Interlayer reinforcement method for continuous fiber additive manufacturing based on pressure-injected z-pin-like structure

Abstract

An interlayer reinforcement method for continuous fiber additive manufacturing based on a pressure-injected Z-pin-like structure. In continuous fiber additive manufacturing, a grid framework is printed within each horizontal slice by using continuous fibers, and grid holes are regularly arranged and combined, such that an intermittent interlayer through-space is formed, and then a thermosetting resin material is pressure-injected into the space to create a continuous longitudinally reinforcing Z-pin-like structure (2) that spans slice layers. In addition, an extrusion pressure is controlled during resin filling, and the resin is guided to infiltrate and progressively fill voids between layer channels that are commonly present in continuous fiber additive manufacturing, such that concomitant void defects in additive manufacturing are suppressed, interlayer reinforcement is ultimately achieved, and the overall performance is improved.

Description

[Corrected according to Rule 26 26.01.2025] A continuous fiber additive manufacturing interlaminar reinforcement method based on pressure injection type Z-pin structure TECHNICAL FIELD

[0001] The application belongs to the field of high-end equipment manufacturing technology; in particular, it relates to a continuous fiber additive manufacturing interlaminar reinforcement method based on pressure injection type Z-pin structure. BACKGROUND

[0002] The inherent property of "layer-by-layer stacking" of continuous fiber additive manufacturing determines that it has a weak interlaminar bonding state (manifested as the distribution of interlayer porosity defects), which is the key to limiting the application of continuous fiber additive manufacturing. Different researchers have carried out extensive research on how to realize interlaminar reinforcement for continuous fiber additive manufacturing, including the use of energy sources such as lasers, infrared radiation, and hot rollers during the forming process to promote the interlaminar molecular chain to intertwine and connect, and the use of ultrasonic compaction, vacuum hot pressing, etc. to reduce interlaminar porosity defects after forming.

[0003] The above process methods have certain limitations on the shape of the target component (such as being suitable for flat plate parts or requiring the use of molds, etc.), which weakens the superiority of the design freedom of additive manufacturing technology, and because the traditional additive manufacturing structure based on horizontal slicing itself lacks longitudinal reinforcement structure, the reinforcement effect of the above methods is limited.

[0004] In fact, for traditional composite laminates, the mainstream technology to improve interlaminar performance is Z-pin technology. Compared with other three-dimensional reinforcement technologies (three-dimensional weaving, stitching toughening), this technology has the advantages of easier operation and easier control of process quality, and is especially suitable for local reinforcement, preparation of lightweight high-strength sandwich structures, and composite material connection. This technology is based on the concept of discontinuous stitching lines, and uses the "pinning" bridging effect of micro-diameter Z-pins. At present, it mainly uses ultrasonic technology to implant needle-shaped reinforcing fibers in the thickness direction of the component to improve the performance in the thickness direction of the component, but at the same time it will cause local material damage, thereby losing part of the in-plane performance.

[0005] In summary, the lack of longitudinal reinforcement structure is the core reason for the weak interlaminar bonding state of current additive manufacturing components, and although the traditional Z-pin technology implants reinforcing fibers in the thickness direction of the component with external force, it can introduce longitudinal structure and improve interlaminar performance, but it is easy to cause damage to the in-plane performance. Therefore, considering the inherent distribution of interlayer porosity defects of additive manufacturing components, if Z-pin structures are directly implanted into the components, it will instead enlarge the original defects and cause a decrease in overall performance, i.e. the direct combination of the two technologies has limited effect. SUMMARY

[0006] To solve the above problems, the application discloses a continuous fiber additive manufacturing interlayer reinforcement method based on a pressure injection type Z-pin structure, aims to provide a continuous fiber and thermosetting resin spatial composite path generation scheme, and realizes the construction of a continuous longitudinal reinforcement type Z-pin structure across the slice layer by pressure injection of a thermosetting resin material in the continuous fiber additive manufacturing based on horizontal slices; at the same time, by controlling the injection pressure, the resin can be guided to penetrate and gradually fill the interlayer pores commonly existing in the continuous fiber additive manufacturing, the pore network is replaced by a resin network, the interlayer bonding performance of the continuous fiber additive manufacturing is reinforced, the accompanying pore defects of the additive manufacturing are inhibited, and finally the overall performance of the product is improved.

[0007] To achieve the above object, the application provides the following scheme:

[0008] A continuous fiber additive manufacturing interlayer reinforcement method based on a pressure injection type Z-pin structure is adopted to perform composite printing and forming by using a continuous fiber printing head and a thermosetting resin extrusion head, wherein the continuous fiber printing head sequentially prints a grid-shaped frame according to the printing layer sequence; the thermosetting resin extrusion head performs pressure injection filling of resin material in the grid holes in the corresponding printing layer; the grid holes in the overall continuous fiber frame form intermittent through spaces between layers in the Z direction, and the extrusion filled thermosetting resin forms a Z-pin structure in the space, and under the control of the extrusion pressure, the resin penetrates and fills the pores between the layers of the continuous fiber frame, and finally realizes the effect of continuous fiber additive manufacturing interlayer reinforcement. The method steps are as follows:

[0009] Step 1: setting the printing layer thickness t, the grid hole size a x b of the continuous fiber grid-shaped frame, the type of the Z-pin structure unit, and the basic extrusion pressure value p corresponding to the above {t, a x b} parameter group and the extrusion pressure coefficient group {K2, K3} corresponding to different Z-pin structure unit types;

[0010] Step 2: based on the printing layer thickness t, the grid hole size a x b of the continuous fiber grid-shaped frame, and the type of the Z-pin structure unit, the model segmentation processing is performed on the target model, which is divided into a continuous fiber frame structure space region model and a Z-pin structure space region model, both of which share a space coordinate system and have the same definition sequence of slice layers;

[0011] Step 3: for the continuous fiber frame structure space region, the path generation of the continuous fiber grid frame of each horizontal slice layer is performed, and the printing path information {G F} of each horizontal slice of the continuous fiber printing head is obtained, that is, the i-th layer information is recorded as {G Fi};

[0012] Step 4: for the Z-pin structure space area, horizontal slicing is performed, the filling area corresponding to each Z-pin structure in each horizontal slice is marked, and the extrusion information {G M} of the thermosetting resin extrusion head in the relevant horizontal slice layer is obtained in combination with the basic extrusion pressure value p and the extrusion pressure coefficient set {K2, K3} of different Z-pin structure unit types, the extrusion information including the extrusion position and the corresponding extrusion pressure of the pressure injection operation in each slice, and the i-th layer information is denoted as {G Mi};

[0013] Step 5: the printing information of the continuous fiber printing head and the extrusion information of the thermosetting resin extrusion head in the relevant horizontal slice layer are combined in the order from bottom to top of each horizontal slice layer, and the final continuous fiber printing head printing information and the thermosetting resin extrusion head extrusion information {G} corresponding to each horizontal slice layer are output, and the i-th layer information is denoted as {G i};

[0014] Step 6: the continuous fiber printing head and the thermosetting resin extrusion head are used to cooperatively print and form according to the automatic operation information, and after the printing is completed, a static curing process is performed.

[0015] Further, the cross section of the thermosetting resin extrusion head is rectangular, and the size is consistent with the size a x b of the grid hole, and the thermosetting resin extrusion head can be inserted into the grid hole to perform resin pressure injection filling.

[0016] Further, the Z-pin structure unit has two types of 2 layers and 3 layers in the through-layer depth, and the two types of structures are uniformly distributed in the form of units in the horizontal plane, but each specific structure unit has only one type of structure in the thickness direction and is distributed at intervals.

[0017] ① transverse interval uniform distribution, as shown in FIG. 5.

[0018] ② horizontal / vertical interval uniform distribution, as shown in FIG. 6.

[0019] Further, the Z-pin structure unit type corresponds to different thermosetting resin extrusion pressure coefficient sets {K2, K3}, K2 and K3 respectively correspond to the extrusion pressure coefficients required for the Z-pin structure filled with 2 layers and 3 layers of resin, and the coefficients are used for adjusting the basic extrusion pressure when filling the specific Z-pin structure.

[0020] The beneficial effects of the present application are as follows:

[0021] (1) Provide a continuous fiber and thermosetting resin space composite path generation scheme, by printing a grid framework in each horizontal slice of continuous fiber additive manufacturing, and arranging and combining the grid holes regularly to form an intermittent through-space between layers, and then using thermosetting resin material to perform pressure injection in the space, a continuous longitudinal reinforced Z-pin structure across the slice layer can be constructed, and interlayer reinforcement of continuous fiber additive manufacturing is realized.

[0022] (2) Based on the provided continuous fiber and thermosetting resin space composite path generation scheme, by controlling the extrusion pressure when the resin material fills the Z-pin structure, the resin can be guided to penetrate and gradually fill the interlayer pores commonly existing in continuous fiber additive manufacturing, thereby suppressing the associated pore defects of additive manufacturing without introducing other auxiliary energy fields, and ultimately improving the overall performance of the part. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of step 2 of the forming scheme of the continuous fiber print head and the thermosetting resin extrusion head for composite printing in the present application.

[0024] Figure 2 is a schematic diagram of the continuous fiber grid framework printing in step 5 of the forming scheme of the continuous fiber print head and the thermosetting resin extrusion head for composite printing in the present application.

[0025] Figure 3 is a schematic diagram of the thermosetting resin filling under extrusion information control in step 5 of the forming scheme of the continuous fiber print head and the thermosetting resin extrusion head for composite printing in the present application.

[0026] Figure 4 is a schematic diagram of step 6 of the forming scheme of the continuous fiber print head and the thermosetting resin extrusion head for composite printing in the present application.

[0027] Figure 5, Z-pin structure unit space distribution characteristic type-lateral spacing uniform distribution;

[0028] Figure 6, Z-pin structure unit space distribution characteristic type-lateral / longitudinal spacing uniform distribution.

[0029] Wherein, 1 - continuous fiber grid framework structure, 2 - Z-pin structure, 2-1 - Z-pin space filled with resin, 2-2 - pore space filled with resin, 3 - continuous fiber print head, 4 - thermosetting resin extrusion head, 5 - front view section. DETAILED DESCRIPTION

[0030] The present application is further illustrated by the following description and accompanying drawings, and it is to be understood that the same are intended to illustrate the application and not to limit the scope thereof. It is noted that the terms "front", "rear", "left", "right", "upper" and "lower" as used in the following description refer to directions in the drawings and the terms "inner" and "outer" refer to directions toward or away from the geometric center of the particular member.

[0031] The target part is a 11x7x2.5mm cube, the continuous fiber material is continuous carbon fiber reinforced PETG(polyethylene terephthalate-1,4-cyclohexane dimethanol) composite wire, and the thermosetting resin material is a mixture of bisphenol epoxy resin(FibreGlast System 4600) and curing agent((System 4690)). The thermosetting resin extrusion head 4 is rectangular in cross section, with dimensions consistent with the grid hole size, and is inserted into the grid hole for resin pressure injection filling.

[0032] The forming scheme of composite printing using the continuous fiber printing head 3 and the thermosetting resin extrusion head 4 in this case is as follows:

[0033] Step 1: set the printing layer thickness to 0.5mm, the grid hole size of the continuous fiber grid frame to 1x1mm, the Z-pin-like structure unit to be shared by 2-layer and 3-layer structures, the specific spatial distribution characteristics of the Z-pin-like structure unit to be transverse interval uniform distribution, the basic extrusion pressure value p to be 0.7MPa, and the extrusion pressure coefficient set {1.4, 1.7};

[0034] Step 2: based on the printing layer thickness, the grid hole size of the continuous fiber grid frame, and the Z-pin-like structure unit type, divide the spatial region of the target model into continuous fiber frame structure 1 and Z-pin-like structure 2, as shown in FIG. 1;

[0035] Step 3: for the continuous fiber frame structure 1 spatial region, generate the path of the continuous fiber grid frame for each horizontal slice layer to obtain the printing path information {G Fi} of the continuous fiber printing head 3 in layers 1-5;

[0036] Step 4: for the Z-pin-like structure 2 spatial region, perform horizontal slice processing, mark the filling area corresponding to each Z-pin-like structure in layers 1-5, and combine the basic extrusion pressure value p and the extrusion pressure coefficient set {K2, K3} of different Z-pin-like structure unit types to obtain the extrusion information {G Mi} of the thermosetting resin extrusion head 4 in the relevant horizontal slice layer;

[0037] Step 5: the printing information of the continuous fiber printing head 3 and the extrusion information of the thermosetting resin extrusion head 4 at the relevant horizontal slice layer are compounded in the order from bottom to top of each horizontal slice layer, and the printing information of the continuous fiber printing head 3 and the extrusion information of the thermosetting resin extrusion head 4 corresponding to each horizontal slice printing layer of 1-5 layers are output{G i The continuous fiber grid frame printing in the whole printing information is as shown in Fig. 2; and the thermosetting resin in the whole printing information realizes the filling printing of the Z-pin structure space 2-1 and fills the interlayer hole 2-2 in the continuous fiber grid frame under the control of the extrusion information, as shown in Fig. 3.

[0038] Step 6: the continuous fiber printing head 3 and the thermosetting resin extrusion head 4 are used to cooperatively print and form according to each automatic operation information, the cooperative printing process is as shown in Fig. 4, and after the printing is completed, a room temperature (25℃) standing for 20 hours is performed for curing treatment.

[0039] The technical means disclosed in the scheme of the present application is not only limited to the technical means disclosed in the above-mentioned embodiments, but also includes the technical scheme composed of any combination of the above technical features.

Claims

1. A continuous fiber additive manufacturing interlaminar reinforcement method based on pressure injection of a Z-pin like structure, characterized in that, The continuous fiber printing head and the thermosetting resin extrusion head are used for composite printing forming, wherein the continuous fiber printing head sequentially prints the grid frame according to the printing layer sequence; The thermosetting resin extrusion head performs pressure injection filling of resin material in the grid hole corresponding to the printing layer; The grid hole in the continuous fiber overall frame forms an intermittent through-space in the Z direction between layers, and the extrusion-filled thermosetting resin forms a Z-pin structure in the space, and the resin penetrates and fills the pores between the continuous fiber frame layers under the control of the extrusion pressure, finally realizing the role of continuous fiber additive manufacturing interlayer reinforcement, and the method steps are as follows: Step 1: set the printing layer thickness t, the grid hole size a×b of the continuous fiber grid frame, the Z-pin structure unit type, and the basic extrusion pressure value p corresponding to the {t, a×b} parameter group and the extrusion pressure coefficient group {K2, K3} corresponding to different Z-pin structure unit types; Step 2: based on the printing layer thickness t, the grid hole size a×b of the continuous fiber grid frame, and the Z-pin structure unit type, the model segmentation processing is performed on the target model, which is divided into a continuous fiber frame structure space region model and a Z-pin structure space region model, both of which share the same space coordinate system and have the same definition sequence of slice layers; Step 3: For the continuous fiber frame structure space area model, the path generation of the continuous fiber grid frame of each horizontal slice layer is performed to obtain the printing path information of each horizontal slice of the continuous fiber printing head {G F}, that is, the i-th layer information is denoted as {G Fi} ; Step 4: for the Z-pin structure space area model, horizontal slicing is performed, and the filling area corresponding to each Z-pin structure in each horizontal slice is marked, and the extrusion information {G M} of the thermosetting resin extrusion head in the relevant horizontal slice layer is obtained in combination with the basic extrusion pressure value p and the extrusion pressure coefficient set {K2, K3} of different Z-pin structure unit types, and the extrusion information includes the extrusion position and the corresponding extrusion pressure of the pressure injection operation in each slice, that is, the i-th layer information is denoted as {G Mi}. Step 5: The printing information of the continuous fiber printing head and the extrusion information of the thermosetting resin extrusion head at the relevant horizontal slice layer are compounded in the order from bottom to top of each horizontal slice layer, and the final continuous fiber printing head printing information and the thermosetting resin extrusion head extrusion information corresponding to each horizontal slice layer are output, that is, the i-th layer information is recorded as {G i}. Step 6: use the continuous fiber printing head and the thermosetting resin extrusion head to perform collaborative printing forming according to the automatic operation information, and perform static curing treatment after printing.

2. A continuous fiber additive manufacturing interleaf reinforcement method based on pressure injection Z-pin like structure according to claim 1, characterized in that, The cross section of the thermosetting resin extrusion head is rectangular, and the size is consistent with the grid hole size a×b, and the thermosetting resin extrusion head is inserted into the grid hole for resin pressure injection filling.

3. A continuous fiber additive manufacturing interleaf reinforcement method based on pressure injection Z-pin like structure according to claim 1, characterized in that: The Z-pin structure unit has two types of 2 layers and 3 layers in the through-layer depth, and the two structures are uniformly distributed in the horizontal plane in the form of units, but each specific structure unit has only one structure form in the thickness direction and is distributed at intervals.

4. The continuous fiber additive manufacturing interleaf reinforcement method based on pressure injection Z-pin-like structure of claim 1, wherein: The Z-pin structure unit type corresponds to different thermosetting resin extrusion pressure coefficient groups {K2, K3}, and K2 and K3 correspond to the extrusion pressure coefficients required for the extrusion of 2 layers and 3 layers of resin-filled Z-pin structures, respectively.

Images