DE2413654A1 - PLASTIC PART WITH A COVER - Google Patents

Description

73-B 111-53 Bremen, March 11, 1974

Sra / ka

United aeronautical engineering T'erke-Fokker Company with limited liability

Plastic part with a cover

The invention relates to a plastic part with a coating for protection against harmful external influences, in particular for protection against lightning strikes.

In aircraft it has been customary for some time to use plastics or to use electrically non-conductive materials to save weight. The fact that these substances are put together has the consequence that the Safety of aircraft that are already endangered by lightning strikes is reduced even further. Lightning strikes "usually cause destruction of the material in a confined space, vas the less electrically conductive the material, the stronger the effect. For some time now, considerations have been made To somehow protect plastic parts against lightning strikes, so that such materials continue to be used for aircraft can be.

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With non-conductive materials, especially with plastic parts, it is well known to apply electrostatic charges Derive antistatic paint layers. Furthermore, it is known to use non-conductors and, preferably, also plastic parts to provide metallic coatings in order to obtain reliable contact. The application of these metallic coatings can be done either by flame spraying, electroplating, sticking foils or by chemical means. Through appropriate Pretreatment of the surface, it is possible to ensure good adhesion between the surface of the body to be protected and the to achieve the applied layer.

The invention is therefore based on the object of producing plastic parts to be provided with a coating so that such in aircraft built-in parts are protected from being destroyed by lightning strikes. According to this invention this object is achieved in that the coating has a layer for heat dissipation, a layer for electricity derivation and an ionization layer, which causes a large area exposure in the event of a lightning strike.

With the help of this measure it is possible to widen a point of impact of a lightning bolt so much that the surface loading is high is reduced. At the same time, the heat dissipation layer counteracts excessive local heat generation, so that this also reduces the risk of destruction. Conductive pigments can be used as ionization layers Resin paints are used. But it is also possible to use fuels with strong soot formation (soot plumes), e.g. tar derivatives, Bitumen, salts etc. or substances with strong temperature-dependent To use volume enlargement.

As layers for heat dissipation can be applied in a known manner Metal oxide layers or metal layers can be used. In the case of a metal layer as a heat dissipation layer, however, it is useful -

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moderate to arrange an electrical insulation layer between the ionization layer and the metal layer. Is on the other hand as a heat dissipation layer a metal oxide layer is provided, then it is advantageous to to arrange a metal layer between this and the ionization layer in order to achieve good heat transfer. this is possible because the metal oxide layer already has an electrically insulating effect.

Further details of the invention will become apparent with reference to the enclosed Drawing explained in more detail. Show it:

Figure 1 · a first embodiment of one with a

Coated plastic part

Figure 2 »a second embodiment of another

plastic part provided with a coating

In the first exemplary embodiment according to FIG. 1, an enlarged section of a plastic part 10 is shown, which consists of a has three layers of coating. The layer 11 applied first to the surface of this plastic part 10 is a Metal layer for heat dissipation. Next up is the heat sink 11 an electrically insulating layer 12 is applied, the current flow between the metallic heat dissipation layer and an imization layer 13 applied over it. These layers can be applied using known methods. For example, it is possible to double the metallic layers Flame spraying, electroplating, sticking foils or by chemical means. The same also applies to the insulation layers, which can be hardened e.g. by spraying on Plastics or gluing foils can be applied. The applied layers can be used to achieve special protective effects

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be applied several times, the order of these layers can be changed at will. It is also possible to strengthen the layers in particularly endangered areas or in less endangered areas Make individual layers to be left out. For the ionization layers Synthetic resin paints with conductive pigments, fire protection paints or fuels with a lot of soot can be used (Soot plumes) can be used.

If a plastic part provided with such a coating is struck by lightning, the ionization layer 13 is first activated by the pre-discharge preceding the impact, with the result that a considerable number of ions are released 2 will be explained in more detail, so that the current density per unit area decreases sharply compared to a small impact point. Since the resulting heat and the electrical current are dissipated in a fan shape, this largely prevents damage the electromagnetic forces acting on the layers during the impact are greatly reduced, so that the adhesion of the layers is also maintained.

The second exemplary embodiment according to FIG. 2 shows a section a plastic part 20 reinforced with fibers 21, which also has a coating. The first layer here is on the Surface of the plastic part 20 is a metal oxide layer 22, namely applied for heat dissipation. A metal layer 23 is on top arranged, which is provided for current dissipation. Above this metal layer 23, an ionization layer 24 is applied to which in turn, a metal layer 25 acting as a protective and conductive layer is applied.

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In the event of a lightning strike, as can be seen from FIG. 2, the point of impact 26 is greatly expanded, since the ionization layer 24 releases a large number of ions due to the pre-discharge preceding the impact. The free ions are in this case indicated dotted, so that - as shown - the cross-section of the flash aufweitetet strongly with increasing proximity to the point of impact t This also has the consequence that the occurring on impact electromagnetic forces are small because of the relatively small curvature in front of the point of impact so that the adhesion of the layers can withstand these forces. The individual layers can - as explained in more detail in FIG. 1 - be applied in a known manner, it being furthermore possible to use substances for the ionization layers which have a strong temperature-dependent change in volume. For example, it is possible, in particular by evaporation, to reduce the surface loading in the event of a lightning strike to a critical value.

With the help of the invention it is possible to produce plastic parts for aircraft while maintaining the weight saving continues to increase because the layers applied to protect against lightning strikes can be very thin compared to the structure and therefore only represent an insignificant weight gain. The layers, which may be applied several times, ensure a very strong one Widening of the point of impact, so that both the current density and the heat are more critical with their fan-shaped dissipation below Worth it.

- patent claims -

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Claims (10)

Claims 1.) Plastic part with a coating to protect against harmful external influences, in particular for protection against lightning strikes, characterized in that the Coating a layer (11, 22) for heat dissipation and a Layer for current dissipation and an ionization layer (13, 24), which has a large in the event of a lightning strike Brings about surface exposure. 2.) Plastic part according to claim 1, characterized in that the layer (22) for heat dissipation from a metal oxide layer applied by known methods consists of a metal layer (23) applied over it Generation of a good heat transfer is assigned. 3 ») Plastic part according to claim 1, characterized in that that the layer (II) for heat dissipation consists of a metal layer applied by known methods, the an electrical insulating layer (12) applied over it is assigned. 4.) Plastic part according to claim 1, characterized in that the ionization layer (13, 24) on one Synthetic resin paint and / or fire protection paint containing conductive pigments. 5.) Plastic part according to claim 1, characterized in that that the ionization layer (13, 24) consists of a fuel with heavy soot formation. -7- 5 09 8 39/0203 2413854 6.) .Plastic part according to claim 1 and / or 4 to 5 »thereby characterized in that the ionization layer (13, 24) is made of a substance with a strong temperature-dependent There is a change in volume. 7 ·) Plastic part according to one of claims 1 to 6, characterized characterized in that several conductive layers (11, 22) as well as alternate to increase the protective effect several ionization layers are applied. 8.) Plastic part according to one of claims 1 to 7 »characterized in that conductive layers (ll, 22) and ionization layers (13» 24) are applied in any order ^{to achieve certain x Schitz effects.} 9 ·) Plastic part according to one of claims 1 to 8, characterized marked,. that the individual layers are reinforced in particularly endangered areas. 10.) Plastic part according to one of the preceding claims, characterized marked that at less endangered Make certain layers are omitted. 509839/0203 Blank page