KR20180069444A - Folded metal plate structure reinforced by fiber reinforced plastic and manufacturing method for the same - Google Patents

Abstract

In the present invention, a metal plate structure having a structure in which a metal plate and a fiber-reinforced plastic are laminated and reinforced by fiber-reinforced plastic so as to prevent peeling of the fiber-reinforced plastic and ensuring excellent crash performance, and a manufacturing method thereof to provide. For this, in the present invention, the fibers oriented in a specific direction are formed at the bottom of the metal plate structure so that sufficient collision performance is ensured, but separation between the fibrous layer and the metal layer does not occur.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal plate structure for a vehicle,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal plate structure for a vehicle and a method of manufacturing the metal plate structure, and more particularly, to a metal plate structure using a fiber reinforced plastic for locally reinforcing the strength of the metal plate structure and a manufacturing method thereof.

Fiber Reinforced Plastic (FRP) has been applied to automobile parts due to its high rigidity and low density compared to conventional steel sheets. However, when applied to a body composed of conventional metal materials, it is difficult to connect between metal and plastic, There is a drawback that the strength of the film is deteriorated.

A method of joining a fiber-reinforced plastic sheet to a steel sheet by press-molding has been developed and applied in order to locally reinforce the strength of the steel sheet while maintaining the same method of joining with existing parts by spot welding. However, due to the difference in coefficient of thermal expansion between steel sheet and polymer, thermal stress due to temperature rise occurs when passing through the body coating process. This causes segregation between the steel sheet and the polymer interface, which reduces the strength and rigidity of the component.

For example, Korean Patent Registration No. 10-1436454 discloses a method for molding a fiber reinforced plastic (FRP), particularly a carbon triple-strength reinforced plastic (CFRP), by injecting or impregnating a polymer resin into oriented fibers, Is molded at a high pressure / high temperature to cure it. Korean Patent Laid-Open Publication No. 2010-0075142 discloses a technique for pressing and thermally fusing a carbon fiber-reinforced resin laminated on a steel sheet in a component shape through a heated press for joining to a steel plate.

In these technologies, the bond between steel sheet and FRP is maintained immediately after forming. The manufactured parts are assembled into the body BIW (Body In White), and the entire BIW is heated to a specific temperature range (150 to 250 ° C) for curing the coating layer during the coating process. During the heating and cooling process, thermal expansion and contraction occur in the steel sheet and the FRP, and interfacial separation occurs due to the difference in thermal expansion coefficient between the steel sheet and the FRP.

Therefore, there is a demand for a technique for laminating FRP on a steel sheet, in particular, a technique capable of securing a uniform bonding quality even when thermal expansion and contraction proceed.

Korean Patent No. 10-1436454 (Aug. 26, 2014) Korean Patent Publication No. 2010-0075142 (July 2, 2010)

SUMMARY OF THE INVENTION The present invention has been conceived in order to solve the above-mentioned problems. In the present invention, a metal plate and a fiber reinforced plastic are stacked to prevent the fiber reinforced plastic from being peeled off. Which is reinforced by plastic, and a method of manufacturing the same.

In order to achieve the above object, in a preferred embodiment of the present invention, a metal plate structure for a vehicle, comprising: a metal plate having a bottom portion and a side wall portion; and a fiber reinforced plastic layer joined to the metal plate, And fibers oriented in a second direction perpendicular to the first direction, wherein the fibers oriented in the second direction comprise a first group of fibers extending from one side wall portion of the metal sheet to the bottom side, And a second group of fibers extending from the other side wall portion of the metal sheet toward the bottom side, wherein the fibers of the first group and the fibers of the second group are disconnected from each other with respect to the traveling direction. A reinforced vehicle metal plate structure is provided.

Wherein the ratio of the total area of the bottom portion to the area of the second direction fibers on the bottom portion is 75% to 85% with respect to the inside of the bottom portion. Lt; / RTI >

In addition, the ratio of the total area of the bottom portion to the area of the bottom portion to which the second directional fibers are applied is 80%.

In addition, the vehicular metal plate structure has a hat-shaped cross-sectional structure, and further provides a metal plate structure reinforced with a fiber-reinforced plastic.

The metal plate structure for a vehicle has a joint part on both sides so as to be joined to other structures.

The fibers of the first group and the fibers of the second group are each composed of two or more fibrous layers, and the fibrous layers of the respective groups are cut off from each other with respect to the fiber direction of the other group of fibrous layers. A vehicle metal plate structure reinforced with reinforced plastic is provided.

Further, the present invention provides a metal plate structure having reinforced fiber-reinforced plastic that is structured such that the fibers oriented in the first direction are not cut in the direction of travel of the fibers.

According to another aspect of the present invention, there is provided a method of manufacturing a metal plate structure reinforced with a fiber reinforced plastic, comprising the steps of: (a) laminating a metal plate on a fiber layer including fibers oriented in a first direction and fibers oriented in a second direction; (b) positioning the metal sheet on which the fibrous layer is laminated on the press mold; (c) pressing the metal plate having the fiber layer laminated by lowering the press mold to produce a metal plate structure having a bottom portion and a pair of side wall portions, wherein in the metal plate structure produced in the step (c) The fibers oriented in the second direction include fibers of a first group extending from one sidewall to bottom of the metal plate and fibers of a second group extending from the other sidewall of the metal plate toward the bottom, Wherein the fibers of the first group and the fibers of the second group are disconnected from each other with respect to the traveling direction.

Wherein the ratio of the total area of the bottom portion to the area of the second direction fibers on the bottom portion is 75% to 85% with respect to the inside of the bottom portion. Of the present invention.

In addition, the ratio of the total area of the bottom portion to the area of the bottom portion to which the second directional fibers are applied is 80%. The present invention also provides a method of manufacturing a metal plate structure reinforced with a fiber reinforced plastic.

In addition, the vehicle metal plate structure manufactured in the step (c) has a hat-shaped cross-sectional structure, and provides a method of manufacturing a metal plate structure reinforced with a fiber-reinforced plastic.

Further, the present invention provides a method of manufacturing a metallic plate structure for a vehicle, which further comprises joining the joining portions of the pair of vehicle metal plate structures manufactured by repeating the steps (a) to (c) twice.

The fibers of the first group and the fibers of the second group are each composed of two or more fibrous layers, and the fibrous layers of the respective groups are cut off from each other with respect to the fiber direction of the other group of fibrous layers. A method of manufacturing a metal plate structure having reinforced plastic reinforced plastic is provided.

The present invention also provides a method of manufacturing a metal plate structure for a vehicle, wherein the fibers oriented in the first direction are reinforced with a fiber reinforced plastic that is configured not to be broken in the fiber direction.

The metal plate structure for a vehicle having reinforced fiber-reinforced plastic according to a preferred embodiment of the present invention and its manufacturing method have the following effects.

First, in manufacturing parts made of metal plate and fiber-reinforced plastic sheet, it is necessary to ensure uniform quality of joint between metal plate and fiber-reinforced plastic after coating even if different thermal expansion / .

Second, by deriving the optimum laminated structure of FRP according to the external stress direction in a vehicle part in which sufficient collision characteristics are required, it is possible to achieve weight reduction of vehicle parts while securing excellent strength reinforcement.

FIG. 1 is a view for explaining a fiber arrangement direction with respect to a vehicle structural body joined to have a box-shaped cross section,
Fig. 2 shows an example in which a pair of structures having a hat-shaped cross-section structure is bonded to a vehicle-use metal plate structure reinforced with fiber-reinforced plastic,
Fig. 3 shows the crash behavior of the vehicle structure of Fig. 2 during a collision,
Fig. 4 conceptually shows separation between the metal plate and the resin layer in the vehicle structure of Fig. 2,
5 is a view illustrating an example of a metal plate structure having a fiber reinforced plastic reinforced according to a preferred embodiment of the present invention,
Fig. 6 shows that the in-interface residual stress between the metal plate and the fibrous layer is relaxed in the structure according to Fig. 5,
FIG. 7 is a graph showing data on the adhesive force and the maximum reaction force according to the bottom area of the metal plate and the fiber application area in the structure according to FIG. 5,
FIG. 8 illustrates a method of manufacturing a metal plate structure having a fiber reinforced plastic reinforced according to a preferred embodiment of the present invention.

In the present invention, a parts structure to be applied to a vehicle, which includes a laminated structure for a structure in which a fiber-reinforced plastic is laminated on a metal plate such as a steel plate, and a manufacturing method for manufacturing the same.

In describing such a component structure, a specific cross-sectional structure is exemplified in the present invention, but the invention described in the claims is not limited to such a cross-sectional structure, and the present invention is not limited thereto. And the cross-sectional structure can also be changed according to the design element. In addition, the cross section of the structure may be a closed end face or an open cross section, and various known joining methods can be applied to the joining method of the members. In this specification, the fibrous layer means a layer containing fibers, and preferably means a plastic composite material layer such as FRP.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a metal plate structure having reinforced fiber-reinforced plastic according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, FIG. 1 is a view for explaining a fiber arrangement direction for a vehicle structure joined to have a box-shaped cross section. Prior to a specific description, the orientation of the fibers present in the fiber-reinforced plastic will be described.

Fiber-reinforced plastics are anisotropic materials with different strengths depending on the direction of fiber, and orient the fibers in a complex direction without orienting the fibers in a single direction for the purpose of strengthening strength and rigidity. That is, as shown in FIG. 1, the mechanical properties of the fiber direction (0 degrees) are the most excellent, and the physical properties of the fibers in the vertical direction (90 degrees) are the weakest. Therefore, fibers in a 0 degree direction and a 90 degree direction are laminated and laminated without orienting the fiber reinforced plastic (FRP) in a single direction. For example, CFRP 0/0/0 (or 0/0/0) refers to a structure in which carbon fibers oriented in the 0-degree direction are laminated in three layers, and FRP 90/0/0 (or 90/0 / 0) refers to a structure in which carbon fibers oriented in directions of 90 degrees, 0 degrees, and 0 degrees are laminated in three layers.

In this specification, for the sake of brevity, the direction of the arrangement of the part structure is referred to as a first direction, and the direction perpendicular to the first direction is defined as a second direction. The direction is defined as a difference in physical properties depending on the fiber direction, and therefore, the first direction and the second direction are not limited to the 0 degree and 90 degree directions exemplified below. For example, the +/- 45 degree direction may be set to the first direction and the second direction, respectively, and it is not necessarily that the directions should be exactly 90 degrees apart.

Figure 1 shows fibers arranged in a first direction and a second direction on a part structure. As shown in Fig. 1, when FRP is applied to the metal member, the fibers arranged in the first direction (0-degree direction) and the fibers arranged in the second direction (90-degree direction) can be applied together.

Fig. 2 shows a cross section of a hat-like structure including the steel plates 11a and 11b and the fibers 12a and 12b oriented in this manner. As shown in Fig. 2, when the component composed of the bottom portion and the side wall portion is applied, the fibers arranged in the second direction of the side wall portion (in the direction of 90 degrees) are most effective for external stress.

Generally, when a component having the structure is broken by an external impact, the same behavior as in FIG. 3 follows. That is, when an external impact is applied, the bent portion (R portion) of the surface to which the impact is applied is broken, and then the upper side break occurs. That is, at the time of the collision, the fiber break in the direction of 90 degrees in the R direction occurs primarily, the side wall is unfolded and the displacement increases to the lower plate, and the fracture occurs between the steel sheet and the FRP interface.

Considering this fracture behavior, reinforcing the R part and the side wall part where the stress is concentrated at the initial stage of the impact and the initial fracture occurs is effective against the case where the whole area (including the bottom part) is reinforced.

On the other hand, it is possible to consider increasing the FRP thickness by increasing the amount of fiber in the 90-degree direction with the greatest strength reinforcing effect or by increasing the number of laminated layers in the 90-degree direction. However, in this case, But also disadvantageously in terms of interfacial separation due to coating.

In the FRP, the thermal expansion coefficient is different according to the fiber orientation. In the component having the cross-sectional structure as shown in FIG. 2, the more the fibers in the second direction (90 degree direction) are increased, the more the phenomenon is separated between the steel sheet and FRP interface. This is because the FRP in the second direction (in the direction of 90 degrees) hardly expands, and the original shape is maintained, so that the separation stress is generated at the interface, compared with the expansion of the steel sheet in the outward direction at the time of temperature rise. That is, as shown in FIG. 4, when the steel sheet expands during the heating process, the fibers in the 90-degree direction generally retain their original shape, and the separation between the metal sheet and the fiber layer occurs due to the difference in the thermal expansion coefficient. On the other hand, in the case of the first direction (0-degree direction) fiber, the difference in the thermal expansion coefficient between the steel sheet and the steel sheet is small, and the phenomenon occurs in accordance with the expansion direction of the steel sheet.

Table 1 below shows the result of performing the interface separation test on the bonding structure between the steel sheet and CFRP. The experiment was carried out by lowering the temperature at 190 ° C to 25 ° C over 30 minutes. The experiment was carried out so that the laminate structures having different orientation directions could be compared. In the above experiment, the stress limit value of the adhesive used at each interface is 50 MPa in the normal Z direction (direction perpendicular to the bottom), and 25 MPa in the shear YZ direction (shear direction of the side surface). In Table 1 below, only the shear YZ direction data related to the separation characteristics are attached.

One 2 3 Laminated structure S / GF / 0/0/0/0 // GF S / GF / 0/90/90/0 // GF S / GF / 90/90/90/90 // GF detach Not occurring Occur Occur Shear YZ-residual stress 20.5 MPa 32 MPa 26 MPa

(S: steel sheet, GF: glass fiber, 0: 0 degree carbon fiber, 90: 90 degree carbon fiber)

The glass fiber layer was applied to prevent galvanic corrosion between the steel sheet and the carbon fiber interface and to improve the appearance of the surface layer, and is independent of the impact performance and separation characteristics.

Considering the data in Table 1 above, it can be seen that the possibility of interface separation increases when carbon fibers in the second direction (90 ° direction) are applied for strength reinforcement.

Meanwhile, according to a preferred embodiment of the present invention, separation is not caused by constituting the disconnection region for the second direction (90 degrees direction) fiber of the separated form at the bottom portion of the structure.

Specifically, FIG. 5 illustrates an example of a metal plate structure having a fiber reinforced plastic reinforced according to a preferred embodiment of the present invention. In particular, in this embodiment, a metal plate structure 100 comprising a metal plate 101 having a bottom portion and a pair of side wall portions and a fiber-reinforced plastic layer bonded to the metal plate 101, And a second direction (90 degree direction) fibers 102a, 102b of the group. Here, the fibers in the second direction (90 degrees) are cut off with respect to the advancing direction (or longitudinal direction) of the fibers. Therefore, as shown in Fig. 5, there is a region disconnected with respect to the fiber advancing direction, that is, a region where no fibers are applied.

Specifically, the fiber-reinforced plastic layer comprises fibers oriented in a first direction and fibers oriented in a second direction perpendicular to the first direction, wherein the fibers oriented in the second direction are oriented in a first direction, A first group of fibers 102a extending from one side wall portion to the bottom portion side and a second group of fibers 102b extending toward the bottom side from the other side wall portion of the metal plate 101, The fibers 102a of the second group and the fibers 102b of the second group are configured to be disconnected from each other.

That is, as shown in FIG. 5, the fibers in the second direction (90-degree direction) are characterized in that the fibers extending from the left and right side portions to the bottom portion are not connected to each other but are formed in a disconnected form. The second direction fibers extending from one side surface portion to the bottom portion side do not extend toward the opposite side surface portion and exist in a shape broken on the bottom portion. Therefore, the fibers in the second direction (in the 90-degree direction) do not have a structure in which the fibers are connected across the left and right side portions as in the structure in Fig. 2, but have a pair of divided second direction (90 degrees direction) fibers.

On the other hand, the fibers oriented in the first direction can be configured not to be broken in the traveling direction of the fibers.

In addition, the metal plate structure according to this embodiment has a hat-shaped cross-sectional structure. At both ends of the hat shape, the metal plate structure 200 has a joint 300 so as to be joined to another metal plate structure 200. Through such a joint 300, a structure having a closed end surface as shown in FIG. 5 can be constructed.

Fig. 6 shows that in the above embodiment, the residual stress in the interface between the metal plate 101 and the fibrous layer is relaxed. That is, when the metal plate 101 such as a steel sheet expands to the left and right, since the fibers in the second direction (in the 90 degree direction) are also disconnected from each other at the center position of the bottom portion as shown in Fig. 6, Respectively, and as a result, it is possible to prevent separation at the steel sheet-fiber interface.

5, it is possible to adjust the application area of the fibers in the second direction (90 degrees). By adjusting the application area of the fibers in this manner, the change in the adhesive force at the interface and the maximum reaction force Change.

That is, the fibers in the second direction (in the 90-degree direction) function to reinforce the strength in the collision. When the application area of the fibers in the second direction (direction of 90 degrees) is reduced to prevent interface separation, The reaction force is reduced.

In particular, the adhesive force and the maximum reaction force are changed according to the ratio of the total area (Y) of the bottom portion to the area (2X) to which the second directional fibers are applied on the basis of the inside of the bottom portion. The applied area ratio is defined as 2X / Y, and the change of the adhesive force and the maximum reaction force is considered according to the ratio.

In this regard, FIG. 7 shows experimental data on adhesion force and maximum reaction force according to the bottom area of the metal sheet and the fiber application area.

As shown in FIG. 7, the maximum reaction force and the adhesive force at the interface are in inverse proportion to each other, and an optimal fiber application area should be applied in order to ensure sufficient collision performance while preventing separation at the interface.

In this regard, the adhesion at the interface tends to decrease sharply when the fiber application area is about 80%, and the maximum reaction force sharply decreases to about 60%.

Particularly, in FIG. 7, the negative adhesive force means that the interface separation occurs. Therefore, the applied area of the fibers in the second direction (90 degrees) is 85% or less, preferably 80% .

On the other hand, when the fiber application area in the second direction (90 ° direction) is maintained at 80% or less, separation is not performed, but the maximum reaction force involved in the collision characteristics is decreased . Thus, the fiber application area is maintained at least 60%, preferably at least 75%. Most preferably, the fiber application area in the second direction (90 degrees) is maintained at 80% level, taking into consideration the correlation between the maximum reaction force and the adhesive force.

A method of manufacturing a metal plate structure reinforced with a fiber-reinforced plastic having such a structure is shown in Fig.

As shown in FIG. 8, in a preferred embodiment of the present invention, a metal plate structure for a vehicle in which a hat-shaped fiber-reinforced plastic is reinforced by press equipment is manufactured.

First, a metal plate and a fiber layer laminated on the metal plate are prepared. Here, the fibrous layer should be laminated so that it can be disposed at a predetermined position in consideration of the shape of the final product to be pressed. Further, an adhesive may be applied between the metal plate and the metal plate during the lamination, and preferably the metal plate and the fiber layer may be laminated by the adhesive during the press forming process. This is because the materials are stretched during the pressing process.

Next, as shown in Fig. 8 (a), the metal plate on which the fiber layers are laminated is placed on the lower mold 400 of the press mold. At this time, as described above, the fiber layer includes fibers oriented in the second direction (90 degrees direction), and the fibers in the second direction (90 degrees direction) are formed in a disconnected form. In this embodiment, only the fiber layer oriented in the second direction (90 degree direction) is shown, but a fiber layer oriented in the first direction (0 degree direction) may be added. In addition, although FIG. 8 exemplifies application of a single second direction (90 degree direction) fiber layer, the number of layers can be varied. For example, a second group of fibers made up of a first group of fibers made of fibers in the second direction (90 degrees direction) at one side wall part and a second direction (90 degrees direction) fibers at the other side wall part , Each of the groups may be composed of two or more fibrous layers, and the fibrous layers of each group may be configured so as to be disconnected from each other with respect to the traveling direction of the fibers with other fibrous layers.

Next, as shown in Fig. 8 (b), the metal sheet having the second fiber layer stacked in the second direction (90 degree direction) is pressed while the upper die 500 is lowered, . At this time, as shown in Fig. 8 (c), the fiber layer in the second direction (in the 90-degree direction) remains disconnected so as to have an unused area on the bottom of the metal plate. Therefore, the metal plate structure produced through the press forming has the first group of fibers including the fibers in the second direction (90 degrees direction) extending from the one side portion to the bottom portion and the second group of fibers extending in the second direction 90 Direction) fibers, wherein the first group of fibers and the second group of fibers are configured to be disconnected from each other.

After the press molding is completed, the upper mold 500 moves upward again (Fig. 8 (d)), and the cap-shaped metal plate structure is demolded (Fig. 8 (e)).

8 (a) to 8 (e) are repeated to produce a metal plate structure having the same hat shape, and the metal plate structure is joined as shown in FIG. 8 (f) to complete a vehicle structure having a closed end face.

According to another embodiment of the present invention, unlike the manufacturing method as shown in Figs. 8 (a) to 8 (f), a method of press-forming a plate and a metal plate formed of a fibrous layer in advance, Lt; / RTI >

That is, in the example of FIG. 8, a method of bonding a fiber layer and a metal plate to each other and then press-molding the fiber layer together is proposed. However, the present invention can be applied to a metal plate structure As shown in Fig.

However, even in such an example, the press-molded fiberboard should be bonded in a disconnected form so as to have an unused area on the bottom of the metal plate.

While the present invention has been described with reference to the preferred embodiments, those skilled in the art will appreciate that modifications and variations are possible in the elements of the invention without departing from the scope of the invention. In addition, many modifications may be made to the particular situation or material within the scope of the invention, without departing from the essential scope thereof. Therefore, the present invention is not limited to the detailed description of the preferred embodiments of the present invention, but includes all embodiments within the scope of the appended claims.

100, 200: metal plate structure for vehicle
101: metal plate
102a, 102b: second direction fibers
300:
400: Lower mold
500: HYPER

Claims (14)

A metal plate structure for a vehicle, comprising a metal plate having a bottom portion and a side wall portion, and a fiber-reinforced plastic layer joined to the metal plate,
Wherein the fiber reinforced plastic layer comprises fibers oriented in a first direction and fibers oriented in a second direction perpendicular to the first direction,
The fibers oriented in the second direction include fibers of a first group extending from one sidewall to bottom of the metal plate and fibers of a second group extending from the other sidewall of the metal plate toward the bottom, Wherein the first group of fibers and the second group of fibers are disconnected from each other with respect to the traveling direction.
The method according to claim 1,
Wherein the ratio of the total area of the bottom portion to the area of the second direction fibers on the bottom portion is 75% to 85% with respect to the inside of the bottom portion.
The method of claim 2,
Wherein the ratio of the total area of the bottom portion to the area on the bottom portion where the second direction fibers are applied is 80%.
The method according to claim 1,
Wherein the metal plate structure for a vehicle has a hat-shaped cross-sectional structure.
The method of claim 4,
Wherein the metal plate structure for a vehicle has a joint part on both sides so as to be able to be joined to another structure.
The method according to claim 1,
Characterized in that the first group of fibers and the second group of fibers are each composed of at least two fiber layers and the fiber layers of each group are disconnected from each other with respect to the fiber direction of the other group of fiber layers Reinforced vehicle metal plate structure.
The method according to claim 1,
Wherein the fibers oriented in the first direction are not separated in the direction of travel of the fibers.
A method of manufacturing a metal plate structure having a fiber reinforced plastic reinforced therein,
(a) laminating a fiber layer on a metal plate comprising fibers oriented in a first direction and fibers oriented in a second direction;
(b) positioning the metal sheet on which the fibrous layer is laminated on the press mold;
(c) pressing the metal plate on which the fibrous layer is laminated by lowering the press mold to produce a metal plate structure having a bottom portion and a pair of side wall portions,
In the metal plate structure produced in the step (c), the fibers oriented in the second direction may be divided into a first group of fibers extending from one sidewall of the metal plate to the bottom portion and a second group of fibers extending from the other sidewall of the metal plate, Wherein the fibers of the first group and the fibers of the second group are disconnected from each other with respect to the traveling direction of the fiber reinforced plastic.
The method of claim 8,
Wherein the ratio of the total area of the bottom portion to the area of the second direction fibers on the bottom portion is 75% to 85% with respect to the inside of the bottom portion. Way.
The method of claim 9,
Wherein the ratio of the total area of the bottom portion to the area on the bottom portion where the second direction fibers are applied is 80%.
The method of claim 8,
Wherein the vehicle metal plate structure manufactured in the step (c) has a hat-shaped cross-sectional structure.
The method of claim 11,
(d) bonding the joints of the pair of vehicle metal plate structures manufactured by repeating the steps (a) to (c) twice.
The method of claim 8,
Characterized in that the first group of fibers and the second group of fibers are each composed of at least two fiber layers and the fiber layers of each group are disconnected from each other with respect to the fiber direction of the other group of fiber layers Wherein the reinforcing plate is formed of a metal plate.
The method of claim 8,
Wherein the fibers oriented in the first direction are not separated in the direction of travel of the fibers.

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