Patent Application
20160207234
The invention relates to a semi-finished product in the form of a sheet or strip that can undergo deep drawing and is intended for producing a three-dimensionally shaped hybrid component of a metal/plastic composite and relates to a use of such a semi-finished product. The invention also relates to a method for producing a three-dimensionally shaped hybrid component of a metal/plastic composite.
In construction, and in particular in vehicle manufacture, highly use is made of lightweight components, which apart from low weight must additionally have high strengths and stiffness. Corresponding lightweight components often serve the purpose in a vehicle body of forming crash-related structural components, such as for instance a B pillar, a bumper or a side impact beam. One approach to achieving such lightweight components is to combine different materials with one another.
In the area of plastic and fiber-reinforced plastic, the company LANXESS AG has worked together with the Institute of Polymer Technology at Erlangen University in developing what is known as the “Erlanger beam”. This is a model beam that is used for standard tests, produced by heating an organometallic sheet (fiber-reinforced plastic) above its melting temperature, placing it into a forming mold, subjecting it to a forming process and subsequently providing it with a three-dimensional ribbed structure by an integrated injection-molding unit. With this model beam, the mechanical characteristic values are significantly higher than they are with a sheet-metal-based equivalent. As a result, such structures can absorb much more energy. Further three-point bending test simulations on the Erlanger beam have shown that a composite comprising a formed steel sheet with a ribbed structure corresponding to the Erlanger beam can absorb forces that are more than twice as high in comparison with the original variant of the Erlanger beam (organometallic sheet with a molded-on ribbed structure). Since, however, the metal and plastic are different types of material, suitable connecting measures have to be provided. The conventional production process comprises the following working steps:
This process is very costly. In particular, modern adhesives for the automobile industry are very expensive. All of this stops many automobile manufacturers or suppliers from using hybrid components of a metal/plastic composite, with the result that they cannot make use of the potential of lightweight construction that is available to this extent.
DE 199 34 545 C1 discloses hybrid components that comprise a profiled body shaped from a metal sheet bar that is back-injection-molded with plastic in such a way that the plastic defines a structural body comprising crossing ribs. To achieve an adequate connection between the metal and the plastic, according to DE 199 34 545 C1 a partial interlocking engagement of the plastic with the metal profiled body is produced. The interlocking engagement is achieved in this case by partial enclosure of the profiled body and by injection-molding of apertures in the profiled body. Anchoring points between the metal and the plastic are produced at the apertures. However, in the case of many components, these points of partial interlocking connection are undesired with regard to the outer appearance of the component. Moreover, the load-absorbing capability of such hybrid components is sometimes unsatisfactory because of the partial interlocking connections.
Against this background, the invention was based on the object of providing a semi-finished product for producing a three-dimensionally shaped hybrid component of a metal/plastic composite that enables automobile manufacturers or their suppliers to produce corresponding hybrid components with a high load-absorbing capability at a much lower cost than is the case with the aforementioned process comprising 6 working steps. The object was also to provide a low-cost method for producing a three-dimensionally shaped hybrid component of a metal/plastic composite.
With regard to the semi-finished product, the stated object is achieved by a semi-finished product with the features of claim 1. With regard to the method, the stated object is achieved by a method with the features of claim 18. Advantageous refinements of the semi-finished product according to the invention and of the method according to the invention are the subject of claims 2 to 17, which refer back to claim 1, and of claims 19 to 26, which refer back to claim 18.
The invention is based on the basic concept of providing for the production of a three-dimensionally shaped hybrid component of a metal/plastic composite a semi-finished product that allows a bonding between the metal and the plastic that adheres over substantially the full surface area without the need for the automobile manufacturer or hybrid component manufacturer to apply a layer of adhesive, in that the semi-finished product is made up of at least one metal sheet in the form of a sheet or strip and at least one layer of thermoplastic applied on it in a material-bonding manner, the side of the metal sheet on which the layer of plastic is applied having a surface that improves the adherence of the layer of plastic, and the layer of plastic being formed as a coupling layer for the material-bonding, adhesive-free attachment of at least one structural body produced or to be produced from plastic.
Depending on the surface treatment, various thermoplastics may be used as the coupling layer, in particular polypropylene (PP), polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), thermoplastic elastomer and compounds of these plastics, with polyamide, polyethylene or mixtures thereof being particularly preferred because of their relatively high thermal stability.
The metal sheet of the semi-finished product according to the invention is preferably produced from steel material, particularly preferably from dual-phase steel or from another lightweight steel. Steel material is distinguished by good formability and high strength. The microstructure of dual-phase steel consists primarily of a soft ferritic matrix, which incorporates islands of a second, hard, predominantly martensitic phase. The ferrite fraction accounts for up to 90%. Apart from martensite, there may also be fractions of residual austenite and bainite. Metal sheets of dual-phase steel are particularly suitable for cold-forming operations involving a high proportion of stretch forming for the production of strength-relevant structural elements and body parts. Hot-rolled dual-phase steel has advantages in particular for the weight-saving production of components such as profiles, body reinforcements and chassis parts. After an appropriate heat treatment, for example the treatment known as bake hardening, additional increases in strength of over 30 MPa are achieved.
The at least one metal sheet of the semi-finished product according to the invention has for example a thickness in the range of 0.1 to 2.5 mm, preferably 0.1 to 1.0 mm, particularly preferably in the range of 0.1 to 0.5 mm
On the other hand, the least one layer of plastic (coupling layer) of the semi-finished product according to the invention may be formed as rather thinner. It has for example a thickness in the range of 0.01 to 1.2 mm, preferably 0.05 to 1.0 mm, particularly preferably in the range of 0.3 to 0.8 mm.
In tests carried out on the part of the applicant it has been found that a semi-finished product according to the invention of which the metal sheet and the coupling layer have thicknesses in the ranges mentioned has good deep-drawing properties in the Erichsen cupping test at room temperature and a mold temperature of 100° C. During the deep drawing of the semi-finished product according to the invention, the layer of thermoplastic serving as the coupling layer flows along with the metal sheet, and in doing so does not lose its adhesion.
Instead of a metal sheet of steel material, the semi-finished product according to the invention may also comprise a metal sheet of magnesium or aluminum.
The function of the layer of thermoplastic (coupling layer) of the semi-finished product according to the invention is that it can be reliably connected in a material-bonding manner to many other plastics without applying an adhesive. In the injection-molding process, the energy of the plastics melt is used here for activating the surface of the coupling layer and producing the material bond. After the melt has cooled down, there is a perfect bond between the coupling layer and the molded-on plastic. The molded-on plastic may be not only a thermoplastic but also a thermoset and/or a plastic from the range of elastomers. It is also possible by plasma or corona pre-treatment before the injection-molding process to additionally activate the surface of the coupling layer in order to widen the range of plastics that can be used.
With the semi-finished product according to the invention, the working steps to be performed at the site of an automobile manufacturer or component supplier for producing a three-dimensionally shaped hybrid component are reduced considerably. This is so because, with the semi-finished product according to the invention, the automobile manufacturer or component supplier has in particular the possibility of producing a three-dimensionally shaped hybrid component by the following process steps:
An advantageous refinement of the semi-finished product according to the invention is characterized in that the layer of plastic (coupling layer) does not cover the side of the metal sheet on which it is applied over the full surface area but partially. This refinement is expedient in particular whenever for example the hybrid component to be produced only partially has a strength- and/or stiffness-increasing ribbed structure of plastic. Consequently, one or more relatively large surface areas of the metal sheet that are not to have a ribbed structure after the completion of the hybrid component can remain uncoated during the coating of the metal sheet with the at least one layer of thermoplastic (coupling layer). This saves material costs and contributes to an optimized weight saving while maintaining adequate strength and stiffness properties.
A further advantageous refinement of the semi-finished product according to the invention is that the layer of thermoplastic is made double, a layer of thermoplastic foam being arranged between the two layers of plastic. It has been found that interposing a layer of thermoplastic foam can contribute greatly to reducing the weight of the hybrid component while maintaining the same strength and stiffness.
According to a further advantageous refinement, the layer of plastic (coupling layer) of the semi-finished product according to the invention is partially coated with at least one organometallic sheet. As a result, the strength and stiffness of the hybrid component to be produced can be greatly improved while maintaining the same overall weight or even with a reduced overall weight.
Alternatively or in addition, according to a further refinement of the semi-finished product according to the invention, its (at least one) metal sheet may also be coated on its side facing away from the layer of plastic (coupling layer) with at least one organometallic sheet. This refinement may also allow the strength and stiffness of the hybrid component to be produced to be increased greatly while maintaining the same overall weight or even with a reduced overall weight. At the same time, according to a further refinement, the organometallic sheet may be coated on its side facing away from the metal sheet with at least one second metal sheet. Hybrid components that are particularly lightweight and at the same time very strong and stiff can be produced from such a semi-finished product, in particular whenever, according to a preferred refinement, the organometallic sheet contains carbon fibers. Moreover, in a further refinement, the second metal sheet may be coated on the outside with a layer of thermoplastic, which is likewise formed as a coupling layer for the material-bonding, adhesive-free attachment of at least one structural body produced or to be produced from plastic. From a semi-finished product according to the invention designed in such a way, hybrid components that have structural bodies produced from plastic, in particular ribbed bodies, on both sides can be advantageously produced without applying an adhesive.
Another advantageous refinement of the semi-finished product according to the invention is that the metal sheet is coated on its side facing away from the layer of plastic with a second layer of thermoplastic, which is likewise formed as a coupling layer for the material-bonding, adhesive-free attachment of at least one structural body produced or to be produced from plastic. Also from such a semi-finished product according to the invention, hybrid components that have structural bodies produced from plastic, in particular ribbed bodies, on both sides can be produced without applying an adhesive.
In this case, the second layer of plastic (coupling layer) may cover the side of the metal sheet on which it is applied over the full surface area or partially. The partial coating of the metal sheet by the second layer of plastic is expedient for example whenever the hybrid component to be produced only partially has on the corresponding side of the metal sheet a ribbed structure of plastic that is attached in a material-bonding manner to the metal sheet without adhesive, by way of the partial coupling layer.
A further advantageous refinement of the semi-finished product according to the invention is that the second layer of plastic is coated on its side facing away from the metal sheet with a second metal sheet. In a further refinement, the second metal sheet may be coated on its side facing away from the second layer of plastic with a third layer of thermoplastic as a coupling layer. Also with semi-finished products according to the invention designed in such a way, lightweight hybrid components with high strength and stiffness can be produced at low cost. The same applies to a further refinement of the semi-finished product according to the invention, in which the second layer of plastic is coated over its full surface area or partially with at least one organometallic sheet.
According to a further refinement of the semi-finished product according to the invention, the respective layer of plastic, serving as a coupling layer, is provided with a protective film that can be peeled off. The protective film protects the surface of the coupling layer while the semi-finished product is being transported and possibly also while the semi-finished product is undergoing forming. As a result, there is no need for laborious cleaning of the coupling layer surface of contaminants such as oil or grease before plastic structures, for example plastic ribs, are molded on. Moreover, as a peeling film, the protective film can improve the sliding properties of the semi-finished product during the forming process.
The semi-finished product according to the invention is preferably formed as a flat product. It may be produced by means of a plate press in a static process, an interval heating press in a discontinuous process or a laminating system, for example a double belt press, in a continuous process. The process parameters are in this case respectively set specifically for the semi-finished product to be produced. Depending on variants of the semi-finished product, panels may be cut out from them; or the semi-finished product in strip form may be rolled up to a coil.
According to a second teaching of the present invention, the object presented above for a method for producing a three-dimensionally shaped hybrid component of a metal/plastic composite is achieved by using a semi-finished product according to the invention in one of the aforementioned refinements, a structural body of plastic being molded in a material-bonding manner onto the layer of plastic formed as a coupling layer by injection molding or press-forming.
As already stated, the semi-finished product according to the invention allows the production of a three-dimensionally shaped hybrid component from metal and plastic with a structural body, preferably a ribbed body, of plastic without applying adhesive. This greatly simplifies the production of the hybrid component.
An expedient refinement of the method according to the invention is that, before the structural body is molded on, the semi-finished product undergoes forming into a three-dimensional form. The forming process is in this case preferably performed by deep drawing or roll-forming.
A further advantageous refinement of the method according to the invention is characterized in that the semi-finished product undergoes forming by means of a forming mold, which has at least one integrated injection-molding cavity and at least one injection-molding channel entering the injection-molding cavity. This refinement offers the possibility of reducing the number of process steps for producing the hybrid component, in that the forming of the semi-finished product or cut-to-size semi-finished blank and the back-injection-molding of the coupling layer to produce the structural body, preferably a ribbed body, are carried out in the same process step.
Another advantageous refinement of the method according to the invention is characterized in that the semi-finished product undergoes forming by means of a forming mold, which has a profile with at least one integrated cavity for the pressing and three-dimensional shaping of a plastics compound. This variant also offers the possibility of reducing the number of process steps for producing the hybrid component, in that the forming of the semi-finished product or cut-to-size semi-finished blank and the pressing of the plastics compound to produce the structural body, preferably a ribbed body, on the coupling layer are carried out in the same process step.
A further variant of the method according to the invention is that the semi-finished product undergoes forming by roll-forming, a rotatable, wheel-shaped tool being used for the press-forming of the structural body during or after the forming of the semi-finished product, and the tool being provided with a profile having at least one cavity for the pressing and three-dimensional shaping of a plastics compound. With this refinement of the method, hybrid components of the type mentioned that are formed as sectional beams can in particular be mass produced effectively.
According to a further refinement of the method according to the invention, at least one integral flange that has the layer of thermoplastic formed as a coupling layer is formed on the hybrid component, a further hybrid component, configured as a metal/plastic composite, or an organometallic sheet being joined onto the layer of plastic by welding. In this way, hybrid components that are formed as half-shells for example can be put together at low cost to form a hollow channel or closed profile. The same applies correspondingly with regard to a combination of a hybrid component according to the invention with an organometallic sheet delimiting the hollow channel or the closed profile. The welded connection of the hybrid components formed as half-shells or the organometallic sheet to form a single hybrid component may be produced for example by friction welding, spot welding, ultrasonic welding, etc.
According to a third teaching of the present invention, the semi-finished product according to the invention is advantageously used for producing a three-dimensionally shaped hybrid component as a component for a vehicle, aircraft, ship or building structure. This is because the semi-finished product according to the invention has advantages wherever a weight saving is required, and for this purpose hybrid components of the type mentioned are to be produced in the fewest possible process steps.
The invention is explained in more detail below on the basis of a drawing representing several exemplary embodiments.
The layer of thermoplastic 1.2 applied in a material-bonding manner to the metal sheet 1.1 serves as a coupling layer for the material-bonding, adhesive-free attachment of at least one structural body 2 produced or to be produced from plastic, for example a ribbed body (cf. in particular
In the case of the semi-finished product 1′ that is schematically represented in
The semi-finished product 1, 1′ may be processed in conventional presses for metal forming processes. The at least one thermoplastic coupling layer 1.2 or 1.4 may exert a sliding effect here, with the result that it is possible to dispense with customary lubricants and sliding agents, such as for instance deep-drawing oils. The forming process may be performed conventionally in a cold state, but also analogously with the semi-finished product 1, 1′ heated up before the pressing process, in that the semi-finished product is heated in a corresponding temperature-control unit, for example a furnace. Alternatively or in addition, the semi-finished product or fabricated workpiece 1, 1′ may also be heated within the forming mold.
Then, in a downstream process step, the formed semi-finished product (workpiece) 1, 1′ is provided with a structural body, for example a ribbed body, of plastic, the structural body (ribbed body) 2 being molded in a material-bonding manner onto the coupling layer 1.2 and/or 1.4 without adhesive. This may take place by injection molding or, as schematically shown in
In the case of the exemplary embodiment that is schematically represented in
In the case of the exemplary embodiment that is schematically represented in
A further exemplary embodiment of a production according to the invention of a hybrid component 5 of a metal/plastic composite is schematically shown in
The embodiment of the invention is not restricted to the exemplary embodiments that are schematically represented in the drawing. Rather, numerous variants are possible, including making use of ways of implementing the invention specified in the claims that differ from the drawing. For instance, the semi-finished product 1, 1′ according to the invention may in particular also have at least one further layer of metal sheet, layer of plastic (coupling layer) and/or layer of organometallic sheet. Furthermore, it is within the scope of the invention to form the semi-finished product 1, 1′ by roll-forming, a rotatable, wheel-shaped tool being used for the press-forming of the structural body 2 during or after the forming of the semi-finished product, and the tool being provided with a profile having at least one cavity for the pressing and three-dimensional shaping of a plastics compound 3.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 109 616.6 | Sep 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/067763 | 8/20/2014 | WO | 00 |
