WO2011001065A1

WO2011001065A1 - Method for treating a painted or unpainted composite material using an ion beam

Info

Publication number: WO2011001065A1
Application number: PCT/FR2010/051261
Authority: WO
Inventors: Denis Busardo; Frédéric GUERNALEC
Original assignee: Quertech Ingenierie
Priority date: 2009-07-03
Filing date: 2010-06-22
Publication date: 2011-01-06
Also published as: FR2947569A1; FR2947569B1

Abstract

The invention relates to a method for treating a painted or unpainted composite material using an ion beam, where: the ion acceleration voltage is between 10 kV and 1000 kV; the maximum temperature of the composite material or the paint covering said material is 180°C; the measured amount of ions per surface unit is selected from within a range of 10¹² ions/cm² to 10¹⁸ ions/cm² such that the composite material is cross-linked in order to increase the water drop contact angle by at least 5°. Composite materials having icephobic properties are thus advantageously obtained.

Description

METHOD FOR TREATING AN ION BEAM OF A COMPOSITE MATERIAL COVERED WITH OR WITHOUT PAINTING

The subject of the invention is a method for treating an ion beam with a composite material and aims to reduce the formation and / or the grip of hoarfrost, either at the leading edge of an aircraft wing, or an aircraft engine nacelle, still at the trailing edge of a wing. The formation of this frost can have disastrous consequences, by weighing down the plane and reducing its lift. These effects have repeatedly produced accidents.

By "composite" is meant a material consisting of two components: a polymer matrix and reinforcements. The polymer matrix, which ensures the cohesion of the structure, can be for example an epoxy resin, polyester, phenolic, polyimide or melamine. The mechanical strength of the composite is provided by the reinforcements which may have the form of unidirectional fibers, a mat, fabrics ... The reinforcements may be for example glass fibers, polymeric fibers (kevlar ...), carbon fibers, mineral reinforcements (asbestos, mica ...), metal fibers, ceramic fibers.

Such composite materials can lead to very advantageous applications, for example in the fields of aeronautics, space or the desired qualities relate to safety in flight or the reduction of costs relating to overweight aircraft.

This results in a need for a surface treatment method of composite material, preferably according to easily industrialized methods, so as to be able to to offer such composite materials in significant quantities and at reasonable costs.

The object of the invention is to provide a method of treating composite material which is inexpensive and makes it possible to treat surfaces which meet the needs of numerous applications.

The invention thus provides a method of ion beam treatment of a composite material which comprises ion bombardment where:

the ions of the ion beam are selected from the ions of the elements of the list consisting of helium (He), boron (B), carbon (C), nitrogen (N), oxygen (O), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe);

the ion acceleration voltage is greater than or equal to 10 kV and less than or equal to 1000 kV;

the temperature of the composite material is less than or equal to 180 ° C .;

the dose of ions per unit area is chosen in a range of between 10 ¹² ions / cm ² and 10 ¹⁸ ions / cm ² so as to crosslink the composite material to increase the contact angle of a drop of water of at least 5 °. The free radical recombination process created by the passage of ions is called crosslinking, giving rise to the formation of a high density of covalent bonds.

According to one embodiment, the composite material is covered with an abrasion-resistant paint. This paint may for example be polyurethane. Its compatibility with the composite material makes its physico-chemical behavior close to that of the composite material. Generally, there is a very strong likelihood that it has hydrophobic characteristics comparable to those of the composite material when it is subjected to the process of the invention. This could be demonstrated in the following example.

According to one embodiment, the composite material is not covered with any paint.

The choice of ions and the bombardment conditions of these ions according to the invention makes it possible advantageously to obtain an increase in the hydrophobicity of the composite material, resulting in an increase in the contact angle and a reduction in the intermolecular forces between the droplet. of water and the treated composite material. These properties are very important to reduce the formation of frost on the leading edge of an aircraft wing, or on its trailing edge of the wing. Ice-phobia or icephobic properties are the behavior and quality of a material to retard, reduce or prevent the formation of a frost layer.

The inventors have found that the ranges chosen according to the invention of acceleration voltage and ion dose per unit area make it possible to select experimental conditions in which the reinforcement of hydrophobic and consequently ice-phobic properties is possible thanks to ion bombardment.

In addition, they have found that the method according to the invention can be implemented "cold", especially at room temperature and that the temperature of the composite material should be less than or equal to the value of 180 ° C. during the implementation of the method. It can thus be advantageously avoided that the composite material undergoes a physicochemical or mechanical modification. The choice of the ion dose per unit area in the dose range according to the invention may result from a prior calibration step where it is bombarded with one of the ions among He, B, C, N, O, Ne , Ar, Kr, Xe, a sample made of the contemplated composite material. The bombardment of this composite material can be carried out in different areas of the material with a plurality of doses of ions, in the range according to the invention, and the treated areas are observed so as to choose an adequate dose according to the contact angle of a drop of water with the composite material or the minimum stall angle of the same drop obtained by inclining the sample relative to a horizontal plane. Beyond this minimum stall angle the drop of water slides hence the impossibility to form frost.

The observation of the treated zones can be carried out by simple observation techniques, such as a photograph of the drop taken in the plane of the composite material placed on a table, or the reading of the angle of inclination. from which the drop moves on the composite material. It is also possible to use more sophisticated analysis techniques such as measuring the tangential force necessary for the separation of two parallel plates of composite material connected by a frost layer.

Without wishing to be bound by any scientific theory, it may be thought that this phenomenon can be explained by the nature of the chemical bonds created by the incident ion in the composite material. The incident ion breaks in its path the covalent bonds, producing free radicals which recombine preferentially in the form of bonds of carbon-carbon type, very weakly polarized. Hence a reduction of the initial polar character. The surface of the material then takes a apolar, in other words, hydrophobic character. On the other hand we can think that the saturation in covalent bonds (crosslinking) induces a superficial physico-chinaic inertia of the composite material. This results in a reduction of Van der Waals forces between the drop of water and the composite material, resulting in a decrease in the adhesion of the drop of water or a reduction in the minimum stall angle.

In addition to reinforcing the hydrophobic properties intimately related to the icephobic properties of which they are at the origin, the method of the invention makes it possible to harden the surface of the composite material to a thickness of the order of one micron without weighing down the composite material. The method of the invention has the advantage of being able to replace paints several hundred microns thick representing a weight of several hundred kilograms.

We can reduce the wings of an airplane or the nacelle of a reactor.

According to different embodiments that can be combined with one another:

the ion dose per unit area is between 10 ¹⁴ ions / cm ² and 5 10 ¹⁷ ions / cm ² ;

the composite material may or may not be coated with a paint layer; we have found that the hydrophobic character is reinforced in both cases;

the ion acceleration voltage is between 20 kV and 200 kV;

the ions are produced by an electron cyclotron resonance (ECR) source that has the advantage of being compact and energy efficient. According to one embodiment, the composite material covered or not with a paint, and subject to the ion beam treatment method according to the invention is a component of an aircraft wing, for example a leading edge or a trailing edge.

According to another embodiment, the composite material covered or not with a paint, and subject to the ion beam treatment method according to the invention is a component of an antenna, including radar. It can be seen that the signal perceived by a radar can be significantly deteriorated when frost or gel covers part of a radar antenna and the implementation of the method according to the present invention on the antenna material is likely to reduce this issue.

Other features and advantages of the present invention will emerge in the following description of nonlimiting exemplary embodiments, in particular with reference to the accompanying drawings in which:

FIGS. 1a to 1d illustrate the effect of the method according to the invention on the contact angle of a drop of water;

FIG. 2 illustrates the effect of the method according to the invention on the evolution of the contact angle of a drop of water according to the dose; on the abscissa we find the dose, on the ordinate the angle of contact expressed in degree;

FIGS. 3a and 3b illustrate the effect of the method according to the invention on the evolution of the minimum stall angle of a drop of water according to the dose; on the abscissa we find the dose, on the ordinate the minimum stall angle expressed in degrees;

FIGS. 4a to 4b illustrate the formation of frost on the leading edge of a wing, in particular treated according to the invention; - Figures 5.a to 5.b illustrate the formation of frost on the trailing edge of a wing, in particular treated according to the invention.

According to exemplary embodiments of the present invention, carbon fiber-reinforced epoxy thermosetting resin composite samples have been investigated for treatment with nitrogen ions emitted by an ECR source. Such surfaces have a porosity max of 2%, on average 0.5% of which 0.1% opening.

The ion beam with an intensity of 7 mA comprises ions N +, N2 +, N3 +; the extraction and acceleration voltage is 45 kV; the energy of N + is 45 keV and that of N2 + 90 keV, N3 + 145 keV.

The sample to be processed moves with respect to the beam with a displacement speed VD of between 0.1 and 1000 mm / s, in this case at 40 mm / s with a lateral advancement pitch at each return of 1 mm. . To reach the required dose the treatment is done in several passes.

The hydrophobicity of the surface can be evaluated by depositing a drop of water on the surface. Figure l.a shows a drop of water in equilibrium on a flat surface. It is possible by measuring the contact angle (A) to quantify the hydrophobicity of the surface with water. The higher the contact angle, the higher the hydrophobicity of the surface. When the contact angle is less than 90 °, the surface is hydrophilic. If the contact angle is greater than 90 °, the surface is hydrophobic.

Tests were made by depositing drops of water on the surfaces treated by the process of the invention for doses ranging from 10 ¹⁶ ions / cm ² to 3.5 × 10 ¹⁶ ions / cm ² . The Figures lb, lc, la show water drop profiles deposited on the virgin composite material or treated according to the method of the invention with different doses. The contact angle increases with the dose. The stiffening of the contact angle is clearly observed by increasing the dose. On the sample of the virgin composite material of FIG. 1b, a contact angle of about 65 ° is measured. For the sample of FIG. 1c treated with an estimated dose of 10 ¹⁶ ions / cm ^2, a contact angle of 71 °, finally for the sample of Figure ld treated with an estimated dose of 2x10 ¹⁶ ions / cm ² , a contact angle of about 85 ° is measured. This changes from a hydrophilic behavior to a hydrophobic behavior.

Table 1 shows all the average results.

Table 1

There is a range of possible doses to achieve a hydrophobic character. It is estimated that a minimum dose has significant effect on composite material coated or not with a paint when the strengthening of the hydrophobic character results in a 5 ° increase in the contact angle of a drop of water. This value of 5 ° corresponds to the standard deviation observed for a contact angle measurement. In the case of this study, the minimum dose is close to 1.5xl0 ¹⁶ ions / cm ² , the contact angle increases from 65.4 ° for the virgin material to 72.2 ° for the treated material, an increase of the contact angle slightly greater than 5 °. The results of this table are shown in Figure 2.

The interaction forces of a drop of water on a surface can be evaluated by measuring the stall angle of the drop on the surface. Fig. 3a shows a device for measuring the stall angle. The drop is placed on a sample whose angle of inclination can be varied with respect to the horizontal plane. We very gradually increase the angle (A). The weight P of the drop is transformed into a tangential force Fg which has the effect of sliding the drop on the inclined plane when the angle (A) is greater than a minimum stall angle which is characteristic of the adhesion force. drop on the sample.

The results are summarized in Table 2.

Table 2

It is found that the samples treated according to the method of the invention have stall angles of 20 ° lower than the stall angle of the blank sample. This means that the force required to slide the drop of water is lower. This sliding force Fg corresponds to the weight of P of the drop projected on the sliding plane: Fg = P x sin (A). Applying this rule it is estimated that the sliding force of the drop for the virgin sample is equal to P x sin (70 °) and for a dose of 1.5xl0 ¹⁶ ions / cm ² equal to P x sin (50 °) ), or a decrease in adhesion of about 30% of the drop on the treated composite material.

Without wishing to be bound by any scientific theory, it may be thought that the bombardment of the ions under the conditions according to the invention causes the cross-linking of the surface of the polymer matrix of the composite. This crosslinking increases the apolar nature of the surface which thus develops less interaction with the water which is a polar liquid. This then results in a strengthening of the hydrophobic character and a decrease in the grip of the water on the composite.

Figure 3.b shows the evolution of the minimum stall angle according to the dose of the method of the invention.

Figures 4.b and 4.a show the areas of formation of frost on a treated surface (Zgt) or virgin (Zgv) according to the method of the invention. The area of the treated surface where the water drops can catch is limited to the upper part of the leading edge (Zgt) which is also the one where the slope relative to the ground is the lowest. On the virgin surface this area is larger, it encompasses the previous area and extends over a lower portion of the leading edge (Zgv) so more inclined relative to the ground.

Figures 5.a and 5.b show the secondary icing process which has the effect of reducing the lift of an aircraft. When the frost in the zone (Zgvl) of the blank leading edge comes off, either by heating or by the pressure of the air produced by the displacement of the aircraft, it moves towards the trailing edge to adhere strongly to it. in the zone (Zgv2). The modification of the aerodynamic profile has the effect of reducing the lift of the aircraft, of increasing its consumption or worse to cause its fall. On the treated leading edge, the frost comes off with a lower pressure force in the zone (Zgtl), and slides more easily to be immediately evacuated by the stream of air (Zgt2).

According to various embodiments of the method according to the present invention, which can be combined with one another:

- The composite material coated or not with a paint is movable relative to the ion beam at a speed, V ₀ , between 0.1 mm / s and 1000 mm / s.

- It is thus possible to move the sample to treat areas whose size is greater than that of the beam.

- The scrolling speed V ₀ , can be constant or variable. According to one embodiment, the composite material covered or not with a paint moves and the ion beam is fixed. According to another embodiment, the ion beam sweeps the composite material covered or not with a paint.

It is also possible that the composite material covered or not with a paint moves when the ion beam is mobile.

According to one embodiment, the same area of the composite material covered or not with a paint is moved under the ion beam in a plurality, N, of passages at the speed V _D.

- It is thus possible to treat the same area of the composite material with or without a paint with a dose of ions corresponding to the sum of the ion doses received by this area after the N passes.

It is also noted that if the size of the composite material coated or not paint allows, the processing step can be static and result from one or more "flash" of ions.

The invention also relates to the use of the method of the invention for reducing the formation of frost composite material covered or not with a paint.

Claims

1. A process for treating an ion beam with a composite material which may or may not be coated with a paint, characterized in that it consists of an ion bombardment in which:

the temperature of the composite material or paint which covers it is less than or equal to 180 ⁰ C;

the dose of ions per unit area is chosen in a range of between 10 ¹² ions / cm ² and 10 ¹⁸ ions / cm ² so as to crosslink the composite material to increase the contact angle of a drop of water of at least 5 °.

2. Method according to the preceding claim characterized in that the dose of ions per unit area is between 10 ¹⁴ ions / cm ² and 5 10 ¹⁷ ions / cm ² .

3. Method according to any one of the preceding claims, characterized in that the acceleration voltage of the ions is between 20 kV and 200 kV.

4. Method according to any one of the preceding claims, characterized in that the crosslinking of the composite material or of the paint is carried out with light ions selected from the ions of the elements of the list consisting of helium (He) , boron (B), carbon (C), nitrogen (N), oxygen (O), neon (Ne).

5. Method according to any one of the preceding claims characterized in that the composite material is movable relative to the ion beam at a speed, V _D , between 0.1 mm / s and 1000 mm / s.

6. Method according to the preceding claim characterized in that a same zone of the composite material is moved under the ion beam in a plurality, N, of passages at the speed V _D.

7. Method according to any one of the preceding claims characterized in that the composite material consists of a polymer matrix selected from the list of epoxy resins, polyester, phenolic, polyimide or melamine.

8. Method according to any one of the preceding claims characterized in that the composite material consists of a reinforcement selected from the list consisting of glass fibers, polymeric fibers, carbon fibers, mineral reinforcements, metal fibers , ceramic fibers.

9. Process according to any one of the preceding claims, characterized in that the paint belongs to the polyurethane family.

10. Method according to any one of the preceding claims, characterized in that the composite material coated or not with a paint, and subject to said ion beam treatment process, is a component of a wing d 'plane.

11. Method according to the preceding claim characterized in that the component of the aircraft wing being the subject of said treatment process is a leading edge or a trailing edge.

12. A method according to any one of claims 1 to 9 characterized in that the composite material coated or not with a paint, and subject to said ion beam treatment process, is a component of a antenna, including radar.

13. Use of the method according to any one of the preceding claims to reduce frost formation of the composite material with or without a paint.