FR2993484A1 - METALLIZATION METHOD AND ASSOCIATED DEVICE - Google Patents

Abstract

The invention relates to a method (1) for surface metallization of a composite material panel (2) composed of a stack (4) of a reinforcing material covered with a layer (6) of a conductive material electricity itself coated with at least one protective layer (8) non-electrically conductive, said part being pierced with a plurality of orifices (10). Said method comprises the steps of positioning, on an orifice (10), a device (26) capable of emitting a spatially and temporally coherent light radiation, anchoring said device (26) on the panel (2) of material composite, by means of a fastening means (28) so as to freeze the distance between said device (24) and said orifice (10), of locating the orifice (10) by means of a locating means (30), centering the light radiation on said orifice (10), and metallizing the annular zone (12) centered on said orifice (10) by said light radiation, according to a predefined metallization geometry.

Description

TECHNICAL FIELD The present invention relates to a method of metallization of composite material panels as well as to the associated device.

STATE OF THE PRIOR ART Current aircraft for the transport of passengers have more and more fuselage panels made of composite material. A composite material consists of a matrix (carbon fibers for example) and a reinforcement (thermoplastic or thermosetting resins). In the aeronautical field, carbon fibers are mainly used: they combine lightness and resistance to effort. However, carbon has the disadvantage of not driving electricity well. However, in the event that the aircraft is struck by lightning or to discharge static electricity, it is important that the fuselage can conduct the electricity. In order to overcome the disadvantage mentioned above, the composite material has an additional layer made of an electrically conductive material. Generally, a copper grating is used to fulfill this function. This conductive layer is then coated with a non-electrically conductive protective layer formed of resin and paint. This protective layer protects the fuselage surface against fiber pulling phenomena, provides surface continuity for a better flow of aerodynamic flow on the fuselage and contributes to the aesthetic appearance of the aircraft.

Once the fuselage panels are manufactured and covered with the protective layer, it is necessary to make contact points for the grounding of the aircraft. The panels are then drilled at predefined locations in order to be able to deposit a metal washer capable of ensuring contact between the layer of conductive material and a grounding device, such as, for example, a metal braid fixed by a fastener screwed into the piercing done. However, beforehand, it is necessary to remove the protective layer so that the contact protective layer-metal washer is effective. This operation is called metallization. Different methods are currently used. A first method consists in masking, by means of a sticky pastille, the zone to be pierced before the deposition of the protective layer. Once the protective layer is deposited, the pellets are removed. These operations must be done manually and increase the manufacturing time of a panel. In addition, despite the presence of the pellets, a portion of the paint creeps under the pellets, forming a parasitic layer disposed on the electrically conductive layer, at the periphery of the zone to be metallized. The presence of this parasitic layer degrades the quality of the contact between the layer of conductive material and the metal washer. Therefore, it is necessary to perform a manual recovery to strip stray paint present in this area. This manual operation is performed with a brush to metallize rotated.

This operation can cause damage to the layer of conductive material because the control of the brush to be metallized is difficult, the control of the quality of the metallization being performed only visually by the operator. Another metallization process is disclosed in EP 1048386. The metallization, as described in this document, is carried out by means of a wafer having a metal edge pressed elastically and moved on the surface of the panel, the stop of the metallization being controlled consecutively to reaching or exceeding a predetermined threshold of electrical conduction between the conductive layer and the metal edge. This method therefore uses a wear part to be regularly changed. As a maximum security, it is stated in this document that the metallization is stopped even if the layer of conductive material has not been denuded in its entirety. Under these conditions, a final manual intervention to remove the residual protective layer is necessary. This intervention is performed with conventional means, such as the brush to metallize already mentioned above and thus introduces the same inconveniences as those stated above. In this document, it is also indicated that the metallization is practically without risk of physical damage to the conductive layer, which however implies that in some cases, the wafer may go too far and damage said layer. This damage then degrades the quality of the contact between the layer of conductive material and the metal washer. In addition, the device requires multiple implementation means, such as a current generator for example. The method as described in EP 1048386 is therefore not repetitive and does not give systematic satisfaction. SUMMARY OF THE INVENTION The purpose of the invention is therefore to propose a method of metallization of a panel made of composite material as well as the associated device, this method and the associated device at least partially overcoming the disadvantages mentioned above relating to the embodiments of the prior art. To do this, the invention firstly relates to a surface metallization process of a composite material panel consisting of a stack of a reinforcing material covered with a layer of a conductive material of the electricity itself coated with at least one non-electrically conductive protective layer, said panel being pierced with a plurality of orifices, said method comprising the following steps: positioning, approximately on an orifice, of a device capable of emitting spatially and temporally coherent light radiation, and anchoring said device on the panel of composite material, by means of a fixing means so as to freeze the distance between said device and said orifice, and; - Location of the orifice using a locating means, and; centering the light radiation on said orifice, and metallization of the annular zone centered on said orifice by said light radiation, according to a predefined metallization geometry. This method makes it possible to achieve metallizations whose quality is identical to each implementation. Indeed, despite a panel geometry that can be complex, the method according to the invention allows metallizations to meet the requirements for the quality required. This quality is obtained by fixing the distance between the device capable of emitting spatially and temporally coherent light radiation and the impact points located around the orifice. This distance is the focal length. The focal length being fixed, the light radiation is ensured to consistently deliver the same power. There is therefore no risk of damaging the electrically conductive material. In addition, the centering of the light radiation on the orifice makes it possible to achieve metallization of identical and repetitive shape at each orifice. Advantageously, the orientation of the light radiation is slaved to the position of the center of the orifice marked by the locating means. Thus, whatever the position of the device capable of emitting light radiation with respect to the orifice, the light radiation will always be recaled on the center of the orifice, thus ensuring metallization of shape and quality systematically identical. In order to implement the method previously described, the invention also relates to a portable device for metallization. This device comprises a device capable of emitting a spatially and temporally coherent light radiation, a fixing means on the panel, a locating means, a servo-control means between the signal emitted by the locating means and said light radiation as well as means for triggering the light radiation.

Thanks to this device, the metallization can be performed with optimal quality by an operator or a robot: in fact, such a device can be used by an operator in manual mode. It simply attaches to the panel using the fixing means, the centering of the light radiation being performed automatically by the servocontrol between the signal emitted by the locating means and said light radiation. The operator then uses the triggering means to perform the metallization. It is also possible to fix the device on a robot head so that the metallization is performed in automatic mode. The robot will then be controlled by a numerical control program to present the device facing the orifices whose position will be approximately known. The metallization will be carried out according to the same operating mode as in manual mode. Advantageously, the device capable of emitting spatially and temporally coherent light radiation is a laser beam. Such a radius has the advantage of not being of high power and of metallizing the orifice without the presence of a flame. According to a first embodiment, the laser beam is emitted by a fiber laser. Such a laser has the advantage of being of reduced size, which allows its use in an industrial environment. It is also lower cost compared to other lasers on the market. For low firepower, it is not necessary to cool it. According to a second embodiment, the laser beam is emitted by a laser with a resonator. Advantageously, the light radiation performs a scanning movement. Thus, the metallization is done more quickly than with fixed radiation that would have to be displaced sequentially. This results in a time saving at each port metallization, which allows the metallization of an entire panel much faster than with prior techniques. Thus, the shape of the scan is adaptable to the form of the grounding device that will be used and may be previously defined before each metallization. Such a scanning movement of the light radiation is advantageously generated by an oscillating system of radiation deflection. Thus, it is possible to define in advance the form of metallization to be made, according to the constraints of manufacture.

According to a first variant embodiment, the oscillating system may comprise at least two oscillating mirrors which, by their movement, will move the radiation according to the selected scanning geometry. According to a second variant embodiment, the oscillating system may comprise a mirror and a motorized mechanical scanning means.

Advantageously, the scanning movement is a concentric movement, centered on the orifice to be metallized. This concentric movement makes it possible to produce circular metallizations, compatible with a circular metal washer shape, able to guarantee the contact between the layer of conductive material and the grounding device.

Advantageously, the fixing means is a vacuum means. This fixing means makes it possible to fix the device on the panel pierced with the orifices. Such a means allows a solid and reliable fixation while avoiding damage to the panel for example by perforating. In addition, it remains easy to use.

The fixing means of the metallization device may be composed of a plurality of pneumatic suction cups. These suction cups have a flexible edge which matches the shape of the panel and which allows a reliable attachment of the metallization device, without damaging said panel.

Advantageously, the locating means is a camera that films the surface of the panel. By processing the resulting image, the position of the orifice is determined, which makes it possible to calculate the orientation to be given to the light radiation. Finally, the power of the light radiation is between 10 and 60 watts. This power makes it possible to metallize the non-electrically conductive protective layer without damaging the layer of conductive material. Other advantages and features of the invention will become apparent in the detailed non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS This description will be made with reference to the accompanying drawings in which: Figure 1 shows a schematic diagram of a portion of a composite panel; FIG. 2 represents the block diagram of the method according to the invention; FIG. 3 represents a schematic diagram of the device according to the invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 represents a simplified diagram of a panel 2 made of composite material. Such a panel consists of a stack of fibers, also called reinforcing material 4. In known manner, these fibers are carbon fibers, widely used in the aeronautical field 25 for their lightness and strength. However, and without departing from the scope of the invention, these fibers may be made of another material, such as glass for example. These fibers may be pre-impregnated with thermosetting or thermoplastic resins, depending on the technologies used. The resin can also be injected during the manufacture of the panel 2, the fibers used are then called "dry". In order to guarantee the electrical conductivity of the panel 2, a layer 6 of an electrically conductive material covers the stack of reinforcing material 4. This material may be, for example, a copper grating. In the form of a mesh, this layer 6 is lighter and does not excessively increase the weight of the panel 2.

Since the panel 2 is in contact with the aerodynamic flow, the layer 6 of conducting material must be protected to avoid delamination phenomena. It is therefore necessary to cover the layer 6 of conductive material with a protective layer 8 which is not electrically conductive. This layer 8 also provides an aesthetic function by covering the panel with a homogeneous layer. It can be composed of a layer of thermoplastic or thermosetting resin associated with a layer of paint. The resin layer provides good bonding cohesion between the carbon fibers of the reinforcing material layer 4 and the electrically conductive material layer 6 while the paint layer provides surface continuity for a better flow of the material. aerodynamic flow on the fuselage. It also participates in the aesthetic appearance of the panel 2. Once the panel 2 covered with the protective layer 8, it is necessary to make contact points for the grounding of the aircraft. This precaution is necessary to take into account the impacts of lightning and the charge of static electricity. The panel 2 is then pierced with a plurality of orifices 10 at predefined locations in order to be able to deposit a metal washer capable of ensuring contact between the layer 6 of conductive material and a grounding device, such as, for example, a metal braid fixed by a fastener screwed into the orifice 10 made. It is therefore necessary to remove the protective layer 8 to expose the conductive layer 6. This operation, called metallization, is performed on a zone which may be annular, materialized by the reference dots 12. Other forms of the metallization may be envisaged without departing from the scope of the invention.

According to the method 1 according to the invention and described in FIG. 2, the metallization is carried out following the steps described below. The first step 14 consists in positioning one of the orifices 10 with a device 26 capable of emitting spatially and temporally coherent light radiation.

As explained below, this positioning can be performed manually by an operator or automatically by a robot. The positioning may be approximate, the centering of the light radiation being refined thereafter. The second step 16 consists in anchoring said device 26 on the panel 2 by means of a fixing means 28. This anchoring makes it possible to freeze the distance between the device 26 and the orifice 10. This distance is called the focal length. The third step 18 consists in locating the orifice 10 by means of a locating means 30. The location of the orifice 10 makes it possible to locate its center. The fourth step 20 consists in centering the light radiation on the orifice 10. It is not necessary for this to change the position of the device 26. Finally, the last step 22 is the metallization step of the annular zone 12, made from the center of the orifice 10, according to a predefined metallization geometry. The metallization geometry may consist, for example, in a concentric sweeping movement, from the center of the orifice 10.

Steps 14, 16, 18, 20 and 22 relating to method 1 according to the invention are repeated on each pierced orifice 10 to achieve the earthing points. According to the subject of the invention, the method 1 is implemented by the portable device 24 described with reference to FIG.

This device is composed of a device 26 capable of emitting light radiation and spatially coherent. Such radiation is easily mastered, which allows a repetitive metallization of good quality. For example, said radiation may be a laser beam. To generate a laser beam, it is possible to use a fiber laser known in the prior art. This fiber laser has a small footprint, which allows its use in an industrial environment. This advantage is particularly significant because the device 26 can then be used on a panel that has just been manufactured, in its manufacturing environment. It can also be used on a panel already in final assembly, on aircraft. Indeed, it can happen, in final assembly, that a new mass point must be added. In this case, the device being of reduced size, it is easy to use it to add this point of metallization in the environment of an assembly line, without hindering the assembly operations in progress. It is also lower cost compared to other lasers on the market. In addition, the firing powers for the metallization being low, it is not necessary to cool it. This second advantage contributes to making the device 24 easily manageable. The device 24 further comprises a fixing means 28 on the panel. The anchoring of the device 24 on the panel makes it possible to freeze the focal length of the device 26. The device 24 then comes to bear on the panel 2, approximately to the right of the orifice 10. This fixing means 26 must avoid the damage to the panel 2, a vacuum means is advantageously used. This vacuum means is represented in a simplified manner by two suckers 28a and 28b. The number of suction cups required must allow a good quality of fixing of the device 24. In fact, if, by mishandling, the focal length were to be modified, the light radiation would no longer be focused and could either damage the conductive layer 6, or do not put it sufficiently bare, thus degrading the contact between the layer 6 of electrically conductive material and the metal washer (not shown). Thus, the anchoring must be strong enough to prevent the device 26 from moving during the metallization. The suction cups (28a, 28b) are easy to use and contribute to the ease of use of the device 24. The device 24 further comprises a tracking means 30. This means 30 is preferably a camera that films the area surrounding the orifice 10. Using digital processing software known in the state of the art, the images of the film are analyzed and the orifice 10 is detected. The digital processing software can thus easily analyze the collected data to locate the center position of said port 10. A servo means 32 uses information relating to the position of the center of the port 10 to direct the light radiation and focus on said center. Standard means are used to direct said radiation, for example mechanical means. Said servo means 32 uses information relating to the difference in position between the center of the orifice 10 and the light radiation to reset said radiation on said center. The device further comprises a trigger means 34 of the light radiation. This triggering means may, for example, be a push button when the device 24 is used by an operator. The triggering of the radiation by the means 34 will start the metallization according to the defined geometry. Different possibilities of metallization geometry can be envisaged. The light radiation can perform a scanning movement. This scanning movement can be generated by an oscillating system of radiation deflection (not shown in FIG. 3). According to a first variant, this oscillating system may comprise at least two oscillating mirrors, the oscillation of the mirrors being controlled according to the scanning geometry to be produced. A second embodiment consists of an oscillating mirror coupled with a motorized mechanical scanning means. This second variant is more complicated to implement than the first variant but it is also more robust because it requires only one oscillating mirror. The power of the light radiation must be sufficient to expose the conductive layer 6 without damaging it. Such power is advantageously between 10 and 60 Watts. Those skilled in the art will conduct calibration operations to determine what power is needed to expose the layer 6 of electrically conductive material 30 and to metallize the panel, taking into account the protective layer 8. The parameters enabling Such metallization is adapted to the characteristics (thickness, composition for example) of the protective layer 8. As already pointed out above, the metallization method 1 according to the invention can be implemented by an operator. This operator will use the device 24 according to the invention to metallize each pierced hole 10 in the panel 2. Said device being configured to be portable, its handling is easy. The operator will fix the device 24 on the panel 2 by means of the fixing means 28. A light or audible indicator may indicate to him the moment when the servo-control means 32 has directed the light radiation onto the center of the orifice 10, indicating that the device 24 is ready to metallize. The operator will then trigger the metallization using the triggering means 34. However, for the sake of efficiency and task automation, the device 24 may also be attached to a robot head.

The size of the device 24 is particularly suitable for such use. All the steps described above are then performed according to a sequencing described in a digital machine program for controlling the robot. In this embodiment, when the position of the light radiation corresponds to the center of the orifice 10, the servo means 32 will send a signal to the device 26 able to emit said light radiation to trigger the metallization. The movement of the light radiation can be chosen from a closed choice of possible geometry, such as, for example, a concentric sweep from the center of the orifice 10, or a horizontal sweep whose initial point is at the center of said orifice. The scanning movement can also be free and defined, for each metallization, by coding by the operator in charge of the coding of the numerically controlled machine. These different possibilities can be envisaged without departing from the scope of the invention.

Claims (15)

REVENDICATIONS1. Method (1) for surface metallization of a composite material panel (2) composed of a stack (4) of a reinforcing material covered with a layer (6) of an electrically conductive material -Even coated with at least one protective layer (8) non-electrically conductive, said part being pierced with a plurality of orifices (10), characterized in that it comprises the following steps: - positioning, approximately on an orifice (10) of a device (26) capable of emitting spatially and temporally coherent light radiation, and; anchoring said device (26) on the panel (2) made of composite material, by means of a fixing means (28) so as to freeze the distance between said device (24) and said orifice (10), and ; locating the orifice (10) with a locating means (30), and; centering of the light radiation on said orifice (10), and; - Metallizing the annular zone (12) centered on said orifice (10) by said light radiation, according to a predefined metallization geometry. 2. Method (1) according to any one of the preceding claims, characterized in that the orientation of the light radiation is slaved to the position of the center of the orifice (10) marked by the locating means (30). 3. portable device (24) for metallization for carrying out the method according to any one of the preceding claims, characterized in that it comprises: - a device (26) capable of emitting a spatially and temporally coherent light radiation , and; - a fixing means (28) on the panel, and; a locating means (30), and; - servo means (32) between the signal transmitted by the locating means (30) and said light radiation, and; - Triggering means (34) of the light radiation. 4. Method according to claim 3, characterized in that the device (26) capable of emitting spatially and temporally coherent light radiation is a laser beam. 5. Method according to claim 4, characterized in that the laser beam is emitted by a fiber laser. 15 6. Method according to claim 3, characterized in that the laser beam is emitted by a laser with resonator. 7. Method according to one of the preceding claims, characterized in that the light radiation performs a scanning movement. 8. Method according to one of the preceding claims, characterized in that the scanning movement of the light radiation is generated by an oscillating system of radiation deflection. 25 9. The method of claim 8, characterized in that the oscillating system comprises at least two oscillating mirrors. 2 9934 84 10.Procédé according to claim 8, characterized in that the oscillating system comprises an oscillating mirror and a motorized mechanical scanning means. 5 11. The method of claim 7, characterized in that the scanning movement is a concentric movement, centered on the orifice (10) to metallize. 12. Method according to any one of the preceding claims, characterized in that the fastening means (28) is a vacuum means. 13. Method according to any one of the preceding claims, characterized in that the fixing means (28) is composed of a plurality of pneumatic suction cups (28a, 28b). 14.Procédé according to any one of the preceding claims, characterized in that the locating means (30) is a camera. 15.Procédé according to any one of the preceding claims, characterized in that the power of the light radiation is between 10 and 60 watts.