Origami-type composite metamaterial sandwich panel

Abstract

Origami-type composite metamaterial sandwich panels belong to the field of multifunctional composite materials. The origami-type composite metamaterial sandwich panels include a plurality of metamaterial structure cells arranged in a periodic array. The metamaterial structure cells have mirror flip symmetry. The metamaterial structure cells include a first base plate, a core layer and a second base plate. The core layer includes a first symmetric body, a second symmetric body and a hollow space. The first symmetric body and the second symmetric body are connected through a central collective support platform. The structural parameters of the metamaterial structure cells can be adjusted. In the sandwich panel of the present invention, the morphology of the metamaterial structure cells is adjusted by adjusting the structural parameters of the metamaterial structure cells, so that different products can be brought about by the same design idea; the hollow space can create an energy-absorbing body space that meets the requirements of multi-condition impact energy absorption, and the hollow space is filled with materials with different characteristics to meet the multifunctional characteristics of the sandwich panel. The technical problem that it is difficult for existing composite materials to simultaneously meet the requirements of multi-functions and adjustable parameters is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of multifunctional composite materials, and in particular relates to an origami-type composite metamaterial sandwich panel. Background Art

[0002] Current technological developments are placing increasingly stringent demands on material characteristics, with a general demand for multifunctional properties in derivative products. For example, the automotive industry is seeking lighter material components to replace traditional metal or alloy parts to achieve lightweight, energy-saving, and emission-reduction goals. At the same time, it hopes that the same material or structure will possess sufficient stiffness and strength, meet other requirements such as impact absorption, and achieve the feasibility of multiple performance capabilities within the same structure to broaden market demand. Furthermore, to further reduce costs, it is hoped that the same design approach can lead to different feedback model products, thereby shortening the R&D process and consumption of new products. For example, the same design model can be transformed into different products, enabling the product line to have the advantages of saving design costs.

[0003] Existing metalworking processes can lead to performance issues such as breakage or reduced strength in finished products due to the inherent properties of the selected base material and the feeding and parameter settings of the processing equipment. Furthermore, existing heat-source welding methods for joining metal materials present technical pain points such as complex and cumbersome processes, environmental pollution, and defects or low dimensional accuracy in the finished product. Existing composite materials struggle to simultaneously meet multifunctional requirements and maintain adjustable parameters, making it difficult to achieve products with different structural forms using the same design approach.

[0004] Therefore, it is of great significance to provide an origami-type composite metamaterial sandwich panel that can meet multifunctional requirements and whose parameters can be adjusted. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides an origami-type composite metamaterial sandwich plate, which can change the structural morphology of the composite material by adjusting parameters, and realize multifunctional requirements, so as to solve or alleviate at least one technical problem existing in the existing composite materials.

[0006] According to a specific embodiment of the present invention, the present invention provides an origami-type composite metamaterial sandwich panel, comprising a plurality of metamaterial structure cells, the plurality of metamaterial structure cells being arranged in a periodic array, each metamaterial structure cell having mirror flip symmetry, and each metamaterial structure cell comprising: a first base plate, a core layer, and a second base plate, the core layer being arranged between the first base plate and the second base plate, the core layer comprising a first symmetrical body, a second symmetrical body, and a hollow space, the first symmetrical body and the second symmetrical body being connected through a central collective support platform, the first symmetrical body being arranged in a mirror flip position of the second symmetrical body, and the structural parameters of the metamaterial structure cell being adjustable.

[0007] Optionally, the protruding assembly composed of the discrete support platforms at the four vertex corners of the first symmetrical body and the collective support platform in the center is welded to the first base plate, and the protruding assembly composed of the discrete support platforms at the four vertex corners of the second symmetrical body and the collective support platform in the center is welded to the second base plate.

[0008] Optionally, the structural morphology of the metamaterial structure unit cell is adjusted by adjusting the size parameters of the first symmetric body and the second symmetric body in the core layer. The size parameters of the first symmetric body and the second symmetric body include: the height h of the metamaterial structure unit cell and the length l of the metamaterial structure unit cell.

[0009] The relationship between h, l, the bottom side length a of the central assembly support platform and the origami angle α of the core layer is:

[0010] Among them, l is a constant value, h is specified as a fixed parameter and an integer value, and the origami angle α of the corresponding core layer is obtained by modifying the bottom side length a of the central collective support platform; the bottom side length a of the central collective support platform is specified as a fixed parameter, and the origami angle α of the corresponding core layer is obtained by assigning h to an integer. The value range of the origami angle α of the core layer is 0-90 degrees.

[0011] Optionally, the fold angle β of the symmetrical base unit valley line formed by flipping the core layer axis, the surface fold angle γ between the inclined surfaces connected by the valley line fold, and the hollow space fold angle δ can be adjusted, the value range of γ is 0-90 degrees, and the value range of β and δ is 0-180 degrees.

[0012] Optionally, the first bottom plate and the core layer are welded by friction stir welding.

[0013] Optionally, the second bottom plate and the core layer are welded by friction stir welding.

[0014] Optionally, the components in the core layer are welded together by friction stir welding.

[0015] Optionally, multiple metamaterial structure unit cells are welded by stir friction.

[0016] Optionally, the origami-type composite metamaterial sandwich panel further includes a porous metal material filled in the hollow space.

[0017] Optionally, the porous metal material includes at least one of foamed aluminum and foamed copper.

[0018] Optionally, the origami-type composite metamaterial sandwich panel further includes an electromagnetic periodic structure membrane, which is arranged on the surfaces of the first base plate and the second base plate.

[0019] Optionally, the origami-type composite metamaterial sandwich panel further includes reinforcing fibers coated on the surfaces of the first base plate and the second base plate.

[0020] Optionally, the thickness of the first bottom plate and the second bottom plate is not less than 0.2 mm, the heights of the plates of the first symmetrical body and the second symmetrical body are both fixed at 1.5-5 mm, and the punching depth of the core layer is 1.25-4.75 mm.

[0021] Compared with the prior art, the above solution of the embodiment of the present invention has at least the following beneficial effects:

[0022] (1) The structural parameters of the metamaterial structure unit cell in the origami-type composite metamaterial sandwich panel provided by the present invention can be adjusted, and then the structural morphology of the metamaterial structure unit cell can be adjusted, so that different feedback model products can be brought about by adopting the same design concept, thereby shortening the research and development process and consumption of new products, making the product line have the advantages of saving design costs.

[0023] (2) The material of the origami-type composite metamaterial sandwich plate provided by the present invention is aluminum alloy, and the core layer structure has a hollow space, so that the origami-type composite metamaterial sandwich plate has the mechanical characteristics of light weight and high strength. For example, the surface density is much smaller than the surface density of existing materials of the same size. The surface density of the sandwich plate of the present invention can be reduced to 5kg / m 2 .

[0024] (3) The core layer of the origami-type composite metamaterial sandwich panel provided by the present invention has a hollow space, which can create an energy-absorbing body space that meets the requirements of multi-condition impact energy absorption. Moreover, the hollow space can be filled with materials with different properties to meet the multifunctional characteristics of the origami-type composite metamaterial sandwich panel. The origami-type composite metamaterial sandwich panel of the present invention is used as a carrier and is composited with porous metal materials such as foam aluminum, reinforced fibers, and electromagnetic periodic structure layers to obtain a multifunctional composite material, thereby achieving multifunctional uses.

[0025] (4) In the origami-type composite metamaterial sandwich plate provided by the present invention, friction stir welding is used to weld the first base plate and the core layer, the second base plate and the core layer, the components in the core layer, and the multiple metamaterial structure cells. This eliminates the need for welding wire and shielding gas, which are necessary for traditional heat source welding and requires complicated preparations such as welding wire and shielding gas. This avoids the defects of pores and thermal cracks caused by the large thermal expansion coefficient of the aluminum alloy itself, and solves the technical pain point of reduced strength due to the softening of the parent material in the core area of ​​the joint. At the same time, friction stir welding can reduce pollution and the secondary hazards of smoke radiation. The resulting finished product has high dimensional accuracy, low internal residual stress, and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying any creative work.

[0027] Figure 1 A schematic top view of the structure of an origami-type composite metamaterial sandwich panel provided by an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the structure of a metamaterial structure unit cell in an origami-type composite metamaterial sandwich panel provided by an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of the structure of a metamaterial structure unit cell in another direction provided by an embodiment of the present invention;

[0030] Figure 4 A schematic structural diagram of the core layer in a unit cell of a metamaterial structure provided by an embodiment of the present invention;

[0031] Figure 5 A schematic cross-sectional view of a unit cell of a metamaterial structure provided by an embodiment of the present invention;

[0032] Figure 6 Schematic diagram of the structural parameters in a unit cell of a metamaterial structure provided by an embodiment of the present invention.

[0033] The accompanying drawings in the specific implementation manner are as follows:

[0034] An origami-type composite metamaterial sandwich panel 100 comprises a metamaterial structure unit cell 10 , a first base plate 1 , a core layer 2 , a first symmetrical body 21 , a second symmetrical body 22 , a central collective support platform 23 , a discrete support platform 24 , and a second base plate 3 . DETAILED DESCRIPTION

[0035] The technical solutions of the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are therefore only provided as examples and are not intended to limit the scope of protection of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] In the description of the present invention, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements, but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0039] References to "embodiments" in this disclosure mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the disclosure. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] In the description of the embodiments of the present invention, the orientations or positional relationships indicated by technical terms such as "upper" and "lower" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present invention and simplifying the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present invention.

[0041] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are used solely to distinguish between different objects and should not be understood to indicate or imply relative importance or to implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0042] See also Figure 1 The embodiment of the present invention provides an origami-type composite metamaterial sandwich panel 100, comprising a plurality of metamaterial structure cells 10, wherein the plurality of metamaterial structure cells 10 are arranged in a periodic array. Figure 2-4 Each metamaterial structure unit cell 10 has mirror flip symmetry, and each metamaterial structure unit cell 10 includes: a first base plate 1, a core layer 2, and a second base plate 3, wherein the core layer 2 is arranged between the first base plate 1 and the second base plate 3. Please refer to Figure 5The core layer 2 includes a first symmetric body 21, a second symmetric body 22, and a hollow space (not shown). The first symmetric body 21 and the second symmetric body 22 are connected by a central collective support platform 23. The first symmetric body 21 is arranged in a mirror-inverted position of the second symmetric body 22. The structural parameters of the metamaterial structure unit cell 10 can be adjusted. A metamaterial structure unit cell 10 is defined as an origami unit.

[0043] The first base plate 1, the second base plate 3 and the core layer 2, the multiple metamaterial structure cells 10 and the components in the metamaterial structure cell 10 can all be connected by welding. Preferably, the first base plate 1, the second base plate 3 and the core layer 2 are all connected by stir friction welding; the components in the metamaterial structure cell 10 are connected by stir friction welding; and the multiple metamaterial structure cells 10 are formed into an origami-type composite metamaterial sandwich plate by stir friction welding. In this embodiment, the convex assembly composed of the discrete support platforms 24 at the four vertex corners of the first symmetrical body 21 and the central collective support platform 23 is stir friction welded to the first base plate 1, and the convex assembly composed of the discrete support platforms 24 at the four vertex corners of the second symmetrical body 22 and the central collective support platform 23 is stir friction welded to the second base plate 3.

[0044] Specifically, before welding, the surface of the weldment is polished and cleaned to remove the aluminum oxide film and stains formed. The interval between the weldments is about 30-40 mm, which is determined by the diameter of the welding needle of the selected welding head. The moving speed range of the welding head can be selected between 150-400 mm / min, and the rotation speed can be selected in the standard constant value range of 1000-2000 rpm. Stir friction welding does not require the addition of welding wire and shielding gas. This method can optimize the complicated preparation work such as welding wire and shielding gas required in the traditional heat source welding process, avoids the defects of pores and thermal cracks caused by the large thermal expansion coefficient of the aluminum alloy itself, and solves the technical pain point of reduced strength due to the softening of the base material in the core area of ​​the joint. At the same time, stir friction welding can reduce pollution and the secondary hazards of smoke radiation. The resulting finished product has high dimensional accuracy, low internal residual stress, and excellent mechanical properties.

[0045] The materials of the first base plate 1, the second base plate 3, the first symmetrical body 21 and the second symmetrical body 22 can be selected according to actual needs. Preferably, the materials of the first base plate 1, the second base plate 3, the first symmetrical body 21 and the second symmetrical body 22 are metal or metal alloys. More preferably, the materials of the first base plate 1, the second base plate 3, the first symmetrical body 21 and the second symmetrical body 22 are light metal or light metal alloys. In this embodiment, the materials of the first base plate 1, the second base plate 3, the first symmetrical body 21 and the second symmetrical body 22 are all aluminum alloy with a density of 2.7g / cm 3Aluminum alloys are characterized by lightness, high rigidity, corrosion resistance, and high metallic activity. Compared to other metals, aluminum alloys are relatively weak in material strength, soft, and easy to process. In this embodiment, the first and second base plates 1 and 3 are produced by aluminum alloy rolling, and the core layer 2 is produced by metal stamping using a custom mold. The components within the metamaterial structure unit cell 10, as well as multiple metamaterial structure units 10, are connected by friction stir welding.

[0046] The cross-sections of the first base plate 1, the second base plate 3, and the metamaterial structure unit cell 10 are preferably, but not limited to, square. The bottom surfaces of the discrete support platforms 24 at the four corners of the first symmetric body 21 and the second symmetric body 22, as well as the bottom surface of the central collective support platform 23, are preferably, but not limited to, square. In this embodiment, the cross-sections of the first base plate 1, the second base plate 3, and the metamaterial structure unit cell 10 are square; the bottom surfaces of the discrete support platforms 24 at the corners and the bottom surface of the central collective support platform 23 are square.

[0047] By adjusting the size parameters of the first symmetric body 21 and the second symmetric body 22 in the core layer 2, the structural morphology of the metamaterial structure unit cell 10 can be adjusted, and thus the structural morphology of the origami-type composite metamaterial sandwich panel 100 can be adjusted. Figure 6 The adjustable dimensional parameters of the first symmetric body 21 and the second symmetric body 22 include the height h of the metamaterial structure unit cell 10 and the side length l of the cross section of the metamaterial structure unit cell 10. The relationship between h, l, the bottom side length a of the central collective support platform 23, and the origami angle α of the core layer 2 is:

[0048]

[0049] Where l is a fixed value. When h is a fixed parameter and an integer value, the origami angle α of the origami unit is obtained by modifying the bottom side length a of the central aggregate support platform 23. When the bottom side length a of the central aggregate support platform 23 is a fixed parameter, the origami angle α of the corresponding core layer 2 is obtained by assigning h an integer value. Preferably, the origami angle α of the core layer ranges from 0 to 90 degrees. The height h of the metamaterial structure unit cell 10 and the side length l of the cross section of the metamaterial structure unit cell 10 can be designed according to actual needs. In some embodiments, the height h of the metamaterial structure unit cell 10 is 6.8 mm, and the bottom side length of the metamaterial structure unit cell 10 is set to 15 mm or 20 mm.

[0050] The core layer of the parameter-adjustable origami unit is composed of symmetrical base unit points along the axis. In addition to the three main adjustment parameters h, a, and α, other derived angles also appear during this process. For example, the fold angle β of the symmetrical base unit valley formed by the axial flipping of the core layer, the surface fold angle γ between the inclined surfaces connected by the valley fold, and the hollow space fold angle δ. As a and α are changed, β, γ, and δ are also adjusted accordingly. The value range of γ is 0-90 degrees, and the value range of β and δ is 0-180 degrees.

[0051] The hollow space includes all spaces between the first base plate 1 and the second base plate 3 that do not have core layer materials, that is, all gaps between the first base plate 1 and the second base plate 3 belong to the hollow space. The hollow space can create an energy-absorbing body space that meets the requirements of multi-condition impact energy absorption. The hollow space can be filled with materials with different properties to meet the multifunctional characteristics of the origami-type composite metamaterial sandwich panel. For example, in some preferred embodiments, the origami-type composite metamaterial sandwich panel also includes a porous metal material, and the porous metal material is filled in the hollow space of the core layer 2. The porous metal material has the characteristics of light weight and soft texture. The hollow space is filled with the porous metal material. The multiple gaps and lightweight soft material can reduce the vibration and sound wave transmission frequency, thereby enhancing the vibration reduction and noise reduction function of the origami-type composite metamaterial sandwich panel. The porous metal material preferably includes, but is not limited to, at least one of foamed aluminum and foamed copper. In this embodiment, the porous metal material is foamed aluminum.

[0052] In some preferred embodiments, the multifunctional structural configuration of the origami-based composite metamaterial sandwich panel further includes an electromagnetic periodic structure membrane disposed on the surfaces of the first base plate 1 and the second base plate 3. Such electromagnetic periodic structure membranes include, but are not limited to, flexible periodic structure planar arrangement metasurfaces or flexible phase gradient metasurfaces. These membranes provide the origami-based composite metamaterial sandwich panel with radiation and electromagnetic interference protection.

[0053] In some preferred embodiments, the origami-based composite metamaterial sandwich panel further includes reinforcing fibers coated on the surfaces of the first and second base plates 1 and 3. The reinforcing fibers include, but are not limited to, at least one of self-reinforced polypropylene fibers, aramid fibers, glass fibers, and carbon fibers. The use of reinforcing fibers for composite construction can yield an origami-based composite metamaterial sandwich panel with superior mechanical properties and a lighter weight. For example, this origami-based composite metamaterial sandwich panel can be used to form bulletproof and explosion-proof panels with improved impact resistance and energy absorption, protecting against penetration by 7.76mm caliber, long-range, high-speed impacts.

[0054] The thickness of the first base plate 1 and the second base plate 3 is preferably, but not limited to, greater than or equal to 0.2 mm. The height of the first symmetrical body 21 and the second symmetrical body 22 is fixed at 1.5-5 mm. The stamping depth of the core layer 2 is 1.25-4.75 mm, which can avoid feeding technical difficulties or excessive thinning rate at the rounded corners that may cause the plate to break. In this embodiment, the thickness of the first base plate 1 and the second base plate 3 is fixed at 4 mm, the thickness of the first symmetrical body 21 and the second symmetrical body 22 is fixed at 3 mm, and the stamping depth of the core layer is 1.5 mm.

[0055] In the present invention, all folded edges of the panels are preferably, but not limited to, radiused to 0.5 mm. The stamping die used is customized based on the parameters and dimensions of the core panel. In this embodiment, the stamping dimensions of the sandwich panel are 640 mm by 1010 mm.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments of the invention herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An origami-type composite metamaterial sandwich panel, characterized in that: It comprises a plurality of metamaterial structure cells, the plurality of metamaterial structure cells are arranged in a periodic array, each metamaterial structure cell has mirror flip symmetry, each metamaterial structure cell comprises: a first base plate, a core layer, and a second base plate, the core layer is arranged between the first base plate and the second base plate, the core layer comprises a first symmetric body, a second symmetric body, and a hollow space, the first symmetric body and the second symmetric body are connected through a central collective support platform, the first symmetric body is arranged at a mirror flip position of the second symmetric body, and the structural parameters of the metamaterial structure cell can be adjusted; The cross section of the metamaterial structure unit cell is a square, and the length of the metamaterial structure unit cell is the side length of the cross section; The structural morphology of the metamaterial structure unit cell is adjusted by adjusting the size parameters of the first symmetric body and the second symmetric body in the core layer, wherein the size parameters of the first symmetric body and the second symmetric body include: the height h of the metamaterial structure unit cell and the length l of the metamaterial structure unit cell, The relationship between h, l, the bottom side length a of the central collective support platform and the origami angle α of the core layer is: Wherein, l is a fixed value, h is specified as a fixed parameter and an integer value, and the origami angle α of the corresponding core layer is obtained by modifying the bottom side length a of the central collective support platform; the bottom side length a of the central collective support platform is specified as a fixed parameter, and the origami angle α of the corresponding core layer is obtained by assigning h to an integer, and the value range of the origami angle α of the core layer is: 0°<α<90°; The fold angle β of the symmetrical base unit valley line formed by the core layer axis flipping, the surface fold angle γ between the inclined surfaces connected by the valley line fold and the hollow space fold angle δ can be adjusted, and the value range of γ is 0°<γ<90°, the value range of β is 0°<β<180°, and the value range of δ is: 0°<δ<180°; The thickness of the first bottom plate and the second bottom plate is not less than 0.2 mm, the heights of the first symmetrical body and the second symmetrical body are fixed at 1.5-5 mm, and the punching depth of the core layer is 1.25-4.75 mm; It also includes an electromagnetic periodic structure film, which is arranged on the surface of the first base plate and the second base plate, and the electromagnetic periodic structure film includes a flexible periodic structure plane arrangement super surface or a flexible phase gradient super surface, and the electromagnetic periodic structure film enables the origami-type composite metamaterial sandwich plate to have the function of radiation protection and electromagnetic interference protection; or, It also includes reinforcing fibers coated on the surfaces of the first base plate and the second base plate, and the reinforcing fibers include at least one of self-reinforced polypropylene fibers, aramid fibers, glass fibers, and carbon fibers.

2. The origami-type composite metamaterial sandwich panel according to claim 1, characterized in that: The convex assembly composed of the discrete support platforms at the four vertex corners of the first symmetrical body and the collective support platform in the center is welded to the first bottom plate, and the convex assembly composed of the discrete support platforms at the four vertex corners of the second symmetrical body and the collective support platform in the center is welded to the second bottom plate.

3. The origami-type composite metamaterial sandwich panel according to claim 1 or 2, characterized in that: The first base plate and the core layer, the second base plate and the core layer, the components in the core layer, and the plurality of metamaterial structure unit cells are all connected by stir friction welding.

4. The origami-type composite metamaterial sandwich panel according to claim 1 or 2, characterized in that: The hollow space is also filled with porous metal material.

5. The origami-type composite metamaterial sandwich panel according to claim 4, characterized in that: The porous metal material includes at least one of foamed aluminum and foamed copper.

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