HK1181433B - Reinforced nonwoven fabric - Google Patents

Description

Reinforced nonwoven fabric

Technical Field

The present invention relates to a woven material that has been reinforced for improved handling during the manufacturing process, a component incorporating the reinforced nonwoven material and uses thereof. In particular, the invention relates to a carbon fiber nonwoven fabric having reinforcing grids contained therein.

Background

During the manufacture of planar textile structures with relatively low cohesion in textile fibres, for example in the case of nonwovens or fleece, the simplest processing processes can cause problems, such as rolling up and unrolling the planar structure and automatically feeding it to further production stages. One possible way to deal with this problem is to integrate the reinforcing mesh into a planar structure. The basic structure of this reinforcing layer introduced between the pile layers represents the starting point of the invention.

A laminate whose surface is formed using a spunbond fabric and which consists of at least two layers of spunbond fabric and at least one layer of fiber fabric (script), preferably made of reinforcing yarns, wherein the fiber fabric layer is located between two respective layers of spunbond fabric is disclosed in DE9207367U1 (DE 9207367U1, page 2, second sentence).

DE102006060241a1 discloses a carrier insert consisting of a planar textile structure and a reinforcing material, wherein the planar textile structure which already exhibits reinforcement is hydraulically stiffened. In particular, spunbond fabrics are described which are produced by randomly placing freshly melt spun (melt-spun) filaments and which consist of non-staple synthetic fibers composed of a melt-spinnable polymeric material (DE 102006060241a1, paragraph [0036 ]).

EP1584737a1 discloses a reinforced flat nonwoven fabric comprising at least two layers of nonwoven fabric of polyester staple-free fibres and a network of glass fibres fixed between the nonwoven layers.

The cited publication is primarily concerned with the use of a flat textile structure for the manufacture of a bituminous treated roof or liner. Melt-spinnable polymers are used here primarily for non-woven materials and not carbon fibres. However, in such applications, no particular requirements in terms of weight reduction and mechanical stability are necessary. For this reason, the known explanations are not suitable for the manufacture of components which are subject to more stringent requirements in this regard, for example in the automotive or aeronautical industry.

These applications therefore also require thin planar textile structures, which allow the final integration of the finished components of the planar textile structure to withstand the highest possible mechanical loads. The present invention is therefore directed to planar textile structures made entirely or predominantly of carbon fibers.

One difficulty posed by carbon fibers in terms of manufacturing techniques is related to the composition of the carbon fiber surface. Carbon fibers have a very smooth surface compared to other polymer fibers. Thus, the carbon fibers in the planar textile structure exhibit very weak adhesion between the fibers, and thus result in low cohesion between the planar textile structures. This low adhesive or cohesive force ultimately affects the manufacturing process of the planar textile structure consisting of carbon fibers, thus making a reinforcing grid necessary.

What is also needed is a planar textile structure that meets certain optical and tactile requirements. The reinforcing grid contained in the non-woven material must be as imperceptible as possible from the outside and the meshes of the reinforcing grid should not create any grooves on the surface of the planar textile structure.

However, the non-woven layer, due to its percentage of carbon fibers, is mainly responsible for the mechanical stability of the final component integrally formed into a planar woven structure, so that the presence of the reinforcing mesh has a detrimental effect on the strength-to-weight ratio of the component.

In addition, the use of reinforcing grids affects the drape characteristics of the nonwoven material. Here, the drapability deteriorates as the strength of the reinforcing mesh increases.

At the same time, however, the reinforcing mesh must meet the objectives for which it is used, in particular to provide sufficient reinforcement for the planar textile structure, so as to ensure improved handling of the planar textile structure during the manufacturing process.

It is therefore an object of the present invention to produce a planar textile structure which largely avoids the disadvantages mentioned while exhibiting the desired properties mentioned.

Disclosure of Invention

The object of the invention is achieved by an advantageous combination of the layer thickness or the weight per unit area of the planar textile structure, the proportion of carbon fibers in the weight per unit area and the suitably proportional weight per unit area of the reinforcing mesh.

One aspect of the invention relates to a textile flat structure comprising a reinforcing grid and at least one pile layer lying flat on at least one surface of the reinforcing grid,

-the planar textile structure exhibits from 40 to 140g/cm²The weight per unit area of (a) is,

the pile layer consists essentially of carbon fibers,

-the carbon fibres represent 60 to 97% of the weight per unit area in the planar textile structure,

-the reinforcing grid exhibits from 2.5 to 12.5g/m²In a suitable proportion, and

-the planar textile structure is stiffened.

Another aspect of the invention is an article comprising at least two planar textile structures according to the invention joined together planarly.

Another aspect of the invention is a component of an article comprising a planar textile structure according to the invention or a saturated polymer matrix according to the invention.

Another aspect of the invention is the use of a component according to the invention for manufacturing a part of a motor vehicle.

Detailed Description

Fig. 1 shows a schematic structural design of a planar textile structure (1) according to one aspect of the invention. The reinforcing grid (3) according to the invention is here fixed between two layers of pile (2) according to the invention, the reinforcing grid (3) being represented by its grid braces (30) and the layers of pile (2) being represented by its fibres (20).

Fig. 2 shows a schematic structural design of a preferred embodiment of a planar textile structure (1) according to the invention. Two vertically stacked pile layers (2) are here located on one side of the reinforcing grid (3), while one pile layer (2) is located on the other side. This embodiment is preferred because the surface of the planar textile structure (1) exhibits better optical and tactile characteristics on the side with two vertically stacked pile layers (2). This is advantageous mainly when only one side of the component is visible in the rear component of the integrally formed planar textile structure (1), for example in the case of a vehicle door.

Fig. 3 shows a schematic structural design of an embodiment of a planar textile structure (1) according to the invention. The two vertically stacked pile layers (2) are here located on one side of the reinforcing grid (3), while the other side of the reinforcing grid (3) remains clean. This embodiment is advantageous, in particular when the optical and tactile requirements relate only to one side of the planar textile structure (1).

The term "pile layer" is well known to the expert. It means a loose layer of a plurality of individual fibers that are not stiffened, entangled randomly, for example by needling.

Methods for producing the pile layer (2) are known to the expert, for example cleaning or carding. Depending on the method, the arrangement of the individual fibers (20) in the pile layer (2) is distributed more or less homogeneously. However, the fibers (20) in the pile layer (2) exhibit a preferred direction in some processes, for example in carding processes. This means that the alignment of the fibres (20) in one particular direction in the pile layer (2) is encountered more frequently than in other directions. This is because the fibers (20) are combed back and forth in the same direction throughout the carding process. Therefore, the final pile layer (2) frequently exhibits greater strength in the longitudinal direction with respect to the preferred direction of the fibers (20) than in the direction perpendicular to the preferred direction of the fibers (20). In the present invention, the term "preferred direction" of the pile layer (2) must be understood according to the definitions provided herein.

"woven" or "woven material" or "woven layer" or "woven material layer" means a layer of pile (2) that has been stiffened, for example by needling.

Methods for hardening the pile layer (2) into a woven layer, such as needling, are well known to the expert. The hardening process may be thermal, mechanical or chemical in nature. For example, heat-hardening generally involves melting away a medium that has been added to a planar textile structure prior to the manufacture of the pile. However, mechanical methods include needle punching and suturing. Chemical methods typically involve spraying on the adhesive. During the hardening of the planar textile structure (1) according to the invention, the method associated with the pile layer (2) is also applied. All layers of pile (2) and reinforcing grids (3) present in the planar textile structure (1) are here joined together. During mechanical hardening, this takes place in such a way that the grid braces of the reinforcing grid (3) are intertwined with the individual fibers of the adjoining pile layer (2), which results in a stronger connection between the reinforcing grid (3) and the pile layer (2).

If the pile layer (2) in the woven fabric, which is further processed, exhibits a preferred direction of the fibers (20), this can often also be discerned from the surface of the woven material, for example after the pile layer (2) has been needled.

Within the framework of the present invention, the planar textile structure (1) according to the invention is referred to in some contexts as "nonwoven folded layers (plies)".

In a preferred embodiment of the invention, the planar textile structure (1) exhibits 80-110g/m²Wherein the carbon fibers in the planar textile structure (1) have a suitable proportion of a weight per unit area of 65 to 84%, and the reinforcing grid (3) has a weight per unit area of 3 to 10g/m²In a suitable ratio. This embodiment is particularly suitable for use in components in the automotive industry to replace thin metal sheets, such as engine hoods, vehicle doors, fenders, and the like.

The reinforcing mesh (3) may be located between two successive pile layers (2) inside the planar textile structure (1). The advantage here is that the desired optical and tactile components can be ensured on both surfaces of the planar textile structure (1).

In addition to that, it can also be advantageous to have the reinforcing mesh (3) on the outside of the planar textile structure (1). A very thin planar textile structure (1) can be produced, at least one side of which exhibits the desired optical and tactile components. This embodiment is therefore particularly suitable for use in components according to the invention which, as intended, are visible only from one side in the finished product (e.g. a vehicle door).

According to the invention, the pile layer (2) is composed mainly of carbon fibers. Within the framework of the present invention, the part not consisting of carbon fibers is referred to as "heterogeneous fiber part". Depending on the background, the foreign fiber fraction can relate to the entire planar textile structure and only to the fleece layer (2). Low-foreign fiber sections are basically desirable, since the stability of the component according to the invention decreases with increasing foreign fiber fraction. However, carbon fibers are very costly. Thus, once sufficient stability of the component has been achieved, it is possible to add foreign fibers to the fibers to be processed in a targeted manner, in particular in such a way that: such that the carbon fibres represent a certain percentage of the total weight per unit area of the planar textile structure (1) according to the subject of the invention, preferably a percentage of the magnitude of 65 to 84%.

There is no particular limitation on the material and composition of the reinforcing mesh (3). It preferably consists of a thread of endless fibres (30) present as a fibre, woven, knit or knitted fabric, with a fibre fabric being preferred because it is the easiest to make and exhibits the smallest layer thickness at the cross-over point compared to a knitted fabric.

For example, the fibres in the reinforcing mesh (3) can consist of polyester, glass, polyamide, polyethylene, aramid fibres and/or carbon, wherein polyester and glass represent preferred materials for reasons of cost as well as the ratio between strength and fibre thickness.

Whether the reinforcing grid (3) consists of a fabric, woven, knit or also of a knit, the structural components of the reinforcing grid (3) are referred to within the framework of the invention as "braces" or "grid braces" and "intersections", in accordance with the general meaning given to the grid.

The preferred size of the riblets (30) in the reinforcing grid (3) is preferably from 120 to 350 dtex. A titer of between 150 and 280 dtex is also preferred, since in this range the best results are achieved with respect to the strength and the range of the grooves formed by the meshes of the reinforcing grid (3) on the surface of the planar textile structure (1) according to the invention, and sufficient drapability is ensured.

The intersections of the reinforcing grid (3) can exhibit adhesive. If the reinforcing grid (3) is a fibrous fabric layer, it is preferred to use an adhesive at the crossing points. There is no particular limitation in the choice of the binder. However, PVAC-based adhesives are preferred because they are heat-sealable and make the manufacturing of the reinforcing grid (3) particularly easy and inexpensive.

In terms of structural design, the reinforcing grid (3) is preferably composed of two to three parallel riblets (30). However, more than three sheets are also possible.

If the structural design consists of two pieces of parallel braces (5 a), a lattice structure (5) is preferred, i.e. the reinforcing grid (3) exhibits square mesh. Fig. 5 provides a schematic drawing depicting a cutout from the structure. Here, the advantage must be associated with the greatest isotropy of the strength of the planar structure, meaning with directionally independent strength. In this embodiment, the distance between the riblets (5 a) is preferably of the order of 10 to 50mm, more preferably 10 to 18mm, since given the smaller mesh, the grooves described above are less pronounced.

If the structural design consists of three parallel braces (4a, 4b, 4c), one brace is referred to as a "longitudinal brace" (4a) and the other two braces are referred to as "diagonal braces" (4b, 4 c). Fig. 4 provides a schematic drawing depicting a cutout from the structure. Here, it is preferred that the construction is such that one of the diagonal braces (4b) is positioned at an angle of more than 45 ° and less than 90 ° relative to the longitudinal brace (4a), while for the other one of the diagonal braces (4c) these angles are less than-45 ° and more than-90 °, and that the angles of the two diagonal braces (4b, 4c) relative to the longitudinal brace (4a) are numerically equal. Viewed separately, the two diagonal braces (4b, 4c) thus form rhomboidal meshes. In this embodiment, the distance between the longitudinal braces (4a) is preferably of the size 5 to 20 mm. In this embodiment, the distance between the diagonal braces (4b, 4c) within one piece is preferably of the order of 7 to 50mm, since the grooves described above are therefore less pronounced, while at the same time sufficient strength is ensured.

Regardless of how the grid (3) is designed, when combining the reinforcing grid (3) and the pile layer (2), the pieces of parallel braces (30) of the reinforcing grid (3) are preferably aligned longitudinally with respect to the preferred direction (if any) of the fibers (20) in the pile layer (2). This helps to simplify the manufacturing process.

The method for manufacturing a planar textile structure (1) according to the invention, in which the reinforcing grid (3) is located between two successive pile layers (2), generally comprises the same steps, preferably in a continuous process:

producing a pile layer (2) having a desired weight per unit area,

producing a further layer of pile (2) as required and applying the further layer of pile (2) to the layer of pile (2) produced in a),

applying a reinforcing grid (3) to the pile layer (2) produced in a), or if necessary, to the pile of pile layers (2) produced in a) and b).

Applying at least one further pile layer (2) on the reinforcing grid (3) prepared in c),

hardening the folded layers placed one on top of the other in a) to d), for example by needling, and

bringing together the planar structure (1) produced in e), for example on a roll.

The method for manufacturing a planar textile structure (1) according to the invention, in which the reinforcing grid (3) is fixed to the outside of the planar textile structure (1), generally comprises the following steps, preferably in a continuous process.

Applying at least one pile layer (2) on the reinforcing grid (3),

hardening the folded layers placed one on top of the other in a), for example by needling, and

bringing together the planar structure (1) produced in b), for example on a roll.

In connection with the above described method, the term "folded layer" denotes both the pile layer (2) and the reinforcing grid (3).

In another aspect of the invention, several folded layers, hereinafter referred to as "nonwoven folded layers", of the planar textile structure (1) according to the invention can be joined together planarly, resulting in an article according to the invention.

The preferred directions of the individual nonwoven folded layers (1), if any, can be aligned parallel to one another. However, depending on how and where the article is used, it may also be advantageous to have the nonwoven folded layers (1) joined at different angular planes to each other with respect to their preferred direction. A preferred embodiment provides a composite of three nonwoven folded layers (1), wherein the preferred directions of the middle and upper nonwoven folded layers (1) are aligned at an angle of 45 ° or-45 ° relative to the preferred direction of the lower nonwoven folded layer (1). This results in increased isotropy to the strength of articles and components made from the composite.

The connection between the nonwoven folded layers (1) according to the invention can be achieved, for example, by merely sewing them together or by renewed needling. However, other types of coupling are also possible.

In a preferred embodiment, at least one grid fold layer may be provided between two or more nonwoven fold layers (1) of the article according to the invention. This allows the polymer material to penetrate preferentially into and optimally saturate the composite of several nonwoven plies without the individual nonwoven plies (1) slipping relative to each other during the impregnation process, for example, when injecting a fluid polymer matrix for the manufacture of a component according to the invention. The grid folded layer may be structured based on the reinforcement grid (3) according to the invention. However, meshes having different structural designs may also be used. Knitted fabrics or fabrics consisting of polyester threads are preferred here because they are easy and inexpensive to manufacture.

In another aspect of the invention, a planar textile structure (1) according to the invention or an article according to the invention is impregnated with a polymer matrix, thereby producing a component according to the invention.

The polymer matrix is not particularly limited in material. Suitable materials for the polymer matrix typically comprise resins used in the manufacture of fiber composites, such as polyester resins, epoxy resins and vinyl ester resins.

Suitable methods for impregnating the planar textile structure (1), such as resin injection or impregnation, are known to the expert. The component is produced in the desired form, for example by subsequent hardening by exposure to elevated temperatures. Therefore, it is most often necessary to hang the planar textile structure (1) beforehand on a rigid mould. The textile flat structure (1) according to the invention is distinguished here by an optimum drapability due to its construction.

In another aspect of the invention, a component according to the invention is used for manufacturing an automotive part. There is no particular limitation in the type and function of the components. Non-load bearing parts are preferred here.

Load-bearing parts in automobiles, such as the a-pillar, B-pillar, or C-pillar, are highly stressed components. If they consist of fiber composites, they are usually produced using woven mats (woventing) or fiber fabrics, in which the fiber bundles in the woven mat or fiber fabric are aligned in such a way that they optimally absorb or transfer forces, i.e. the fiber bundles in the woven mat of fiber fabric are preferably aligned in the direction of the applied force. In the nonwoven material, the strength is distributed in all directions due to the structure, wherein the preferred direction produced by the carding pile can once again increase the anisotropy of the strength of the nonwoven material. This is why fibre composite materials made of nonwoven fabrics can be used in high-stress components of vehicles. However, a combination of a nonwoven material and a woven mat or fiber fabric is also possible, for example in the form of a nonwoven fiber fabric composite.

Claims (17)

1. A flat textile structure (1), said flat textile structure (1) comprising a reinforcing grid (3) and at least one pile layer (2) lying flat on at least one surface of said reinforcing grid (3),

-said planar textile structure (1) exhibits from 40 to 140g/m²The weight per unit area of (a) is,

-said pile layer (2) consisting essentially of carbon fibers,

-the carbon fibres in the planar textile structure (1) represent 60 to 97% of the weight per unit area,

-said reinforcing grid (3) exhibits from 2.5 to 12.5g/m²In a suitable ratio of the weight per unit area,

-the planar textile structure (1) is hardened, and

-wherein the pile layer is a loose layer of randomly entangled individual fibers.

2. A planar textile structure (1) according to claim 1, wherein:

-said planar textile structure (1) exhibits 80-110g/m²The weight per unit area of (a) is,

-the carbon fibres in the planar textile structure (1) have a suitable proportion of a weight per unit area of 65 to 84%, and

-the reinforcing grid (3) has 3 to 10g/m²In a suitable ratio.

3. Planar textile structure (1) according to claim 1 or 2, wherein the reinforcing grid (3) is located on the outside of the planar textile structure (1).

4. A flat textile structure (1) according to claim 1 or 2, wherein the reinforcing mesh (3) is located between two successive pile layers.

5. Planar textile structure (1) according to claim 1 or 2, wherein the material of the reinforcing grid (3) comprises polyester and/or glass fibres.

6. A planar textile structure (1) according to claim 1 or 2, wherein the riblets (30) of the reinforcing grid exhibit a titer of 120 to 350 dtex.

7. A planar textile structure (1) according to claim 1 or 2, wherein an adhesive is used at the intersections of the reinforcing grid (3).

8. A textile planar structure (1) according to claim 1 or 2, characterised in that the reinforcing grid (3) is designed as a laid fibre fabric.

9. Planar textile structure (1) according to claim 1 or 2, wherein said reinforcing grid (3) exhibits: -a piece of parallel longitudinal braces (4a) in a specific direction, and-a plurality of parallel diagonal braces (4b, 4c) diagonal to the parallel longitudinal braces, wherein one piece of parallel diagonal braces (4b) is positioned at an angle greater than 45 ° and less than 90 ° with respect to the parallel longitudinal braces (4a), and for the other piece of parallel diagonal braces (4c) the angle is less than-45 ° and greater than-90 °, and the angles of the two pieces of parallel diagonal braces (4b, 4c) with respect to the parallel longitudinal braces (4a) are numerically equal.

10. A textile flat structure (1) according to claim 9, characterised in that said longitudinal braces (4a) are mutually spaced by 5 to 20mm and said diagonal braces (4b, 4c) are mutually spaced by 7 to 50 mm.

11. A planar textile structure (1) according to claim 1 or 2, wherein the reinforcing grid (3) has a latticed design consisting of two parallel pieces of riblets.

12. A flat textile structure (1) according to claim 11, wherein the parallel braces are spaced apart from each other by 10 to 50 mm.

13. A textile flat structure (1) according to claim 1 or 2, characterised in that the pile layer (2) consists essentially of staple fibres.

14. An article comprising at least two planarly coupled planar textile structures (1) according to one of claims 1 to 13.

15. A component comprising a planar textile structure (1) according to one of claims 1 to 13, characterized in that the planar textile structure (1) is impregnated with a polymer matrix.

16. A component comprising the article of claim 14, wherein the article is impregnated with a polymer matrix.

17. Use of a component according to one of claims 15 or 16 for the manufacture of automotive parts.