DE10000767A1 - Bodywork outer element for vehicles, comprises a fiber reinforced plastic foam core which after molding has an open-cell structure - Google Patents

Abstract

The bodywork outer element of fiber reinforced plastic composite material for vehicles comprises a fiber reinforced plastic foam core (1) which after molding has an open-cell structure. An Independent claim is also included for a method for producing such an element. It involves production of a fiber reinforced plastic foam core with an open-cell structure after molding.

Description

The present invention relates to exterior body parts for vehicles fiber-reinforced plastic composite material and a method for their Manufacturing.

Fiber reinforced plastic composite materials are due to their excellent mechanical properties increasingly for applications used in which formerly only metals or sheets were used found. This also applies to exterior body parts in vehicle construction. There are generally high demands on exterior parts of vehicles for vehicles in terms of their mechanical stability and surface quality posed. You must have a perfect surface (so-called Class A), so they can be painted with as little rework as possible or without rework. In particular, sufficient adhesion of the paint to the Surface must be guaranteed. With the previously used only Metals and sheets could easily meet the requirements mentioned become.

In the not previously published patent application DE 199 39 111.4 Composite elements described, which consist of a fiber-reinforced polyisocyanate Polyaddition product and a thermoplastic film adhering to it  exist on which a paint can be applied. The described Composite elements can be used as body components for motor vehicles become.

The article "PUR hardtop for the Audi Cabriolet" from the conference proceedings "Plastics in automotive engineering, March 25/26, 1998, VDI-Verlag ISBN 3-18- 234212-6, by Hans-Günther Haldenwanger, Josef Heiß and Herwig Reim the production of a hardtop from fiber-reinforced PUR composite material for a passenger car. This hardtop consists of two fiber-reinforced (GF) PUR foam cores (GF-PUR), with one on one side Coating made of compact PUR, which is also called coating (so-called Three-layer structure). This coating can be followed by varnish be applied. The PUR foam cores consist of a foam system from Elastogran GmbH with the designation Polyol D07-001 / OA and isocyanate B237. This foam system creates a closed-cell foam structure. The Hardtop thus consists of three individual layers. It has been shown that at Body parts made of fiber-reinforced plastic composite material according to the prior art with the influence of temperature on the coating a so-called. "Orange peel" can form. This is due to tension, which due to the temperature influence between the foam core and the one on it can form applied PUR coating.

If a thermoplastic, deep-drawn plastic film or thin metal sheets are used as a covering layer on the glass fiber reinforced PUR foam core with closed-cell foam structure, disturbances on the surface can also occur under the influence of temperature. Such phenomena are described in detail in KU Kunststoffe 89 ( 1999 ), pp. 128ff.

The present invention has for its object high quality Body exterior parts made of fiber-reinforced plastic composite material ready make the simple and inexpensive, d. H. economical, manufactured can, a high quality surface (Class-A surface) ensure and maintain this permanently even under the influence of temperature.

This task is solved by an outer body part for vehicles fiber-reinforced plastic composite material, which is a fiber-reinforced Foam core made of polyurethane (PUR) foam, characterized records that the foam core has an open-cell foam structure.

Within the scope of the present invention, a method for producing exterior parts of the body from fiber-reinforced plastic composite material for vehicles is also provided, in which a fiber-reinforced foam core is formed from polyurethane foam in a method step 1 , the foam core after the molding having an open-cell foam structure or an open-cell cell structure having.

It has been shown that when using a PUR foam with open cell structure for the foam core even with long lasting high Influence of temperature (e.g. during the climate change test) on the Body part no tension occur, so that the surface of the Coating does not form any surface unevenness. The present The invention thus ensures a high quality surface (Class A) in the long term. It has also been shown that the open structure of the foam structure the heat storage times (tempering times) of the foam core considerably can be shortened, or even completely dispensed with heat storage which can be used with the otherwise used closed cell Foam systems is necessary.  

Open-celled in the sense of the present application means a volume fraction of open cells in the foam structure without fiber reinforcement of more than about 50% by volume. In the context of the present invention, foam cores are preferred which, without fiber reinforcement, have a volume fraction of open cells in their foam structure of preferably more than about 60% by volume, more preferably of about 70 to 90% by volume, particularly preferably of about 80 to 90% Have vol .-%. The proportion by volume of open cells in the foam structure without fiber reinforcement is determined in accordance with DIN ISO 4590 . The term "without fiber reinforcement" means that the volume fraction of open cells is determined using a sample foam core that has no fiber reinforcement.

Vehicles in the sense of the present invention are all vehicles on land, too Water and in the air. These include, for example, motor vehicles such as Cars and trucks, motorcycles, ships and planes.

Body exterior parts are all from the outside in the sense of the present invention visible body parts on a vehicle. With these parts it comes in Usually on a surface of high quality, since such exterior parts of the body sometimes have to serve a decorative purpose on the vehicle. Exterior parts of the body are, for example, roofs, doors, bonnets, Trunk lid and bumpers, for example for passenger cars. A preferred exterior body part in the context of the present invention is a Hardtop. Hardtops are removable rigid roofs for cars of the Cabriolet type. High demands are made of these in many respects. Hardtops must be light in weight so that they can be easily mounted on the car and can be removed. You need high mechanical stability (Roll over the car in an accident) and have a high degree  Ensure noise insulation, watertightness, temperature resistance. In all of this, a high, constant surface quality must above all (Class-A) to be guaranteed to meet the high optical needs wear that differ from car manufacturer to car manufacturer can.

The term PUR foams in the context of the present invention any polyisocyanate polyadducts such as polyurethane and / or Polyisocyanurate. These are obtainable from a reaction of (a) isocyanates with (b) isocyanate-reactive compounds, optionally in Presence of (c) catalysts, (d) blowing agents, (e) auxiliaries and additives.

As isocyanates (a), generally known (cyclo) aliphatic and / or in particular aromatic polyisocyanates are used. To make the Body exterior parts according to the invention are particularly aromatic Diisocyanates, preferably diphenylmethane diisocyanate (MDI) and Toluene diisocyanate (TDI). The isocyanates can be in the pure form Compound or in modified form, for example in the form of uretdiones, Isocyanurates, allophanates or biurets, preferably in the form of urethane and reaction products containing isocyanate groups, so-called Isocyanate prepolymers can be used.

As (b) isocyanate-reactive compounds, the usual, generally known compounds with at least two with isocyanate reactive hydrogen atoms are used, for example polycarbonate diols, polyether polyols and / or polyester polyols, hereinafter referred to as "polyols" designated. Preferred are polyols with a functionality of 2 to 8, in particular from 2 to 4, a hydroxyl number from 250 to 1000 mg KOH / g and 10 to 100% primary hydroxyl groups. The polyols preferably have  Molecular weight of 60 to 500 g / mol on polyetherols are due to their higher hydrolysis stability is particularly preferred. The polyetherols are mostly by base-catalyzed addition of lower alkylene oxides, in particular ethylene oxide and / or propylene oxide, on 2 to 8-functional, in particular 2 to 5-functional starter substances. The content of primary hydroxyl groups can be achieved by using the polyols to Finalized with ethylene oxide. The above compounds (b) can optionally be mixed with other known Isocyanate-reactive compounds, for example conventional polyols with a Functionality from 2 to 8, in particular 2 to 4, which differ from distinguish the above compounds (b) in the hydroxyl number or based on polycarbonate diols and / or polyesterols. To the opposite Isocyanate-reactive compounds (b) can also chain extension and / or crosslinking agents. With chain extenders it is predominantly two or three functional alcohols with Molecular weights from 60 to 499, for example ethylene glycol, Propylene glycol, 1,4-butanediol, 1,5-pentanediol. With the crosslinking agents are compounds with molecular weights from 60 to 499 and 3 or more active H atoms, preferably amines and especially preferably alcohols, for example glycerol, trimethylolpropane and / or Pentaerythritol.

Conventional compounds which can be used as catalysts (c) are: for example, the reaction of component (a) with component (b) strongly accelerate. For example, tertiary amines and / or organic metal compounds, especially tin compounds. Prefers are used as catalysts that are as low as possible Fogging, d. H. for the lowest possible release of volatile compounds lead from the polyisocyanate polyaddition product, for example tertiary Amines with reactive end groups and / or higher boiling amine catalysts.  

For example, the following compounds can be used as catalysts: triethylene diamine, aminoalkyl and / or aminophenyl imidazoles, for example 4-chloro-2, 5-dimethyl-1- (N-methylaminoethyl) imidazole, 2-amino propyl-4, 5 -dimethoxy-1-methylimidazole, 1-aminopropyl-2,4,5-tributylimidazole, 1-aminoethyl-4-hexylimidazole, 1-aminobutyl-2, 5-dimethylimidazole, 1- (3-aminopropyl) -2-ethyl-4 -methylimidazole, 1- ( 3- aminopropyl) imidazole and / or 1- ( 3- aminopropyl) -2-methylimidazole, tin (II) salts of organic carboxylic acids, for example tin (II) diacetate, tin ( II) dioctoate, tin (II) diethylhexoate and tin (II) dilaurate and dialkyltin (IV) salts of organic carboxylic acids, e.g. B. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate.

Well-known chemical or physical blowing agents (d) can be used acting connections are used. As a chemical blowing agent can preferably be used water, which by reaction with the Isocyanate groups form carbon dioxide. Examples of physical blowing agents, e.g. H. those inert compounds, which under the conditions of Evaporating polyurethane formation are, for example, (cyclo) aliphatic Hydrocarbons, preferably those with 4 to 8, particularly preferably 4 to 6 and in particular 5 carbon atoms, partially halogenated hydrocarbons or Ethers, ketones or acetates. The amount of blowing agent used depends on according to the desired density of the foams. The different blowing agents can be used individually or in any mix with each other come. Only water is particularly preferably used as the blowing agent. Physical blowing agents are preferred in an amount of <0.5% by weight, based on the weight of component (b) used.

The reaction is optionally carried out in the presence of auxiliary and / or Additives such as B. fillers, cell regulators, surface-active  Compounds and / or stabilizers against oxidative, thermal or microbial degradation or aging.

The starting materials (a), (b), (c), (d) and (e) must be selected in this way and in proportions used to each other that get an open-cell foam structure becomes.

The volume fraction of open cells in the foam structure can, for example be increased in which auxiliary substances (e) to promote the open cell Reaction mixture are added. These can be excipients (s) that are not in the foam structure can be built in and thereby destabilization of the building up cell walls. The excipients can in the Reaction mixture optionally microdispersed. examples for Auxiliaries (e) are internal release agents such as oleic acid compounds, esters Polyisobutylene succinic anhydride (PIBSA) and sorbitan monooleate as well Polyester from adipic acid, oleic acid and pentaerythritol.

These compounds have no or a small OH number, i. H. no functional OH groups, and are therefore not or only weakly in the PUR molecular scaffold installed. You can thus on the surface of the curing foam and a separating layer to form form. Since they are molecules with a high molecular weight, they work destabilizing on the formation of cell walls.

An open cell foam structure can also be achieved by using special Compounds (b) reactive towards isocyanates can be achieved. Here are for example, to mention solid organic fillers in disperse distribution. Such organic fillers include polymer polyols and polyurea  Polyols. The disperse phase is obtained by graft polymerization directly in the polyether generated.

A polymer polyol is a group of polyol dispersions that by radical polymerization of suitable olefinic monomers in the polyether used as the graft base. The polymer In addition to the graft copolymers, polyol predominantly contains the Homopolymers of olefinic compounds, such as. B. acrylonitrile, styrene, Vinyl acetate, vinyl chloride, acrylic acid esters and mixtures of two or more from that.

In addition to these polyols with partially chemically bound organic fillers filled polyethers can also be mixed with finely divided organic Plastic powders or inorganic substances can be obtained. The stability such suspension is due to the lack of chemical bonding to the polyether often less. Silicates, carbonates, Use aluminum powder or glass fibers, etc.

The open cell can also be determined by the mixing ratio of (a) to (b) to be changed.

In addition, the open cell can also be set via the reaction kinetics become. By selective catalysts (c) or autocatalytic polyols (b) and Polyols with a high EO content can cause the blowing and crosslinking reaction the open cell in a manner well known to those skilled in the art, e.g. B. by choice a suitable catalyst.  

According to the present invention, the foam core is fiber reinforced. The fibers can either be present as loose individual fibers in the foam core, or as a composite of fibers, for example as fabrics, knitted fabrics and / or pressed webs based on fibers. Flat fiber-based structures are preferably used which have a weight per unit area of 100 to 1000 g / m ² , particularly preferably of 200 to 600 g / m ² . The fibers come, for example, glass fibers, synthetic fibers, e.g. B. those based on polyamide, polyurethane, polyester and / or polycarbonate and / or natural fibers such. B. flax, sisal, hemp, coconut, cotton, wool and / or cellulose in question, for example conventional textile fabrics. In a particularly preferred embodiment, the foam core contains a flat glass fiber matrix for reinforcement, which is used in process step 1 . The fibers can be in the form of continuous fibers or individual fibers of limited length. In the context of the present invention, pressed glass fiber mats made of continuous fiber are preferred.

The fibers for reinforcing the foam core can also, for example entered into the mold simultaneously with the PUR reaction mixture. An example of such a method is the LFI (Long Fiber Injection) method from Krauss Maffai. In the so-called LDI (Low Density Structure) process however, fiber mats are used, on which the reaction mixture is applied.

The GF-PUR foam core can consist of one, two or more layers in the Sandwich system exist. Preferably, the outer layers of the Sandwich systems the fiber reinforcement. In a preferred one Embodiment, the foam core consists of only a single molded part. Preferably, this foam core is with two close to its surface, however Glass fiber mats completely reinforced in the foam structure. There is preferably a spacer between the glass fiber mats, so that the glass fiber mats a desired one when molding the foam core  Keep a distance from each other (= so-called sandwich structure). This spacer remains in the foam core after molding. As a spacer preferably a reticulated foam, for example a polyurethane foam preferably coarse structure used. As a rule, this has a flat surface Structure, for example in the form of a foam mat. This preferably has a thickness of 4 to 20 mm, more preferably 6 to 10 mm and particularly preferably from 6 to 8 mm. A so-called Enka mat can also be used as a spacer from Akzo-Nobel. This consists of continuous threads (Polyamide), which are distributed irregularly to leave gaps.

According to the use as an outer body part, the foam core preferably has a flat structure. The thickness of the foam core is preferably 2 to 100 mm, more preferably 5 to 50 mm and particularly preferably 10 to 20 mm.

The exterior parts of the body according to the invention can be made according to the known one- shot or the prepolymer process, which is also known. In the known prepolymer process in a first step usually from (a) and in deficit (b) an isocyanate group Prepolymer prepared, which then with further (b) to the desired Products.

The implementation of the product can be done, for example, by hand casting High-pressure or low-pressure machines, or by RIM processes (reaction injection molding) are preferably carried out in open molds. Suitable PU processing machines are commercially available (e.g. from Elastogran, isothermal, Hennecke, Krauss Maffei u. a.).

The PUR dosing systems preferably adhere to the following parameters:
Discharge capacity polyol component: 150 g / s to 350 g / s, particularly preferably 200 to 300 g / s
Discharge rate isocyanate: 300 g / s to 600 g / s, particularly preferably 320 g / s to 480 g / s
Component pressures in the high pressure circuit:
Isocyanate: 120 to 200 bar
Polyol: 120 to 200 bar
Component pressure in the storage containers: 1.5 to 4.5 bar.
Temperature of the polyol component in the storage container: 16 ° C to 30 ° C
Temperature of the isocyanate component in the storage container: 16 ° C to 30 ° C

When processing with polyurethane machines, it is also advantageous if the processing containers are under reduced pressure during processing.

The starting components are usually dependent on Application at a temperature of 20 to 36 ° C, preferably from 20 to 24 ° C, mixed and, for example, introduced into the mold. The Mixing can be carried out using a stirrer or a stirring screw be, or can be done in a conventional high pressure mixing head.

The reaction mixture can be reacted, for example, in customary preferably heatable and closable molds are carried out. in the The present invention particularly includes molds preferred, the surface of which is as smooth as possible and preferably none Unevenness, cracks, scratches or contamination. The surface the molds can be treated, for example, by polishing.  

Usual and commercially available tools are used, their surface for example made of steel, aluminum, enamel, teflon, epoxy resin or one other polymeric material, the surface optionally chrome-plated, for example hard chrome-plated. They should preferably Molding tools can be tempered to the preferred. Set temperatures too can, closable and preferably to exert pressure on the Be equipped. The temperature of the mold is preferably 30 to 60 ° C, more preferably 40 to 50 ° C. In the Implementation of polyisocyanate polyadducts is a temperature of Starting components of preferably 18 to 35 ° C, particularly preferably 20 up to 25 ° C preferred. The implementation of the polyisocyanate polyadducts preferably takes place in a time of usually 2.5 to 25 minutes, especially preferably 2.5 to 15 minutes.

According to the present invention, the foam core preferably has a coating of compact plastic, preferably polyurethane plastic (PUR). As a rule, this coating is applied to the side of the foam core on its surface, to which a decorative layer, for example a varnish, is subsequently to be applied. As a rule, these are the surfaces that face the outside of the vehicle. The coating with the compact plastic is generally carried out in a process step 2 following process step 1 in which the foam core was formed.

The polyisocyanate polyaddition products described above can be used as plastics for the coating, but a compact, non-cellular structure is desired. This can be achieved, for example, by using no blowing agents (d). Any water contained in components (a) to (e) should preferably be largely, particularly preferably completely removed in order to avoid an undesirable propellant reaction. In the context of the present invention, the outer body part preferably has a coating made of elastic plastic. The tensile strength of such a plastic is preferably 10 to 30, more preferably 15 to 25 N / mm ² , the elongation at break is preferably 60 to 85%, particularly preferably 75 to 85% and the tear strength 50 to 90 N / mm, particularly preferably 50 to 75 N / mm, the above values being measured in accordance with the relevant DIN standards. The coating is usually applied over a large area and preferably on one side to the foam core. The coating preferably has a thickness of 1.5 to 5 mm, more preferably 2 to 3 mm and particularly preferably 2 to 2.5 mm. The coating is usually not fiber reinforced.

A preferred embodiment of the present invention provides that both the foam core which is shaped in process step 1 and the coating which is applied to the foam core in process step 2 consist of a polyurethane polyaddition product.

Instead of a coating, the exterior parts of the body according to the invention can have a thermoplastic or metallic film which is located on at least part of the surface of the foam core. If necessary, paint can be applied to this thermoplastic film, for example by means of a lacquer. The outer body part is produced by spraying the PUR foam in process step 1 , in which the foam core is formed, against an optionally thermoformed thermoplastic or metallic film and thus adhering to it. In this embodiment, the fiber reinforcement is preferably carried out by means of loose fibers which are contained in the reaction mixture (LFI process).

Generally known films can be used as the thermoplastic film, for example, conventional films based on acrylonitrile butadiene styrene (ABS), polymethyl methacrylate (PMMA), acrylonitrile styrene acrylic ester (ASA), Polycarbonate (PC), thermoplastic polyurethane, polypropylene, polyethylene, and / or polyvinyl chloride (PVC). The foils preferably have a thickness of 1.0 to 1.5 mm. At least one is preferred as the thermoplastic film two layers of film are used, one layer being an ASA and / or contains polycarbonate material. It is particularly preferably used a two-layer film, the first layer being based on PMMA and the second Layer on ASA and / or ASA / PC. If you use a two-layer film, so the rigid foam plastic adheres preferentially to ASA and / or ASA / PC.

To ensure a high mechanical stability, which is necessary for some applications, the exterior body part according to the invention can have a reinforcing frame, for example made of aluminum profiles. As a rule, this is firmly foamed with the foam core in process step 1 .

The exterior parts of the body according to the invention can be produced by the fiber material to reinforce the foam core into the mold inserted, then the reaction mixture for the PUR foam in the Form entered and the form is subsequently closed. The fibers for Reinforcement of the foam core can be both contained in the Reaction mixture can be used (LFI method), as well, as above described, in the form of mats or fabrics. Before filling the Reaction mixture can also be a reinforcement frame, for example made of aluminum profiles, are placed in the mold.

If a thermoplastic film is used, this is preferred before Flame in the tool. In the case of metal foils, the  Foam side treated with a primer (epoxy resin), which adheres to the PUR improved. The side of the thermoplastic film is preferably flamed, that comes into contact with the PUR foam. The flame can be so take place with a burner, for example with a noisy, reducing blue flame (propane gas, approx. 1300 ° C) in a uniform Speed, the thermoformed film is inflamed, causing an ignition and Deformation of the film is avoided. This preferred flaming effect additionally a significant improvement in liability between the thermoplastic film and the PUR foam.

A preferred embodiment of the method according to the invention provides the starting components or the reaction mixture for the foam core with a robot-guided mixing head into the mold. This Procedure has the advantage that the starting components for the Rigid foam can be introduced into the mold in a reproducible manner is not always guaranteed with an insertion by hand. A very uniform entry of the starting components or the reaction mixture in the mold can be achieved by using a slot die (fan nozzle) Injecting the starting components into the mold is used.

The shaped, fiber-reinforced foam cores can be machined Processing in further procedural steps can be further processed, for example by milling or drilling. The coating itself can go through Sanding and cleaning to be prepared for the subsequent painting.

When using a thermoplastic film, this can be applied directly without further Processing a decorative layer like varnish to be applied.  

The present invention will now become apparent from the following drawing and the subsequent manufacturing example explained in more detail.

Fig. 1 shows schematically a cross section through an embodiment of an outer body part according to the invention, in particular a hard top.

The outer body part shown in FIG. 1 consists of a PUR foam core 1 with a coating 2 of compact PUR applied to it on one side. The foam core 1 contains two glass fiber mats 3 , which are foamed in the foam core near the two side surfaces of the foam core. The foam core 1 consists of PUR foam and has an open-cell foam structure. In the foam structure of the foam core 1 there is also a spacer 4 made of reticulated PUR foam. Reference number 5 denotes a profile frame which ensures the mechanical stability of the overall component and is also foamed in the foam structure.

Example of the production of a hardtop from glass fiber reinforced PUR Production of the foam core in process step 1

An aluminum tool is used for the foam core. The top of the Tool can be opened using the toggle lever.

Three pressed glass fiber mats made of continuous fiber, each with a basis weight of 0.450 kg / m ² from Vetrotex (Unifolio U 816), were used as fiber reinforcement. In order to achieve the desired three-dimensional design of the glass fiber mat, it can be preformed. The glass fiber mat is dimensioned so that it extends over the entire surface of the hardtop.

A correspondingly deep-drawn glass fiber mat was attached to the upper part of the tool by means of a reinforcement frame made of aluminum profile. Two correspondingly deep-drawn glass fiber mats were also placed on the lower part of the tool. A mat made of reticulated foam from Reisgies (Regicell 10 ) was placed on the glass fiber mats in the lower part of the mold and extends essentially over the entire cavity.

The temperature of the mold was between 35 and 70 ° C, preferably 50 and 60 ° C.

Subsequently, a PUR foam system was used in programmed path curves With the help of a robot through a mixing head into the lower part of the tool reticulated foam and the glass fiber mat underneath. The Entry time was 10 to 35 s, preferably 12 to 16 s.

The foam system used provides an open-cell PUR foam with a volume fraction of open cells in its matrix of about 70 to 90% by volume. The volume fraction of open cells in the foam structure without fiber reinforcement was determined in accordance with DIN ISO 4590 .

After completing the entry, the tool was held for a period of 5 to 30 minutes. preferably closed for 10 to 20 minutes, so that the floating foam counteracts the closed tool rises. The foaming reaction mixture encapsulates the reinforcement frame and fills the voids and imperfections Fiberglass mats.  

After the reaction time, the tool was opened and the one produced Demolded component. The foam core can be used to improve the Adhesion between foam core and coating can be mechanically roughened. For example, grinding or sandblasting can be considered.

Application of the coating in process step 2

The foam core produced in this way was placed in another mold, at which the lower part of the tool was slightly larger than the foam core itself.

The foam core was used to coat the foam core with the coating attached to the top of the mold and then the tool closed. The tool was at 45 to 70 ° C, preferably 50 to 60 ° C tempered. A compact PUR system was opened into the free space via a sprue injected between the foam core and the lower part of the tool.

After the reaction time, the tool was opened and the hardtop taken.

The hardtop can be machined in further process steps (Milling, drilling, etc.) can be processed further. The coating can pass through Grinding and cleaning can be prepared for subsequent painting.

Claims (11)

1. outer body part for vehicles made of fiber-reinforced plastic composite material which has a fiber-reinforced foam core ( 1 ) made of polyurethane (PUR) foam, characterized in that the foam core has an open-cell foam structure. 2. Body outer part according to claim 1, characterized in that the foam core ( 1 ) without fiber reinforcement has a volume fraction of open cells of more than about 50 vol.% In its foam structure. 3. outer body part according to claim 1 or 2, characterized in that the foam core ( 1 ) without fiber reinforcement has a volume fraction of open cells of about 70 to 90 vol .-% in its spatial structure. 4. outer body part according to one of the preceding claims, characterized in that the foam core ( 1 ) has a coating ( 2 ) made of a compact plastic. 5. outer body part according to one of the preceding claims, characterized in that the foam core ( 1 ) and / or the coating ( 2 ) consist of a polyisocyanate polyaddition plastic. 6. outer body part according to one of claims 1 or 2, characterized in that there is at least on a part of the surface of the foam core ( 1 ) a thermoplastic or metallic foil. 7. outer body part according to one of the preceding claims, characterized in that the foam core ( 1 ) for reinforcement contains a flat glass fiber matrix ( 3 ). 8. A process for the production of exterior body parts made of fiber-reinforced plastic composite material for vehicles according to one of claims 1 to 7, in which in a method step 1 a fiber-reinforced foam core ( 1 ) is formed from polyurethane (PUR) foam, characterized in that the foam core according to Forms has an open-cell foam structure. 9. The method according to claim 8, characterized in that in a step 2 subsequent to step 2 of the foam core is coated with a compact plastic ( 2 ). 10. The method according to any one of claims 8 or 9, characterized in that 1 auxiliary substances to promote the open-cell structure of the foam structure are added to the polyurethane (PUR) foam. 11. The method according to any one of claims 8 to 10, characterized in that the polyurethane (PUR) foam is injected in step 1 against a thermoplastic or metallic film.