WO2023064966A1

WO2023064966A1 - Method for manufacturing a fibre laminate, fibre laminate, and use of a fibre laminate

Info

Publication number: WO2023064966A1
Application number: PCT/AT2022/000006
Authority: WO
Inventors: Peter KRICKER; Gerald PLOT; Klaus Krenn
Original assignee: Isosport Verbundbauteile Gesellschaft M.B.H.
Priority date: 2021-10-19
Filing date: 2022-09-19
Publication date: 2023-04-27
Also published as: AT525587A1

Abstract

The invention relates to a method for manufacturing a fibre laminate (1), in which method - a matrix (2) in a liquid state as well as fibres (3) are provided, - the fibres (3) are embedded in the matrix (2) while the matrix (2) is in the liquid state, - during a curing process, a time is allowed to elapse until the matrix (2) reaches a gel point, from which time the matrix (2) has substantially changed from the liquid to a plastic state, - when the matrix (2) is in the plastic state, a surface structure (10) is imprinted on the matrix (2) together with the fibres (3) embedded therein, and - the curing process is terminated, resulting in the production of the fibre laminate (1) which contains the matrix (2) and the fibres (3) embedded therein and which has the imprinted surface structure (10).

Description

Method for producing a fiber laminate, a fiber laminate and a use of a fiber laminate

The present invention relates to a method for producing a fiber laminate, a fiber laminate and the use of a fiber laminate in the manufacture of gliding devices, in particular skis or snowboards, and/or in the manufacture of wind blades.

The production of fiber laminates, for example in the pultrusion process, is of course known per se. Here, fibers are embedded in a matrix while the matrix is in the liquid state.

Fiber laminates are used, for example, in the production of skis. Here, the fiber laminates must have a surface structure, because otherwise air pockets can form during the pressing process with which the skis are manufactured. A surface structure prevents this because the surface structure creates a certain spacing of layers located above or below the fiber laminate almost until the end of the pressing process. The air can then escape through the resulting gaps.

Another positive effect of the surface structure is improved adhesion between the layers.

In the prior art, the mentioned surface structure of the fiber laminate is produced by grinding the surface of the previously produced fiber laminate, which has disadvantages. First of all, the grinding of fiber laminate is fundamentally undesirable because grinding the fibers can produce dust (e.g. glass fiber dust) which, due to the particle size, is complex and difficult to dispose of. In case of improper handling, the grinding dust would also pose a significant environmental burden.

Furthermore, grinding the fiber laminate produced in advance is undesirable because this means that more material is used than would actually be necessary. In this regard, too, grinding the fiber laminate is disadvantageous in terms of material utilization and environmental compatibility.

Since the fibers in the laminate are not evenly distributed and in some cases are even arranged one above the other, the fibers are ground to different degrees during grinding, resulting in inhomogeneous mechanical material properties of the laminate.

The grinding also creates micro-fractures in the laminate, which become predetermined breaking points in the finished product.

The object of the invention is therefore to provide a method for producing fiber laminates and a fiber laminate with a surface structure in which material can be saved and/or fewer harmful by-products, such as grinding dust, are produced and/or more homogeneous material properties are achieved.

With regard to the production method, this object is achieved by the features of claim 1, namely by providing a matrix in a liquid state and fibers, the fibers are embedded in the matrix while the matrix is in the liquid state, awaiting a curing process, until the matrix reaches a gel point at which the matrix im has essentially changed from the liquid to a plastic state, in the plastic state of the matrix a surface structure is imprinted on the matrix together with the fibers embedded therein and the curing process is terminated, whereby the fiber laminate containing the matrix and the fibers embedded therein is obtained, which the imprinted Has surface structure.

With regard to the fiber laminate, the object is achieved by the features of claim 9, namely in that the surface of the fiber laminate has an embossed surface structure.

The embossing of a surface structure on a fiber laminate is not possible at any time. If the surface structure is changed too early during the curing process, the surface structure will not remain as the liquid matrix simply returns to its original state. Likewise, the surface structure cannot be embossed after the curing process has ended, because the matrix is no longer plastically deformable at this point.

According to the invention, the imprinting of a surface structure on a fiber laminate takes place after the gel point has been reached, but before the curing process has ended. A basic aspect of the invention is therefore that it is possible to imprint a surface structure on the matrix together with the fibers embedded in it if one waits for the relatively short period of time in which the matrix is in a plastic state (from the gel point) and the curing process is not yet finished.

According to the invention can be completely dispensed with post-processing, such as grinding fen, which Material can be saved and undesirable by-products, such as grinding dust, can be completely avoided. The fiber laminates according to the invention can therefore be used directly for further production, for example of gliding devices or wind blades.

On the one hand, the elimination of the grinding improves the working conditions in the vicinity of the plant for producing the fiber laminates. In addition, as mentioned, no precautions have to be taken to dispose of the grinding dust. Worn grinding belts also do not have to be changed.

Because the laminates do not have to be sanded at all, the material properties are more homogeneous, in particular mechanical properties such as elasticity, fracture toughness and resistance to delamination. In concrete tests by the applicant, the mechanical tolerances of a fiber laminate according to the invention could be reduced from 15% to 8%.

A further effect of the invention is that the surface structure can be chosen almost freely and thus adapted to the desired application.

According to the invention, a surface structure is understood to mean a structure which has elevations and/or depressions, ie is not smooth, and corresponds at least to a certain degree to the embossing structure of an embossing tool.

In particularly preferred embodiments of the invention, the fibers can be embedded in the liquid matrix by a pultrusion process. Embedding the fibers in the liquid matrix can also be referred to as impregnation. The liquid matrix preferentially wets all of the fibers.

In particularly preferred embodiments, the fibers are embedded in the matrix in a substantially unidirectional manner, resulting in a fiber laminate with fibers aligned in a substantially unidirectional manner. Embodiments with a non-unidirectional orientation of the fibers are of course conceivable in principle.

Protection is also sought for the use of a fiber laminate in the manufacture of gliding devices, particularly skis or snowboards, and/or in the manufacture of wind blades. Wind blades can be understood to mean the blades of a wind power plant.

Advantageous embodiments of the invention are defined in the dependent claims.

A reactive and/or duroplastic matrix system can be used as the matrix.

That is, the matrix can be a resin or a reactive polymer precursor that after impregnation of the fibers - for example. assisted by the influence of pressure and/or temperature - hardens.

The matrix can specifically be at least one of the following:

• Unsaturated polyester resins

• Vinyl ester resins

• diallyl phthalate resins

• Methyl methacrylate resins

• Epoxy resins • Polyurethanes

• phenol-formaldehyde resins

• Amino resins

• Thermoplastic resin systems

• Biopolymers

As mentioned, the fibers can be embedded in the matrix essentially unidirectionally.

The fibers (also referred to as filaments) can be provided in the form of bundles (rovings). The bundles can consist of fibers that are aligned essentially parallel or fibers that are wound or braided around one another. Mixed forms are of course also conceivable in principle.

Examples of fibers that can be used with the present invention are at least one of the following:

Glass fibers (Glass fibers are the most commonly used types of fibers mainly because of their relatively low price. There are types of glass fibers for different areas of application.) Carbon fibers (also: carbon fibres; These have high strength and low weight at the same time. Disadvantages can be found in a brittle fracture behavior and a low elongation at break. )

Basalt fibers (Basalt fibers are mineral fibers which, because of their good chemical resistance and temperature resistance, are primarily used in containers and

Vehicle construction is used. ) Ceramic fibers (endless ceramic fibers made of aluminum oxide, mullite (mixed oxide of aluminum oxide and silicon dioxide) , SiBCN, SIGN, SiC etc . are expensive special fibers for high-temperature-resistant composite materials with a ceramic matrix . The non-oxide fibers are similar to me such as carbon fibers, obtained from organic resins that contain silicon as well as carbon.) Aramid fibers (aramid is short for aromatic polyamides. The manufacturing process is very expensive and the price of aramid fibers is therefore comparable to that of carbon fibers. The essential properties are their low density and good damping properties.) Steel fibers (Steel fibers are mainly used in the construction industry for steel fiber concrete. This application is growing rapidly and has particular economic advantages.) Natural fibers (The fibers most commonly used for the production of fiber composite materials are the domestic wood fibers, Flax and hemp fibers as well as subtropical and tropical fibers such as jute, kenaf, ramie or sisal fibers.)

Nylon fibers (Fibers with a high elongation at break are advantageous when the fiber laminate must absorb shock.)

It can be provided that the fibers are drawn through a bath with the matrix in the liquid state and thereby embedded in the matrix.

The matrix together with the fibers embedded therein can be guided through a nozzle in order to at least partially define a geometric shape, in particular a thickness, of the fiber laminate.

The fact that the nozzle at least partially defines the geometric shape can be understood to mean that, for example, a thickness of the fiber laminate is defined by the nozzle to a certain degree of accuracy. Subsequent processes (e.g. shrinkage during the curing process, embossing of the surface structure) can further change the geometry of the fiber laminate. By guiding the matrix together with the fibers embedded in it through a pair of rollers (before or after the embossing of the surface structure) the thickness can ultimately be determined, but this is not mandatory.

Alternatively, the nozzle can also only partially define the geometry of the fiber laminate, so that the nozzle only partially defines the geometric shape of the fiber laminate in this way.

In order to initiate and/or accelerate the curing process, the matrix together with the fibers embedded therein can be heated, preferably by means of at least one heating plate.

In particularly preferred exemplary embodiments, two heating plates can be provided, between which the matrix together with the fibers embedded therein is passed.

In particularly preferred exemplary embodiments, the at least one heating plate is in contact with the matrix and/or the fibers embedded therein in order to improve heat transfer.

Provision can also be made for the at least one heating plate to exert a defined pressure and/or a defined force on the matrix together with the fibers embedded therein.

Hot plates can be heated directly with electrical energy or by means of a heating medium (e.g. water or oil).

In principle, other devices, such as radiant heaters, can also be used instead of heating plates.

The temperature and/or the applied force and/or the applied pressure can be controlled or regulated.

As already mentioned, it can be provided that the matrix together with the fibers embedded therein—preferably before embossing the surface structure - is guided by at least one pair of rollers in order to define a thickness of the resulting fiber laminate. In principle, embodiments in which the pair of rollers for adjusting the thickness is arranged in front of the at least one embossing roller in a feed direction are also conceivable.

The pair of rollers can be arranged opposite each other, so that the matrix together with the fibers embedded in it is in contact with both rollers of the pair of rollers at the same time.

The rollers of the roller pair can preferably have an essentially smooth surface in order not to disturb the embossed surface structure. The rolls of the pair of rolls can accordingly also be referred to as "smooth rolls".

Provision can be made for the rollers in the pair of rollers to have a defined, controlled and/or regulated distance from one another in order to adjust the thickness of the fiber laminate.

The surface structure can be embossed onto the matrix together with the fibers embedded therein by means of at least one embossing roller. The embossing roller has a negative structure for this, which shows up as the surface structure of the fiber laminate after embossing.

The negative structure has indentations and/or elevations which, upon contact with the at least one embossing roller, produce corresponding elevations and/or indentations in the matrix together with the fibers embedded therein and thus the surface structure.

Two embossing rollers can be used, which are arranged opposite one another, so that the matrix together with the embedded fibers is in contact with the embossing rollers at the same time.

In principle, more than two embossing rolls could also be used, some of which are arranged sequentially, for example.

Not all of the embossing rolls have to have the negative structure mentioned. However, at least one of the embossing rollers must have a negative structure so that the surface structure can be embossed.

If two or more embossing rollers are used, the surface structure of the matrix including the fibers embedded in it can be embossed on two sides. According to the invention, a fiber laminate can therefore be provided which has the surface structure on one or two sides.

As an alternative to embossing rollers, it would also be possible in principle to use strips which have the negative structure mentioned.

The fact that embossing rollers or smoothing rollers are in contact with the matrix together with the fibers embedded therein can be understood to mean that these rollers are arranged at the same point in relation to a feed direction of the matrix together with the fibers embedded therein, so that they are in contact in the feed direction with the same area of the matrix including the fibers embedded in it (i.e. "simultaneously" in

reference to a feed position) .

It can be provided that the embossing produces a surface structure with a peak-to-valley height of Rz=0.01 to 1 μm, preferably Rz=0.03 to 0.5 μm, particularly preferably Rz=

0.03 to 0.3 pm. Particularly when using an embossing roller, particularly if at least one pair of rollers is arranged upstream of the embossing roller, particularly favorable surface qualities can be achieved, such as the roughness depths mentioned above.

In order to reach the gel point without the curing process of the matrix being terminated before the surface structure is imprinted, defined temperature ranges and/or distances between a point at which the curing time begins and a point at which the surface structure is imprinted can be used.

In tests by the applicant in the form of a pultrusion process, target temperatures of less than 400° C. (particularly with radiant heaters), less than 200° C. (particularly with electrically heated heating plates) and/or less than 100° have been found C (particularly in the case of heating plates heated by means of a heating medium) turned out to be advantageous.

Furthermore, with a movement speed of the matrix together with the fibers embedded in it during pultrusion of less than 12 m per minute, the following distance ranges have emerged at which the curing process can be ended (according to the invention, the surface structure is imprinted before the curing time): after a nozzle: 7 m to 12 m after entering a heating zone: 5.5 m to 10.5 m

Further advantages and details of the invention can be seen from the figures and the associated description of the figures. Show : Fig. 1 is a schematic diagram of a

Embodiment of a manufacturing method according to the invention,

Fig. 2a and 2b Photographic representations of two

Examples of an embossing roller,

3 shows a photographic representation of a laminate according to the invention,

4a and 4b two diagrams of the method according to the prior art and

5 is a diagram showing the gel point.

Fig. 1 shows a schematic diagram of a

Embodiment of the manufacturing method according to the invention.

From a supply 8 of fibers 3 in bundle form (rovings), the fibers 3 are guided via a roving creel 9 and rollers through a bath 4 in which the matrix 2 is present in liquid form. As a result, the fibers 3 are embedded in the matrix 2, i.e. impregnated with the matrix 2.

In this exemplary embodiment, the matrix 2 is an epoxy resin based on bisphenol A with an isophorone diamine hardener.

The fibers 3 are guided through the bath 4 in a direction parallel to one another, so that ultimately a unidirectional orientation of the fibers 3 in the fiber laminate 1 results.

After impregnation in the bath 4, the matrix 2 together with the fibers 3 embedded therein is guided through a nozzle 5, which roughly defines the geometry of the fiber laminate 1. The geometry of the fiber laminate 1 can be seen in FIG. A trigger 12 is provided for feeding (actually: pulling) the fibers 3 through the roving creel 9, the bath 4, the nozzle 5 and the following elements. The trigger 12 contains two chain straps, which pull the matrix 2 together with the fibers 3 embedded therein through the mentioned elements.

In this respect, the present production process is a known pultrusion process, with which fiber laminates can be produced in endless production.

After the nozzle 5 the matrix 2 together with the fibers 3 embedded therein is moved through a heating zone 11 . The heating zone 11 contains heating plates 14 which heat the matrix 2 . The curing process of the matrix 2 is started and/or accelerated by the heating.

The length of the heating zone and the pull-through speed are selected so that the matrix 2 reaches the gel point at the end of the heating zone and after being guided through a pair of rollers 7, at which the matrix 2 is in a plastic state (hardening due to the formation of long-chain molecules).

Embossing rollers 6 are provided at this point, which emboss the surface structure 10 onto the matrix 2 together with the fibers 3 present therein by means of depressions and elevations (negative structure).

In this embodiment, only the top in FIG

Embossing roller 6 provided with the negative structure. The lower embossing roller is therefore smooth in this embodiment.

After the surface structure 10 has been embossed according to the invention, the curing process of the matrix 2 continues until it is completely cured, so that the matrix 2 changes from the aforementioned plastic state to a fully hardened state. In this completely hardened state, it would no longer be possible to emboss a structure, since the matrix 2 would only deform slightly elastically or would break under the influence of the embossing.

In the present exemplary embodiment, a pair of rollers 7 is provided in front of the embossing rollers 6, by means of which the thickness of the fiber laminate 1 can be adjusted. The matrix 2 is also still in the plastic state at the location of the pair of rollers 7 .

The embossing rollers 6 and the pair of rollers 7 are arranged spatially close to one another and therefore form a smoothing and embossing unit.

After stripping 12, the fiber laminate can be trimmed as desired.

As mentioned, FIGS. 2a and 2b show two exemplary embodiments of embossing rollers 6, different negative structures being evident.

FIG. 3 shows fiber laminates 1 which have been provided with a surface structure 10 according to the production method described in connection with FIG.

In the exemplary fiber laminates 1 shown in FIG. 3, there are usually several layers of fiber bundles one on top of the other.

For comparison, a production method according to the prior art was illustrated in FIG. 4a and in FIG. 4b. It can be seen that the fiber bundles (rovings) are not ideally level in the laminate 21 . Through the subsequent grinding process a surface with a certain structure is produced by means of an abrasive belt 22 . However, the individual fibers are ground to different depths or even ground away completely. It is obvious that this not only creates harmful grinding dust, but also that the material properties vary, depending on the local position of the fibers in the laminate 21 .

In contrast to this, a fiber laminate 1 can be produced with the invention without wasting material, which furthermore has far more homogeneous material properties and a freely selectable surface structure.

Fig. 5 shows an exemplary diagram for clarifying the gel point. On the one hand, the temperature curve (solid line) of a volume element of the matrix 2 during the pultrusion and on the other hand the viscosity (dotted line) of the same, in each case against time, are plotted.

After an initial drop in viscosity due to the increasing temperature in the heating zone 11 and a subsequent flat course of the viscosity, during which the curing reaction of the matrix 2 begins, the viscosity rises relatively steeply. The latter is the result of the hardening reaction, by which long-chain molecules are formed in the matrix 2 .

During this period, the gel point (vertical line) falls. It marks the time from which the matrix 2 is plastically deformable. The strong increase in viscosity that continues after the gel point ultimately leads to a hardened state in which the matrix 2 is no longer plastically deformable.

It can be seen that due to the strong increase in viscosity, only a relatively short time window is available in which the Matrix 2 is plastically deformable. A basic aspect of the invention is to utilize this short time window in order to emboss the surface structure 10 onto the matrix 2 with plastic deformation.

Claims

patent claims

1. A method for producing a fiber laminate (1), wherein a matrix (2) in the liquid state and fibers (3) are provided, the fibers (3) are embedded in the matrix (2), while the matrix (2) in is in the liquid state, waiting during a curing process until the matrix (2) reaches a gel point, from which point the matrix (2) has essentially changed from the liquid to a plastic state, in the plastic state of the matrix (2) a surface structure (10 ) is embossed onto the matrix (2) together with the fibers (3) embedded therein and the curing process is terminated, whereby the fiber laminate (1) containing the matrix (2) and the fibers (3) embedded therein is obtained, which the embossed on Has surface structure (10).

2. The method according to claim 1, wherein a reactive and/or duroplastic matrix system is used as the matrix (2).

3. The method according to any one of the preceding claims, wherein the fibers (3) are embedded essentially unidirectionally in the matrix (2).

4. The method according to any one of the preceding claims, wherein the fibers (3) are drawn through a bath (4) with the matrix (2) in the liquid state and thereby embedded in the matrix (2).

5. The method according to any one of the preceding claims, wherein the matrix (2) together with the fibers (3) embedded therein is guided through a nozzle (5) to a geometric shape, in particular a thickness of the fiber laminate (1) at least partially fixed. Method according to one of the preceding claims, wherein the matrix (2) together with the fibers (3) embedded therein, preferably by means of at least one heating plate (14), is heated in order to trigger and/or accelerate the curing process. Method according to one of the preceding claims, wherein the

Matrix (2) together with the fibers (3) embedded therein - preferably before the surface structure (10) is embossed - is guided through at least one pair of rollers (7) in order to determine a thickness of the resulting fiber laminate (1). Method according to one of the preceding claims, in which the surface structure (10) is embossed onto the matrix (2) together with the fibers (3) embedded therein by means of at least one embossing roller (6). Method according to one of the preceding claims, wherein by embossing a surface structure (10) with a surface roughness of Rz = 0.01 to 1 pm, preferably Rz = 0.03 to 0.5 pm, particularly preferably from Rz = 0.03 to 0.3 pm. Fiber laminate, in particular produced according to one of

Claims 1 to 9, with fibers (3) embedded in a matrix (2), characterized in that a surface of the fiber laminate (1) has an embossed surface structure (10).

Use of a fiber laminate (1) according to claim 10 and/or produced according to any one of claims 1 to 8 in manufacture 19 of gliding devices, in particular skis or snowboards, and/or for the production of wind blades.