A preparation process of controllable heat transfer metamaterial based on continuous fiber 3D printing

Abstract

A preparation process for a heat transfer controllable metamaterial based on continuous fiber 3D printing, firstly, according to the application scenario, target function and shape of the heat flow control area of ​​the thermal metamaterial, coordinate transformation is used to determine the thermal conductivity distribution map of the thermal metamaterial; then, according to the properties of the continuous fibers and substrate materials constituting the thermal metamaterial and the forming accuracy of the 3D printer, the continuous thermal conductivity distribution map of the thermal metamaterial is discretized to obtain the trajectory of the continuous fibers and the ratio of the continuous fibers and substrate materials, i.e., the three-dimensional model of the thermal metamaterial; finally, the three-dimensional model of the thermal metamaterial is imported into the 3D printer, and a continuous fiber-reinforced composite material 3D printing process is used to realize the integrated manufacturing of the thermal metamaterial; on the one hand, the present invention can realize the rapid manufacturing of thermal metamaterials based on coordinate transformation, and on the other hand, it can also break through the difficulties of three-dimensional thermal metamaterials and promote the thermal metamaterials from theoretical exploration to engineering application.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials, and in particular relates to a preparation process of a heat transfer controllable metamaterial based on continuous fiber 3D printing. Background Art

[0002] In recent years, with the rapid development of manufacturing technology, metamaterials have achieved remarkable development in many fields. Metamaterials made through fine manufacturing can exhibit excellent electromagnetic, mechanical, thermal and acoustic properties. Among them, heat transfer control is one of the main functions of thermal metamaterials. However, in the field of thermal metamaterials, most anisotropic metamaterials obtained based on coordinate transformation require materials with different thermal conductivities to be spliced ​​together (such as copper and PDMS). As a result, the current manufacturing of thermal metamaterials is relatively rough and often limited to two-dimensional verification. The designable area is often limited to regular shapes such as circles and ellipses. There are great manufacturing difficulties for the control of heat conduction in complex two-dimensional or even three-dimensional shapes ([1] Shen, X.; Li, Y.; Jiang, C.; Ni, Y.; Huang, J., Thermal cloak-concentrator. Applied Physics Letters 2016, 109(3); [2] Yang, T.; Wu, Q.; Xu, W.; Liu, D.; Huang, L.; Chen, F., A thermal groundcloak. Physics Letters A 2016,380(7-8),965-969;【3】Sun,T.;Wang,X.;Yang,X.;Meng,T.;He,R.;Wang,Y.,Design of thermal cloak and concentrator with interconnected structure.International Journal of Heat and Mass Transfer 2022,187.). At present, the common preparation process of thermal conductive metamaterials is mainly a combination of machining and manual filling, which leads to serious manufacturing errors and is difficult to automatically control, which brings great difficulties to the promotion of thermal stealth metamaterials in complex areas.

[0003] Heat flow control has important research value in both aerospace and military reconnaissance. For example, by reasonably controlling heat flow transmission, thermal invisibility of important instruments or personnel can be achieved; based on the directional heat conduction of thermal metamaterials, the heat flow of various parts of the object can be gathered to the designated position, thereby achieving thermal protection of fragile components. Therefore, the realization of integrated, automated and rapid manufacturing of complex three-dimensional configurations is a key problem that needs to be solved in the field of thermal metamaterials, and continuous fiber composite 3D printing technology has brought new solutions to this problem. For example, the anisotropic heat transfer characteristics of carbon fiber materials in the axial and radial directions provide a perfect solution for the preparation of thermal metamaterials. The reasonable combination of fibers with heat transfer anisotropy and substrate materials with low thermal conductivity can realize the integrated, low-cost and rapid manufacturing of complex thermal metamaterials. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a preparation process of heat transfer controllable metamaterials based on continuous fiber 3D printing, which can, on the one hand, realize the rapid manufacturing of thermal metamaterials based on coordinate transformation, and on the other hand, break through the difficulties of three-dimensional thermal metamaterials and promote thermal metamaterials from theoretical exploration to engineering application.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A preparation process of a heat transfer controllable metamaterial based on continuous fiber 3D printing, comprising the following steps:

[0007] 1) According to the application scenario, target function and shape of the heat flow control area of ​​the thermal metamaterial, the thermal conductivity distribution map of the thermal metamaterial is determined by coordinate transformation;

[0008] 2) According to the properties of the continuous fiber 1 and the base material 2 constituting the thermal metamaterial, combined with the forming accuracy of the 3D printer, the continuous thermal conductivity distribution map of the thermal metamaterial is discretized to obtain the trajectory direction of the continuous fiber 1 and the ratio of the continuous fiber 1 and the base material 2, that is, the three-dimensional model of the thermal metamaterial;

[0009] 3) The three-dimensional model of the thermal metamaterial in step 2) is imported into a 3D printer, and a continuous fiber reinforced composite material 3D printing process is adopted to realize the integrated manufacturing of the thermal metamaterial 3.

[0010] The coordinate transformation in step 1) is specifically as follows:

[0011] First, establish the relationship between the virtual space spherical coordinates (r, θ, φ) before transformation and the physical space spherical coordinates (r′, θ′, φ′) after transformation:

[0012]

[0013] Among them, r and r' are the distances from a certain point in the virtual space before transformation and in the physical space after transformation to the origin, respectively, and θ and θ' are the zenith angles between the line connecting the point in the virtual space before transformation and in the physical space after transformation to the origin and the z-axis, respectively. and are the line connecting the point to the origin in the virtual space before transformation and the physical space after transformation, the projection line on the xy plane, and the azimuth angle between the point and the x-axis;

[0014] According to the Jacobian matrix Λ, the transformation matrix of the thermal conductivity of virtual space and physical space is established, and finally the thermal conductivity matrix κ′ of the physical space is obtained:

[0015]

[0016]

[0017] After constructing the thermal conductivity parameters of the physical space, they are input into the COMSOL Multiphysics software to determine the continuous thermal conductivity distribution map of the thermal metamaterial before it is discretized.

[0018] The discrete processing of step 2) is specifically as follows: the discretization method is to use the conformal circle approximation method to characterize different areas with small fan-shaped blocks; specifically, the transformation area is first divided into 40 fan-shaped areas along the central area according to the angle, and the fan angle of each fan-shaped area is 9 degrees; then each fan-shaped area is divided into 20 sub-areas along the axial direction, and each sub-area represents a discrete unit; finally, the thermal conductivity coefficient continuous in step 1) is discretely assigned to each discrete unit, thereby obtaining the trajectory direction of the continuous fiber 1 and the ratio of the continuous fiber 1 and the base material 2.

[0019] The continuous fiber 1 has a high thermal conductivity, including carbon fiber, metal wire, etc.; the base material 2 has a low thermal conductivity, including ABS, nylon, PDMS, PLA, PEEK or PPS, etc. The continuous fiber 1 and the base material 2 are selected according to actual application requirements.

[0020] By controlling the continuous fiber path of 3D printing, the integrated, lightweight and rapid prototyping of thermal metamaterials with a specified thermal conductivity distribution map is achieved.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention utilizes the anisotropic characteristics of heat-conductive continuous fibers and applies continuous fiber 3D printing to the preparation of thermal metamaterials. The configuration of thermally stealthy metamaterials in complex areas can be realized in experiments, and the method has the advantages of integrated, automated, low-cost and rapid manufacturing.

[0023] (2) The present invention combines thermal metamaterials with 3D printing. The fiber material can be selected from high thermal conductivity materials such as carbon fiber and metal wire, and the base material can be selected from low thermal conductivity materials such as ABS, nylon, PDMS, and PLA, which has a wide range of material selection space.

[0024] (3) The present invention uses a continuous fiber reinforced composite material 3D printing process to manufacture thermal metamaterials, which improves the design freedom of thermal metamaterials. It can not only achieve a variety of heat transfer functions such as thermal stealth, heat flow convergence, and heat flow directional transmission, but also achieve thermal conduction control in areas of any shape. Taking thermal stealth as an example, the automated manufacturing approach allows the design of the stealth area to break through the limitations of traditional regular shapes such as circles and ellipses, and the stealth area of ​​any shape can be freely designed without having to consider manufacturing difficulties. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the thermal conductivity k of the thermal stealth metamaterial in the embodiment of the present invention rr Distribution diagram of the components.

[0026] Figure 2 is the thermal conductivity k of the thermal stealth metamaterial in the embodiment of the present invention rφ Distribution diagram of the components.

[0027] Figure 3 is the thermal conductivity k of the thermal stealth metamaterial in the embodiment of the present invention φφ Distribution diagram of the components.

[0028] Figure 4 This is a discrete diagram of the thermal stealth metamaterial according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0030] A preparation process of a heat transfer controllable metamaterial based on continuous fiber 3D printing, comprising the following steps:

[0031] 1) According to the application scenario, target function and shape of the heat flow control area of ​​the thermal metamaterial, the thermal conductivity distribution map of the thermal metamaterial is determined by coordinate transformation;

[0032] Taking the coordinate transformation under spherical coordinates as an example, first establish the relationship between the virtual space coordinates (r, θ, φ) before the transformation and the physical space coordinates (r′, θ′, φ′) after the transformation:

[0033]

[0034] Among them, r and r' are the distances from a certain point in the virtual space before transformation and in the physical space after transformation to the origin, respectively, and θ and θ' are the zenith angles between the line connecting the point in the virtual space before transformation and in the physical space after transformation to the origin and the z-axis, respectively. and are the line connecting the point to the origin in the virtual space before transformation and the physical space after transformation, the projection line on the xy plane, and the azimuth angle between the point and the x-axis;

[0035] According to the Jacobian matrix Λ, the transformation matrix of the thermal conductivity of virtual space and physical space is established, and finally the thermal conductivity matrix κ′ of the physical space is obtained:

[0036]

[0037]

[0038] After constructing the thermal conductivity parameters of the physical space, they are input into the COMSOL Multiphysics software to determine the continuous thermal conductivity distribution diagram of the thermal metamaterial before it is discretized. The thermal conductivity k of the thermal stealth metamaterial in this embodiment is rr , k rφ , k φφ like Figure 1-Figure 3 As shown, the three coefficient components k of thermal conductivity in the spherical coordinate system are shown respectively. rr , k rφ , k φφ From the distribution of the three components, we can see that the distribution of the three components in space is not uniform, which brings certain difficulties to the subsequent discrete processing;

[0039] 2) According to the properties of the continuous fiber 1 and the base material 2 constituting the thermal metamaterial, combined with the forming accuracy of the 3D printer, the continuous thermal conductivity distribution map of the thermal metamaterial is discretized to obtain the trajectory direction of the continuous fiber 1 and the ratio of the continuous fiber 1 and the base material 2, that is, the three-dimensional model of the thermal metamaterial;

[0040] The discretization method is to use the conformal circle approximation method to represent different areas with fan-shaped blocks; specifically, the transformation area is first divided into 40 fan-shaped areas along the central area according to the angle, such as Figure 4 As shown, the fan angle of each fan-shaped area is 9 degrees; then each fan-shaped area is divided into 20 sub-areas along the axial direction, and each sub-area represents a discrete unit; finally, the thermal conductivity coefficient obtained in step 1) is discretely assigned to each discrete unit, thereby obtaining the trajectory direction of the continuous fiber 1 and the ratio of the continuous fiber 1 and the base material 2;

[0041] 3) The three-dimensional model of the thermal metamaterial in step 2) is imported into a 3D printer, and a continuous fiber reinforced composite material 3D printing process is adopted to realize the integrated manufacturing of the thermal metamaterial 3.

[0042] The continuous fiber 1 has a higher thermal conductivity, including carbon fiber, metal wire, etc.; the base material 2 has a lower thermal conductivity, including ABS, nylon, PDMS, PLA, PEEK or PPS, etc. The continuous fiber 1 and the base material 2 are selected according to actual application requirements.

[0043] The present invention realizes the integrated, lightweight and rapid prototyping of thermal metamaterials with a specified thermal conductivity distribution diagram by controlling the continuous fiber path of 3D printing, which meets the specialized and customized needs of heat flow regulation in industry and has potential application value in aerospace, space exploration, military reconnaissance and other fields.

Claims

1. A preparation process of heat transfer controllable metamaterial based on continuous fiber 3D printing, characterized in that: The following steps are involved: 1) According to the application scenario, target function and shape of the heat flow control area of ​​the thermal metamaterial, the continuous thermal conductivity distribution map of the thermal metamaterial is determined by coordinate transformation; The coordinate transformation is specifically: First, establish the relationship between the virtual space coordinates (r, θ, φ) before transformation and the physical space coordinates (r′, θ′, φ′) after transformation: Among them, r and r' are the distances from a certain point to the origin in the virtual space before transformation and the physical space after transformation, respectively, and θ and θ' are the zenith angles between the line connecting the point to the origin in the virtual space before transformation and the physical space after transformation and the z-axis, respectively. and are the line connecting the point to the origin in the virtual space before transformation and the physical space after transformation, the projection line on the xy plane, and the azimuth angle between the point and the x-axis; According to the Jacobian matrix Λ, the transformation matrix of the thermal conductivity of virtual space and physical space is established, and finally the thermal conductivity matrix κ′ of the physical space is obtained: After constructing the thermal conductivity parameters of the physical space, they are input into the COMSOL Multiphysics software to determine the continuous thermal conductivity distribution map before the thermal metamaterial is discretized; 2) According to the properties of the continuous fiber (1) and the base material (2) constituting the thermal metamaterial, and in combination with the forming accuracy of the 3D printer, the continuous thermal conductivity distribution diagram of the thermal metamaterial is discretized to obtain the trajectory direction of the continuous fiber (1) and the ratio of the continuous fiber (1) and the base material (2), i.e., the three-dimensional model of the thermal metamaterial; The discrete processing is specifically as follows: the discretization method is to use the conformal circle approximation method to characterize different areas with fan-shaped small blocks; specifically, the transformation area is firstly divided into 40 fan-shaped areas along the central area according to the angle, and the fan angle of each fan-shaped area is 9 degrees; then each fan-shaped area is divided into 20 sub-areas along the axial direction, and each sub-area represents a discrete unit; finally, the thermal conductivity coefficient continuous in step 1) is discretely assigned to each discrete unit, so as to obtain the trajectory direction of the continuous fiber (1) and the ratio of the continuous fiber (1) and the base material (2); 3) The three-dimensional model of the thermal metamaterial in step 2) is imported into a 3D printer, and a continuous fiber reinforced composite material 3D printing process is used to achieve integrated manufacturing of the thermal metamaterial (3).

2. The preparation process according to claim 1, characterized in that: The continuous fiber (1) has a high thermal conductivity and includes carbon fiber and metal wire; the base material (2) has a low thermal conductivity and includes ABS, nylon, PDMS, PLA, PEEK or PPS. The continuous fiber (1) and the base material (2) are selected according to actual application requirements.

3. The preparation process according to claim 1, characterized in that: By controlling the continuous fiber path of 3D printing, the integrated, lightweight and rapid prototyping of thermal metamaterials with a specified thermal conductivity distribution map is achieved.

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