The present invention relates to a manufacturing method of a sandwich panel with a truss type core between upper/lower face sheets.
In general, sandwich panels are constituted by high-density high-strength upper/lower face sheets and low-density low-strength cores. When compared to general panels formed of a uniform one material, sandwich panels have been widely used in structures of which lightweight and high strength and stiffness are required because of high strength and stiffness to weight ratio. Thus, sandwich panels are being widely used in furniture, civil engineering, and constructive materials as well as high-priced advanced structures such as wings for airplane and the bottom of passenger room. A fiber reinforced plastic (FRP) face sheet and a honeycomb core may be considered as the most ideal combination in sandwich panels. However, since the honeycomb core has a closed inner space, the inner space of the honeycomb is not used. Also, since the core and the face sheet are connected to each other by using an adhesive having low adhesion strength, the sandwich panels may be vulnerable to, particularly, a fatigue load.
In recent, a lightweight structure having a periodical truss structure has been developed as a material for cores. Since the lightweight structure has a truss structure designed to provide optimum strength and stiffness through accurate mathematical/mechanical calculation, the lightweight structure may have superior mechanical properties. Here, the most general truss in structural shape may be a pyramid truss and an octet truss (see R. Buckminster Fuller, 1961, U.S. Pat. No. 2,986,241). Recently, as a modification of the octet truss, Kagome truss has been known (see S. Hyun, A. M. Karlsson, S. Torquato, A. G. Evans, 2003. Int. J. of Solids and Structures, Vol. 40, pp. 6989-6998). In this case, if the whole members constituting the truss have the same length when thin and long members having the same section constitute the truss, each of truss elements constituting the Kagome truss may have just a length equal to half of that of each of truss elements constituting the octet truss. Thus, buckling that is a main fracture phenomenon of trusses may be more effectively restricted. Also, even though the buckling occurs, the truss may more stably collapse. For example, each of the pyramid, octet, and Kagome trusses is three-dimensionally illustrated in
Methods for manufacturing a truss-type porous lightweight structure are known as follows. First, there is a method in which a truss structure is manufactured using a resin, and then a metal is molded by using the truss structure as a mold (see S. Chiras, D. R. Mumm, N. Wicks, A. G. Evans, J. W. Hutchinson, K. Dharmasena, H. N. G. Wadley, S. Fichter, 2002, International Journal of Solids and Structures, Vol. 39, pp. 4093-4115) (hereinafter, referred to as “Prior art 1”). Second, there is a method in which a thin metal plate is punched at a predetermined interval to manufacture a mesh-shaped plate, the mesh-shaped plate is bent to form a truss intermediate layer, a face plate is attached on each of upper and lower portions of the truss intermediate layer (see D. J. Sypeck and H. N. G. Wadley, 2002, Advanced Engineering Materials, Vol. 4, pp. 759-764) (hereinafter, referred to as “Prior art 2”). In this case, when it is intended to manufacture a multilayered structure including at least two layers, the truss intermediate layer that is bent as described above is attached on an upper face plate, and then a face plate is attached again on the truss intermediate layer. Third, there is a method in which wires disposed in two directions perpendicular to each other are woven in a mesh shape to form iron meshes, and then the iron meshes are stacked on each other (see D. J. Sypeck and H. G. N. Wadley, 2001, J. Mater. Res., Vol. 16, pp. 890-897) (hereinafter, referred to as “Prior art 3”).
However, Prior art 1 may have a complicated manufacturing process and an expensive manufacturing cost. Also, since Prior art 1 is applied to only a metal having superior moldability, an application scope may be narrow. In addition, the resultant product may have many defects on the cast structure and low strength. According to Prior art 2, a large amount of materials is lost when the thin metal plate is punched. Even though there is no special problem when the truss intermediate layer is manufactured as one body, if a plurality of truss intermediate layers are stacked, the number of bonded portions may increase, and thus there are disadvantageous in aspects of bonding costs and structural strength. Also, in the case of Prior art 3, since the truss does not have an ideal structure such as the tetrahedron or pyramid structure, the truss may have inferior mechanical strength. In addition, since the iron meshes should be stacked and bonded in the same method as that of Prior art 2, the number of bonded portions may increase, and thus there are disadvantageous in aspects of bonding costs and structural strength.
Thus, to solve the above-described problems of Prior arts 1, 2, and 3, a 3D porous lightweight structure in which a manufacturing method in which a wire group in which six-directional continuous wires having an azimuth of about 60 degrees to about 120 degrees are crossed with each other in a space to form a truss having a shape similar to that of the ideal Kagome or octet truss, and a manufacturing method thereof are developed by the present inventors, i.e., Kang Ki-ju et al. The structure and manufacturing method are concretely disclosed in KR Patent Registration No. 0708483. Also, a 3D porous lightweight structure woven using a spiral wire, in which a continuous wire is formed in a spiral shape, and then, the spiral-shaped wire is rotated and inserted to manufacture the 3D porous lightweight structure, and a manufacturing method thereof are proposed as a method for more effectively manufacturing the 3D porous lightweight structure by the same inventors. The structure and manufacturing method are concretely disclosed in KR Patent Publication No. 2006-0130539.
A method for manufacturing a new 3D porous lightweight structure which may be manufactured using a spiral wire and have a shape different from that of the Kagome truss is proposed in KR Patent Application No. 10-2009-0080085 by the same inventors.
Also, a new 3D lattice truss structure which may be manufactured using the spiral wire and have a structure in which only two wires meet each other at a wire cross point to manufacture the 3D lattice truss structure by using a spiral wire having a more less spiral radius, and a manufacturing method thereof are proposed in KR Patent Application No. 10-2010-00 59690 by the same inventors.
A similar truss structure using a continuous wire is being evaluated as a metal sandwich panel having superior mechanical performance in strength to weight ratio and high mass productivity (see Yong-Hyun Lee, Byeong-Kon Lee, Insu Jeon and Ki-Ju Kang, 2007, Acta Materialia, Vol. 55, pp. 6084-6094. Yong-Hyun Lee, Ji-Eun Choi and Ki-Ju Kang, 2009, Materials and Design, Vol. 30, Issue 10, pp. 4459-4468). Since wire crossing portions and portions contacting face sheets of the similar truss structure formed of the metal are bonded using brazing or welding, the truss structure may have bonding strength as superior as that of a mother material of the wire or face sheet. However, in a case where a similar truss structure using a wire such as FRP or tungsten in which the performing of the welding or brazing is difficult is manufactured, only a method using a synthetic resin adhesive may be utilized to bond wire crossing portions and portions contacting face sheets to each other. In this case, bonding strength may be significantly inferior to that of the welded or brazed metal. Particularly, the portions bonded to the face sheets may be vulnerable to separate cores from the face sheets.
A process for manufacturing a sandwich panel from an intermediate product of an existing velvet weaving process has been developed by Belgium's and Germany's research teams (see Drechsler K, Brandt J, Arendts FJ. Integrally woven sandwich structures. Proc ECCM-3, Bordeaux 1989. p. 365-371. Verpoest I, Bonte Y, Wevers M, de Meester P., Declercq P. 2.5D- and 3D-fabrics for delamination resistant composite structures. Proc European SAMPE, Milano, Italy 1988. p. 13-21).
In order to solve the above technical problems, an embodiment of the present invention provides a method for manufacturing a new sandwich panel in low costs and large quantities, in which a core and a face sheet are coupled to each other by using a flexible continuous wire, and the core is formed in a 3D truss shape to increase separation resistance between the core and the face sheet and compression, shearing, and banding strength to weight ratio, reduce a weight thereof, and utilize an empty space therein.
According to an aspect of the present invention, a method for manufacturing a panel including a core having a truss structure between upper and lower face sheets includes: disposing the upper and lower face sheets in parallel to each other at a predetermined distance; repeatedly performing, several times, a process in which a plurality of flexible wires vertically pass through the upper and lower face sheets to reciprocation-connect the upper and lower face sheets to each other, thereby sewing the upper and lower face sheets after the upper and lower face sheets horizontally move in parallel to each other; and maximally spacing both face sheets in a vertical direction while being maintained in a parallel to each other after a relative displacement of the upper and lower face sheets is solved, and fixing the face sheets and the wires to each other.
The sewing of the upper and lower face sheets may include: (a) relatively moving the upper and lower face sheets in parallel to each other so that a virtual z-directional vertical axis passing through the upper and lower face sheets is inclined on an x-z plane at a first angle in a positive direction of an x-axis and on a y-z plane at a second angle in a negative direction of a y-axis; (b) performing a first sewing process in which the upper and lower face sheets are reciprocation-sewed in a y-axis direction by using a first wire, wherein a sewing distance in the y-axis direction corresponds to a second displacement distance of the face sheets according to the second angle, continuous wire sewing rows are spaced apart from each other by a first displacement distance of the face sheets according to the first angle, and ends of the sewing rows adjacent to each other are displaced by about ½ of the second displacement distance in the y-axis direction; (c) relatively moving the upper and lower face sheets in parallel to each other so that a support shaft is inclined on the y-z plane at an angle corresponding to about two times of the second angle in the positive direction of the y-axis; (d) performing a second sewing process in which the upper and lower face sheets are reciprocation-sewed in the y-axis direction by using a second wire, wherein, since through-positions of the wires with respect to the face sheets are the same as those of the wires in the first sewing process, the second sewing process is performed through the same method as the first sewing process; (e) relatively moving the upper and lower face sheets in parallel to each other so that the support shaft is inclined on the y-z plane at the second angle in the negative direction of the y-axis, and the support shaft is inclined on the x-z plane at an angle corresponding to about two times of the first angle in a negative direction of the x-axis; and (f) reciprocation-sewing the upper and lower face sheets in an x-axis direction by using a third wire, wherein a sewing distance in the x-axis direction is double first displacement distance, continuous wire sewing rows are spaced about ½ of the second displacement distance from each other, and ends of the sewing row adjacent to each other are displaced by the first displacement distance in the x-axis direction.
The sewing distances in the x-axis direction and the y-axis direction may be four times and two times the first and second displacement distances, respectively.
The sewing of the upper and lower face sheets may include: (a) relatively moving the upper and lower face sheets in parallel to each other so that a virtual z-directional vertical axis passing through the upper and lower face sheets is inclined on an x-z plane at a first angle in a positive direction of an x-axis and on a y-z plane at a second angle in a negative direction of a y-axis; (b) performing a first sewing process in which the upper and lower face sheets are reciprocation-sewed in a y-axis direction by using a first wire, wherein a sewing distance in the y-axis direction corresponds to a second displacement distance of the face sheets according to the second angle, and continuous wire sewing rows are spaced apart from each other by a first displacement distance of the face sheets according to the first angle; (c) relatively moving the upper and lower face sheets in parallel to each other so that a support shaft is inclined on the x-z plane at an angle corresponding to about two times of the first angle in a negative direction of the x-axis; (d) performing a second sewing process in which the upper and lower face sheets are reciprocation-sewed in the x-axis direction by using a second wire, wherein through-positions of the wires with respect to the face sheets are the same as those of the wires in the first sewing process, a sewing distance in the x-axis direction corresponds to the first displacement distance of the face sheets according to the first angle, and continuous wire sewing rows are spaced apart from each other by the second displacement distance of the face sheets according to the second angle in the y-axis direction; (e) relatively moving the upper and lower face sheets in parallel to each other so that a support shaft is inclined on the y-z plane at an angle corresponding to about two times of the first angle in a positive direction of the y-axis; (f) performing a third sewing process in which the upper and lower face sheets are reciprocation-sewed in the y-axis direction by using a third wire, wherein through-positions of the wires with respect to the face sheets are the same as those of the wires in the first and second sewing processes, a sewing distance in the y-axis direction corresponds to the second displacement distance of the face sheets according to the second angle, and continuous wire sewing rows are spaced apart from each other by the first displacement distance of the face sheets according to the first angle in the x-axis direction; (g) relatively moving the upper and lower face sheets in parallel to each other so that a support shaft is inclined on the x-z plane at an angle corresponding to about two times of the first angle in a positive direction of the x-axis; and (h) performing a fourth sewing process in which the upper and lower face sheets are reciprocation-sewed in the x-axis direction by using a fourth wire, wherein through-positions of the wires with respect to the face sheets are the same as those of the wires in the first to third sewing processes, a sewing distance in the x-axis direction corresponds to the first displacement distance of the face sheets according to the first angle, and continuous wire sewing rows are spaced apart from each other by the second displacement distance of the face sheets according to the second angle in the y-axis direction.
The sewing distances in the x-axis direction and the y-axis direction may be two times the first and second displacement distances, respectively.
At least one panel may be added between the upper and lower sheets.
The wire through-positions on the upper and lower sheets may be different from each other in the sewing processes.
The method may further include coupling a reinforcing plate to at least one of the upper and lower sheets after the face sheets and the wires are fixed.
The plurality of wires may include one continuous wire.
Each of the wires may be formed of the fiber material, and face sheet contact parts, the wires, and wire crossing parts may be cured and fixed at the same time by using an adhesive.
According to another aspect of the present invention, a method for manufacturing a panel comprising a core having a truss structure between upper and lower face sheets includes: disposing the upper and lower face sheets in parallel to each other at a predetermined distance; repeatedly performing, several times, a process in which a plurality of flexible wires vertically pass through the upper and lower face sheets to reciprocation-connect the upper and lower face sheets to each other in a state where the upper and lower face sheets are fixed; and fixing the face sheets and the wires to each other.
In the method for manufacturing the panel according to the present invention, the manufacturing process may be simplified, and the sandwich panel having the truss core may be manufactured with a low cost by using only existing developed technologies.
Also, the sandwich panel manufactured according toe the present invention may have significantly superior resistance against the core/face sheet separation when compared to that of the existing composite/honeycomb sandwich panel even though other material such as the resin or filler metal is not used for the bonding parts of the upper and lower face sheets and the wire because the wire constituting the core is connected to the face sheets without being cut off.
Also, since the sandwich panel manufactured according to the present invention has the 3D truss structure in which the core is not bent nearly, the strength to weight ratio may be relatively high, and the inner space thereof may be utilized.
Also, in the sandwich panel manufactured according to the present invention, in case where the core is formed of the flexible wire (e.g., a metal) having a predetermined stiffness in itself, satisfied compression, shearing, and bending strength to weight ratio on the basis of the stiffness of the wire in itself and mechanical structure of the truss may be achieved. If the core is formed of a wire material having an insufficient stiffness in itself such as the uni-directional yarn, the 3-D truss structure may be formed, and then, a separate resin may be sprayed to impregnate the 3-D truss structure in the resin, thereby curing the 3-D truss structure. As a result, the face sheet contact parts, the wire, and wire cross parts may be fixed at the same time to manufacture the economical and high-strength sandwich panel having the simple structure.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Throughout the drawings, equal or similar reference numerals are used to denote equal or similar components, and the terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In the drawings which illustrate each of embodiments of the present invention, a plane defined by upper and lower face sheets of a sandwich panel is defined as an x-y panel, and an axis perpendicular to the face sheets is defined as a z-axis. Here, the virtual z-axis may correspond to a length direction of a support shaft described in the embodiments. Also, with regard to a horizontal moving direction of each of the face sheets or an insertion angle of a wire, when a direction of the z-axis inclined with respect to an x-axis or a y-axis is a clockwise direction, the direction of the z-axis will be defined as a positive direction. On the other hand, when the direction of the z-axis is a counterclockwise direction, the direction of the z-axis will be defined a negative direction.
First, a face sheet is attached to each of the upper and lower frames to manufacture a complex.
Next, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on an x-z plane at a predetermined angle ψ in a clockwise direction (see
In the next process, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on the y-z planes at a predetermined angle 2θ in the clockwise direction. Thus, the support shaft may be inclined at an angle θ in a direction exactly opposite to that of
In the next process, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on the x-z planes at a predetermined angle 2ψ in the counterclockwise direction (see
Lastly, the support shaft between the upper and lower face sheets is separated, and then the upper and lower face sheets extends in directions opposite to each other so that both face sheets are away from each other. Then, in a state where the wires loosely arranged above the upper face sheet and under the lower face sheet and the wires inserted between the upper and lower face sheets are straightly pulled in parallel to each other during the sewing process of the wires, contact parts between the wires and the upper and lower face sheets are fixed.
In case where a core is formed of a flexible wire (e.g., a metal) having a predetermined stiffness in itself, satisfied compression, shearing, and bending strength to weight ratio on the basis of the stiffness of the wire in itself and mechanical structure of the truss may be achieved. If the core is formed of a wire material having an insufficient stiffness in itself such as a uni-directional yarn, a 3-D truss structure may be formed by using a semi-cured wire in which a coupling material such as a resin is previously impregnated to cure the 3-D truss structure. Alternatively, a 3-D truss structure may be formed, and then, a separate resin may be sprayed to impregnate the 3-D truss structure in the resin, thereby curing the 3-D truss structure. As a result, the face sheet contact parts, the wire, and wire crossing parts may be fixed at the same time to manufacture an economical and high-strength sandwich panel having a simple structure. Particularly, in case where the wire material includes carbon and glass yarn, a 3D truss structure may be formed in a semi-cured state in which a coupling material such as a resin is previously impregnated to cure the 3D truss structure. Alternatively, a 3D truss structure may be formed, and then, separate liquid syntactic resin bond such as epoxy may be sprayed or coated, or the 3D truss structure is impregnated into the liquid syntactic resin bond to cure the 3D truss structure.
First, upper and lower face sheets move in parallel to each other so that a support shaft rotates on an x-z plane at a predetermined angle ψ in a clockwise direction (see
In the next process, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on the x-z planes at a predetermined angle 2ψ in the counterclockwise direction. Thus, the support shaft may be inclined at an angle ψ in a direction exactly opposite to that of
In the next process, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on the y-z planes at a predetermined angle 2θ in the clockwise direction (see
In the next process, the upper and lower face sheets move in parallel to each other so that the support shaft rotates on the x-z planes at a predetermined angle 2ψ in the clockwise direction (see
Lastly, like the first embodiment, the support shaft between the upper and lower face sheets is separated, and then the upper and lower face sheets extends in directions opposite to each other so that both face sheets are away from each other. Then, in a state where the wires loosely arranged above the upper face sheet and under the lower face sheet and the wires inserted between the upper and lower face sheets are straightly pulled in parallel to each other during the sewing process of the wires, contact parts between the wires and the upper and lower face sheets are fixed.
Also, like the foregoing first embodiment, in case where a core is formed of a flexible wire (e.g., a metal) having a predetermined stiffness in itself, satisfied compression, shearing, and bending strength to weight ratio on the basis of the stiffness of the wire in itself and mechanical structure of the truss may be achieved. If the core is formed of a wire material having an insufficient stiffness in itself such as a uni-directional yarn, a 3-D truss structure may be formed by using a semi-cured wire in which a coupling material such as a resin is previously impregnated to cure the 3-D truss structure. Alternatively, a 3-D truss structure may be formed, and then, a separate resin may be sprayed to impregnate the 3-D truss structure in the resin, thereby curing the 3-D truss structure. As a result, the face sheet contact parts, the wire, and wire crossing parts may be fixed at the same time to manufacture an economical and high-strength sandwich panel having a simple structure. Particularly, in case where the wire material includes carbon and glass yarn, a 3D truss structure may be formed in a semi-cured state in which a coupling material such as a resin is previously impregnated to cure the 3D truss structure. Alternatively, a 3D truss structure may be formed, and then, separate liquid syntactic resin bond such as epoxy may be sprayed or coated, or the 3D truss structure is impregnated into the liquid syntactic resin bond to cure the 3D truss structure.
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A sewing process in which upper and lower face sheets previously move in parallel to each other, and a wire vertically passes through the upper and lower face sheets to connect the upper and lower face sheets to each other may be performed through a process in which a wire inclinedly passes through upper and lower face sheets in a state where the upper and lower face sheets are fixed to sew the upper and lower face sheets, like the manufacturing process of the sheets according to the first and second embodiments. In this case, it is unnecessary to perform a process in which positions of the upper and lower face sheets which are relatively displaced after the sewing process is performed are recovered to their original positions or a process for maximally space sheets from each other after the sewing is finished.
That is, the eighth embodiment illustrates an example of the method in which the wire inclinedly passes through the upper and lower face sheets in the state where the upper and lower face sheets are fixed to sew the upper and lower face sheets. Thus, the manufactured sandwich panel may have the same structure as that of the sandwich panel according to the foregoing first embodiment. Also, a support used for manufacturing the sandwich panel according to the current embodiment may have a structure and a coupling configuration with a frame which are equal to those of each of the sandwich panels according to the foregoing first and second embodiments.
First, a wire is changed insertion angle so that the wire is inclined on an x-z plane at a predetermined angle ψ (hereinafter, referred to as a “first angle”) in a counterclockwise direction and inclined on a y-z plane at a predetermined angle θ (hereinafter, referred to as a “second angle”) in a clockwise direction. Then, the flexible wire passes through the upper and lower face sheets to reciprocation-sew the upper and lower face sheets. In this case, a sewing distance yo may be a displacement (hereinafter, referred to as a “second displacement”) between wire through-parts of each of the upper and lower face sheets according to the second angle on the y-z plane. In a state where an x-axis coordinate is fixed, the face sheets are sewed from one ends thereof to the other ends in a y-axis direction to form a sewing row. When the sewing position reaches ends of the face sheets, the sewing position moves by a predetermined distance xo in the x-axis direction, and then, a sewing start point is displaced by half of the sewing distance yo to sew the face sheets in a reverse direction. In this case, the sewing distance xo may be a displacement (hereinafter, referred to as a “first displacement”) between wire through-parts of each of the upper and lower face sheets according to the first angle on the x-z plane. When the sewing position reaches an opposite end, the x coordinate and the sewing start point are adjusted to repeatedly perform the sewing process. The above-described sewing process is called a “primary sewing”.
In the next process, a wire is changed insertion angle so that the wire is inclined on the x-z plane at the predetermined angle w in the counterclockwise direction and inclined on the y-z plane at the predetermined angle θ in the clockwise direction. Thus, the insertion angle of the wire is inclined on the y-z plane at the angle θ in a direction exactly opposite to that of
In the next process, a wire is changed in insertion angle so that the wire is inclined on the x-z plane at the predetermined angle ψ in the counterclockwise direction. In this case, the insertion angle of the wire on the y-z plane is perpendicular to the x-y plane. The face sheets are sewed from one end on the y-axis in the x-axis direction. In a state where a sewing distance may be maintained to a certain distance 2xo, and a y coordinate may be fixed, the face sheets are straightly sewed from one ends thereof to the other ends in the x-axis direction. When the sewing position reaches ends of the face sheets, the sewing operation pauses, and then a y coordinate increases by a predetermined value yo/2. Then, a sewing start point is displaced by half of the sewing distance xo to sew the face sheets in a reverse direction. When the sewing position reaches an opposite end, the y coordinate and the sewing start point are adjusted to repeatedly perform the sewing process. The above-described sewing process is called a “tertiary sewing”.
Lastly, contact parts between the wire inserted between the upper and lower face sheets and the upper and lower face sheets in the wire sewing process are fixed.
In case where a core is formed of a flexible wire (e.g., a metal) having a predetermined stiffness in itself, satisfied compression, shearing, and bending strength to weight ratio on the basis of the stiffness of the wire in itself and mechanical structure of the truss may be achieved. If the core is formed of a wire material having an insufficient stiffness in itself such as a uni-directional yarn, a 3-D truss structure may be formed by using a semi-cured wire in which a coupling material such as a resin is previously impregnated to cure the 3-D truss structure. Alternatively, a 3-D truss structure may be formed, and then, a separate resin may be sprayed to impregnate the 3-D truss structure in the resin, thereby curing the 3-D truss structure. As a result, the face sheet contact parts, the wire, and wire cross parts may be fixed at the same time to manufacture an economical and high-strength sandwich panel having a simple structure. Particularly, in case where the wire material includes carbon and glass yarn, a 3D truss structure may be formed in a semi-cured state in which a coupling material such as a resin is previously impregnated to cure the 3D truss structure. Alternatively, a 3D truss structure may be formed, and then, separate liquid syntactic resin bond such as epoxy may be sprayed or coated, or the 3D truss structure is impregnated into the liquid syntactic resin bond to cure the 3D truss structure.
The sandwich panel manufactured through the above-described process may be equal to that of
That is, the ninth embodiment illustrates an example of the method in which the wire inclinedly passes through the upper and lower face sheets in the state where the upper and lower face sheets are fixed to sew the upper and lower face sheets. Thus, the manufactured sandwich panel may have the same structure as that of the sandwich panel according to another embodiment. Also, a support used for manufacturing the sandwich panel may have a structure and a coupling configuration with a frame which are equal to those of each of the sandwich panels according to the foregoing first, second, and eighth embodiments.
First, an insertion angle of a wire is changed so that the wire is inclined on an x-z plane at a predetermined angle ψ (hereinafter, referred to as a “first angle”) in a counterclockwise direction and inclined on a y-z plane at a predetermined angle θ (hereinafter, referred to as a “second angle”) in a clockwise direction. A flexible wire passes through upper and lower face sheets to reciprocation-sew the upper and lower face sheets. Here, a sewing distance yo may be a displacement (hereinafter, referred to as a “second displacement”) between wire through-parts of each of the upper and lower face sheets according to the second angle on the y-z plane. In a state where an x coordinate is fixed, the face sheets are sewed from one ends thereof to the other ends in a y-axis direction. Then, when the sewing position reaches ends of the face sheets, the sewing operation pauses, and then the x coordinate increases by a predetermined value xo. Thereafter, the face sheets are reversely sewed in a direction parallel to the y-axis direction. The sewing distance xo may be a displacement (hereinafter, referred to as a “first displacement”) between wire through-parts of each of the upper and lower face sheets according to the first angle on the x-z plane. When the sewing position reaches an opposite end, the x coordinate is adjusted to repeatedly perform the sewing process. The above-described sewing process is called a “primary sewing”.
In the next process, an insertion angle of a wire is changed so that the wire is inclined on the x-z plane at the predetermined angle ψ in a clockwise direction and inclined on the y-z plane at the predetermined angle θ in a counterclockwise direction. Thus, the insertion angle of the wire is inclined at the angle ψ in a direction exactly opposite to that of
In the next process, an insertion angle of a wire is changed so that the wire is inclined on the x-z plane at the predetermined angle ψ in the clockwise direction and inclined on the y-z plane at the predetermined angle θ in the counterclockwise direction. In a state where the x coordinates of the face sheets are fixed, the face sheets are sewed from a right end to a left end on the y-axis. The face sheets are sewed at a constant sewing distance yo. Then, when the sewing position reaches ends of the face sheets, the sewing operation pauses, and then the x coordinate increases by a predetermined value xo. Thereafter, the face sheets are reversely sewed in a direction parallel to the y-axis direction. When the sewing position reaches an opposite end, the x coordinate is adjusted to repeatedly perform the sewing process in a reverse direction. The above-described sewing process is called a “tertiary sewing”.
In the next process, an insertion angle of a wire is changed so that the wire is inclined on the x-z plane at the predetermined angle ψ in the counterclockwise direction and inclined on a y-z plane at the predetermined angle θ in the clockwise direction. In a state where the y coordinates of the face sheets are fixed, the face sheets are sewed from a right end to a left end on the x-axis. The face sheets are sewed at a constant sewing distance xo. Then, when the sewing position reaches ends of the face sheets, the sewing operation pauses, and then the y coordinate increases by a predetermined value yo. Thereafter, the face sheets are reversely sewed in a direction parallel to the x-axis direction. When the sewing position reaches an opposite end, the y coordinate is adjusted to repeatedly perform the sewing process in a reverse direction. The above-described sewing process is called a “quartic sewing”.
Lastly, like the eighth embodiment, the support shaft between the upper and lower face sheets is separated, and then the upper and lower face sheets extends in directions opposite to each other so that both face sheets are away from each other. Then, in a state where the wires inserted between the upper and lower face sheets are straightly pulled in parallel to each other during the sewing process of the wires, contact parts between the wires and the upper and lower face sheets are fixed.
Also, like the foregoing eighth embodiment, in case where a core is formed of a flexible wire (e.g., a metal) having a predetermined stiffness in itself, satisfied compression, shearing, and bending strength to weight ratio on the basis of the stiffness of the wire in itself and mechanical structure of the truss may be achieved. If the core is formed of a wire material having an insufficient stiffness in itself such as a uni-directional yarn, a 3-D truss structure may be formed by using a semi-cured wire in which a coupling material such as a resin is previously impregnated to cure the 3-D truss structure. Alternatively, a 3-D truss structure may be formed, and then, a separate resin may be sprayed to impregnate the 3-D truss structure in the resin, thereby curing the 3-D truss structure. As a result, the face sheet contact parts, the wire, and wire cross parts may be fixed at the same time to manufacture an economical and high-strength sandwich panel having a simple structure. Particularly, in case where the wire material includes carbon and glass yarn, a 3D truss structure may be formed in a semi-cured state in which a coupling material such as a resin is previously impregnated to cure the 3D truss structure. Alternatively, a 3D truss structure may be formed, and then, separate liquid syntactic resin bond such as epoxy may be sprayed or coated, or the 3D truss structure is impregnated into the liquid syntactic resin bond to cure the 3D truss structure.
The sandwich panel manufactured through the above-described process may be equal to that of
The technical concepts of the present invention are used only for explain a specific exemplary embodiment while not limiting the present invention, and thus, the detailed description may be amended or modified according to viewpoints and applications, not being out of the scope, technical idea and other objects of the present invention.
For example, the plurality of wires used in the sewing process may be provided as physically separated wires or continuous one wire.
Also, the frame serving as a face sheet fixing unit described in the embodiments and the support serving as a frame spacing unit may be substituted with other units, respectively.
Also, the sewing process may be performed by twisting an upper thread and a lower thread with respect to each other like a general sewing process, but not reciprocating one wire between the upper and lower face sheets (see
Number | Date | Country | Kind |
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10-2010-0137476 | Dec 2010 | KR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/KR2011/000979 | 2/14/2011 | WO | 00 | 6/28/2013 |