Patent Description:
Conventionally, a honeycomb core, which is an assemblage of hexagonal cells (hexagonal cylinders), is known as a light and strong core member. The honeycomb core is used as a core member in many structures. For example, if plate members are attached to opposite faces of the honeycomb core (i.e., the core member), a combination of the plate members and the honeycomb core becomes a planar or panel-like structure. Such structures are used, for example, in building walls, aircraft bodies, and stages (tables) of large processing equipment.

When the honeycomb core is formed from a plurality of members whose material is paper, aluminum, plastic or the like, the honeycomb core may be manufactured by applying an adhesive linearly onto opposite faces of each of the members, laminating the members to prepare a block-like laminate, cutting the laminate to a desired width and spreading the laminate.

However, when the honeycomb core is made of a carbon-fiber-reinforced plastics (CFRP) having characteristics such as high specific stiffness, a low density and a low coefficient of thermal expansion, the above-described manufacturing method cannot be adopted.

Patent Literature Document <NUM> (Patent No. <CIT>) discloses a core member that includes a large number of cylindrical CFRP pieces arranged side by side and joined with each other by an adhesive. Each of the CRRP pieces has a hollow cylindrical portion. Patent Literature Document <NUM> also discloses a core member that includes a large number of hexagonal cylindrical CFRP pieces arranged side by side and joined by an adhesive. Each of the CRRP pieces has a hollow cylindrical portion.

Core members made of a plurality of rectangular flat plate members including a comb-teeth portion are known from <CIT>, <CIT> and <CIT>. The comb-teeth portion is defined by a plurality of notches extending parallel to a short side of the rectangular shape and open to at least one of long sides of the rectangular shape. The notches are engaged with each other such that the plurality of flat plate members cross each other and the crossing flat plate members create a plurality of hollow cylindrical portions between them.

Patent Literature Document <NUM>: <CIT> <CIT>, <CIT>, <CIT>.

In the technique described in Patent Literature Document <NUM> (<CIT>), a CFRP is molded into a cylindrical shape or a hexagonal cylindrical shape, and a large number of molded CFRP cylinders are arranged side by side and bonded to each other. Thus, the manufacturing process is complicated. In addition, a special and dedicated processing machine and a special and dedicated assembling machine are required. Thus, the cost is increased accordingly.

It is an object of the present invention to provide a honeycomb-like core member which can be easily manufactured and a structure using the core member.

In order to achieve the above-mentioned object, one aspect of the present invention provides a core member as claimed in present claim <NUM>.

Thus, it is possible to obtain a honeycomb-like core member having a simple configuration by merely intersecting the flat plate members having a comb-teeth portion at the notches. Therefore, it is possible to create the core member in a simple manner without requiring a dedicated processing machine and a dedicated assembling machine. Further, since a portion where two planar segments overlap each other (the portion where the thickness of the wall of the core member is doubled) and a portion where two planar segments do not overlap (the portion where the single planar member extends alone) are not mixed in the core member, the mechanical properties and thermal characteristics in a plane perpendicular to the thickness direction of the core member are equalized. Therefore, distortion of the core member due to temperature change or the like can be suppressed or avoided.

The notches of the core member may be engaged with each other such that the flat plate members cross each other at an angle of <NUM> degrees.

In this configuration, the first cylindrical portions become the hexagonal cylindrical portions, each of which has an equilateral hexagonal shape, and the second cylindrical portions become the triangular cylindrical portions, each of which as an equilateral triangular shape. Therefore, the core member possesses excellent stability.

In the core member, the flat plate members having the comb-teeth portions may include a plurality of first flat plate members, each of which has the notches open to one of the long sides of the rectangular plate member at equal intervals and may also include a plurality of second flat plate members, each of which has the notches open to one of the long sides of the rectangular plate member at equal intervals and the notches open to the other of the long sides of the rectangular plate member at the equal intervals. The notches open to the other of the long sides of the second flat plate members may be shifted from the notches open to the above-mentioned one of the long sides of the second flat plate members at a half of the interval.

In this configuration, it is possible to constitute the honeycomb-like core member from only two types of flat plate members.

A length (depth) of each of the notches in the core member may be longer than a half of a length of the short side of the rectangular plate member.

In this configuration, a gap can be formed in the vicinity of each of the notches when the flat plate members are engaged with each other. In other words, the inside of each of the first cylindrical portions and the inside of each of the second cylindrical portions are not hermetically sealed. Thus, it is possible to impart air permeability (breathability) to the cylindrical portions, and to suppress the distortion that would occur in the core member due to the pressure change inside the cylindrical portions upon temperature change.

A width of each of the notches is set to a value that forms a gap in the vicinity of each of the notches when the flat plate members are engaged with each other.

This configuration also prevents the inside of the first cylindrical portion and the second cylindrical portion from being sealed. Thus, it is possible to suppress the distortion that would occur in the core member due to the pressure change inside the cylindrical portions upon temperature change. Further, when the flat plate members are engaged with each other, it is possible to prevent the flat plate members from bending at the notches.

Each of the flat plate members of the core member may be made of a carbon fiber reinforced plastic in which a plurality of prepregs are laminated. In this configuration, the honeycomb-like core member has characteristics of the carbon fiber reinforced plastics (CFRP) such as high specific stiffness, a small density and a small coefficient of thermal expansion.

Fibers of the carbon fiber reinforced plastic of the core member may extend in a direction parallel to the short side of the flat plate member. This configuration can prevent fluctuation (strain) to the short side of the flat plate member due to temperature change.

The carbon fiber reinforced plastic of the core member may be a cross-ply laminate. In this configuration, it is possible to impart isotropy in a pseudo manner.

According to another aspect of the present invention, there is provided a method of manufacturing a core member comprising the features of present claim <NUM>.

In this manner, the honeycomb-like core member can be manufactured by simply crossing and combining the flat plate members having the comb-teeth portions at the notches. That is, it is possible to create the core member in a simple manner without requiring a dedicated processing machine and a dedicated assembling machine.

According to still another aspect of the present invention, there is provided a structure that includes the above-described core member and plate members bonded to opposite faces of the core member.

Thus, it is possible to make a structure using the honeycomb-like core member, which is easy to manufacture. Since the mechanical properties and thermal characteristics of the core member in a plane perpendicular to the thickness direction are uniform, the resulting structure can suppress distortions due to temperature change or the like.

According to the present invention, it is possible to provide a honeycomb-like core member which can be easily manufactured without requiring a dedicated processing machine and a dedicated assembling machine.

The above-mentioned objects, aspects and advantages of the present invention and other objects, aspects and advantages of the present invention will be understood by those skilled in the art from the following detailed description of the invention by referring to the accompanying drawings and the appended claims.

In this embodiment, a honeycomb-like core member in which two types of plate members shown in <FIG> are assembled will be described.

<FIG> shows a first flat plate <NUM> which is a plate member of a honeycomb-like core member of this embodiment. <FIG> shows a second flat plate <NUM> which is another plate member of the honeycomb-like core member of this embodiment.

As shown in <FIG>, the first flat plate <NUM> is a rectangular plate member and has a plurality of notches or cutouts 11a, each of which is open to one of long sides (upper long side in <FIG>) of the rectangular plate. Thus, the first flat plate <NUM> is a comb-shaped member (having comb teeth on one side) and each of the notches 11a extends parallel to the short side of the rectangular plate. The notches 11a are formed at equal intervals L in the long side direction. The length (depth) f of each of the notches 11a is slightly longer than a half of the length g of the short side. The width w of the notch 11a is greater than the thickness of the first flat plate <NUM>. The interval L may be referred to as a pitch of the notches 11a.

As shown in <FIG>, the second flat plate <NUM> is a rectangular plate member and has a plurality of lower notches 12a, each of which is open to one of the long sides (lower long side in <FIG>) of the rectangular plate and a plurality of upper notches 12b, each of which is open to the other long side (upper long side) of the rectangular plate. Each of the notches 12a extends parallel to the short side of the rectangular plate. Each of the notches 12b extends parallel to the short side of the rectangular plate. Thus, the second flat plate <NUM> is another comb-shaped member (having comb teeth on both sides).

In the second flat plate <NUM>, the notches 12a are formed at equal intervals <NUM> in the long side direction, and the notches 12b are formed at equal intervals <NUM> in the long side direction. The interval <NUM> may be referred to as a pitch of the notches 12a (or 12b). The notches 12a and the notches 12b are shifted from each other by a half of the interval <NUM> in the long side direction. In other words, the notches 12a and the notches 12b are alternately formed at the constant distance L in the long side direction. The length f and the width w of each of the notches 12a is equal to the length f and the width w of the notch 11a of the first flat plate <NUM>.

The thickness of the first flat plate <NUM> is equal to the thickness of the second flat plate <NUM>. The thicknesses of each of the first flat plate <NUM> and the second flat plate <NUM> may be set to a value (e.g., <NUM> or more) that enables each of the first flat plate <NUM> and the second flat plate <NUM> to stand alone. The thickness of each of the first flat plate <NUM> and the second flat plate <NUM> may be appropriately set depending on the strength required.

The first flat plate <NUM> and the second flat plate <NUM> may be made of carbon fiber reinforced plastics (CFRP).

A CFRP plate is formed by stacking a plurality of prepregs. The prepreg is a sheet-like member in which a carbon fiber is impregnated with a resin while maintaining directionality of fibers. The resin in the prepreg is, for example, a thermosetting epoxy resin. It should be noted that the resin in the prepreg is not limited to the thermosetting epoxy resin, i.e., the resin may be, for example, a thermosetting resin such as an unsaturated polyester, a vinyl ester, a phenol, a cyanate ester, or a polyimide.

The CFRP plate is formed by laminating a plurality of layers of prepregs (e.g., <NUM> layers to <NUM> layers of prepregs) in a mold such that the fibers are arranged in different directions, heating the laminate of the prepreg layers to about <NUM> degree C to <NUM> degrees C under reduced pressure, and pressurizing (pressure-bonding) the laminate of the prepreg layers to cure the laminate. The prepreg may be, for example, a UD (Uni-Direction) material. The UD material is a material in which the direction of the fiber extends in only one direction.

The CFRP plate, which is the first flat plate <NUM> and the second flat plate <NUM>, may be a cross-ply laminate (multilayer plate) in which the prepregs are laminated, with the fibers extending in a <NUM>-degree direction and the fibers extending in a <NUM>-degree direction being alternately laminated. The CFRP plate may be a symmetrical cross-ply laminate in which the laminate is vertically symmetrical with respect to a center plane (upper half has a mirror symmetry of a lower half). In <FIG>, one of the directions of the fibers is the vertical direction and the other direction is the horizontal direction.

The CFRP plate prepared in the above-mentioned manner is a plate material that is less dense (i.e., lighter) than metallic materials such as iron and aluminum, but yet has a higher strength. In addition, this plate material is quasi-isotropic.

A plurality of first flat plates <NUM> and a plurality of second flat plates <NUM> are prepared in this embodiment. Then, the first flat plates <NUM> and the second flat plates <NUM> are assembled by engaging the notches 11a of the first flat plates <NUM> with the notches 12a of the second flat plates <NUM> such that the first flat plates <NUM> and the second flat plates <NUM> intersect with each other. Thus, the assemblage of the first flat plates <NUM> and the second flat plates <NUM> creates a honeycomb-like core member that includes a plurality of hexagonal cylindrical portions (first cylindrical portions) and a plurality of triangular cylindrical portions (second cylindrical portions).

A process of assembling the first and second flat plates to obtain the core member of this embodiment will now be described in detail.

This embodiment will describe a structure in which the flat plates <NUM> and <NUM> are engaged with each other at an angle of <NUM> degrees such that the equilateral hexagonal cylinder portions and the equilateral triangular cylinder portions are created in the honeycomb-like core member.

As shown in <FIG>, a plurality of first flat plates <NUM> with the openings of the notches 11a facing upward (hereinafter referred to as "first flat plates 11A") are arranged in parallel to each other. The first flat plates 11A are spaced from each other at predetermined distances <NUM> (twice the pitch of the notches 11a) in the direction of <NUM> degrees with respect to the plane of the first flat plate 11A. The first flat plates 11A are arranged side by side in parallel.

As shown in <FIG>, a plurality of second flat plates <NUM> are engaged with the first flat plates 11A arranged in the first step. Specifically, the notches 12a which open to the lower sides of the second flat plates <NUM> are fitted in the notches 11a of the first flat plates 11A. It should be to be noted that the first flat plates 11A and the second flat plates <NUM> are not bonded to each other (the interfaces between the first and second flat plates are free of adhesives) in the second step.

The second flat plates <NUM> are spaced from each other at the predetermined distances <NUM> in the direction of <NUM> degrees with respect to the plane of the second flat plate <NUM>, and are arranged side by side in parallel. In <FIG>, the intersecting angle θ between the first flat plate 11A and the second flat plate <NUM> is <NUM> degrees.

The notches 12a of the second flat plates <NUM> are inserted into every other one of the notches 11a of each of the first flat plates 11A.

As shown in <FIG>, a plurality of first flat plates <NUM> with the openings of the notches 11a facing downward (hereinafter referred to as "first flat plates <NUM> B") are engaged with the first flat plates 11A and the second flat plates <NUM> assembled in the second step. Specifically, the notches 11a of the first flat plates 11B are fitted in the empty notches 11a of the first flat plates 11A, which have not yet received the second flat plates <NUM>, and the notches 12b, which open to the upper sides of the second flat plates <NUM>. The first flat plates 11A and the first flat plates 11B are not bonded to each other and the second flat plates <NUM> and the first flat plates 11B are not bonded to each other.

The first flat plates 11B are spaced from each other at the predetermined distances <NUM> in the direction of <NUM> degrees with respect to the plane of the first flat plate 11B. The first flat plates 11B are arranged side by side in parallel. In <FIG>, the intersecting angle θ' between the first flat plate 11A and the first flat plate 11B is <NUM> degrees and the intersecting angle θ" between the second flat plate <NUM> and the first flat plate 11B is also <NUM> degrees.

In this manner, the honeycomb-like core member <NUM> is manufactured.

As described above, the first flat plates <NUM> shown in <FIG> are used in the first step and the third step in the assembling process for the core member <NUM>. On the other hand, the second flat plates <NUM> shown in <FIG> are used only in the second step. Therefore, the number of the first flat plates <NUM> used for the core member <NUM> is greater than the number of the second flat plates <NUM>.

<FIG> is a plan view of the honeycomb-like core member <NUM> of this embodiment.

As shown in <FIG>, the core member <NUM> includes the first flat plates 11A and 11B and the second flat plates <NUM>. The notches of these flat plates are engaged with each other such that the flat plates intersect each other at an angle of <NUM> degrees. In the core member <NUM>, therefore, a plurality of hexagonal cylindrical portions (regular hexagonal cells) <NUM> and a plurality of triangular cylindrical portions (equilateral triangular cells) <NUM> are defined by the first flat plates 11A and 11B and the second flat plates <NUM>.

A conventional (or ordinary) honeycomb core, when viewed from the top (in a plan view), is an assemblage of regular hexagonal cells (equilateral hexagonal cells). On the other hand, the core member <NUM> of this embodiment, has a configuration in which the cells of the equilateral triangle are arranged around the cells of the equilateral hexagon. Therefore, the core member <NUM> of this embodiment is not called a true honeycomb core, but a honeycomb-like core (a quasi honeycomb core). However, the core member <NUM> can have the same strength as that of an ordinary honeycomb core.

Since the core member <NUM> of this embodiment is constituted by CFRP, the core member <NUM> can be a honeycomb-like core member having CFRP properties such as high specific stiffness, a small density and a small thermal expansion coefficient.

When an ordinary honeycomb core is made from CFRP, a plurality of hexagonal cylindrical CFRP members <NUM> as shown in <FIG> are used in a manufacturing method. Specifically, the CRRP members <NUM> are arranged side by side without a gap and bonded to each other as shown in <FIG>. However, this manufacturing method requires a step of forming a CFRP member to a hexagonal cylindrical shape, a step of preparing and arranging a large number of CFRP members <NUM> and a step of bonding the CFRP members. This manufacturing method is complicated.

When making a panel or a planar stage (flat stage) as a structure that has a honeycomb core as a core member, a plate member is bonded to the top of the core member and another plate member is attached (bonded) to the bottom of the core member. As a result, the inside of each of the hexagonal cylindrical portions of the honeycomb core will be completely sealed by the plate members. In general, a thermosetting adhesive is used for attaching the plate members to the core member, and the honeycomb core is heated at the time of attaching the plate members. If the interior of the honeycomb core is sealed (closed), a pressure difference arises between the inside and the outside of the sealed space upon finishing the attachment of the plate members and lowering the temperature. This pressure difference may cause distortions to occur in the structure. Furthermore, even during use of the structure, the above-mentioned pressure difference arises as the environmental temperature changes. This may also cause distortions to occur in the structure.

To prevent the inside of the first cylindrical portion and the second cylindrical portion from beingsealed, the walls of the hexagonal cylinder portions need to have openings that communicate to the outside for leakage of the inside air to the outside. This makes the manufacturing process further complicated.

When making an ordinary honeycomb core from CFRP, there is another method: a CFRP member <NUM> is bent at a plurality of positions with equal intervals as shown in <FIG> such that the CFRP member <NUM> has a zigzag shape, and a plurality of such CFRP members are prepared. Then, the CFRP members <NUM> are partially bonded as shown in <FIG> to form a plurality of hexagonal cylinder portions.

In order to bend the plate member at equal intervals as shown in <FIG>, however, a special processing device is required. Further, similar to the honeycomb core shown in <FIG>, it is necessary to make holes that allow the air to leak to the outside.

The honeycomb core created by bonding the CFRP members <NUM> as shown in <FIG> includes a mixture of portions where the thickness of the wall of the honeycomb core is doubled because two planar segments of the CFRP members are bonded to each other (the segments indicated by the circle in <FIG>) and portions where the thickness of the wall is unchanged because a single planar segment of the CFRP member exists, as shown in <FIG>. If the direction parallel to the wall whose thickness becomes double (ribbon direction) is referred to as a first direction and the direction perpendicular to the first direction is referred to as a second direction, the mechanical properties and thermal properties of the honeycomb core, such as the strength, rigidity and thermal expansion coefficient, in the first direction are different from those in the second direction.

This will become a problem when the honeycomb core is used, for example, as a core member of a stage of a processing machine to which processing precision is required. This is because there is a possibility that distortion may occur on the stage surface due to a force applied to the stage, a temperature change of the environment in which the device is placed, or the like.

On the other hand, the core member <NUM> of this embodiment is constructed by engaging the notches of the comb-teeth-shaped flat plates with each other such that the flat plates intersect each other. Therefore, the core member does not have a portion (or portions) where the flat segments overlap. In each of the portions where the flat plates 11A, 11B and <NUM> intersect (i.e., the notches of the flat plates), the flat plates are in contact with each other, but they are in partial contact, and the flat plates are not firmly fixed to each other by an adhesive or the like.

Therefore, unlike the honeycomb core shown in <FIG>, the core member of this embodiment has no anisotropy in mechanical and thermal characteristics, i.e., the mechanical and thermal characteristics of the core member in the first direction are the same as those in the second direction. Thus, it is possible to suppress or avoid the generation of distortions due to a temperature change or the like.

In addition, the core member <NUM> of this embodiment can be manufactured by simply fitting the notches of the comb-shaped flat plates into the notches of the comb-shaped flat plates. Therefore, a special and dedicated processing machine and/or a special and dedicated assembling machine is unnecessary, and accordingly, the core member of this embodiment can be produced at low cost.

The length f of the notch formed in the flat plate <NUM>, <NUM> is longer than a half of the length g of the short side of the flat plate. As a result, a gap can be formed at (or in the vicinity of) every intersecting portion of every two flat plates (at the engaging portion of every two notches of every two flat plates). This gap serves as the above-described hole for leakage of the air to the outside. That is, the notches formed to allow the flat plates to intersect each other also serve as the holes for leakage of the air to the outside. Therefore, even when the plate members are attached to the top and bottom of the core member <NUM>, the inside of each of the hexagonal cylindrical portions <NUM> and the inside of each of the triangular cylindrical portions <NUM> of the core member <NUM> are not sealed from the outside. Therefore, the step of forming holes for air leakage is not required. This reduces the production time of the core member <NUM> and contributes to the cost reduction of the core member <NUM>.

The width w of the notch 11a, 12a, 12b formed in the flat plate is greater than the thickness of the flat plate. Specifically, the width w of the notch is set to a value that allows a gap to be left at the interface between every two engaged notches of every two flat plates when the two flat plates are engaged with each other at the predetermined angle. Every two flat plates are engaged with each other at the intersecting angle of <NUM> degrees in this embodiment, and therefore the width w of each of the notches is set to a sum of a first value and a second value. The first value allows the two flat plates to engage with each other at the angle of <NUM> degrees (i.e., the first value is decided based on the thickness of the flat plate (design value of the flat plate) d and the intersecting angle θ (<NUM> degrees) of the plates). The second value is predetermined play (margin). The play is preferably set in consideration of a manufacturing error or tolerance of the thickness of the flat plate.

If the width w of the notch is too large (if the play is too large), the initial posture of the flat plate at the time of assembling the flat plates becomes oblique, and accordingly the resulting core member would become easy to buckle or collapse. Therefore, it is preferable that the play of the width w of the notch is set to a small value to such an extent that the buckling does not occur, i.e., to such an extent that the initial posture of the flat plate does not become oblique.

As described above, the core member <NUM> of this embodiment is a honeycomb-like core member that has the uniform (same) mechanical properties and thermal characteristics in a plane perpendicular to the thickness direction, does not require a special processing machine and does not need a machining step for making air leakage holes.

The core member <NUM> of this embodiment can be used as a core member of various structures. For example, as shown in <FIG>, two plate members <NUM> may be disposed to sandwich the core member <NUM> from above and below and bonded to the top and bottom of the core member <NUM> with bonding members <NUM> to obtain a panel-like structure <NUM>.

Each of the bonding members (adhesive members) <NUM> may be a sheet-like adhesive or a liquid adhesive. It is desirable that the core member <NUM> and the plate members <NUM> are made of the same material. By using the same material, the thermal expansion coefficient of the core member <NUM> becomes equal to the thermal expansion coefficient of the plate member <NUM>, and therefore it is possible to suppress or avoid the distortion of the structure <NUM> due to temperature changes.

If the material of the core member <NUM> is CFRP and the material of the plate members <NUM> is also CFRP, it is possible to make a strong panel-shaped structure <NUM> that has light weight and generates small thermal deformation (small thermal expansion).

CFRP has a small coefficient of thermal expansion in the direction parallel to the fiber and a small fluctuation (strain) due to heat, in the direction parallel to the fiber. Therefore, if the direction of the fibers of CFRP is aligned with a direction parallel to the short side of each of the flat plates of the core member <NUM>, it is possible to prevent surface fluctuations (deformations and/or strains) in a direction perpendicular to the surface of the plate member <NUM>, which would otherwise be caused by temperature changes.

In this embodiment, the CFRP plate that constitutes each of the flat plates of the core member <NUM> is a cross-ply laminate (multilayer plate) in which the prepregs are laminated such that the directions of the fibers of the prepregs become the angle of <NUM> degree and the angle of <NUM> degrees alternately. It should be noted, however, that the present invention is not limited to such configuration. For example, the directions of the fibers in the cross-ply laminate may also include an angle of <NUM> degrees (intermediate angle) and/or an angle of <NUM> degrees (another intermediate angle) in addition to the angle of <NUM> degree and the angle of <NUM> degrees. Use of such laminate of CFRP gives the core member <NUM> the isotropy in terms of the stiffness and expansion/contraction. Thus, the core member <NUM> may be used in various applications and structures.

Such structure <NUM> may be used, for example, as building walls, aircraft bodies, space equipment, stages of large processing machines, and the like.

Although the hexagonal cylindrical portions <NUM> having the equilateral hexagonal shape and the triangular cylindrical portions <NUM> having the equilateral triangular shape are formed in the core member <NUM> of the above-described embodiment, each of the hexagonal cylindrical portions <NUM> is not limited to the equilateral hexagonal shape and each of the triangular cylindrical portions <NUM> is not limited to the equilateral triangular shape.

For example, as shown in <FIG>, a core member 10A may have hexagonal cylindrical portions 13A and triangular cylindrical portions 14A. The core member 10A shown in <FIG> includes a plurality of first flat plates 11A, a plurality of second flat plates <NUM>, and a plurality of third flat plates <NUM>. The third flat plate <NUM> has the same configuration as the first flat plate 11B except for the distance (pitch) between every two adjacent notches. In the core member 10A, the intersecting angle θ between the first flat plate 11A and the second flat plate <NUM> is <NUM> degrees, the intersecting angle θ' between the first flat plate 11A and the third flat plate <NUM> is <NUM> degrees, and the intersecting angle θ" between the second flat plate <NUM> and the third flat plate <NUM> is <NUM> degrees. The distance between every two adjacent third flat plates <NUM> is denoted by L.

Although a plurality of flat plates are engaged with each other such that the flat plates cross each other at the angle of <NUM> degrees in the above-described embodiment, the intersecting angle of the flat plates is not limited to the above-mentioned angle, i.e., it can be any suitable angle. It should be noted, however, that if the flat plates are engaged with each other such that the flat plates cross at the angle of <NUM> degrees, the core member has excellent stability, which is preferable.

Although the honeycomb-like core member <NUM> is formed using two types of flat plates in the above-described embodiment, three or more types of flat plates may be used to form the honeycomb-like core member.

Although the notches of the second flat member <NUM> are formed at equal intervals (pitches) and shifted from each other by a half of the pitch in the above-described embodiment, the notches of the second flat member may not be formed at equal intervals and/or may not be shifted from each other by a half of the pitch. In such configurations, the cross-sectional shapes of the triangular cylindrical portions made around the hexagonal cylindrical portions have the different sizes from those shown in <FIG>. Even if there is a certain difference in the size of each of the triangular cylindrical portions, there is no problem in the strength of the core member.

Claim 1:
A core member (<NUM>) comprising a plurality of flat plate members (<NUM>, 11A, 11B, <NUM>), each of said plurality of flat plate members having a rectangular shape, each of said plurality of flat plate members including a comb-teeth portion, the comb-teeth portion being defined by a plurality of notches (11a, 12a, 12b) formed in each of said plurality of flat plate members such that the plurality of notches extend parallel to a short side of the rectangular shape and open to at least one of long sides of the rectangular shape,
wherein said plurality of notches (11a, 12a, 12b) of the plurality of flat plate members (<NUM>, 11A, 11B, <NUM>) are engaged with each other such that the plurality of flat plate members cross each other and the crossing flat plate members create a plurality of cylindrical portions having a triangular cylinder shape (<NUM>),
characterized in that
the crossing flat plate members create a plurality of first cylindrical portions each having a hexagonal cylinder shape (<NUM>) and a plurality of second cylindrical portions each having a triangular cylinder shape (<NUM>), and
a width (w) of each of the notches (11a, 12a, 12b) is set to a value that forms a gap in the vicinity of each of the notches when the flat plate members (<NUM>, 11A, 11B, <NUM>) are engaged with each other.