Process for reinforcing continuous fiber additively manufactured laminates

Abstract

A method for manufacturing composite parts using a 3D printer. This method involves forming a part by depositing a plurality of part layers on top of each other in a continuous manner, wherein each part layer is deposited by laying multiple rows of filaments made of a thermoplastic composite material. Reinforcing Z-pins are then inserted through the part layers to reinforce the part in the Z direction. A plurality of additional part layers are then deposited on top of each other in a continuous manner on the part layer including the reinforcing Z-pins, wherein each additional part layer is also deposited by laying multiple rows of filaments made of a thermoplastic composite material. Reinforcing Z-pins are also inserted through the additional part layers to reinforce the part in the Z direction.

Description

Technical Field

[0001] This disclosure generally relates to a method for laminating thermoplastic composite structures, and more specifically, to a method for laminating thermoplastic composite structures comprising providing reinforcing Z-shaped pins through the layers of the structure. Prior Technology

[0002] Many structural components and parts in aircraft, satellites, spacecraft, and other structures require lightweight yet robust construction to meet their intended uses. To meet these requirements, composite structures comprising multiple layers are typically used, such as fiberglass layers, fiber-reinforced plastic layers, and carbon fiber layers. For example, some aircraft surface structures comprise around thirty layers, each approximately 0.005–0.030 inches thick. Generally, these composite layers are formed by laying out a pattern of interwoven fibers (e.g., carbon fibers) impregnated in a liquid resin, which is then cured by heating, thus hardening the composite. Using suitable bonding techniques, such as co-curing and adhesive bonding, the layers are joined or secured together.

[0003] One known technique for manufacturing some of these parts using carbon fiber composite technology involves laying multiple layers of carbon fiber onto a tool, wherein each layer or sheet of carbon fiber comprises carbon fibers impregnated with resin, and wherein the fibers are interwoven into a fabric or strip. The carbon fiber layers are laid on the tool in a continuous stacking manner, wherein each group of predetermined numbers of layers undergoes a vacuum and heating step to compress the layers together and remove air, which could otherwise cause a loss of part integrity. Once all layers have been established, a vacuum membrane or bag is placed on the assembled layers and sealed to the tool, wherein the bag is evacuated to a certain vacuum pressure. The tool and sealed part are then placed in an autoclave or furnace to cure the resin and form a hardened part.

[0004] In these types of composite laminates, the fiber orientation typically exhibits high strength in the X and Y directions along the fiber length, but relatively low strength in the Z direction across the fibers. Therefore, it is known in the art to provide mechanical fasteners inserted across these layers to offer increased strength in the Z direction. A well-known technique is called Z-pinning, which utilizes Z-pins inserted in the Z direction across the composite laminate to improve delamination resistance, increase out-of-plane shear force, and increase damage tolerance by providing reinforcement in the Z direction of the structure rather than simply relying on adhesive bonding.

[0005] Typical Z-pins are very small in diameter, for example, 0.010–0.020”, and a large number of these Z-pins (e.g., 60–600) can be interleaved into a laminate structure per square inch. In one insertion technique, with the laminate in a partially cured or pre-preg state, the Z-pins are partially inserted into the top surface of one of the laminates, where the resin is still softened and flexible. An ultrasonic tool is positioned over a group of Z-pins, where ultrasonic energy generates a degree of heat that further softens the resin and allows the Z-pins to be inserted through the laminate without disturbing the fibers.

[0006] Traditional Z-pins are cylindrical in shape. However, more modern Z-pins come in a variety of shapes and sizes. U.S. Patent No. 6,514,593, entitled "Mechanically Locking Z-Pin" to Jones et al., is assigned to the assignee of this application and is incorporated herein by reference, discussing the disadvantages of traditional Z-pins and proposing Z-pins of a specific shape with increased Z-pinning capability in the Z direction. Z-pins of this specific shape generally offer superior performance compared to traditional cylindrical Z-pins because they reduce pullout from the composite matrix by increasing the surface area for adhesive bonding, mechanically locking into the matrix, and locking into the fiber reinforcement. However, due to the shape of these types of Z-pins, they are more difficult to insert into the laminated structure using ultrasonic tools while it is in the prepreg state, because the shape of the Z-pin alters the position of the fibers in the composite layer upon insertion. Typically, this type of damage to the fibers during the insertion of Z-pins of this specific shape can affect the structural integrity of the layer.

[0007] Traditional complex composite manufacturing methods (e.g., autoclave-cured hand lay-up, pre-placement of fibers, tapes, etc.) are labor-intensive, expensive, require long lead times and costly tools, and typically require skilled manufacturing technicians. Therefore, alternative methods have been developed.

[0008] Fused filament fabrication (FFF) is an additive manufacturing (AM) process for 3D printing. More specifically, the FFF process feeds a raw material, such as a filament from a mandrel or granules in a hopper, to a heated nozzle, from which it is extruded as a heated, molten filament to be deposited as adjacent rows of strips to form layers, wherein the molten filament begins to harden immediately upon being extruded from the nozzle. Multiple layers in a specific configuration are built in this way to produce desired parts. A known exemplary system is the scalable composite robotic additive manufacturing (SCRAM) system available from Electroimpact, an industrial-grade, true 6-axis continuous fiber-reinforced 3D printer that enables tool-free, rapid manufacturing of aerospace-grade integrated composite structures.

[0009] Various materials can be used as raw materials, such as high-performance amorphous or semi-crystalline thermoplastics, including polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polystyrene (PPSF or PPSU), polyetherimide (PEI), and polystyrene (PPS). Other materials that may be suitable for FFF include acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA), polycarbonate (PC), polyamide (PA), polystyrene (PS), lignin, rubber, carbon fiber, glass fiber, quartz fiber, Kevlar fiber, ultra-high molecular weight polyethylene (UHMWPE), Dyneema, impact-resistant polystyrene (HIPS), nylon, high-density polyethylene (HDPE) eutectic material, plasticine, room temperature vulcanizing (RTV) silicone, etc.

[0010] All laminated continuous fiber composites manufactured using placement heads and bonded pre-impregnated filaments or other configurations (e.g., braided tape, braided tube, etc.) will lack interlaminar strength due to the lack of interlaminar reinforcement.

[0011] U.S. Patent No. 9,782,928, granted to Barnes et al. on October 10, 2017, is assigned to the assignee of this application and is incorporated herein by reference. It describes a system for reinforcing thermoplastic polymer workpieces using linear Z-pins that have been at least partially formed by a lamination manufacturing process. An ultrasonic energy source applies ultrasonic energy to the Z-pins to ultrasonically heat them, thereby locally melting the workpiece material on the subject surface and / or the workpiece body to create molten workpiece material. One end of the Z-pin is inserted into the molten workpiece material to create an inserted Z-pin length, which is maintained by solidifying the molten workpiece material within the workpiece around the inserted Z-pin length to reinforce the workpiece. Summary of the Invention

[0012] The following discussion discloses and describes a method for manufacturing composite parts using a 3D printer. This method involves forming a part by depositing multiple part layers on top of each other in a sequential manner, wherein each part layer is deposited by laying multiple rows of filaments made of thermoplastic composite material. Reinforcing Z-pins are then inserted through the part layers to reinforce the part in the Z direction. Multiple additional part layers, including the reinforcing Z-pins, are then deposited on top of each other in a sequential manner, wherein each additional part layer is also deposited by laying multiple rows of filaments made of thermoplastic composite material. Reinforcing Z-pins are also inserted through the additional part layers to reinforce the part in the Z direction. Reinforcing Z-pins can be inserted through multiple layers to provide any suitable reinforcement configuration.

[0013] The additional features of this disclosure will become clear from the following description in conjunction with the accompanying drawings and the appended claims. Simple Explanation of the Diagram

[0014] [Figure 1] is an isometric view of a 3D printer including a robot and an end effector, with the end effector positioned relative to a part being manufactured on a build plate;

[0015] [Figure 2] is an illustration of a thermoplastic composite layered part manufactured by a laminated manufacturing process and reinforced by Z-pins;

[0016] [Figure 3] is an illustration of another thermoplastic composite layered part manufactured by a laminated manufacturing process and reinforced by Z-pins;

[0017] [Figure 4] is an illustration of another thermoplastic composite layered part manufactured by a laminated manufacturing process and reinforced by Z-pins;

[0018] [Figure 5] is an illustration of the end effector of the robot shown in Figure 1, used to provide holes in the part for receiving Z-pins; and

[0019] [Figure 6] is an illustration of the end effector of the robot shown in Figure 1, used to insert the Z-pin into the hole. Implementation

[0020] The following discussion of embodiments of the disclosure, including a method for manufacturing thermoplastic composite structures by lamination of reinforced Z-pins, is merely illustrative in nature and is not intended to limit the invention, or its application or use in any way.

[0021] This disclosure proposes an automated method to enhance the interlayer properties of a multilayered composite structure by inserting rods, filament bundles, pins, filaments, or whiskers (referred to herein as Z-pins or rods) in the Z-direction into the composite structure using thermal, mechanical, ultrasonic, chemical (solvent for softening) energy, or any combination thereof. The Z-pins directly contact the part surface while the attachment is inserted into the multilayering head. Insertion may occur during or after the build-up process, simultaneously with the multilayering process, or during layer addition. Z-pin insertion may occur in all or some layers, and may be staggered layer by layer or multiple layers, varying in all or only specific areas of the part. The pin tip and at least part of the pin body of the Z-pin are inserted into a hard, molten, or softened region of the workpiece material, and the insertion constitutes the main part or all of the Z-pin length. The inserted Z-pin length is maintained within the material volume by solidifying the molten workpiece material near the inserted Z-pin length to enhance the composite structure. This process can be performed manually or via automated and / or robotic manufacturing systems. By inserting Z-pins into the structure during the lamination process in the stacking process, interlaminar reinforcement will critically strengthen the structure in the thickness direction for structural composite materials. It should be noted that while thermoplastic composites are preferred for the techniques discussed herein, thermosetting composites may also be used, which may have been preheated to mechanically and physically exhibit thermoplasticity.

[0022] Figure 1 is an isometric view of a 3D printer 10 capable of creating parts using an FFF process that includes providing Z-pin insertions as discussed above. The machine 10 is intended only as a representative of any additive manufacturing machine capable of performing the methods and processes discussed herein. The machine 10 includes a robot 12 having a base portion 14, an extension arm 16 coupled to the base portion 14 via a rotation and pivot joint 18, and a working arm 20 coupled to the extension arm 16 opposite to the base portion 14 via an elbow pivot joint 22. An end effector 26 is coupled to the working arm 20 at an angle opposite to the pivot joint 22 via a pivot joint 28 having a coupling mechanism 30. The robot 12 is intended to represent any suitable positioning device for the end effector 26. The end effector 26 operates as a printhead assembly for depositing molten filaments to create complex composite structures as discussed herein. Various end effectors can be used, which operate in a specific manner and have specific characteristics, and can be attached to robot 12. It should be noted that during operation, machine 10 may or may not be positioned in an oven (not shown) to control the temperature of the printing process.

[0023] The end effector 26 includes a housing 34 and a rotatable connector 36 releasably connected to a coupling mechanism 30, and the end effector 26 is shown as transparent to reveal the various components within it. These components include multiple mandrels 40 on which a plurality of raw material filaments 42 of various materials are wound; a drive mechanism 44 for selectively and independently drawing the filaments 42 from the mandrels 40; a material extruder 48 through which the filaments 42 are drawn by the drive mechanism 44; a heater 46 for heating the extruder 48 and melting the filaments 42; and a nozzle 50 for extruding the molten filaments 42 from the end effector 26 so that they are deposited on a build plate 52 mounted on a platform 54. Since the part 56 is being built layer by layer on a support structure 58 formed on the build plate 52, the part 56 is shown as being manufactured by machine 10. The mandrel 40 may be mounted in the end effector 26 or remotely mounted together with the material to be supplied to the end effector 26 via a tube (not shown). Alternatively, the raw material may be supplied by granules instead of using filaments 42.

[0024] Figure 2 illustrates a structure 60 being manufactured using a lamination process (e.g., by machine 10). The structure 60 includes a lower laminate segment 62 having four layers 64 formed by laying multiple rows of square filaments side-by-side on the previous layers in the manner discussed above. Lines in the layers 64 indicate the orientation of the fibers 66 within the filaments and the direction in which the filaments are laid. Each layer 64 may have a thickness of 1 / 10,000 inch. It is evident that the filaments are laid from one layer 64 to the next at 90 degrees relative to each other by rotating the building plate 52 90 degrees as each layer 64 is completed. The filaments are made of a thermoplastic composite material, such as carbon fibers formed in a thermoplastic matrix or resin.

[0025] As discussed above, this type of structure, created by a laminated manufacturing process, may separate between layers 64, thus reducing the interlayer integrity of structure 60 in the Z direction. To reinforce structure 60, Z-shaped pins are provided through layers 64 in the Z direction. To achieve this in one embodiment, a needle 70 is inserted through layer 64 to form a hole 72 in layer 64, and then a rod 74 (Z-shaped pin) is inserted through the hole 72, wherein the rod 74 has a pointed tip 76 and a flat end 78. The needle 70 can form the hole 72 in any suitable manner. For example, the needle 70 can be ultrasonically vibrated to provide heat and insertion energy into layer 64, wherein the composite material of layer 64 is likely to be softened or flexible immediately after formation. Alternatively, the needle 70 can be heated by a suitable heat source to allow it to be inserted into layer 64. In a non-limiting embodiment, the rod 74 is a carbon fiber pultruded rod. The rod 74 may be shorter than the thickness of segment 62, have the same length as the thickness of segment 62, or be longer than the thickness of segment 62, such that the flat end 78 extends from segment 62 or any combination of these lengths. The spacing between rods 74 and the dimensions of rods 74 may be tailored to the specific application for which a particular structure 60 is to be manufactured. Furthermore, rods 74 may be placed in specific areas of segment 62 and not in other areas where reinforcement may not be required. More specifically, the surface density of rods 74 may be customized for a specific application, with higher density rods 74 in one location and lower density rods 74 in another. For example, the surface density of rods 74 may be 4% in one location and transition to 0% over a specified area or length of structure 60. Furthermore, while rods 74 are cylindrical in this embodiment, they may be Z-shaped pins of different shapes and configurations in other embodiments.

[0026] The method described above includes the steps of creating the hole 72 and then inserting the rod 74. In an alternative embodiment, the rod 74 may be made of sufficient material and have sufficient robustness, wherein, for example, ultrasonic energy may be used to drive them into the layer 64 without requiring the already created hole 72. Furthermore, in addition to using a needle to form the hole 72, a suitable solvent may be used to form the opening for the rod 74.

[0027] Once the rod 74 has been inserted into layer 64, structure 60 can continue to be manufactured. This is illustrated by a segment 80 having a layer 82 formed in the same manner as segment 62, which will be formed layer by layer on segment 62 as described. Layer 82 can be the same material as layer 64, or it can be a different material depending on the specific application and design. Once segment 80 is formed, it can also receive the rod in the same manner as segment 62, so that it is also reinforced in the Z direction. If the end of rod 74 protrudes from segment 62, for example, as shown by rod 84, then the filaments that subsequently form layer 82 can be guided around rod 74. The position of rod 74 in segment 80 can be offset from the position of rod 74 in segment 62, so that they are not aligned with each other. The number of layers formed before the insertion of rod 74 will depend on many factors, such as layer thickness, layer material, etc.

[0028] Figure 3 is an illustration of a thermoplastic composite structure 90 manufactured by a lamination process. The thermoplastic composite structure 90 includes a layer 92 formed by laying multiple rows of square filaments side by side on the previous layer in the manner discussed above. The illustration shows how the layer 92 can be stitched together by a rod 94 in a specific reinforcing configuration.

[0029] Figure 4 is an illustration of a thermoplastic composite structure 100 manufactured by a lamination process. The thermoplastic composite structure 100 includes a layer 102 formed by laying multiple rows of square filaments side by side on a previous layer in the manner discussed above. The illustration shows how the layer 102 can be stitched together by a rod 104 in another reinforcing configuration.

[0030] In practical implementation, multiple needles 70 can be used to simultaneously form multiple holes 72. Figure 5 is a front view of an end effector 110, which can replace end effector 26 and is coupled to coupling mechanism 30 on machine 10, allowing machine 10 to form holes 72. End effector 110 includes a plurality of needles 112, which can be used to simultaneously form a plurality of holes 72 in layer 64. An ultrasonic or heating source 114 vibrates and / or heats the needles 112, and device 116 applies downward pressure to the needles 112 to form holes 72.

[0031] Figure 6 is a front view of end effector 120, which replaces end effector 26 and is coupled to coupling mechanism 30 on machine 10, allowing machine 10 to insert rod 74 into bore 72. End effector 100 includes a plurality of rods 122, which are simultaneously inserted into a plurality of bores 72 of layer 64 and released by release mechanism 124. For certain applications, ultrasonic source 126 can be used to vibrate and drive rod 122 into layer 64 without providing bores 72.

[0032] The foregoing discussion discloses and describes only exemplary embodiments of the disclosure. From this discussion, as well as from the accompanying drawings and the claims, those skilled in the art will readily understand that various changes, modifications, and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.

[0033] 10: 3D Printing Machine 12: Robot 14: Base section 16: Extend your arms 18: Rotary and pivot joints 20: Working arm 22: (Elbow pivot) Joint 26: End effector 28: Pivot Joint 30: Coupling mechanism 34: Outer shell 36: Rotatable connector 40: Mandrel 42: (Raw material) fine filaments 44: Drive mechanism 46: Heater 48: (Materials) Extruder 50: Nozzle 52: Construction board 54: Platform 56: Parts 58: Supporting Structure 60: Structure 62: (Lower stacked) section 64: Floor 66: Fiber 70: needle 72: Kong 74: Rod body 76: Tip 78: Flat end 80: (Upper) Section 82: Floor 84: Rod body 90: Thermoplastic composite structure 92: Floor 94: Rod body 100: Thermoplastic composite structure 102: Floor 104: Rod body 110: End effector 112: Needle 114: Ultrasound or heating source 116: Device 120: End effector 122: Rod body 124: Release mechanism 126: Ultrasonic source

Claims

1. An automated method for manufacturing composite parts, the method comprising: A plurality of component layers are deposited sequentially on top of each other, wherein each layer is deposited by laying multiple rows of filaments made of thermoplastic composite material; a plurality of reinforcing Z-pins are inserted through the component layers to reinforce the composite component in the Z direction, wherein inserting the plurality of reinforcing Z-pins through the component layers includes forming a plurality of holes through the component layers and then inserting the plurality of reinforcing Z-pins into the holes, and at least a portion of the reinforcing Z-pins having their rear ends protruding from the component layers; a plurality of additional component layers are deposited sequentially on top of each other on the component layers including the reinforcing Z-pins, wherein each additional component layer is deposited by laying multiple rows of filaments made of thermoplastic composite material, wherein at least a portion of the additional component layers have the multiple rows of filaments laid around the rear end of the reinforcing Z-pin; and reinforcing Z-pins are inserted through the additional component layers to reinforce the composite component in the Z direction.

2. An automated method for manufacturing composite parts as described in claim 1, wherein, The reinforcing Z-pins of at least a portion of the component layers and the additional component layers are misaligned and not aligned with each other.

3. An automated method for manufacturing composite parts as described in claim 1, wherein, Inserting reinforcing Z-pins involves fully inserting such reinforcing Z-pins through such part layers.

4. An automated method for manufacturing composite parts as described in claim 1, wherein, Inserting reinforcing Z-pins involves inserting such reinforcing Z-pin portions through such part layers.

5. An automated method for manufacturing composite parts as described in claim 1, wherein, The insertion of reinforced Z-pins includes such reinforced Z-pins providing a higher density in one location than in other locations.

6. An automated method for manufacturing composite parts as described in claim 5, wherein, Inserting reinforcing Z-pins involves changing the surface density of these reinforcing Z-pins from higher density locations to lower density locations.

7. An automated method for manufacturing composite parts as described in claim 1, wherein, Inserting reinforcing Z-pins through the component layers includes ultrasonic vibration of the reinforcing Z-pins and forcing the reinforcing Z-pins into the component layers.

8. An automated method for manufacturing composite parts as described in claim 1, wherein, Creating multiple holes involves using at least one needle.

9. An automated method for manufacturing composite parts as described in claim 8, wherein, The formation of multiple holes includes at least one needle for ultrasonic seismic vibration.

10. An automated method for manufacturing composite parts as described in claim 8, wherein, Forming multiple holes involves heating at least one needle.

11. An automated method for manufacturing composite parts as described in claim 8, wherein, Forming a plurality of holes involves simultaneously inserting a plurality of needles into the layers of such components.

12. An automated method for manufacturing composite parts as described in claim 1, wherein, Forming multiple pores involves the use of solvents.

13. An automated method for manufacturing composite parts as described in claim 1, wherein, These reinforced Z-shaped pins are rods.

14. An automated method for manufacturing composite parts as described in claim 13, wherein, These rods are carbon fiber pultruded rods.

15. An automated method for manufacturing composite parts as described in claim 1, wherein, This thermoplastic composite material is carbon fiber in a thermoplastic matrix.

16. A method for manufacturing a composite part, the method comprising: A plurality of component layers are deposited on top of each other in a continuous manner, wherein each component layer is deposited by laying multiple rows of filaments made of thermoplastic composite material; simultaneously, a plurality of reinforcing rods are inserted through the component layers to reinforce the composite component in the Z direction, such that at least a portion of the rear ends of the reinforcing rods extend from the component layers; a plurality of additional component layers are deposited on top of each other in a continuous manner on the component layers including the reinforcing rods, wherein each additional component layer is deposited by laying multiple rows of filaments made of thermoplastic composite material, wherein at least a portion of the additional component layers have the multiple rows of filaments laid around the rear ends of the reinforcing rods; and reinforcing rods are inserted through the additional component layers to reinforce the composite component in the Z direction.

17. The method for manufacturing a composite part as described in claim 16, wherein, The reinforcing rods include those that provide a higher density at one location than at other locations.

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