, and forms a local reinforcement structure by weaving a high-strength continuous fiber prepreg wire through the overlap of the two continuous fiber prepreg wires, or adding a high-strength continuous fiber prepreg wire to the overlap of the two continuous fiber prepreg wires to form a "lock-type" rectangular structure, thereby forming a local reinforcement structure. While enhancing the bonding strength between layers, it avoids the problem of fracture caused by stress concentration at the opening of the part, ensures that the mechanical properties of the final part meet the use requirements, and greatly reduces the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the manufacturing process of the additive manufacturing method based on double continuous fiber weaving local reinforcement of the present invention.

[0045] Figure 2 It is a partial structural schematic diagram of an exemplary additive manufacturing system based on double continuous fiber weaving local reinforcement of the present invention.

[0046] Figure 3 It is a flow chart of the manufacturing process of one of the embodiments of the present invention.

[0047] Figure 4 It is a flow chart of the manufacturing process of another embodiment of the present invention.

[0048] Figure 5 It is a schematic structural diagram of a silk-making die used in an embodiment of the present invention.

[0049] Figure 6 Schematic diagram of one of the paths of continuous printing in an embodiment of the present invention.

[0050] Figure 7 These are SEM test images of parts of Example 3 (A) of the present invention and Comparative Example 4 (B). DETAILED DESCRIPTION

[0051] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0052] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which many illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways.

[0053] Additive manufacturing technology is a manufacturing method that uses raw materials to form the final product layer by layer. Compared with traditional manufacturing technology, the application of additive manufacturing technology to the manufacture of composite materials can overcome the limitations of molds in traditional composite manufacturing to composite material manufacturing to a certain extent. At the same time, the use of additive manufacturing technology to obtain components has a high material utilization rate, can form complex structures, and has a simple process, which can effectively reduce production costs.

[0054] When the additive manufacturing process is used to prepare resin-based composite materials with added continuous fibers, problems such as poor interface bonding may occur, resulting in mechanical properties that fail to meet expectations.

[0055] Therefore, in order to solve the cost problem while further ensuring the mechanical properties of resin-based composite materials, the present invention proposes a new additive manufacturing method based on double continuous fiber weaving and local reinforcement. The method adopts a fused deposition additive manufacturing process and uses high-strength and high-cost continuous fibers and general-strength and low-cost continuous fibers for coordinated deposition, which greatly reduces the manufacturing cost. By designing a weaving structure and a local reinforcement structure, the molded parts are transferred to the fibers through the resin after being loaded, and then transferred to the layers at the junction of the fibers. While enhancing the bonding strength between the layers, it avoids the problem of fracture caused by stress concentration at the openings of the parts, thereby ensuring that the mechanical properties of the final parts meet the use requirements.

[0056] Additive manufacturing system based on local reinforcement of double continuous fiber braiding

[0057] Combination Figure 1 and Figure 2 The additive manufacturing system based on double continuous fiber weaving local reinforcement of the exemplary embodiment shown includes:

[0058] The substrate 10 is used as a working platform for printing components.

[0059] The printing system 20 disposed above the substrate 10 is provided with at least a plurality of print heads, including a first print head 21 for printing the first prepreg wire material, and a second print head 22 for printing the second prepreg wire material; the print head can adopt a commercially available FDM universal print head, and the caliber edge of the print head can preferably be rounded, so as to avoid the continuous fiber being worn off by the caliber edge of the print nozzle during the deposition process in a molten state, affecting the integrity of the printing of the continuous fiber material.

[0060] The substrate 10 and each print head can move in three dimensions. In a specific embodiment, Figure 2 As shown, a robotic arm can be used to achieve movement in three dimensions, thus achieving multi-dimensional and multi-directional forming in the additive manufacturing process.

[0061] The feeding system 30 is provided with at least two wire feeding mechanisms 31, which are respectively connected to the printing heads. Each wire material is fed into the corresponding printing head through the wire feeding mechanism 31; the wire feeding mechanism can adopt the wire feeding mechanism commonly used in the field of additive manufacturing.

[0062] Additive manufacturing method based on local reinforcement of double continuous fiber braiding

[0063] In combination with the additive manufacturing system based on double continuous fiber weaving local reinforcement of the aforementioned embodiment of the present invention, the additive manufacturing process of resin-based fiber composite materials is carried out using the system.

[0064] Combination Figure 3 The process shown, in one preferred embodiment, includes the following steps:

[0065] S11, Raw material silk making

[0066] Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber;

[0067] S21, Fused Deposition Modeling

[0068] The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows:

[0069] S211, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain the outer frame structure of the printed part (such as Figure 3 ① part);

[0070] S212, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range (such as Figure 3 The black line of part ②);

[0071] S213, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range (such as Figure 3 The gray line of part ②);

[0072] S214, the first print head continues to deposit the third deposition layer in a single pass, wherein in the third deposition layer, the single deposition layer passes through the overlapping point of the first deposition layer and the second deposition layer, and the two ends overlap with the outer frame structure (such as Figure 3 The orange line in part ③);

[0073] S215, the first print head continues to deposit the fourth deposition layer between the gaps of each adjacent single-pass deposition layer in the first deposition layer, and then the second print head deposits the fifth deposition layer between the gaps of each adjacent single-pass deposition layer in the second deposition layer (eg, Figure 3 ④ and ⑤ of );

[0074] S216, the second print head continues to deposit the sixth deposition layer in a single pass, wherein in the sixth deposition layer, the single deposition layer passes through the overlapping point of the fourth deposition layer and the fifth deposition layer, and the two ends overlap with the outer frame structure (such as Figure 3 The bright yellow line in the ⑥ part);

[0075] S217. Repeat steps S211, S212, S213, S214, S215 and S216, accumulating layer by layer until deposition is completed to obtain a printed part.

[0076] Combination Figure 4 The process shown, in another preferred embodiment, includes the following steps:

[0077] S12, Raw material silk making

[0078] Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber;

[0079] S22, Fused Deposition Modeling

[0080] The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows:

[0081] S221, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain the outer frame structure of the printed part (such as Figure 4 ① part);

[0082] S222, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range (such as Figure 4 The black line of part ②);

[0083] S223, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range (such as Figure 4 The gray line of part ②);

[0084] S224, the first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the first deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the second deposition layer (such as Figure 4 ③ part);

[0085] The first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the second deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the first deposition layer (e.g. Figure 4 ③ part);

[0086] S225, the first print head continues to deposit between the gaps between each adjacent single-pass deposition layer in the first deposition layer, and the single-pass deposition layer overlaps the rectangular structure (such as Figure 4 The orange line of the ④ part);

[0087] The second print head deposits between the gaps between each adjacent single-pass deposition layer in the second deposition layer, and the single-pass deposition layer overlaps the rectangular structure (such as Figure 4 ⑤The bright yellow line of part 5);

[0088] S226. Repeat steps S221, S222, S223, S224 and S225, accumulating layer by layer until deposition is completed to obtain a printed part.

[0089] In an optional embodiment, the first continuous fiber includes a mixture of one or more of carbon fiber, carbon nanotube fiber, aramid fiber, ceramic fiber, and titanium fiber.

[0090] In an optional embodiment, the second continuous fibers include a mixture of one or more of glass fibers, basalt fibers, boron fibers, copper fibers, and aluminum fibers.

[0091] In an optional embodiment, the original filament diameter of the first continuous fiber and the second continuous fiber is 1 mm. After the surface is wrapped with a resin matrix, the diameters of the obtained first prepreg wire and the second prepreg wire are between 1.75 and 2 mm. The specific diameter is determined according to the diameter of the print head throat, so that it can pass through the throat. The required diameter can be obtained by the nozzle diameter of the corresponding wire making equipment.

[0092] In an optional embodiment, the resin substrate includes a mixture of one or more of PLA material, ABS resin material, PEEK material, PEKK material, nylon material, PEI material, PAEK material, polycarbonate material, and polyimide material.

[0093] In an optional embodiment, the first spacing is greater than or equal to the width of the deposition path of the first deposition layer; the second spacing is greater than or equal to the width of the deposition path of the second deposition layer. The distance of the gap will change the distribution density of the fiber, thereby affecting its mechanical properties, and the gap distance can be selected according to the actual working conditions of the printed part.

[0094] In a preferred embodiment, when depositing between the gaps of each adjacent single-pass deposition layer, the position of the new single-pass deposition layer is located at the center line of the gap, thereby ensuring symmetry and mechanical properties.

[0095] In an optional embodiment, specific parameters of the first print head include:

[0096] The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

[0097] In an optional embodiment, specific parameters of the second print head include:

[0098] The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

[0099] In an optional embodiment, the raw material is made into silk using Figure 5 The mold shown fixes the continuous fiber precursor 40 at the starting end of the silk making equipment, enters the impregnation mold 60 through the traction device 50, pours the resin particles 70 into the hopper, and enters the impregnation mold 60 under the action of the twin-screw extruder 80. During the up and down shaking of the mold, the continuous fiber precursor is evenly coated with the resin and passes through the nozzle 90, and is wound under the action of the traction roller to obtain a continuous fiber prepreg wire material.

[0100] In an optional embodiment, the outer frame structure, and the printing paths of the first deposition layer and the second deposition layer may adopt a continuous zigzag path, for example Figure 6 As shown, in part ①, the first print head is used for printing first. The first print head starts from position 1 and moves to position 2, and then moves to position 3, position 4, position 5, and position 6 in sequence to complete the printing of the outer frame structure. At this time, there is no need to cut the filament. Starting from position 6, the first print head moves to position 7, position 8, position 9, position 10, position 10, position 11, position 12, and position 13 in sequence to complete the printing of the first deposition layer.

[0101] Afterwards, if Figure 6 As shown in the second part, a second print head is used to start from position 1, and then to position 2, position 3, position 4, position 5, position 6, position 7, and position 8 to complete the printing of the second deposition layer.

[0102] The same method is used to deposit two types of fibers in the gap, such as Figure 6 As shown in Part ③ and Part ④.

[0103] It is understandable that when printing the local reinforcement structure at the overlap of two types of fibers, a continuous printing method may be adopted, or a discontinuous, i.e., broken-filament, printing method may be adopted according to actual needs.

[0104] In this way, by adopting the method of continuous fiber uninterrupted planning, the continuity of the tow can be ensured while printing the woven structure, the integrity of the structure can be achieved, and the mechanical properties of the parts can be further enhanced.

[0105] It can be understood that each deposited layer is not in the same plane, thereby forming a three-dimensional woven structure.

[0106] In another preferred embodiment of the present invention, a UAV frame is also provided, which can be prepared by respectively using the above-mentioned two additive manufacturing methods based on local reinforcement of double continuous fiber weaving.

[0107] For better understanding, the present invention is further described below in conjunction with several specific examples, but the processing technology is not limited thereto, and the content of the present invention is not limited thereto.

[0108] Unless otherwise specified, the raw materials and equipment used in the present invention are commercially available, and the nozzle diameter of the print head used is 0.4 mm.

[0109] Example 1

[0110] Taking the preparation of a 50mm×50mm×20mm flat plate part using continuous carbon fiber and glass fiber prepreg filaments and PLA resin pellets as an example, the following steps are included:

[0111] [Preparation of continuous carbon fiber prepreg]

[0112] Toray's 1K continuous carbon fiber precursor is fed into the impregnation mold through a traction device at a speed of 3mm / s. At the same time, Chimei's PLA resin particles are poured into the hopper and enter the impregnation mold under the action of a twin-screw extruder. The impregnation mold is heated to 250°C to melt the PLA resin particles. Toray's continuous carbon fiber precursor is evenly wrapped with PLA resin and rolled up through a nozzle under the action of a traction roller to obtain a continuous carbon fiber prepreg wire with a diameter of 1mm.

[0113] [Preparation of continuous glass fiber prepreg]

[0114] The SE1200 600Tex continuous glass fiber precursor of Shanghai Weiger is fed into the impregnation mold through a traction device at a speed of 3mm / s. At the same time, the PLA resin particles of Chimei are poured into the hopper and enter the impregnation mold under the action of the twin-screw extruder. The impregnation mold is heated to 250℃ to melt the PLA resin particles. The SE1200 600Tex continuous glass fiber precursor of Shanghai Weiger is evenly wrapped with PA resin and rolled up through a nozzle under the action of a traction roller to obtain a continuous glass fiber prepreg wire with a diameter of 1mm.

[0115] [Additive Manufacturing]

[0116] 1. Place different continuous fiber prepreg wires into the print heads of their respective printing systems (the print head for printing continuous carbon fiber prepreg wires is defined as print head No. 1, and the print head for printing continuous glass fiber prepreg wires is defined as print head No. 2). Convert the drawn flat 3D model into an STL file and import it into the slicing software Simplify3D. Set the process parameters to generate G code and import it into the printer.

[0117] 2. In the first step, preheat the substrate to 60°C and set the printing parameters of continuous carbon fiber prepreg filaments and continuous glass fiber prepreg filaments, which are: wire feeding speed of 5mm / s, printing temperature of 250°C, single-pass layer thickness of 0.7mm, and printing path width of about 0.4mm.

[0118] The second step is to use continuous carbon fiber prepreg filaments to print a 50mm×50mm square frame. The filaments remain continuous, such as Figure 6 As shown in part ①, it starts from position 1 and moves to position 2, and then moves to position 3, position 4, position 5, and position 6 in sequence to complete the printing of the outer frame structure.

[0119] Continue to use continuous carbon fiber prepreg filaments to print the first deposition layer at intervals of 2 mm in the horizontal direction inside the square frame, starting from position 6, and proceeding to position 7, position 8, position 9, position 10, position 10, position 11, position 12, and position 13 in sequence to complete the continuous printing of the first deposition layer.

[0120] The third step is to print the second deposition layer above it at a vertical interval of 2 mm. The material is continuous glass fiber prepreg wire, such as Figure 6 As shown in the second part, starting from position 1, in turn, position 2, position 3, position 4, position 5, position 6, position 7, position 8, with the square frame as the transition to keep the continuous fiber unbroken, the printing of the second deposition layer is completed.

[0121] In the fourth step, at the overlap of the previous two layers of deposition paths, a single-pass broken-filament printing method is used to print continuous carbon fiber prepreg filaments in a +45° direction and let the path pass through their overlap, and the two ends overlap with the outer frame structure (such as Figure 3 ③ part of the orange line).

[0122] The fifth step is to print the continuous carbon fiber prepreg wire in the gap left by the previous continuous carbon fiber prepreg wire deposition (path as shown in Figure 6 The orange line in part ③ of the figure shows the starting point of the deposition path, which is the end point of the first deposition path ( Figure 6 ① part of the position 13).

[0123] Step 6: Print the continuous glass fiber prepreg wire in the gap left by the previous continuous glass fiber prepreg wire deposition (path as shown in Figure 6 The starting point of the deposition path is the end point of the deposition path in the third step ( Figure 6 The second part is position 8).

[0124] Step 7: Print the continuous glass fiber prepreg filament at the overlap of the first two deposition paths at a -45° direction and pass through their overlap, with both ends overlapped with the outer frame structure (such as Figure 3(the bright yellow line in the ⑥ part).

[0125] 3. Repeat the above process alternately until the height in the Z direction reaches 20 mm, then end the printing and obtain the FDM print.

[0126] Example 2

[0127] Taking the preparation of a 50mm×50mm×20mm flat plate part using continuous carbon fiber and glass fiber prepreg filaments and PLA resin pellets as an example, the following steps are included:

[0128] [Preparation of continuous carbon fiber prepreg]

[0129] Toray's 1K continuous carbon fiber precursor is fed into the impregnation mold through a traction device at a speed of 3mm / s. At the same time, Chimei's PLA resin particles are poured into the hopper and enter the impregnation mold under the action of a twin-screw extruder. The impregnation mold is heated to 250°C to melt the PLA resin particles. Toray's continuous carbon fiber precursor is evenly wrapped with PLA resin and rolled up through a nozzle under the action of a traction roller to obtain a continuous carbon fiber prepreg wire with a diameter of 1mm.

[0130] [Preparation of continuous glass fiber prepreg]

[0131] The SE1200 600Tex continuous glass fiber precursor of Shanghai Weiger is fed into the impregnation mold through a traction device at a speed of 3mm / s. At the same time, the PLA resin particles of Chimei are poured into the hopper and enter the impregnation mold under the action of the twin-screw extruder. The impregnation mold is heated to 250℃ to melt the PLA resin particles. The SE1200 600Tex continuous glass fiber precursor of Shanghai Weiger is evenly wrapped with PA resin and rolled up through a nozzle under the action of a traction roller to obtain a continuous glass fiber prepreg wire with a diameter of 1mm.

[0132] [Additive Manufacturing]

[0133] 1. Place different continuous fiber prepreg wires into the print heads of their respective printing systems (the print head for printing continuous carbon fiber prepreg wires is defined as print head No. 1, and the print head for printing continuous glass fiber prepreg wires is defined as print head No. 2). Convert the drawn flat 3D model into an STL file and import it into the slicing software Simplify3D. Set the process parameters to generate G code and import it into the printer.

[0134] 2. In the first step, preheat the substrate to 60°C and set the printing parameters of continuous carbon fiber prepreg wire and continuous glass fiber prepreg wire, which are: wire feeding speed of 5mm / s, printing temperature of 250°C, single-pass layer thickness of 0.7mm, and printing path width of about 0.4mm.

[0135] The second step is to use continuous carbon fiber prepreg filaments to print a 50mm×50mm square frame. The filaments remain continuous, such as Figure 6 As shown in part ①, it starts from position 1 and moves to position 2, and then moves to position 3, position 4, position 5, and position 6 in sequence to complete the printing of the outer frame structure.

[0136] Continue to use continuous carbon fiber prepreg filaments to print the first deposition layer at intervals of 2 mm in the horizontal direction inside the square frame, starting from position 6, and proceeding to position 7, position 8, position 9, position 10, position 10, position 11, position 12, and position 13 in sequence to complete the continuous printing of the first deposition layer.

[0137] The third step is to print the second deposition layer above it at a vertical interval of 2 mm. The material is continuous glass fiber prepreg wire, such as Figure 6 As shown in the second part, starting from position 1, in turn, position 2, position 3, position 4, position 5, position 6, position 7, position 8, with the square frame as the transition to keep the continuous fiber unbroken, the printing of the second deposition layer is completed.

[0138] The fourth step is to print a rectangular structure between the gaps between each adjacent single-pass deposition layer in the first deposition layer and the second deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the second deposition layer and the first deposition layer, respectively (e.g. Figure 4 ③ part).

[0139] The fifth step is to print the continuous carbon fiber prepreg wire in the gap left by the previous continuous carbon fiber prepreg wire deposition (path as shown in Figure 6 The orange line in part ③ of the figure shows the starting point of the deposition path, which is the end point of the first deposition path ( Figure 6 ① part of the position 13).

[0140] Step 6: Print the continuous glass fiber prepreg wire in the gap left by the previous continuous glass fiber prepreg wire deposition (path as shown in Figure 6 The starting point of the deposition path is the end point of the deposition path in the third step ( Figure 6 The second part is position 8).

[0141] 3. Repeat the above process alternately until the height in the Z direction reaches 20 mm, then end the printing and obtain the FDM print.

[0142] Example 3

[0143] A 50 mm×50 mm×20 mm open hole flat plate part was prepared using the same materials and methods as in Example 1, and the diameter of the hole was 20 mm.

[0144] Comparative Example 1

[0145] The printed parts and materials used are the same as those in Example 1.

[0146] The difference between the preparation process and Example 1 is that in the additive manufacturing process, after the first step, the second step, the third step, the fifth step and the sixth step are performed in sequence, the above process is repeated alternately until the height in the Z direction reaches 20 mm, and the printing is terminated to obtain an FDM print.

[0147] Comparative Example 2

[0148] The printed parts and materials used are the same as in Example 1, but only continuous carbon fiber is used for printing.

[0149] The difference between the preparation process and Example 1 is that, in the additive manufacturing process, only continuous carbon fiber is used to perform the first step, the second step, the third step, the fifth step and the sixth step in sequence, and the above process is repeated alternately until the height in the Z direction reaches 20 mm and the printing is terminated to obtain an FDM print.

[0150] Comparative Example 3

[0151] The printed parts and materials used are the same as in Example 1, but only continuous carbon fiber is used for printing.

[0152] The difference between the preparation process and Example 1 is that, in the additive manufacturing process, only continuous carbon fiber is used to print in the horizontal direction in sequence, with no gap between adjacent single-pass deposition layers, and then printing in the vertical direction, with no gap between adjacent single-pass deposition layers. The above process is repeated alternately until the height in the Z direction reaches 20 mm, and the printing is terminated to obtain an FDM print.

[0153] Comparative Example 4

[0154] A 50 mm×50 mm×20 mm open hole flat plate part was prepared using the same materials and methods as in Comparative Example 1, and the diameter of the hole was 20 mm.

[0155] test

[0156] The molded parts of Examples 1-2 and Comparative Examples 1-3 were subjected to strength tests such as tensile tests, and the test results are shown in Table 1.

[0157] Table 1

[0158]

[0159] The results show that the mechanical properties of resin-based composite parts printed using the method of the present invention are reduced by about 17% compared to those using only carbon fiber, but the cost is reduced by about 45%. This is because about half of the glass fiber is used in the process of printing the parts. Although the mechanical properties of glass fiber are one-half to one-third less than the tensile strength of carbon fiber, its selling price is only one-tenth of that of carbon fiber, which greatly reduces the cost of printing.

[0160] We have improved the double continuous fiber prepreg wire weaving process to find the balance between cost and performance. In the weaving structure, two continuous fiber prepreg wires of different strengths are used to deposit the woven grid structure, and high-strength continuous fiber prepreg wires are woven through the overlap of the two continuous fiber prepreg wires. Or, a "lock-type" rectangular structure formed by adding high-strength continuous fiber prepreg wires to the overlap of the two continuous fiber prepreg wires is formed to form a local reinforcement structure. While enhancing the bonding strength between layers, it avoids the fracture problem caused by stress concentration at the opening of parts, improves the mechanical properties to a certain extent, and is more suitable for the requirements of parts that require openings such as drone frames.

[0161] When the opening of the composite material is subjected to stress load, the continuous fiber of the conventional process is interrupted at the opening, resulting in no direction of force transmission at the opening. By comparing Example 3 with Comparative Example 4, the results are as follows: Figure 7 As shown, it can be seen that by adopting the additive manufacturing method of the present invention, through the design of the structure, the load is transmitted in three dimensions through the enhanced path, avoiding the phenomenon of stress concentration at the opening ( Figure 7 A part, while the hole part of the structure without the present invention has stress concentration ( Figure 7 of the Regulations).

[0162] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. An additive manufacturing method based on double continuous fiber braiding local reinforcement, characterized in that: include: S11, Raw material silk making Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber; S21, Fused Deposition Modeling The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows: S211, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain an outer frame structure of the printed part; S212, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range; S213, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range; S214, the first print head continues to deposit the third deposition layer in a single pass, wherein in the third deposition layer, the single deposition layer passes through the overlapping point of the first deposition layer and the second deposition layer, and both ends overlap with the outer frame structure; S215, the first print head continues to deposit the fourth deposition layer between the gaps of each adjacent single-pass deposition layer in the first deposition layer, and then the second print head deposits the fifth deposition layer between the gaps of each adjacent single-pass deposition layer in the second deposition layer; S216, the second print head continues to deposit the sixth deposition layer in a single pass, wherein in the sixth deposition layer, the single deposition layer passes through the overlapping point of the fourth deposition layer and the fifth deposition layer, and both ends overlap with the outer frame structure; S217. Repeat steps S211, S212, S213, S214, S215 and S216, accumulating layer by layer until deposition is completed to obtain a printed part.

2. An additive manufacturing method based on double continuous fiber braiding local reinforcement, characterized in that: include: S12, Raw material silk making Respectively wrapping the surfaces of the precursor of the first continuous fiber and the precursor of the second continuous fiber with a resin substrate to obtain a first prepreg wire material and a second prepreg wire material for standby use; wherein the precursor strength of the first continuous fiber is higher than the precursor strength of the second continuous fiber; S22, Fused Deposition Modeling The first prepreg wire material and the second prepreg wire material obtained in step S1 are respectively fed into the first print head and the second print head of the printer, and the fused deposition modeling process is adopted to perform printing according to a preset program. The printing process is as follows: S221, the first print head deposits the first prepreg wire material on the substrate according to the planned path to obtain an outer frame structure of the printed part; S222, the first print head continues single-pass interval deposition inside the outer frame structure obtained in step S21 to obtain a first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within the first spacing range; S223, the second print head deposits the second deposition layer in a single-pass interval in a manner orthogonal to the first deposition layer, and the gap between adjacent single-pass deposition layers is maintained within a second spacing range; S224, the first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the first deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the second deposition layer; The first print head prints a rectangular structure between the gaps between each adjacent single-pass deposition layer in the second deposition layer, and the rectangular structure overlaps the single-pass deposition layer in the first deposition layer; S225, the first print head continues to deposit between the gaps of each adjacent single-track deposition layer in the first deposition layer, and the single-track deposition layer overlaps the rectangular structure; The second print head deposits between the gaps between each adjacent single-track deposition layer in the second deposition layer, and the single-track deposition layer overlaps the rectangular structure; S226. Repeat steps S221, S222, S223, S224 and S225, accumulating layer by layer until deposition is completed to obtain a printed part.

3. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The first continuous fibers include a mixture of one or more of carbon fibers, carbon nanotube fibers, aramid fibers, ceramic fibers, and titanium fibers.

4. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The second continuous fibers include a mixture of one or more of glass fibers, basalt fibers, boron fibers, copper fibers, and aluminum fibers.

5. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The resin substrate includes a mixture of one or more of PLA material, ABS resin material, PEEK material, PEKK material, nylon material, PEI material, PAEK material, polycarbonate material, and polyimide material.

6. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The first spacing is greater than or equal to the width of the deposition path of the first deposition layer; the second spacing is greater than or equal to the width of the deposition path of the second deposition layer.

7. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The specific parameters of the first print head include: The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

8. The additive manufacturing method based on double continuous fiber braiding local reinforcement according to claim 1 or 2, characterized in that: The specific parameters of the second print head include: The print head nozzle diameter is 0.2~1mm, the printing temperature is 180~260℃, the temperature of the hot bed is 60~120℃, the feed speed is 1~10cm / s, and the printing layer height is 0.1~0.5mm.

9. A UAV frame, prepared by the additive manufacturing method based on double continuous fiber braiding local reinforcement as described in claim 1.

10. A drone frame, prepared by the additive manufacturing method based on double continuous fiber braiding local reinforcement as described in claim 2.

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