EP2303511B1 - Method for treating a surface of a fiber composite material - Google Patents

Abstract

The present invention provides a method and a device for treating a surface of a fiber composite material which contains fibers of a specific hardness, the surface of the fiber composite material being removed abrasively by an abrasion means, the hardness of which is less than the hardness of the fibers contained in the fiber composite material and is greater than the hardness of a plastics material in which the fibers of the fiber composite material are embedded.

Description

The invention relates to a method for treating a surface of a fiber composite material, in particular a carbon fiber reinforced plastic (CFRP).

In aircraft construction fiber composite materials are increasingly used. Fiber composites are materials that are reinforced by embedded fibers. Most commonly used are glass fiber reinforced plastics (GRP), carbon fiber reinforced plastics (CFRP) and aramid fiber reinforced plastics (AFK).

For bonding components to carbon fiber reinforced plastics, it is necessary to treat the surface of such fiber composites. For example, adhesive surfaces of the upper and lower shell on wings must be carefully pretreated before they are glued to a finished wing.

The aircraft parts that are extremely exposed during flight operations must not fail. Splices that have lower strength than the base material can be a cause of the weakening of a structural part.

To avoid such weak spots, the surfaces intended for further processing by gluing are traditionally first ground. When sanding laminated rough surfaces there is a risk that the strength-determining Fibers are damaged by the grinding process.

Fig. 1A, 1B show schematically a surface treatment of a fiber composite material in which the fiber composite material is ground in a conventional manner.

As in Fig. 1A shown, fibers F1, F2 are embedded in a plastic K of the fiber composite material to give the material a higher strength. The fibers F of the composite have a relatively high hardness and are relatively brittle. How to get in Fig. 1 can recognize, the fibers F, which are embedded in the plastic K of the composite material, a certain waviness. As in the Fig. 1A, 1B For example, as the surface of the composite is abraded, some of the fibers embedded therein, such as those in the Fig. 1A, 1B represented fiber F1, are severed. With a severing of one or more fibers, the strength of the composite is reduced.

When grinding the surface of a fiber composite material there is thus the risk that the strength-determining fibers are damaged or severed by the grinding process. This can be determined by measuring the surface resistance, since the fibers are usually electrically conductive.

It was therefore in the DE 103 025 94 A1 proposed a method for the preparation of surfaces of carbon fiber reinforced plastics for the further processing of supporting structural parts, wherein the treatment of the surface of the carbon fiber reinforced plastic is carried out with a blasting abrasive using sharp-edged corundum.

However, this method according to the prior art has the disadvantage that the corundum grains in the surface treatment of the composite material not only ablate the plastic, but also attack the brittle fibers thereby exposed. It can therefore also come with this, conventional methods of the prior art to a separation of fibers of the composite material.

document US5261191 shows a method of treating a surface of a fiber composite material containing fibers of a certain hardness, wherein the surface of the fiber composite material is abraded with a Abtragungsmittel whose hardness is greater than the hardness of the plastic in which the fibers are embedded.

It is therefore an object of the present invention to provide a method and apparatus for treating a surface of a fiber composite that does not compromise the strength of the fiber composite and yet exposes the fibers to form the composite.

This object is achieved by a method having the features specified in claim 1.

The invention provides a method for treating a surface of a fiber composite material containing fibers of a certain hardness,
wherein the surface of the fiber composite material is abraded with a Abtragungsmittel whose hardness is less than the hardness of the fibers contained in the fiber composite material and whose hardness is greater than the hardness of a plastic in which the fibers of the fiber composite material embedded, and wherein in the fiber composite material contained fibers are exposed without damaging them.

In one embodiment of the method according to the invention, the ablation agent is irradiated onto the surface of the fiber composite material by means of a gaseous fluid.

In one embodiment of the method according to the invention, the ablation agent is irradiated onto the surface of the fiber composite material by means of a liquid fluid.

In one possible embodiment of the method according to the invention, the gaseous fluid is formed by air.

In one possible embodiment of the method according to the invention, the liquid fluid is formed by water.

In a further embodiment of the method according to the invention, the ablation agent is thrown onto the surface of the fiber composite material.

In one possible embodiment of the method according to the invention, the erosion agent is formed by urea resin.

In one possible embodiment of the method according to the invention, the hardness of the ablation agent is 3 to 4 Mohs.

In the method according to the invention, the surface of the fiber composite material is preferably prepared for bonding.

In one possible embodiment of the method according to the invention, the grains of the ablation agent have a grain size of 0.10 to 1.80 mm.

In a possible preferred embodiment of the method according to the invention, the grains of the ablation agent have a particle size of 0.10 to 0.50 mm.

In one possible embodiment of the method according to the invention, the fiber composite material is a carbon fiber reinforced plastic.

In one possible embodiment of the method according to the invention, the fiber composite material is a glass fiber reinforced plastic.

In one embodiment of the method according to the invention, the treated surface is blown off with compressed air to remove the ablation agent used.

In one embodiment of the method according to the invention, an adhesive is applied to the treated surface of the fiber composite material and then a component is pressed.

In one possible embodiment of the ablation agent, the ablation agent comprises urea resin.

In one possible embodiment of the ablation means, the ablation means consists of grains whose grain shapes are sharp-edged and irregular.

In one possible embodiment of the ablation agent, the grains of the ablation agent have a grain size of 0.10 to 1.80 mm.

In one embodiment of the ablation agent, the grains of the ablation agent have a grain size of 0.10 to 0.50 mm.

In one possible embodiment of the ablation agent, the ablation agent has a hardness between 3 and 4 Mohs.

In one embodiment of the device for carrying out the method according to the invention, the ablation agent is irradiated by a jet device onto the surface of the fiber composite material by means of a gaseous or liquid fluid under pressure.

In an alternative embodiment of the device, the ablation means is spun on the surface of the fiber composite material by a spinner.

The device abrades a surface layer of the fiber composite abrading agent to an adjustable depth without damaging fibers contained in the fiber composite.

In the following, embodiments of the method according to the invention for the treatment of a surface of a fiber composite material will be described with reference to the attached figures.

Fig. 1A, 1B

Schnittansichten durch einen Faserverbundwerkstoff zur Darstellung eines herkömmlichen Schleifvorgangs nach dem Stand der Technik zur Oberflächenbehandlung des Faserverbundwerkstoffes;

Fig. 2A, 2B

Schnittansichten durch einen Faserverbundwerkstoff zur Erläuterung des erfindungsgemäßen Verfahrens;

Fig. 3

ein Diagramm zur Erläuterung des erfindungsgemäßen Verfahrens;

Fig. 4

ein Ablaufdiagramm zur Darstellung wesentlicher Verfahrensschritte zum Ankleben eines Bauteils an einen Faserverbundwerkstoff.

Show it:

Fig. 1A, 1B

Cross-sectional views through a fiber composite material to illustrate a conventional prior art grinding process for surface treatment of the fiber composite material;

Fig. 2A, 2B

Sectional views through a fiber composite material for explaining the method according to the invention;

Fig. 3

a diagram for explaining the method according to the invention;

Fig. 4

a flow diagram for illustrating essential process steps for adhering a component to a fiber composite material.

How to get out Fig. 2A recognize, there is a process to be treated according to the invention fiber composite material 1 of a plastic 2 in the fibers 3-1, 3-2 are embedded. The fibers 3-1, 3-2 are high strength fibers which provide strength to the composite. The fibers 3-1, 3-2 may, for example, be carbon fibers, the fibers being impregnated, for example, in resin. The plastic 2 or the resin may be, for example, a thermoset. In a fiber composite with plastic matrix, the fibers are impregnated with the resin. Either this happens in layers, ie alternately resin and fiber mat, in a laminated composite or by tailored pre-impregnates, which harden at elevated temperature and elevated pressure in molds to form components. Due to different orientation of the fibers 3-i, the properties of the fiber composite material 1 can vary. At the in Fig. 2A Fiber composite 1 shown may also be a glass fiber reinforced Plastic GRP, or to trade an aramid fiber reinforced plastic AFK. The plastic 2 in which the fibers 3-i are embedded has a certain hardness H _K. The embedded in the plastic 2 fibers 3-i also have a predetermined hardness H _F.

In the method according to the invention, as described in Fig. 2A is shown schematically, a Abtragungsmittel 5 is irradiated or thrown on a surface 4 of the fiber composite material 1. This ablation means 5 contains a plurality of grains 5-1 to 5-5. Due to the impact of the grains 5-i on the surface 4 of the fiber composite material 1, the surface 4 is abraded abradingly, since the ablation means 5 or the grains 5-i of the ablation means 5 have a hardness H _A which is greater than the hardness H _K of Plastic 2 in which the fibers 3-i of the fiber composite material 1 are embedded. As in the Fig. 2A, 2B shown, starting from the original surface 4 of the fiber composite material 1 bishin to the surface 4 'of the fiber composite material 1 abraded by the Abtragungsmittel 5. As soon as grains of the ablation agent 5 strike a fiber 3-i embedded in the plastic 2, they bounce off the fiber 3-i, as in FIG Fig. 2B shown. How to get out Fig. 2B For example, the grain 5-3 of the ablation means 5 strikes an exposed fiber 3-1 embedded in the plastic 2.

In the method according to the invention, a removal agent 5 is used whose hardness H _{A is} less than the hardness H _{F of} the fibers 3-i contained in the fiber composite material 1. At the same time, the removal means 5 has a hardness H _A which is greater than the hardness H _{K of} the plastic 2, in which the fibers 3-i of the fiber composite material 1 are embedded. This is explained in the diagram according to Fig. 3 clarified. The hardness H _{A of} the ablation agent 5 is in a range between the hardness H _{K of} the plastic matrix and the hardness H _{F of} the fibers 3: $${\mathrm{H}}_{\mathrm{K}}\mathrm{<}{\mathrm{H}}_{\mathrm{A}}\mathrm{<}{\mathrm{H}}_{\mathrm{F}}$$

In one embodiment, the hardness H _{A of} the ablation agent 5 is in a range between 3 to 4 Mohs.

After removal of a certain amount of the fiber composite material 1 on its surface, for example a layer of several micrometers, the surface 4 'of the fiber composite material 1 is ready for further manufacturing steps, such as the sticking of a component.

Fig. 4 shows manufacturing steps that use the inventive method for treating a surface of a fiber composite material 1.

First, in a step S1, the original surface 4 of the fiber composite material 1 is removed abradingly with a removal agent 5 whose hardness H _{A is} less than the hardness H _{F of} the fibers 3 contained in the fiber composite material 1 and whose hardness H _{A is} greater than the hardness H _K a plastic 2 in which the fibers 3 of the composite material 1 are embedded. The fibers 3 are for example carbon fibers.

Alternatively, the fibers 3 may also be glass fibers of a specific hardness. It is also possible that the fibers are aramid fibers of a certain hardness. The hardness H _{A of} the ablation means 5 used is thus selected as a function of the predetermined hardness H _{F of} the fibers 3 embedded in the plastic 2. Moreover, the hardness H _{A of} the ablation means 5 is selected as a function of the predetermined hardness H _{K of} the plastic 2.

In one possible embodiment, the depth or extent of the ablation is A, as in FIG Fig. 2B shown, adjustable. Once the abrasive removal is completed in step S1, in step S2, the treated surface 4 'of the fiber composite material 1 is blown off with compressed air to remove the ablation agent. In a further step S3 z. B. adhesive applied to the freed from the Abtragungsmittel surface 4 'of the fiber composite material 1.

In a further step S4, a component to be bonded is pressed onto the adhesive-coated treated surface 4 ', which can be done at elevated temperature.

In one possible embodiment of the method according to the invention, the removal means 5 is formed by urea resin, the grains 5-i of the removal means 5 having a particle size in a range from 0.10 to 1.80 mm, preferably in a range from 0.10 to 0.50 mm , lie.

The removal means 5 can be radiated onto the surface 4 of the fiber composite material 1 in step S1 by means of a gaseous fluid. This gaseous fluid is, for example, air.

Alternatively, the ablation means 5 can be irradiated onto the surface 4 of the fiber composite material 1 by means of a liquid fluid. This fluid may be, for example, water.

In a further embodiment, the ablation means 5 is spin-coated on the surface of the fiber composite material 1 by a spinner.

This in Fig. 4 The method illustrated may be performed by a manufacturing apparatus having a device for treating a surface of a fiber composite material 1. This device for treating a surface 4 of a fiber composite material has a unit which the surface 4 of the fiber composite material 1 directs a Abtragungsmittel 5 or radiates the hardness H _{A is} less than the hardness H _F of fibers contained in the fiber composite material 1 3 and its hardness H _{A is} greater than the hardness H _{K of} a plastic 2 in the Fibers 3 of the fiber composite material 1 is embedded.

The ablation means 5 is located in a possible embodiment in a memory or container of the surface treatment device.

In a variant of the surface treatment apparatus, the latter contains a jet device which irradiates the removal means 5 on the surface 4 of the fiber composite material 1 by means of a fluid under pressure. The pressure is preferably adjustable. The fluid may be a gaseous or liquid fluid residing in a container of the surface treatment device.

In an alternative embodiment, the treatment device has a spinner device which hurls the ablation means 5 onto the surface 4 of the fiber composite material 1.

The surface treatment apparatus abrades a degraded surface layer of the fiber composite material 1 to an adjustable depth without damaging the fibers 3 contained in the fiber composite material 1 because the hardness H _{A of} the ablation material 5 used is less than the hardness H _F embedded in the fiber composite material 1 Fibers 3.

Claims (12)

1. A method for treating a surface of a fibre composite (1), which contains fibres (3) of a specific hardness (H_F), wherein the surface (4) of the fibre composite (1) is abrasively removed using an abrasion medium (5), whose hardness (H_A) is lower than the hardness (H_F) of the fibres (3) contained in the fibre composite (1) and whose hardness (H_A) is greater than the hardness (H_K) of a plastics material (2) in which the fibres (3) of the fibre composite (1) are embedded, and wherein fibres (3) contained in the fibre composite (1) are exposed without being damaged.
2. A method according to claim 1, wherein the abrasion medium (5) is propelled onto the surface (4) of the fibre composite (1) by means of a gaseous or liquid fluid.
3. A method according to claim 2, wherein the fluid takes the form of air or of water.
4. A method according to claim 1, wherein the abrasion medium (5) is propelled centrifugally onto the surface (4) of the fibre composite (1).
5. A method according to any one of preceding claims 1 to 4, wherein the abrasion medium (5) takes the form of urea resin.
6. A method according to any one of preceding claims 1 to 5, wherein the hardness (H_A) of the abrasion medium (5) is three to four on the Mohs hardness scale.
7. A method according to any one of preceding claims 1 to 6, wherein the surface (4) of the fibre composite (1) is prepared for adhesive bonding or coating.
8. A method according to any one of preceding claims 1 to 7, wherein grains (5-i) of the abrasion medium (5) exhibit a grain size of 0.10 to 1.80 mm.
9. A method according to claim 8, wherein the grains (5-i) of the abrasion medium (5) exhibit a grain size of 0.10 to 0.50 mm.
10. A method according to any one of preceding claims 1 to 9, wherein the fibre composite (1) is a carbon fibre-reinforced plastics material (CFRP) or a glass fibre-reinforced plastics material.
11. A method according to any one of preceding claims 1 to 10, wherein the treated surface (4') of the fibre composite (1) is blasted with compressed air (S2) to remove the abrasion medium (5).
12. A method according to claim 11, wherein an adhesive is applied to the treated surface (4') of the fibre composite (1) (S3) and a component is pressed onto the treated surface (S4).

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