阅读说明：本技术 具有同向曲率变形特性的夹层板材及其制造方法 (Sandwich plate with homodromous curvature deformation characteristic and manufacturing method thereof ) 是由 姜基洲 朴银星 金嘉恩 于 2019-06-21 设计创作，主要内容包括：本发明提供能够有效应用于可穿戴设备(wearable device)的夹层板材及其制造方法。本发明的夹层板材的情况下,具有在普通的芯材两面附着二维拉胀性材料作为面材的形态,从而能够进行轻薄制作,也能够赋予预定的强度和刚性,而且按三维拉胀性材料而相对于弯曲力矩赋予同向曲率变形行为,改善与被覆物的密合性,由此能够有效用作可穿戴设备的结构材。此外,将二维拉胀性材料线加工成面材形态后,对于普通的芯材能够利用单纯附着的方式以低费用简单地制造,并且赋予相当于三维拉胀性材料的行为,因此可以容易地克服以往利用三维拉胀性材料单纯构成薄的板状结构材时制造难度变大且结构材的强度过度降低而在应用于可穿戴设备时成为障碍的实际局限。(The present invention provides a sandwich panel which can be effectively applied to wearable devices (wearable devices) and a method for manufacturing the same. The sandwich sheet material of the present invention can be produced in a thin and light weight manner by attaching a two-dimensional auxetic material as a surface material to both sides of a general core material, can impart predetermined strength and rigidity thereto, and can be effectively used as a structural material for a wearable device by imparting a homodromous curvature deformation behavior against a bending moment to a three-dimensional auxetic material to improve the adhesion to a covering. Further, since the two-dimensional auxetic material wire can be simply manufactured at low cost by simply attaching a general core material after being processed into a surface material form, and a behavior corresponding to a three-dimensional auxetic material is given, it is possible to easily overcome practical limitations that the manufacturing difficulty becomes large and the strength of the structural material is excessively reduced when a thin plate-shaped structural material is simply constituted by a three-dimensional auxetic material in the past, which becomes an obstacle when applied to a wearable device.)

1. A sandwich plate is characterized in that,

the composite material comprises a core material and surface materials attached to two sides of the core material, wherein the surface materials are two-dimensional auxetic materials.

2. Sandwich sheet according to claim 1,

a neutral plane based on bending moment is formed in the core material.

3. Sandwich sheet according to claim 1,

the core material is made of porous materials.

4. Sandwich sheet according to claim 1,

the core material is any one of polymer, ceramic or metal.

5. Sandwich sheet according to claim 1,

the face material is metal, polymer, ceramic or composite material.

6. Sandwich sheet according to claim 1,

the face stock has a density, strength and rigidity greater than the core material.

7. A method for manufacturing a sandwich plate is characterized in that,

comprising a step of processing a surface material and a step of attaching the surface material to both sides of a core material,

the facestock is processed to have a two-dimensional auxetic structure.

8. The method for manufacturing a laminated plate according to claim 6,

the processing of the facestock with a two-dimensional auxetic structure is,

the sheet-shaped base material is subjected to linear cutting by laser, electron beam, electric discharge, or water jet, or is subjected to photolithography, press working, or etching.

9. The method for manufacturing a laminated plate according to claim 6,

the processing of the facestock with a two-dimensional auxetic structure is carried out by weaving or forming a unidirectional composite into a bias-ply structure.

Technical Field

The present invention relates to a laminated plate and a method for manufacturing the same, and more particularly, to a laminated plate which can be effectively applied to wearable devices (wearable devices) and a method for manufacturing the same.

Background

In the near future, mobile devices are expected to develop into wearable device (able device) modalities. Wearable devices need to be lightweight, have strength and flexibility as structural materials, and have excellent body adhesion and wearing properties. In particular, since most of the parts to which the wearable device is expected to be attached, such as muscles of the buttocks, chest, arms, or legs, have a convex shape, it is necessary to flexibly deform the wearable device in accordance with the convex shape of the corresponding body part in order to improve the fit of the wearable device to the body.

In this case, the deformation of the wearable device occurring when in contact with a raised body part can be considered as deformation caused by a bending moment, and the deformation characteristics caused by such a bending moment and the body fit based thereon may differ depending on the material used. Specifically, fig. 1 shows two deformation modes occurring when a z-direction bending moment acts on a large plate-like structural material in the x-z plane. As shown in fig. 1 (a), a general solid structural material having a poisson's ratio of positive (+) value has an inverse back curvature (anti curvature) deformation characteristic in which bending occurs in opposite directions to each other on x-y plane and y-z plane due to a bending moment. When such a plate-shaped structural member having deformation characteristics of the curvature of the back side is applied to a wearable device, the adhesion to a raised body part is not good. On the other hand, as shown in fig. 1 (b), a solid structural material having a poisson's ratio of a negative (-) value, such as an expandable material described later, has a same-directional curvature (simultaneous curvature) deformation characteristic in which bending due to bending moment occurs in the same direction on the x-y plane and the y-z plane, and is excellent in adhesion when such a plate-shaped structural material having the same-directional curvature deformation characteristic is applied to a wearable device (y.liu and h.hu, Scientific Research and Essays vol.5, pp.1052-1063,2010.a. alderson and k.l.alderson proc.ecimen Part G: j.aeronautical Engineering, vol.221, 565-575,2007).

In general, a material contracts in a direction perpendicular to a stretching direction when stretched, and conversely, elongates in a direction perpendicular to a compression direction when compressed. That is, deformation in the direction perpendicular to the load application direction (lateral deformation) and deformation in the load application direction (longitudinal deformation) are opposite to each other, and in the case of a normal material, the Poisson's ratio defined by giving a negative (-) value to the ratio of lateral deformation to longitudinal deformation has a positive (+) value, and the deformation characteristics by the bending moment are as shown in fig. 1 (a). On the other hand, a material having a specific structure has a negative (-) poisson's ratio, and such a material is called an Auxetic material (automatic material). Such auxetic materials may have a two-dimensional or three-dimensional structure, and may be identified in a wide range from a microscopic level such as a molecular structure to a macroscopic level of several centimeter units. Fig. 2 and 3 show two-and three-dimensional structural diagrams of representative conventionally known auxetic materials (Juan Carlos a ' lvarez Elipe and Andre's D ' | az Lantada, Smart mater.struct. (Smart material structure), vol.21, article id.105004, 2012.).

Here, the two-dimensional auxetic material or structure means a structure in which a structure is two-dimensional and deformation occurs only in-plane (in-plane), and the three-dimensional auxetic structure means a structure and deformation both defined in a three-dimensional space.

Such two-dimensional or three-dimensional auxetic materials have inherent names according to their geometries. Further, in the case of an open type foamed material (foam material), it is known that if compression is performed in 3 directions perpendicular to each other, it is deformed into the above-described concave structure (re-directed structure) to be able to impart the characteristics of an auxetic material (r.s. lakes, Science, vol.235, pp.1038-1040,1987).

However, when the plate-like structural member is formed only with such an auxetic material, the three-dimensional auxetic material shown in fig. 3 needs to be used in order to have the same-direction curvature deformation characteristic as shown in fig. 1 (b), and the two-dimensional auxetic material shown in fig. 2 cannot be used. Specifically, as shown in fig. 4, the bending moment M in the z-axis direction acts on a plate-like structural member having a predetermined thickness_zThe two-dimensional auxetic material is deformed uniformly in the thickness direction, and does not have different deformation behaviors in the vertical direction with respect to the neutral plane of the bending moment located inside the thickness thereof. However, when a plate-shaped structural member for a wearable device is produced using only a three-dimensional auxetic material, in order to generate a homodromous curvature deformation characteristic by realizing deformation behaviors in opposite directions in upper and lower portions having a relatively thin thickness based on a neutral plane of a bending moment, a unit cell (unit cell) of the three-dimensional auxetic material needs to be formed very minutely, so that the production difficulty increases and the strength of the structural member becomes highToo low, there are practical limitations in application to wearable devices.

On the other hand, it is known that a sandwich panel is generally a structural material formed of two materials, i.e., a thick porous/low-strength core material (core) and thin high-density/high-strength face materials (face sheets) attached to both surfaces thereof, and is designed such that the face materials bear bending moment and the core material bears relatively low shear force, and has high strength and rigidity with respect to weight. As an example of the application of an auxetic material to a sandwich panel in recent years, studies have been reported on a sandwich panel in which an auxetic material is used as a core material and a general (con) material is used as a surface material, but a sandwich panel having such a structure is used for manufacturing a panel having high impact resistance or a curved surface shape, and is not concerned with the improvement of the problem of deformation characteristics due to bending moment.

Disclosure of Invention

Technical subject

The present invention provides a sandwich panel which is light and thin, has required strength and rigidity, and has the same-direction curvature deformation characteristic when flexibly deformed, and can be effectively used as a structural material of wearable equipment, and a manufacturing method thereof.

Means for solving the problems

The present inventors have studied a sandwich plate material formed by laminating and adhering two kinds of materials as a structural material for a wearable device related to the above-mentioned problems, and have confirmed that, in the case of a sandwich plate material formed in a state in which a two-dimensional auxetic material is adhered as a surface material to both sides of a common (composite) core material, the sandwich plate material can be manufactured to be thin and thin, and has predetermined strength and rigidity required for a wearable device, and particularly, the two-dimensional auxetic material adhered to both sides of the core material performs the auxetic behaviors in opposite directions to each other in the upper and lower directions of a bending moment neutral plane to make the entire plate material have the same-direction curvature deformation characteristic, thereby achieving excellent wearability, and on the other hand, have found that it is possible to overcome a practical limitation that the manufacturing difficulty becomes large and the strength of the structural material becomes too low and becomes an obstacle when the sandwich plate material is simply formed of a thin plate-shaped structural material using a three-dimensional auxetic material and applied to, thus, the present invention has been completed. The gist of the present invention is as follows based on the recognition and understanding of the above-described problems.

(1) A laminated sheet material comprising a core material and surface materials attached to both surfaces of the core material, wherein the surface materials are two-dimensionally auxetic materials.

(2) The sandwich panel material according to the above (1), wherein a neutral plane based on a bending moment is formed in the core material.

(3) The laminated plate according to the above (1), wherein the core material is a porous material.

(4) The laminated plate material according to the above (1), wherein the core material is any one of a polymer, a ceramic and a metal.

(5) The laminated board according to the above (1), wherein the surface material is a metal, a polymer, a ceramic or a composite material.

(6) The laminated plate material according to the above (1), wherein the density, strength and rigidity of the surface material are higher than those of the core material.

(7) A method for producing a laminated sheet, characterized by comprising a step of processing a surface material and a step of attaching the surface material to both surfaces of a core material, wherein the surface material is processed to have a two-dimensional auxetic structure.

(8) The method for producing a laminated plate material according to item (6) above, wherein the surface material having a two-dimensional auxetic structure is processed by linear cutting using a laser, an electron beam, an electric discharge, or a water jet, or by photolithography, press working, or etching, with respect to a sheet-like base material.

(9) The method for producing a laminated sheet material according to the above (6), wherein the surface material having a two-dimensional auxetic structure is processed by knitting or forming a unidirectional (uni-directional) composite material into an angle-ply laminates structure.

Effects of the invention

The sandwich sheet material of the present invention can be produced in a thin and light weight manner by attaching a two-dimensional auxetic material as a surface material to both sides of a general core material, can impart predetermined strength and rigidity thereto, and can be effectively used as a structural material for a wearable device by imparting a homodromous curvature deformation behavior against a bending moment to a three-dimensional auxetic material to improve the adhesion to a covering. Further, since the two-dimensional auxetic material wire can be simply manufactured at low cost by simply attaching a general core material after being processed into a surface material form, and a behavior corresponding to a three-dimensional auxetic material is given, it is possible to easily overcome practical limitations that the manufacturing difficulty becomes large and the strength of the structural material is excessively reduced when a thin plate-shaped structural material is simply constituted by a three-dimensional auxetic material in the past, which becomes an obstacle when applied to a wearable device. In addition, the outer shape is beautiful, the mechanical properties can be easily adjusted by combining the materials and the structures of the surface material and the core material, and the manufacture is obviously easy. In addition, when the conductive surface material is used, a function of receiving or shielding a radio wave signal can be provided.

Drawings

Fig. 1 is a schematic view of the deformation characteristics of a plate-like structural material caused by the application of a z-direction bending moment.

Fig. 2 is a structural view of a two-dimensional auxetic material of a conventionally known example.

Fig. 3 is a structural view of a three-dimensional auxetic material of a conventionally known example.

FIG. 4 is a deformation diagram showing the characteristics of the same-direction curvature deformation when a z-direction bending moment is applied.

Fig. 5 is a structural view of a sandwich panel according to an embodiment of the present invention.

FIG. 6 is a schematic illustration of the deformation characteristics of a sandwich panel material according to an embodiment of the invention when a z-direction bending moment is applied.

Fig. 7 is a top view photograph of a two-dimensional auxetic facestock made according to an embodiment of the present invention.

Fig. 8 is a top view photograph of a two-dimensional auxetic facestock made according to another embodiment of the present invention.

Fig. 9 is a photograph of a sheet-shaped polyurethane foam constituting a sandwich panel according to an embodiment of the present invention.

Fig. 10 is a photograph of a sandwich panel in which the face material of fig. 7 is applied to the core material of fig. 9 according to an example of the present invention.

Fig. 11 is a photograph of a sandwich panel in which the facestock of fig. 8 is applied to the core material of fig. 9, according to an example of the present invention.

Detailed Description

The present invention will be described in detail below with reference to examples. In the foregoing, the terms or words used in the present specification and claims should not be construed as being limited to the meanings in the general or dictionary, but interpreted according to the meanings and concepts conforming to the technical idea of the present invention on the basis of the principle that the inventor can appropriately define the concept of the terms in order to explain his invention in the best way. Therefore, the configuration of the embodiment described in the present specification is only the most preferable embodiment of the present invention and does not represent all the technical ideas of the present invention, and therefore it should be understood that various equivalents and modifications can be substituted for them at the time point of the application of the present invention. On the other hand, in the drawings, the same or similar reference numerals are given to the same or equivalent components, and when a part is referred to as "including" a certain component in the context of the specification, unless there is a description to the contrary, it means that other components may be further included, but other components are not excluded.

Fig. 5 shows a structural view of the sandwich panel 10 of the embodiment of the present invention. The laminated sheet material 10 includes a core member 110, and surface materials 120a and 120b attached to both surfaces of the core member 110.

The core member 110 serves to support the upper surface member 120a and the lower surface member 120b, and also serves to separate the upper surface member 120a and the lower surface member 120b into individual volume units in the interlayer thickness direction with reference to a neutral plane (CF) of bending moment. The core member 110 is not particularly limited as long as it is made of a material that can be flexibly deformed when it is provided in a thin shape, and is preferably made of a lightweight porous polymer, or may be made of a metal. Further, in the case of ceramics known as a general lightweight brittle material, flexible deformation is possible even in recent years when the material is formed to have a nano thickness, and therefore, the material can be used as the core material 110 of the present invention. In addition, from the viewpoint of weight reduction, it is preferable that the core member 110 is made of a porous material or a low-density material, and if the core member 110 made of a porous or low-density material is used, the rigidity is lower than that of the surface members 120a and 120b, that is, the core member is made flexible, and the poisson's ratio is close to 0, so that the core member is easily deformed together without being restricted by the surface members 120a and 120b when they are subjected to auxetic deformation. However, such a core member 110 is preferably determined based on the relationship with the surface materials 120a and 120b, and may not be suitable as the core member 110, for example, in the case of a flexible material, but a material which may restrict the dilatant deformation of the surface materials 120a and 120b as an incompressible solid such as rubber having a poisson's ratio of + 0.5.

The surface members 120a and 120b serve to provide the same-direction curvature deformation characteristic as shown in fig. 1 (b) when a bending moment is applied, by forming respective upper and lower volume units in the thickness direction of the sandwich plate material 10 with reference to the neutral plane (CF) of the bending moment, and providing the three-dimensional auxillary material characteristic to the entire sandwich plate material 10. For this purpose, the top surface member 120a and the bottom surface member 120b are provided in pairs and each is made of a two-dimensional auxetic material.

The geometry of the two-dimensional auxetic material constituting the surface members 120a and 120b is not particularly limited, and may be provided in various forms as illustrated in fig. 2, for example. In addition, the geometry of the two-dimensional auxetic materials of the upper face material 120a and the lower face material 120b may be the same or different from each other. The material of the surface members 120a and 120b is not particularly limited, and may be selected in consideration of the degree of flexible deformation required when applied to a wearable device, a processing method for a two-dimensional geometric structure described later, and the like, and such surface members 120a and 120b are preferably a material having high density, high strength, and rigidity with respect to the core material 110, and may be formed of a polymer, ceramic, or composite material, for example, in addition to metal.

Fig. 6 shows a schematic diagram of the deformation behaviour when a z-direction bending moment is applied to the sandwich panel 10 according to an embodiment of the invention. As illustrated in fig. 6 (a), the core material 110 is adhered to both surfacesThe laminated sheet material 10 having a predetermined thickness and formed by the pair of surface materials 120a and 120b is applied with a bending moment M in the z-axis direction_zIn this case, a neutral plane (CF) based on a bending moment is formed inside the core member 110, and the upper surface member 120a and the lower surface member 120b form respective upper and lower volume units in the thickness direction of the sandwich panel 10. In this case, the position of the neutral plane (CF) can be influenced by the thicknesses and young's moduli of the upper surface member 120a and the lower surface member 120b, and by adjusting such factors, the position of the neutral plane (CF) can be formed inside the core member 110. The upper surface member 120a having a geometry of a two-dimensional auxetic material is subjected to a tensile stress in the x-axis direction and is also subjected to a tensile deformation in the z-direction perpendicular thereto, thereby being subjected to an isotropic elongation in the x-z plane as illustrated in fig. 6 (b). In contrast, the lower surface material 120b having another geometry of a two-dimensional auxetic material is subjected to a compressive stress in the x-axis direction and is also subjected to a compressive deformation in the z-direction perpendicular thereto, and thus undergoes isotropic shrinkage in the x-z plane as illustrated in fig. 6 (c). As a result, when a bending moment is applied, the sandwich panel 10 macroscopically has the same-direction curvature deformation characteristic as illustrated in fig. 1 (b) due to the isotropic elongation and isotropic compression deformation independently formed for each of the upper surface material 120a and the lower surface material 120b separated into individual volume units with reference to the neutral plane (CF) in the thickness direction of the sandwich panel 10, which can induce the same deformation behavior as in the case of forming a plate-shaped structural material with only the auxetic material of fig. 3 in which the cells are microscopically controlled in order to satisfy a thin thickness.

On the other hand, in the case where the laminated sheet material 10 of the present invention can be produced in a simple manner by including a step of processing the surface materials 120a and 120b and a step of attaching the processed surface materials 120a and 120b to both sides of the core material 110, the step of processing the surface materials 120a and 120b as a step of processing the surface materials to have a two-dimensional auxetic structure can be carried out in various ways.

Fig. 7 shows a top view photograph of a three-dimensional auxetic facestock 120a, 120b fabricated according to an embodiment of the present invention. A stainless steel plate having a thickness of 0.2mm was engraved with a two-dimensional auxetic pattern shown in fig. 2 (d) by photolithography (photo lithography) using a sheet-like base material made of a metal material. In fig. 7, the size of the two-dimensional auxetic pattern is adjusted according to the application. In general, photolithography is often used in a printed circuit board (printed circuit board) processing process of electronic products, and is suitable for mass production of precise patterns. A method of printing a pattern on the surface of a metal plate by photolithography, and then chemically etching and removing the exposed metal portion. On the other hand, although such a sheet-like base material is used, in the case of a polymer or ceramic material which is not suitable for the application of photolithography and etching, a two-dimensional auxetic pattern can be realized by linear cutting processing using laser, electron beam, electric discharge, or water jet, or by mechanical processing such as press forming.

Fig. 8 shows a top view photograph of a two-dimensional auxetic facestock 120a, 120b manufactured according to another embodiment of the present invention. Fig. 8 (a) is another example of a two-dimensional auxetic facestock 120a, 120b according to an embodiment of the present invention. After a plurality of finely cut unidirectional prepreg (prepreg) threads are plain woven (plain weaving) to form a mesh pattern having a certain period, as shown in fig. 8 (b), the threads are forcibly inserted into a mold in which the two-dimensional auxetic pattern of fig. 2 (h) is engraved, so that the threads are bent and deformed, and are heated and cured, thereby obtaining the composite face materials 120a and 120b in the mesh pattern. Further, a small amount of an ultra-low viscosity epoxy resin (epoxy) is applied to the crossing joints between the lines of the composite material, and then cured by heating again, thereby preventing shear deformation from occurring between the prepregs crossing each other. In this case, the composite materials may be woven together to increase the bonding force between the two direction composite materials.

On the other hand, in addition to the method of weaving the unidirectional composite material shown in fig. 8, the processing of the two-dimensional expandable face materials 120a and 120b may be a method of forming a so-called cross-ply structures (z.wang, a.zulifqar, h.hu, adaptive composites in aerospace engineering, 2016) by laminating unidirectional composite prepregs in a specific oblique direction. In the production of the two-dimensional auxetic material having an oblique laminate structure, a lamination method specifically designed to exhibit auxicity in an in-plane or out-of-plane direction by using dedicated software is used, and a material produced to have auxicity in an in-plane direction can be used when the present invention is applied.

Fig. 9 and 10 show an implementation of the core material 110 and the sandwich panel 10, respectively, of an embodiment of the invention. Fig. 9 shows a photograph of a sheet-like polymer surface material 120a or 120b serving as the core material 110, and fig. 10 shows a photograph of a sandwich plate material 10 in which the metal surface materials 120a and 120b of fig. 7 are attached to the core material 110 of fig. 9 with an epoxy resin. Fig. 11 is a photograph showing a real object of the laminated sheet 10 in which the face materials 120a and 120b of fig. 8 prepared by weaving (plain-weaving) the unidirectional composite material are attached to the core material 110 of fig. 9.

As described above, in the case of the sandwich panel 10 of the present invention, the two-dimensional auxetic material is adhered to both surfaces of the general core member 110 as the surface members 120a and 120b, so that the sandwich panel can be manufactured to be thin and light, and can be provided with predetermined strength and rigidity, and the three-dimensional auxetic material is provided with the same-direction curvature deformation behavior with respect to the bending moment, so that the sandwich panel can be effectively used as a structural member of a wearable device by improving the adhesion with the covering. Further, since the two-dimensional expandable material wire is processed into the surface members 120a and 120b, the two-dimensional expandable material wire can be easily manufactured at low cost by a simple adhesion method with respect to the general core member 110, and a behavior corresponding to the three-dimensional expandable material is provided, it is possible to easily overcome practical limitations that the manufacturing difficulty becomes large and the strength of the structural material is excessively reduced when a thin plate-shaped structural material is simply constituted by the three-dimensional expandable material in the related art, which becomes an obstacle when the two-dimensional expandable material wire is applied to a wearable device. In the case of the metal surface materials 120a and 120b, a beautiful appearance can be achieved by using a pattern unique to the unique gloss and the auxetic structure, and the mechanical properties can be easily adjusted by combining the materials and structures of the surface materials 120a and 120b and the core material 110, and the production is remarkably easy. When the conductive surface materials 120a and 120b are used, they can be used as an antenna for a mobile device or a shielding function, and can receive radio signals.

The foregoing description relates to specific embodiments of the present invention. The above-described embodiments of the present invention should not be construed as limiting the matters disclosed for the purpose of illustration or the scope of the present invention, but it should be understood that various changes and modifications can be made by those skilled in the art without departing from the essence of the present invention. Therefore, it is to be understood that all such modifications and variations are intended to fall within the scope of the invention as disclosed in the claims and their equivalents.