Preparation method of 3D printing composite material

Abstract

The invention provides a preparation method of a 3D printing composite material, which comprises the following steps: S10, providing a 3D printing skeleton which is printed by adopting a first thermoplastic material and has a three-dimensional communicated open pore structure, and reserving a layer grain structure formed in the printing process on the surface of the 3D printing skeleton; s20, the 3D printing framework is placed in a constant-temperature environment of 70-90 DEG C and kept dry; s30, the heated 3D printing framework is moved into a cavity of an injection mold, the mold is closed, and the temperature of the cavity of the injection mold is set to be 30-60 DEG C; s40, a molten second thermoplastic material is injected into the cavity, so that the second thermoplastic material wraps the 3D printing framework and fills the groove of the layer grain structure; the shore hardness of the second thermoplastic material is lower than that of the first thermoplastic material, and the softening temperature of the first thermoplastic material is higher than the melt injection temperature of the second thermoplastic material. According to the 3D printing composite material prepared by the preparation method, the problem that the comfort degree of an existing 3D printing insole is relatively low can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing composite materials, and particularly relates to a preparation method of a 3D printing composite material. BACKGROUND

[0002] With the development of additive manufacturing technology (3D printing), especially in the field of shoe material manufacturing, the lattice structure midsole printed by using TPU and other elastomers gradually becomes a research hotspot in the industry due to its lightweight, high resilience and customizability. Compared with traditional EVA or ETPU foaming materials, the 3D printed midsole can realize fine mechanical property distribution by adjusting the lattice structure. However, the existing 3D printed midsole is usually manufactured by using a single hardness wire, and the hardness is usually high, which directly affects the comfort when used on the sole. In order to solve this problem, the existing technology usually stacks a soft foaming material on the 3D printing material, but this simple stacking has the problem of easy delamination due to repeated deformation of the sole during movement. SUMMARY

[0003] The present application aims to overcome the above-mentioned defects or problems in the background art, and provide a preparation method of a 3D printing composite material, which can improve the low comfort problem of the existing 3D printed midsole.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: Technical solution one: a preparation method of a 3D printing composite material, comprising the following steps: S10: providing a 3D printing skeleton with a three-dimensional interconnected open pore structure printed by using a first thermoplastic material, the surface of the 3D printing skeleton retaining a layer structure formed during the printing process; S20: placing the 3D printing skeleton in a constant temperature environment of 70-90 DEG C and keeping it dry; S30: moving the heated 3D printing skeleton into the cavity of an injection mold and closing the mold, and setting the cavity temperature of the injection mold to 30-60 DEG C; S40: injecting a molten second thermoplastic material into the cavity, so that the second thermoplastic material covers the 3D printing skeleton and fills the grooves of the layer structure; the Shore hardness of the second thermoplastic material is lower than the Shore hardness of the first thermoplastic material, and the softening temperature of the first thermoplastic material is higher than the melting injection temperature of the second thermoplastic material.

[0005] Technical solution two based on technical solution one: in step S10, the diameter of a single rod of the 3D printing skeleton is not less than 1.2 millimeters, and the layer height of the layer structure is 0.15-0.3 millimeters.

[0006] Technical Solution 3 based on Technical Solution 1: In step S10, the first thermoplastic material is selected from thermoplastic polyurethane, polyether block amide, or thermoplastic polyester elastomer, and its hardness is Shore 85A-95A; In step S40, the second thermoplastic material is selected from styrene-based thermoplastic elastomer or thermoplastic vulcanized rubber, and its hardness is Shore 20A-35A.

[0007] Technical Solution 4 based on Technical Solution 1: In step S20, the temperature of the constant temperature environment is 80℃±2℃, and the 3D printed skeleton is kept in the constant temperature environment for 35 minutes to 45 minutes.

[0008] Technical Solution 5 based on Technical Solution 1: In step S30, the cavity temperature of the injection mold is set to 40℃-50℃.

[0009] Technical Solution Six based on Technical Solution One: In step S30, the time interval from removing the 3D printed skeleton from the constant temperature environment to completing the mold closure is less than 30 seconds; in step S40, the time interval from completing the mold closure to starting injection is less than 1 second.

[0010] Technical solution seven based on technical solution one: In step S40, the injection speed of the second thermoplastic material is 80 mm / s to 120 mm / s, and the peak injection pressure is 90 MPa to 100 MPa.

[0011] Technical solution eight based on technical solution one: In step S10, a positioning boss with a height equal to the designed coating layer thickness is integrally printed at the outer node of the 3D printed skeleton; in step S30, the positioning boss is used to abut against the inner wall of the cavity, so that the 3D printed skeleton is in a suspended state in the cavity.

[0012] Technical Solution Nine based on Technical Solution One: In step S10, the minimum net aperture P of the lattice unit of the 3D printed skeleton and the thickness t of the coating layer formed in step S40 satisfy the relationship: P>4t.

[0013] Technical solution ten based on technical solution one: In step S10, the inner core skeleton is printed as a concave structure with a negative Poisson's ratio effect, and the concave structure is configured to contract inward when subjected to an external compressive load to compress the thermoplastic elastomer covering the surface of the inner core skeleton.

[0014] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects: The first embodiment of the present invention provides a method for preparing a 3D printed composite material. The 3D printed composite material prepared by this method has a thermoplastic material with lower hardness inside the 3D printed skeleton, thereby improving the overall resilience of the 3D printed composite material. Moreover, this coating structure allows the thermoplastic material with lower hardness to form a strong bond with the thermoplastic material with higher hardness, avoiding debonding and separation between different thermoplastic materials in the 3D printed composite material, thereby ensuring the durability of the 3D printed composite material.

[0015] The 3D printing composite material preparation method provided in this solution effectively improves the problem of balancing structural stability and interfacial bonding strength in thermoplastic lattice framework structures during insert injection molding, compared to conventional insert injection molding processes. In conventional insert injection molding processes, if the insert is a thermoplastic with poor temperature resistance and a fine lattice structure, a high mold temperature or a long holding time is usually required to maintain the diffusion of polymer chains at the interface in order to ensure the fusion strength between the molten material and the insert surface. However, this can cause the framework with low heat capacity to soften, deform, or collapse under the scouring of high-temperature and high-pressure fluids. But if the mold temperature is lowered to protect the framework structure, the high-temperature melt will form a condensed skin when it comes into contact with the low-temperature framework surface due to the large temperature difference. This results in the coating layer only making contact with the framework without substantial adhesion, making the product prone to interfacial delamination under stress. This method first preheats the 3D-printed skeleton to 70-90°C, placing the skeleton material surface in an activated state close to or within the glass transition range, thus offsetting heat loss during subsequent contact. Then, a low-temperature mold at 30-60°C is used to rapidly dissipate the heat accumulated in the melt and skeleton. When the melt contacts the skeleton, the interface temperature remains sufficient to support molecular wetting and diffusion. Before heat is conducted to the skeleton's core, causing it to soften and fail, the coating layer has already cooled and solidified. Simultaneously, the layered structure formed on the skeleton surface using the 3D printing process allows for the forced injection of a more fluid thermoplastic material into the micro-grooves created by the layered structure. After cooling and solidification, the material filling the grooves forms numerous micro-mechanical interlocking structures. This physical mechanical interlocking provides sufficient interfacial shear strength even when the rapid cooling process results in weaker chemical bonds, further ensuring a strong connection between the coating layer and the skeleton. Therefore, in the 3D printed composite material prepared by the above process, the outer layer of material with lower hardness provides a soft touch and initial cushioning, while the inner layer of skeleton with higher hardness provides structural rigidity and rebound support. The two work together to enable the 3D printed composite material to take into account both rebound and shock absorption performance, and has good wearing comfort.

[0016] In technical solution two, the diameter of a single rod of the skeleton is limited to ensure that the skeleton has sufficient heat capacity so that it can withstand the impact pressure and thermal shock of the melt during injection molding, preventing the skeleton from softening or bending; at the same time, the layer height of the skeleton is limited to ensure that grooves of appropriate depth are formed so that the melt can completely fill them, and to ensure that the mechanical interlocking structure is deep enough to generate effective shear resistance.

[0017] In technical solution three, the skeleton is made of high-hardness TPU, PEBA, or TPEE materials, utilizing their high modulus properties to provide elastic support and energy feedback for the composite material. The covering layer is made of low-hardness TPS or TPV materials, so that the surface of the 3D printed composite material has a soft touch, achieving initial energy absorption, while the interior can maintain a high load-bearing capacity through the skeleton.

[0018] In technical solution four, the constant temperature and holding time in step S20 are limited to ensure that the molecular chains of the framework remain in an activated state without softening or deforming, while also removing moisture and preventing the formation of bubbles at the interface. Furthermore, the pre-existing heat energy can compensate for heat loss during transfer to a lower-temperature mold, preventing interface condensation and thus ensuring the quality of the hot-melt layer.

[0019] In technical solution five, the mold temperature is further limited. This temperature range can prevent the melt from freezing due to excessive cooling when it comes into contact with the mold, ensuring that the melt can flow and fill the grooves of the layered structure. At the same time, it can effectively dissipate the heat of the melt, block the heat from being conducted to the deep layers of the skeleton, ensure that the skeleton maintains its shape and prevents collapse due to heat accumulation.

[0020] In technical solution six, the transfer time and injection delay time are limited to reduce the passive cooling time of the skeleton, so that the surface temperature of the skeleton can be maintained above the activation threshold before contacting the melt, thereby avoiding the formation of a cold boundary layer.

[0021] In technical solution seven, the injection temperature and pressure of the second thermoplastic material are limited. By utilizing the shear thinning property of the melt, the intrinsic viscosity is reduced, so that the melt can quickly penetrate and fill the grooves of the layered structure before cooling and thickening. At the same time, the rapid filling method can shorten the thermal contact time between the high-temperature melt and the skeleton, reducing the risk of thermal deformation of the skeleton.

[0022] In technical solution eight, positioning bosses are integrally printed on the outer nodes of the skeleton. These bosses abut against the inner wall of the cavity, enabling the skeleton to be precisely positioned and suspended. This positioning method ensures that the thickness of the covering layer around the skeleton is uniform and consistent, avoiding structural defects caused by skeleton displacement or adhesion to the wall due to high-pressure injection molding impact.

[0023] In technical solution nine, the relationship between the minimum net pore size of the lattice unit in the framework and the thickness of the cladding layer is defined to ensure that the lattice structure remains connected and open after cladding. This avoids the pores of the lattice unit inside the framework being blocked due to excessive cladding material, thus preserving the air permeability and lightweight of the lattice structure. It also provides sufficient space for the cladding layer to deform under pressure, preventing performance degradation due to interference from the framework material.

[0024] In technical solution ten, the skeleton adopts an inward concave structure with a negative Poisson's ratio effect, which causes the skeleton to shrink inward after the composite material is compressed, actively squeezing the second thermoplastic material covering its surface, increasing the internal stress of the composite material, thereby further improving the composite material's ability to absorb stress under high loads. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise expressly defined, the use of terms such as "first," "second," or "third" in the claims and description of this invention is for distinguishing different objects, not for describing a specific order.

[0027] In the claims and description of this invention, the terms "comprising," "having," and variations thereof are used to mean "including but not limited to."

[0028] This invention relates to a method for preparing 3D printed composite materials, which mainly includes the following steps: S10: Provide a 3D printed skeleton with a three-dimensional interconnected opening structure printed using a first thermoplastic material, wherein the surface of the 3D printed skeleton retains the layer texture structure formed during the printing process; S20: Place the 3D printed skeleton in a constant temperature environment of 70 to 90°C and keep it dry; S30: The heated 3D printed skeleton is moved into the cavity of the injection mold and the mold is closed. The cavity temperature of the injection mold is set to 30 to 60°C. S40: Inject molten second thermoplastic material into the cavity, so that the second thermoplastic material covers the 3D printed skeleton and fills the grooves of the layered structure; the Shore hardness of the second thermoplastic material is lower than that of the first thermoplastic material, and the softening temperature of the first thermoplastic material is higher than that of the second thermoplastic material.

[0029] The following will provide a detailed explanation of each of the above steps.

[0030] Step S10 is used to provide a 3D printed skeleton. In step S10, the 3D printed skeleton is prepared by a fused deposition modeling (FDM) process. This process involves feeding a filament of a first thermoplastic material into a heated nozzle for melting. The nozzle moves along a pre-defined 3D digital model slicing path on a forming platform, extruding the molten material and stacking and cooling it layer by layer to construct a solid skeleton structure. The first thermoplastic material used is selected from thermoplastic polyurethane, polyether block amide, or thermoplastic polyester elastomer, and its hardness range is set to Shore A 85A to 95A.

[0031] The fabricated 3D-printed skeleton exhibits a macroscopically interconnected three-dimensional open-pore structure. This structure means that the internal voids of the skeleton are not closed or isolated chambers, but rather a continuous network formed by countless lattice units arranged regularly or irregularly in three-dimensional space. The pores within the skeleton are interconnected along the X, Y, and Z axes, forming continuous fluid channels leading from the skeleton surface to its deep interior. The microscopic lattice units of the skeleton employ a concave structure with a negative Poisson's ratio effect. Geometrically, this concave structure is characterized by the ribs or connecting rods of the lattice units forming inwardly concave angles, such as concave hexagonal structures or double-arrowhead structures, where the vertices of the lattice units point towards the geometric center rather than protruding outwards. For the solid parts constituting the 3D-printed skeleton, the diameter of a single rod is set to be no less than 1.2 mm. The diameter of a single rod refers to the cross-sectional diameter or width of a single solid support or connecting rib constituting the lattice unit skeleton, and this dimension is controlled by the 3D printing nozzle orifice diameter and extrusion flow rate. Furthermore, the net aperture P is set to be greater than four times the thickness t of the cladding layer formed in subsequent step S40 to ensure sufficient open space within the framework. The minimum net aperture P of a lattice unit refers to the minimum linear distance in space between the surfaces of two adjacent rods in the lattice structure.

[0032] The surface of the 3D printed skeleton retains the layer texture structure formed during the printing process. Layer texture refers to the step-like micro-texture formed on the sidewalls along the stacking direction (Z-axis) due to the fused deposition modeling (FDM) process of stacking materials layer by layer. Each layer's edge has a slight geometric discontinuity relative to the edges of adjacent layers, creating regular undulating ripples on the macroscopically smooth surface. The layer height of this texture structure, i.e., the height of each step along the Z-axis, is set to 0.15 mm to 0.3 mm by the printing slicing parameters. The completed skeleton retains this original printed state without undergoing post-processing steps such as chemical fumigation, flame polishing, or mechanical sandblasting to remove surface roughness.

[0033] Furthermore, during the 3D printing process of the skeleton, positioning bosses are integrally printed at the outermost nodes of the overall skeleton outline. These positioning bosses are solid protrusions extending outwards from the skeleton structure, continuously printed using the same material as the main skeleton body. The height of the positioning boss is defined as the vertical distance from the surface of the skeleton node to the top of the boss, a distance equal to the thickness of a pre-defined second thermoplastic overlay layer. For 3D printed skeletons with shoe sole structures, these positioning bosses can be distributed at key support locations such as the forefoot, heel, and sidewall edges.

[0034] After the 3D printed skeleton is prepared, step S20 is performed. In step S20, the prepared 3D printed skeleton is placed in a heating device that can provide constant temperature conditions. This heating device is a forced-air drying oven or a constant-temperature heating chamber, whose internal space can maintain uniform hot air circulation. The 3D printed skeleton is placed on a tray or rack in this constant-temperature environment, ensuring that there are gaps around the skeleton so that the hot air can fully contact all surfaces of the skeleton, thereby ensuring that the skeleton is heated evenly.

[0035] The temperature parameters of the constant-temperature environment are set within the range of 70 to 90 degrees Celsius. Preferably, the temperature of the constant-temperature environment is specifically set to 80 degrees Celsius, and the allowable temperature fluctuation range is controlled within ±2 degrees Celsius. The holding time of the 3D printed skeleton in this constant-temperature environment is set to 35 to 45 minutes. This holding time refers to the duration calculated from the time the internal temperature of the equipment reaches the set value and the skeleton is placed inside. During this period, the 3D printed skeleton not only heats up but also remains dry. Maintaining dryness means evaporating and expelling the moisture adsorbed inside the skeleton material through the dehumidification function of the heating equipment, or controlling the relative humidity in the heating chamber to a low level to prevent the skeleton from absorbing moisture during heating. After the above time and temperature treatment, the core and surface temperatures of the 3D printed skeleton reach the same level, and the surface is in a dry and activated state without any moisture adhering to it.

[0036] After step S20 is completed, step S30 is executed immediately. The heat-treated 3D-printed skeleton is removed from the constant-temperature environment and transferred to the cavity of the injection mold. The injection mold is pre-temperature-regulated using a mold temperature controller or cooling water system, setting the surface temperature of the cavity within the range of 30°C to 60°C. In this embodiment, to match the preheated skeleton state, the cavity temperature of the injection mold is specifically controlled between 40°C and 50°C. The cavity temperature refers to the measured temperature of the inner wall of the mold cavity in direct contact with the injection material. The time interval from the moment the 3D-printed skeleton is removed from the constant-temperature environment to the moment the 3D-printed skeleton is placed and the injection mold is closed is controlled to be less than 30 seconds. This time interval covers the entire process of the skeleton being removed from the furnace, transported, placed into the mold cavity for positioning, and the injection molding machine's mold closing mechanism locking the mold.

[0037] When placing the 3D-printed skeleton into the mold cavity, positioning bosses integrally printed at the outer nodes of the skeleton in step S10 are used for positioning. The 3D-printed skeleton is placed inside the cavity so that the tops of the positioning bosses distributed along the skeleton's edges directly contact the inner wall surface of the mold cavity. Because the positioning bosses have a preset height, when their tops contact the inner wall of the mold, the main body of the 3D-printed skeleton is supported, thus placing the 3D-printed skeleton in a suspended state inside the cavity. This suspended state means that there is a distance between the surface of the 3D-printed skeleton and the inner wall of the mold cavity; this distance is determined by the height of the positioning bosses, and this gap area constitutes the space for subsequent flow and filling of the second thermoplastic material. As the mold closes, the positioning bosses are clamped by the combined force of the upper and lower mold plates, thereby fixing the three-dimensional position of the 3D-printed skeleton within the cavity.

[0038] After mold closure is completed in step S30, step S40 is immediately executed. In step S40, a second thermoplastic material in a molten state is injected into the now-closed mold cavity via the screw or plunger of the injection molding machine. The time interval from the completion of mold closure to the start of injection is controlled to be less than 1 second. The injected second thermoplastic material is selected from styrene-based thermoplastic elastomers or thermoplastic vulcanized rubber, with a hardness range of Shore 20A to 35A. The Shore hardness value of this second thermoplastic material is lower than that of the first thermoplastic material in step S10, thereby creating a hardness gradient of hardness inside and softness outside in the composite material. At the same time, in terms of material thermal properties, the Vicat softening temperature of the first thermoplastic material is higher than the melt injection temperature of the second thermoplastic material. This temperature difference ensures that when the molten second thermoplastic material comes into contact with the solid 3D printed skeleton, the skeleton body will not melt or collapse due to heat, and only microscopic thermal effects will occur at the interface.

[0039] During the injection molding process, to ensure that the molten material can rapidly fill the complex lattice gaps and penetrate into the microstructure, the injection speed of the second thermoplastic material was set to 80 mm / s to 120 mm / s, and the peak injection pressure was set to 90 MPa to 100 MPa. Driven by high pressure and high speed, the molten second thermoplastic material with shear-thinning properties rapidly fills the gap between the mold cavity and the 3D printed skeleton. The molten material flows along the surface of the 3D printed skeleton and is forced to penetrate and fill the grooves of the layered structure retained on the skeleton surface, smoothing out the stepped texture of the skeleton surface.

[0040] As the molten material fills the cavity and cools and solidifies, a second thermoplastic material forms a coating layer covering the outer surface of the 3D printed skeleton. The thickness t of this coating layer is determined by the distance between the inner wall of the mold cavity and the surface of the skeleton, which is the height of the positioning boss mentioned in step S10. At this time, the minimum net aperture P of the lattice unit set in step S10 and the thickness t of the coating layer satisfy the relationship that P is greater than 4t. This means that after the coating layer is formed, the lattice unit still retains more than three-quarters of the original size of open space, which is not completely blocked by the coating material, so that the final 3D printed composite material maintains a three-dimensional interconnected open topology.

[0041] To further illustrate the technical effects of the technical solutions adopted in this invention, the following embodiments and comparative examples are provided in this specification.

[0042] To ensure that those skilled in the art can reproduce the technical solution of the present invention, the main raw material specifications used in the following embodiments and comparative examples are as follows: The first thermoplastic material is thermoplastic polyurethane (TPU) filament, grade WHT-1190 from Wanhua Chemical. This material has a Shore hardness of 90A, a Vicat softening temperature of 105℃, and a melt processing temperature range of 200℃ to 220℃. The filament diameter is 1.75 mm.

[0043] The second thermoplastic material is a styrene-ethylene / butene-styrene block copolymer (SEBS) based thermoplastic elastomer granules, brand name KRAIBURG TF3AAA. This material has a Shore hardness of 30A, high fluidity, and a recommended injection molding temperature of 180℃ to 200℃.

[0044] Example 1 This embodiment describes the preparation of a 3D-printed composite material shoe midsole.

[0045] First, step S10 is performed, using an FDM 3D printer to print the aforementioned TPU filament into a shoe midsole skeleton. The printing nozzle temperature is set to 215℃, the layer height to 0.2 mm, and the printing speed to 40 mm / s. The skeleton structure is designed as a concave hexagonal negative Poisson's ratio lattice, with a single rod diameter of 1.5 mm and a minimum net lattice aperture of 4 mm. During the printing process, no surface smoothing post-processing is performed, preserving the layer texture structure of the skeleton surface. Simultaneously, positioning bosses with a height of 0.8 mm are printed at the edges of the skeleton.

[0046] Next, proceed to step S20, place the printed skeleton into a forced-air drying oven, set the temperature to 80℃, heat at a constant temperature and keep drying for 40 minutes.

[0047] Then, step S30 is executed, where the preheated skeleton is moved from the oven into the injection mold cavity within 20 seconds. The injection mold has been pre-connected to a mold temperature controller, and the cavity surface temperature is stabilized at 45°C. The skeleton is suspended and fixed using locating bosses, and then the mold is closed.

[0048] Finally, execute step S40, starting the injection molding machine within 0.5 seconds after mold closing. Inject TPE material with a melt temperature of 195°C into the mold. Set the injection speed to 100 mm / s and the peak injection pressure to 95 MPa. The TPE material rapidly fills the cavity and covers the skeleton, with a coating thickness of 0.8 mm. After holding the pressure for 20 seconds, cool and demold to obtain the finished product.

[0049] Example 2 The only difference between this embodiment and Embodiment 1 is the adjustment of preheating and mold temperature parameters, in order to verify the adaptability of the process window.

[0050] In step S20, the ambient temperature is set to 90°C and maintained for 35 minutes.

[0051] In step S30, the cavity temperature of the injection mold is set to 30°C.

[0052] The remaining steps and parameters are consistent with those in Example 1.

[0053] Example 3 The difference between this embodiment and Embodiment 1 lies in the adjustment of the skeleton structure.

[0054] In step S10, the lattice structure of the skeleton is designed as an open-cell Kelvin foam structure, the diameter of a single rod is adjusted to 1.2 mm, and the layer height is set to 0.15 mm.

[0055] The remaining steps and parameters are consistent with those in Example 1.

[0056] Comparative Example 1 (3D printing with a single material) Only step S10 of Example 1 was performed to prepare a 3D-printed shoe midsole made of pure TPU material. No subsequent overlay process was performed; it was directly used as a finished product for testing. This comparative example is used to simulate existing ordinary 3D-printed midsoles.

[0057] Comparative Example 2 (Traditional Adhesive Bonding Process) First, a TPU skeleton is prepared according to step S10 of Example 1. Then, a TPE soft layer (material same as in Example 1) matching the shape of the skeleton is injection molded separately. Using industrial-grade polyurethane adhesive (PU adhesive) and a treatment agent, the soft layer is bonded to the upper and lower surfaces of the TPU skeleton. This comparative example is used to simulate existing physical superposition composite schemes.

[0058] Comparative Example 3 (removal of layered texture) The only difference from Example 1 is that after step S10, the TPU skeleton undergoes chemical fumigation and polishing to remove the surface layered structure, making its surface smooth. The remaining preheating and injection molding process parameters are completely consistent with Example 1. This comparative example is used to verify the influence of layered structure on interfacial bonding.

[0059] Comparative Example 4 (without preheating treatment) The only difference from Example 1 is that step S20 is omitted, and the TPU skeleton at room temperature (25°C) is directly placed into a mold at 45°C for injection molding. All other parameters are the same as in Example 1. This comparative example is used to verify the necessity of thermal activation pretreatment.

[0060] Comparative Example 5 (Mold temperature too high) The only difference from Example 1 is that the injection mold cavity temperature in step S30 is set to 80°C (the standard TPE injection mold temperature). All other parameters are the same as in Example 1. This comparative example is used to verify the protective effect of the low-temperature mold on the skeletal structure.

[0061] The above embodiments and comparative examples were tested according to the following standards: Interfacial peel strength test: The test is conducted according to GB / T 2791-1995 "Adhesives - Test Method for Peel Strength of Flexible Materials - Flexible Materials". A standard specimen is cut from the composite material, and the bond strength between the coating layer and the skeleton is tested. A higher value indicates a tighter bond.

[0062] Energy rebound rate test: The drop ball rebound test was conducted according to GB / T 1681-2009 "Determination of resilience of vulcanized rubber". The overall rebound performance of the composite material was tested.

[0063] Compression fatigue performance test: According to GB / T 20991-2007 "Test methods for personal protective equipment shoes", 100,000 consecutive compression cycles were performed, and the appearance and structure of the sample were observed to see if collapse or delamination occurred.

[0064] Structural integrity assessment: Visual inspection and section microscopy are used to determine whether the skeleton has undergone thermal deformation or collapse.

[0065] The test results are as follows:

[0066] Based on the test results above, the 3D printed composite materials prepared in Examples 1 to 3 all exhibited excellent performance in terms of interfacial peel strength, energy rebound rate, and structural integrity. Their bonding strength was significantly better than that of Comparative Example 2, which used a traditional adhesive process, and they also achieved a soft touch and strong resilience that Comparative Example 1 could not achieve. The peel strength of Comparative Example 3 decreased after removing the layer texture, demonstrating the necessity of retaining the layer texture as a technical means. The omission of the preheating step in Comparative Example 4 resulted in a decrease in interfacial strength, demonstrating the necessity of the thermal activation step. Although the use of a conventional high-temperature mold in Comparative Example 5 ensured the bonding force, it led to the softening and collapse of the skeleton and blockage of pores.

[0067] The foregoing description of the specifications and embodiments is intended to explain the scope of protection of this invention, but does not constitute a limitation on the scope of protection of this invention. Modifications, equivalent substitutions, or other improvements to the embodiments of this invention or a portion thereof that can be obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation, based on the teachings of this invention or the foregoing embodiments, in conjunction with common knowledge, general technical knowledge, and / or existing technology, should all be included within the scope of protection of this invention.

Claims

1. A method for preparing a 3D printed composite material, characterized in that, Includes the following steps: S10: Provide a 3D printed skeleton with a three-dimensional interconnected opening structure printed using a first thermoplastic material, wherein the surface of the 3D printed skeleton retains the layer texture structure formed during the printing process; S20: Place the 3D printed skeleton in a constant temperature environment of 70 to 90°C and keep it dry; S30: The heated 3D printed skeleton is moved into the cavity of the injection mold and the mold is closed. The cavity temperature of the injection mold is set to 30 to 60°C. S40: Inject molten second thermoplastic material into the cavity, so that the second thermoplastic material covers the 3D printed skeleton and fills the grooves of the layered structure; the Shore hardness of the second thermoplastic material is lower than that of the first thermoplastic material, and the softening temperature of the first thermoplastic material is higher than that of the second thermoplastic material.

2. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S10, the diameter of a single rod of the 3D printed skeleton is not less than 1.2 mm, and the layer height of the layered structure is 0.15 mm to 0.3 mm.

3. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S10, the first thermoplastic material is selected from thermoplastic polyurethane, polyether block amide, or thermoplastic polyester elastomer, and its hardness is Shore 85A-95A; in step S40, the second thermoplastic material is selected from styrene-based thermoplastic elastomer or thermoplastic vulcanized rubber, and its hardness is Shore 20A-35A.

4. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S20, the temperature of the constant temperature environment is 80℃±2℃, and the 3D printed skeleton is kept in the constant temperature environment for 35 minutes to 45 minutes.

5. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S30, the cavity temperature of the injection mold is set to 40℃-50℃.

6. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, in In step S30, the time interval from removing the 3D printed skeleton from the constant temperature environment to completing the mold closing is less than 30 seconds; in step S40, the time interval from completing the mold closing to starting injection is less than 1 second.

7. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, in In step S40, the injection speed of the second thermoplastic material is 80 mm / s to 120 mm / s, and the peak injection pressure is 90 MPa to 100 MPa.

8. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S10, a positioning boss with a height equal to the designed coating layer thickness is integrally printed at the outer node of the 3D printed skeleton; in step S30, the positioning boss is used to abut against the inner wall of the cavity, so that the 3D printed skeleton is suspended in the cavity.

9. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S10, the minimum net aperture P of the lattice unit of the 3D printed skeleton and the thickness t of the coating layer formed in step S40 satisfy the following relationship: P > 4t.

10. The method for preparing a 3D printed composite material as described in claim 1, characterized in that, In step S10, the inner core skeleton is printed as a concave structure with a negative Poisson's ratio effect, the concave structure being configured to contract inward under external compressive load to compress the thermoplastic elastomer covering the surface of the inner core skeleton.

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