Patent Description:
A composite material such as carbon fiber reinforced plastic (CFRP) is used in some aircraft components, such as a fuselage and a main wing.

A CFRP structural member (composite material structure) constituting an aircraft component can have any type of cross-sectional shape. One method for manufacturing such a composite material structure is a method in which a plurality of fiber sheets (e.g., pre-preg sheets) are stacked to produce a laminate of flat fiber sheets (also referred to as a "charge"), and this laminate is shaped using a molding die into any suitable shape.

One such shape is a kink shape. A kink shape is a shape including a first surface having a bent shape (kink) and a second surface intersecting the first surface.

The molding die used for shaping the laminate into the kink shape has a kink surface having a bent shape and a placement surface intersecting the kink surface.

When the laminate is shaped using the molding die, if the laminate laid on the kink surface of the molding die is bent toward the placement surface of the molding die, the laminate is compressed on the placement surface, which may cause strain that wrinkles the laminate. Such wrinkles are undesirable because they significantly decrease the strength of the components.

As a molding die for shaping a laminate into a substantially similar shape, for example, there is a molding die disclosed in Patent Document <NUM>.

Although not a molding die for shaping a kink shape, for example, there is a molding die disclosed in Patent Document <NUM>.

In Patent Document <NUM>, a surface of a molding die corresponding to the first surface is provided in advance with a protrusion, and a laminate laid on a surface of a molding die corresponding to the second surface is bent toward the surface of the molding die corresponding to the first surface.

However, depending on the ratio between the length dimension of the first surface and the length dimension of the second surface, a shaping method using this molding die is theoretically possible but may not be realistic. For example, in a case where the dimension of the first surface is sufficiently larger than the dimension of the second surface, when an attempt is made to shape the laminate laid on the surface of the molding die corresponding to the second surface, bending the laminate toward the surface of the molding die corresponding to the first surface, deformation caused by the bending extends over a wide range of the entire surface corresponding to the first surface, which increases the risk of wrinkles.

In Patent Document <NUM>, while wrinkles caused by excess fibers can be prevented, the molding die cannot be given a flat surface required for forming the laminate with a flat interface in contact with other components. <CIT> discloses a moulding die for bending a laminate formed by stacking a plurality of fibre sheets, the moulding die comprising a kink surface on which the laminate is laid, and a placement surface intersecting the kink surface.

The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a molding die and a shaping method with which a laminate placed on a placement surface is less likely to wrinkle when shaping the laminate into a kink shape.

In order to solve the above problems, the molding die and the shaping method of the present disclosure employ the following means.

That is, a molding die according to an aspect of the present disclosure is a molding die for bending a laminate formed by stacking a plurality of fiber sheets, the molding die including: a kink surface on which the laminate is laid; and a placement surface intersecting the kink surface and on which the laminate is placed by bending the laminate laid on the kink surface, in which the kink surface is bent so as to protrude in a second direction orthogonal to a first direction, with a kink line extending along the first direction connecting a first kink point and a second kink point as a boundary, the placement surface has a normal direction substantially coinciding with the first direction and has a bending line extending in a third direction orthogonal to the first direction and the second direction, the kink surface has a first boundary line connecting a first intersection on the bending line and the first kink point, and a second boundary line connecting a second intersection on the bending line and the first kink point, the first intersection is positioned closer to one end of the bending line relative to the first kink point in the third direction, the second intersection is positioned closer to the other end of the bending line relative to the first kink point in the third direction, the first kink point is positioned between the first intersection and the second intersection and the second kink point in the first direction, and the bending line between the first intersection and the second intersection convexly protrudes toward the kink line in the second direction.

A shaping method according to an aspect of the present disclosure is a shaping method for shaping the laminate using the molding die described above, the shaping method including laying the laminate on the kink surface, and bending, toward the placement surface along the bending line, the laminate laid on the kink surface.

According to the present disclosure, a laminate placed on a placement surface is less likely to wrinkle when shaping the laminate into a kink shape.

Hereinafter, an embodiment of a molding die and a shaping method according to the present disclosure will be described with reference to the drawings.

In the following description, terms such as a height direction Dh (first direction), a depth direction Dd (second direction), and a width direction Dw (third direction), as well as terms such as upward and downward are used for convenience of description, and do not necessarily limit an orientation of an actual object.

Here, the height direction Dh, the depth direction Dd, and the width direction Dw are orthogonal to one another.

A molding die <NUM> is for shaping a laminate <NUM> (charge) including a plurality of laminated fiber sheets into a kink shape.

The fiber sheet includes, for example, a fiber base material aligned such that the fiber direction becomes parallel to the longitudinal direction of the fiber sheet, and a resin impregnated into the fiber base material.

As the fiber base material, carbon fiber, glass fiber, or the like is used.

As the resin impregnated into the fiber base material, a thermosetting resin that is cured by being heated, such as an epoxy resin, polyimide, polyurethane, or unsaturated polyester, is used. Alternatively, a thermoplastic resin, such as polyamide, polyethylene, polystyrene, and polyvinyl chloride, which are solidified through heating, may be used.

As illustrated in <FIG>, the molding die <NUM> is a die including a kink surface <NUM>, a placement surface <NUM>, and a transitional surface <NUM>.

The kink surface <NUM> is a bent surface having a first kink surface <NUM> (surface on the left side in <FIG>) and a second kink surface <NUM> (surface on the right side in <FIG>), and is bent such that the position in the depth direction Dd changes along the width direction Dw.

Each of the first kink surface <NUM> and the second kink surface <NUM> is a flat surface, and a kink line <NUM> is a boundary line between the two surfaces. Here, the kink line <NUM> is a line (ridge line) extending along the height direction Dh and connecting a top end point 118a (first kink point) and a bottom end point 118b (second kink point).

That is, the kink surface <NUM> is a bent surface to which the flat first kink surface <NUM> and the flat second kink surface <NUM> are connected with the kink line <NUM> extending along the height direction Dh as a boundary line, and which is bent so as to protrude in the depth direction Dd (front side in <FIG>) with the kink line <NUM> extending along the height direction Dh as a ridge line.

The upper side of the first kink surface <NUM> has a first boundary line <NUM> and a first top end line <NUM>. Similarly, the upper side of the second kink surface <NUM> has a second boundary line <NUM> and a second top end line <NUM>.

Each of the first boundary line <NUM> and the second boundary line <NUM> is a line (ridge line) connected to the top end point 118a of the kink line <NUM>, and is a bifurcated line that is separated from each other in the width direction Dw as it goes upward in the height direction Dh from the top end point 118a.

The first top end line <NUM> is a straight line (ridge line) connected to the first boundary line <NUM> and extends in the width direction Dw. Similarly, the second top end line <NUM> is a straight line (ridge line) connected to the second boundary line <NUM>, and extends in the width direction Dw.

The placement surface <NUM> is a flat surface intersecting the kink surface <NUM>, and the normal direction substantially coincides with the height direction Dh. That is, the placement surface <NUM> is a flat surface substantially orthogonal to the kink surface <NUM>.

The side (side on the front side in <FIG>) in contact with/adjacent to the kink surface <NUM> of the placement surface <NUM> is a bending line <NUM>.

The bending line <NUM> is a line (ridge line) extending in the width direction Dw and connecting a first end portion 121a (end portion on the left side in <FIG>) and a second end portion 121b (end portion on the right side in <FIG>). The bending line <NUM> convexly protrudes in the depth direction Dd (front side in <FIG>) as a whole.

The bending line <NUM> is positioned upper than the top end point 118a of the kink line <NUM> in the height direction Dh. That is, the top end point 118a is positioned between the bending line <NUM> and the bottom end point 118b in the height direction Dh. At this time, the dimension along the height direction Dh from the bending line <NUM> to the top end point 118a of the kink line <NUM> is defined as a height h (see <FIG>).

Such the bending line <NUM> has a bending straight line <NUM>, a bending straight line <NUM>, and a bending convex line <NUM>.

The bending straight line <NUM> is a part of the bending line <NUM> in a straight shape including the first end portion 121a, and coincides with the first top end line <NUM> of the first kink surface <NUM>. That is, the bending straight line <NUM> and the first top end line <NUM> are the same straight line. Therefore, the bending straight line <NUM> is also connected to the first boundary line <NUM>. Here, a boundary point (connection point) between the bending straight line <NUM> and the first boundary line <NUM> is defined as a first intersection 121c. The first intersection 121c is positioned closer to the first end portion 121a relative to the top end point 118a in the width direction Dw.

The bending straight line <NUM> is a part of the bending line <NUM> in a straight shape including the second end portion 121b, and coincides with the second top end line <NUM> of the second kink surface <NUM>. That is, the bending straight line <NUM> and the second top end line <NUM> are the same straight line. Therefore, the bending straight line <NUM> is also connected to the second boundary line <NUM>. Here, a boundary point (connection point) between the bending straight line <NUM> and the second boundary line <NUM> is defined as a second intersection 121d. The second intersection 121d is positioned closer to the second end portion 121b relative to the top end point 118a in the width direction Dw.

The bending convex line <NUM> is a part of the bending line <NUM> between the first intersection 121c and the second intersection 121d.

The bending convex line <NUM> is a curved line convexly protruding in the depth direction Dd (front side in <FIG>). The curve is preferably a continuous smooth line, but may be discontinuous (for example, stepwise) in a microscopic view. This curve has a predetermined radius of curvature, for example, an arc having a radius Rf (see <FIG>).

The transitional surface <NUM> is a curved surface surrounded by the bending convex line <NUM>, the first boundary line <NUM>, and the second boundary line <NUM>.

That is, the transitional surface <NUM> is a substantially triangular curved surface connected to the placement surface <NUM>, the first kink surface <NUM>, and the second kink surface <NUM>.

<FIG> illustrates horizontal cross-sectional views (cross-sectional views taken along planes extending in the depth direction Dd and the width direction Dw) of the molding die <NUM> in a plurality of different positions H1, H2, and H3 in the height direction Dh.

As illustrated in <FIG>, the transitional surface <NUM> is a curved surface in which a curve having a shape following the shape of the bending convex line <NUM> gradually decreases in length (circumferential length) toward the top end point 118a of the kink line <NUM>. The lowermost part of the transitional surface <NUM> is a point coinciding with the top end point 118a of the kink line <NUM>.

The above-described circumferential length is preferably gradually changed. Therefore, the first boundary line <NUM> and the second boundary line <NUM> are preferably smooth curves. Specifically, as illustrated in <FIG>, the first boundary line <NUM> is preferably a smooth curve convexly protruding toward the second end portion 121b, and the second boundary line <NUM> is preferably a smooth curve convexly protruding toward the first end portion 121a.

As illustrated in <FIG>, the dimension along the height direction Dh from the bending line <NUM> to the top end point 118a of the kink line <NUM> is the height h. The bending convex line <NUM> is, for example, an arc having the radius Rf. Hereinafter, a method of determining the height h and the radius Rf will be described.

The height h and the radius Rf are determined based on the "allowable value of dθ/ds" depending on the material properties (type of fiber base material, type of resin, density between fiber base materials, and the like) of the laminate <NUM> and the fiber sheet.

As illustrated in <FIG>, when a curve S extending from the first end portion 121a as a starting point toward the second end portion 121b along the bending line <NUM> is considered, dθ/ds is a change rate of an angle of a normal line (normal line with respect to the bending line <NUM>) when moving by a minute distance ds from a position s1 to a position s2. In other words, dθ/ds is a ratio of a change amount dθ of the angle when the angle of a normal line Ns1 at the position s1 is compared with the angle of a normal line Ns2 at the position s2 with respect to the minute distance ds.

Ts1 illustrated in <FIG> is a tangent line with respect to the bending line <NUM> at the position s1, and Ts2 is a tangent line with respect to the bending line <NUM> at the position s2.

Since the bending line <NUM> (that is, the bending straight line <NUM>) from the first end portion 121a to the first intersection 121c and the bending line <NUM> (that is, the bending straight line <NUM>) from the second intersection 121d to the second end portion 121b are straight lines, dθ/ds = <NUM> (zero) is true. Since the bending line <NUM> (that is, the bending convex line <NUM>) from the first intersection 121c to the second intersection 121d is a curved line (for example, an arc), |dθ/ds| > <NUM> is true.

A value obtained by integrating the change amount dθ of the angle from the first intersection 121c to the second intersection 121d at the position s is an angle α.

Based on the above, the "allowable value of dθ/ds" is a limit value of the change rate of the angle at which, in consideration of the compressive stress locally acting on the fiber sheet when the change rate of the angle is dθ/ds and the relaxation of the compressive stress due to the shear deformation of the fiber sheet, the laminate <NUM> and the fiber sheet are not wrinkled based on appearance, even when subject to the compressive stress and shear deformation, and the fiber sheets are not shifted in the laminate <NUM>.

For example, when the change rate of the angle is equal to or less than the allowable value of dθ/ds, even if a local compressive force acts on the laminate <NUM> and the fiber sheet, only the resin between the fiber base materials is compressed within a range that is not wrinkled.

The above shear deformation is applied to relax the compressive stress acting on the fiber sheet by stretching, in the width direction Dw, the compressed fiber sheet.

As illustrated in <FIG>, when a position spaced apart by a distance 1f from the first intersection 121c along a normal line (normal line with respect to the bending line <NUM>) at the first intersection 121c is defined as a point C, and a position spaced apart by the distance 1f from the second intersection 121d along a normal line (normal line with respect to the bending line <NUM>) at the second intersection 121d is defined as a point D, a length of a curve substantially parallel to the bending line <NUM> from the point C to the point D is defined as L3. The distance 1f will be described below.

At this time, the difference between L2 and L3 is expressed by the following Equation <NUM>.

dθ/ds is expressed by the following Equation <NUM> based on Equation <NUM>.

Since dθ/ds is determined by the material properties and the angle α is determined by the angle between the first kink surface <NUM> and the second kink surface <NUM>, the radius Rf according to the allowable value of dθ/ds can be determined using Equation <NUM>.

As illustrated in <FIG>, when an intersection of a line extending downward along the height direction Dh from the first intersection 121c and the bottom edge of the first kink surface <NUM> is defined as a point A, and an intersection of a line extending downward along the height direction Dh from the second intersection 121d and the bottom edge of the second kink surface <NUM> is defined as a point B, a length of the bottom edge (bending line) of the kink surface <NUM> from the point A to the point B is defined as L1. The length (that is, the length of the bending convex line <NUM>) of the bending line <NUM> from the first intersection 121c to the second intersection 121d is defined as L2.

At this time, the difference between L1 and L2 is expressed by the following Equation <NUM>.

Here, the angle α is an angle between the normal line (normal line with respect to the bending line <NUM>) at the first intersection 121c and the normal line (normal line with respect to the bending line <NUM>) at the second intersection 121d, and depends on the angle between the first kink surface <NUM> and the second kink surface <NUM>.

Since dθ/ds is determined by the material properties and the angle α is determined by the angle between the first kink surface <NUM> and the second kink surface <NUM>, the height h according to the allowable value of dθ/ds can be determined using Equation <NUM>.

As illustrated in <FIG>, first, the laminate <NUM> is laid on the kink surface <NUM>.

By laying the laminate <NUM> onto the kink surface <NUM>, the laminate <NUM> is bent following the kink surface <NUM>, and a kink line portion <NUM> extending along the kink line <NUM> provided on the kink surface <NUM> is formed in the laminate <NUM>.

At this time, a part of the laminate <NUM> in surface contact with the kink surface <NUM> is defined as a first portion <NUM>, and a part of the laminate <NUM> protruding upward from the kink surface <NUM> is defined as a second portion <NUM>. The dimension along the height direction Dh of the second portion <NUM> is the distance 1f.

Next, the second portion <NUM> of the laminate <NUM> is bent toward the placement surface <NUM> along the bending line <NUM> to be placed on the placement surface <NUM>.

In the process of bending the second portion <NUM> toward the placement surface <NUM>, both sides of the second portion <NUM> are close to the center, and the laminate <NUM> (fiber sheet) corresponding to the second portion <NUM> is compressed in the width direction Dw to generate strain.

However, as illustrated in <FIG>, since the angle θ of the normal line continuously and gradually changes from the first intersection 121c to the second intersection 121d on the bending line <NUM>, the change rate dθ/ds of the angle maintains a value equal to or less than the allowable value from the first intersection 121c to the second intersection 121d. That is, since there is a range between the first intersection 121c and the second intersection 121d, the change in the angle θ of the normal necessary for giving the kink shape to the laminate <NUM> is dispersed within the range, and the change rate dθ/ds of the angle is reduced as a whole.

Due to this, the total strain amount in the width direction Dw that should be generated in the laminate <NUM> (fiber sheet) corresponding to the second portion <NUM> is dispersed in the range between the first intersection 121c and the second intersection 121d, and therefore the total strain amount is avoided from locally concentrating, and the laminate <NUM> (fiber sheet) is less likely to wrinkle.

Since the graph illustrated in <FIG> assumes a case where the bending convex line <NUM> is an arc having the radius Rf, the angle change rate dθ/ds is constant in range between the first intersection 121c and the second intersection 121d.

However, as long as the change rate dθ/ds of the angle becomes equal to or less than the allowable value in the same range, the change rate dθ/ds of the angle may necessarily be not constant. That is, the radius of curvature of the bending convex line <NUM> may be changed in the same range.

If a molding die <NUM> (without equivalents of the first boundary line <NUM>, the second boundary line <NUM>, and the bending convex line <NUM> of the molding die <NUM>) as illustrated in <FIG> is used, the change in the angle θ of the normal line necessary for giving the kink shape to the laminate <NUM> is concentrated on a vertex <NUM>.

Therefore, as illustrated in <FIG>, the change rate dθ/ds of the angle has a peak greatly exceeding the allowable value near the vertex <NUM>. As a result, the total strain amount is locally concentrated, and wrinkles <NUM> are generated in the laminate <NUM> (fiber sheet).

If a molding die <NUM> (with all equivalents of the first boundary line <NUM>, the second boundary line <NUM>, and the bending convex line <NUM> of the molding die <NUM> being straight lines) as illustrated in <FIG> is used, the change in the angle θ of the normal line necessary for giving the kink shape to the laminate <NUM> is concentrated on a vertex <NUM> and a vertex <NUM>.

Therefore, as illustrated in <FIG>, the change rate dθ/ds of the angle peaks near the vertex <NUM> and the vertex <NUM>. Each peak has a lower numerical value than that in the case of Comparative Example <NUM>, but exceeds the allowable value. As a result, the total strain amount is locally concentrated, and the wrinkles <NUM> are generated in the laminate <NUM> (fiber sheet).

With the present embodiment, the following effects are achieved.

Since the bending line <NUM> between the first intersection 121c and the second intersection 121d convexly protrudes toward the kink line <NUM> in the depth direction Dd, when the laminate <NUM> laid on the kink surface <NUM> is bent to be placed on the placement surface <NUM>, the total strain amount that should be generated in the laminate <NUM> by the laminate <NUM> being compressed in the width direction Dw on the placement surface <NUM> is dispersed in a wide range (range wider than a case where at least the bending line is bent at one point (vertex <NUM>) or two points (vertex <NUM> and vertex <NUM>)) of the bending line <NUM> between the first intersection 121c and the second intersection 121d. Therefore, the total strain amount is avoided from locally concentrating, and the laminate <NUM> on the placement surface <NUM> is less likely to wrinkle.

When the bending line <NUM> between the first intersection 121c and the second intersection 121d is a smooth curve, the change rate dθ/ds of the angle with respect to the minute distance ds on the bending line <NUM> between the first intersection 121c and the second intersection 121d can be made smooth. Therefore, the change rate dθ/ds is avoided from locally increasing, and the laminate placed on the placement surface <NUM> less likely to wrinkle.

Since the kink surface <NUM> is bent with the kink line <NUM> as a boundary and has the first boundary line <NUM> and the second boundary line <NUM>, it is possible to provide a range (bending convex line <NUM>) convexly protruding as described above in the bending line <NUM> while securing, on the kink surface <NUM>, a flat surface for forming, in the laminate <NUM>, a flat interface with which other components are in contact.

When the first boundary line <NUM> is a smooth curve convexly protruding toward the second intersection 121d and the second boundary line <NUM> is a smooth curve convexly protruding toward the first intersection 121c, it is possible to smooth the change rate in the distance from the first boundary line <NUM> to the second boundary line <NUM> in the height direction Dh, that is, the change rate in the circumferential length in the height direction Dh on the transitional surface <NUM>. Therefore, the change rate is avoided from locally increasing, and the laminate <NUM> on the transitional surface <NUM> is less likely to wrinkle.

The present embodiment described above is understood as follows, for example.

That is, the molding die (<NUM>) according to a first aspect of the present disclosure is a molding die for bending the laminate (<NUM>) formed by stacking a plurality of fiber sheets, the molding die (<NUM>) including: the kink surface (<NUM>) on which the laminate is laid; and the placement surface (<NUM>) intersecting the kink surface and on which the laminate is placed by bending the laminate laid on the kink surface, in which the kink surface is bent so as to protrude in the second direction (Dd) orthogonal to the first direction (Dh) with the kink line (<NUM>) extending along the first direction connecting the first kink point (118a) and the second kink point (118b) as a boundary, the placement surface has a normal direction substantially coinciding with the first direction and has the bending line (<NUM>) extending in the third direction (Dw) orthogonal to the first direction and the second direction, the kink surface has the first boundary line (<NUM>) connecting the first intersection (121c) on the bending line and the first kink point, and the second boundary line (<NUM>) connecting the second intersection (121d) on the bending line and the first kink point, the first intersection is positioned closer to one end (121a) of the bending line relative to the first kink point in the third direction, the second intersection is positioned closer to the other end (121b) of the bending line relative to the first kink point in the third direction, the first kink point is positioned between the first intersection and the second intersection and the second kink point in the first direction, and the bending line between the first intersection and the second intersection convexly protrudes toward the kink line in the second direction.

According to a molding die according to the present aspect, since the bending line between the first intersection and the second intersection convexly protrudes toward the kink line in the second direction, when the laminate laid on the kink surface is bent to be placed on the placement surface, the total strain amount that should be generated in the laminate by the laminate being compressed in the third direction on the placement surface is dispersed in a wide range (range wider than a case where at least the bending line is bent at one point or two points) of the bending line between the first intersection and the second intersection. Therefore, the total strain amount is avoided from locally concentrating, and the laminate placed on the placement surface is less likely to wrinkle.

Since the kink surface is bent with the kink line as a boundary and has the first boundary line and the second boundary line, it is possible to provide a range convexly protruding as described above in the bending line while securing, on the kink surface, a flat surface for forming, in the laminate, a flat interface with which other components are in contact.

In a molding die according to a second aspect of the present disclosure, in the first aspect, the bending line between the first intersection and the second intersection is a smooth curve convexly protruding toward the kink line.

According to the molding die according to the present aspect, since the bending line between the first intersection and the second intersection is a smooth curve convexly protruding toward the kink line, the change rate of the angle with respect to the minute distance on the bending line between the first intersection and the second intersection can be made smooth. Therefore, the change rate is avoided from locally increasing, and the laminate placed on the placement surface is less likely to wrinkle.

In a molding die according to a third aspect of the present disclosure, in the second aspect, the bending line between the first intersection and the second intersection is an arc.

According to the molding die according to the present aspect, since the bending line between the first intersection and the second intersection is an arc, the change rate of the angle with respect to a minute distance on the bending line between the first intersection and the second intersection can be made constant. Therefore, the change rate is avoided from locally increasing, and the laminate placed on the placement surface is less likely to wrinkle.

In a molding die according to a fourth aspect of the present disclosure, in any of the first to third aspects, the first boundary line is a smooth curve convexly protruding toward the second intersection, and the second boundary line is a smooth curve convexly protruding toward the first intersection.

According to the molding die according to the present aspect, since the first boundary line is a smooth curve convexly protruding toward the second intersection, and the second boundary line is a smooth curve convexly protruding toward the first intersection, it is possible to smooth the change rate in the distance from the first boundary line to the second boundary line in the first direction, that is, the change rate in the circumferential length in the first direction on the surface (hereinafter, called the "transitional surface") surrounded by the three lines of the bending line, the first boundary line, and the second boundary line. Therefore, the change rate is avoided from locally increasing, and the laminate placed on the transitional surface is less likely to wrinkle.

Claim 1:
A molding die (<NUM>) for bending a laminate (<NUM>) formed by stacking a plurality of fiber sheets, the molding die comprising:
a kink surface (<NUM>) on which the laminate is laid; an
a placement surface (<NUM>) intersecting the kink surface (<NUM>) and on which the laminate is placed by bending the laminate laid on the kink surface (<NUM>),
characterized in that the kink surface (<NUM>) is bent so as to protrude in a second direction (Dd) orthogonal to a first direction (Dh), with a kink line (<NUM>) extending along the first direction connecting a first kink point (118a) and a second kink point (118b) as a boundary,
the placement surface (<NUM>) has a normal direction substantially coinciding with the first direction (Dh) and has a bending line (<NUM>) extending in a third direction (Dw) orthogonal to the first direction (Dh) and the second direction (Dd),
the kink surface (<NUM>) has a first boundary line (<NUM>) connecting a first intersection (121c) on the bending line (<NUM>) and the first kink point, and a second boundary line (<NUM>) connecting a second intersection on the bending line and the first kink point,
the first intersection (121c) is positioned closer to one end of the bending line relative to the first kink point in the third direction,
the second intersection (121d) is positioned closer to an other end of the bending line relative to the first kink point in the third direction,
the first kink point is positioned between the first intersection (121c) and the second intersection (121d) and the second kink point in the first direction, and
the bending line between the first intersection and the second intersection convexly protrudes toward the kink line in the second direction.