DE102017011819A1 - Composite element, in particular for a vehicle - Google Patents

Abstract

The invention relates to a composite element (10), in particular for a vehicle, with cover layers (14, 16) of fiber-reinforced plastic and with a core layer (18) arranged between the cover layers (14, 16) and connected to the cover layers (14, 18). from a plastic foam. A first cover layer (14) of the cover layers (14, 16) has fibers with a first fiber length and a lower extensibility than a second cover layer (16) of the cover layers (14, 16), which fibers with a smaller compared to the first fiber length, second fiber length.

Description

The invention relates to a composite element, in particular for a vehicle, according to the preamble of patent claim 1.

From the DE 10 2016 000 726 A1 is a generic composite element with cover layers of fiber-reinforced plastic and with a arranged between the cover layers and connected to the outer layers core layer of a plastic foam known. A first of the cover layers is designed as a side facing away from the core layer unclad cover layer and has natural fibers as reinforcing fibers. A second of the cover layers is laminated on a side facing away from the core layer by means of at least one decoration of the composite element and has different reinforcing fibers from the natural fibers.

The DE 10 2012 006 609 A1 shows a sandwich component with a honeycomb core layer and a fiber-reinforced thermoplastic cover layer. The cover layer is connected to the honeycomb core layer by means of a thermoplastic material. At least one side of the sandwich component has a decorative layer which is arranged on the cover layer. The sandwich component also comprises a foam layer connected to the cover layer and the decorative layer, which is arranged between the cover layer and the decorative layer.

Furthermore, from the DE 198 32 721 A1 a layered composite for stabilizing a core component of molded articles, wherein respective layers of the composite consist of a thermoplastic layer and a fabric containing natural fibers and a longitudinal and transverse stretchable cover layer.

In vehicles composite elements, in particular in the form of pressed trim parts are used, wherein such trim parts are used in particular as interior trim parts and are installed in the interior of vehicles. The pressed trim parts are often made from hybrid thermoplastic nonwovens. These denote a combination of reinforcing and plastic fibers, which form a composite material by confused arrangement, in particular natural or glass fibers can be used as a reinforcing component.

The composite elements may generally form a sandwich composite of a plurality of outer layers with a plastic formed as a thermoplastic matrix and an associated core material, which may also be referred to as the core layer. Due to this sandwich composite, the composite elements have a high rigidity and at the same time low weight.

3 shows an example of a forming process in the production of a known from the prior art composite element 100 in which a plastic, so a matrix, respective cover layers 102 . 104 is present in each molten form, which is a transformation, so a shape of the composite element 100 by means of a forming tool 108 favors, or allows. Between the two cover layers 102 . 104 there is a core layer 106 , which can also be referred to as a foam core. At the in 3 shown composite element 100 are the two cover layers 102 . 104 made of a composite of polypropylene (PP) and reinforcing fibers and the core layer 106 formed as a thermoplastic foam core.

The problem with the shaping is that, in particular in strong deformation of the composite element 100 a strong, at least local material expansion occurs, resulting in so-called thinning 110 especially at the, the forming tool 108 facing away cover layer 102 can lead. This can cause excessive stretching of the cover layer 102 and even cracking on the topcoat 102 occur.

Another problem with shaping (reshaping) is that of the forming tool 108 removed covering layer 102 in shaping by one, by the forming tool 108 given, convex shape due to tensile stresses due to the deformation corresponding normal forces on the between the outer layers 102 . 104 lying core layer 106 of the composite element 100 exercises. As a result, the core layer becomes 106 compressed and loses it in the field of thinning 110 at height. This leads to unfavorable stiffness losses of the composite element 100 , where the core layer 106 (Foam core) are even completely crushed in extreme cases, and thus a sandwich effect at least in a portion of the composite element 100 almost completely lost. This leads, in particular at high draw depths, to radius regions of the composite element 100 strongly weakened and thus the entire composite element 100 can not meet the corresponding load requirements, although no such thinning or no such compression takes place in Radienfernen areas.

Object of the present invention is to provide a composite element of the type mentioned, which has particularly favorable forming properties.

This object is achieved by a composite element with the features of claim 1. Advantageous embodiments with expedient developments of the invention are specified in the remaining claims.

The invention is based on a composite element, in particular for a vehicle, with cover layers of fiber-reinforced plastic and with a core layer of a plastic foam arranged between the cover layers and connected to the cover layers. The cover layers thus comprise respective fibers, which are connected to the plastic. The first cover layer and the second cover layer may also be formed as a respective nonwoven. In other words, the first cover layer may be formed as a first nonwoven and the second cover layer as a second nonwoven.

In order to create a composite element, in particular for a vehicle, of the type indicated in the preamble of patent claim 1, which has particularly favorable forming properties, it is provided according to the invention that a first cover layer of the cover layers has fibers with a first fiber length and a lower extensibility than a second cover layer the cover layers, which has fibers with a smaller compared to the first fiber length, second fiber length. Due to the different fiber lengths of the respective outer layers, the two outer layers are different from each other. In other words, the composite element thereby has an asymmetric material structure, whereby known from the prior art problems of unwanted thinning or unwanted compression can be avoided.

The first cover layer may preferably be formed as a high resistance composite which may comprise a matrix of plastic such as polypropylene and reinforcing fibers. The second cover layer may preferably be formed as a composite with a low tensile resistance in comparison to the first cover layer, which likewise may have a matrix of plastic, such as, for example, polypropylene and reinforcing fibers.

In a shaping (reshaping) of the composite element, it is advantageous to arrange the cover layers relative to the forming tool, that the second cover layer is located on a convex side of the composite element during forming of the composite element, that is arranged away from the forming tool, so that the second cover layer at least can not absorb high tensile forces at their processing temperature. Thus, the second cover layer in the deformation is not able to exert a high normal force on the core layer, whereby the core layer is compressed only slightly during deformation (compressed) is. As a result, there is no impairment of the rigidity of the composite element, especially since the core layer is hardly compressed and, accordingly, its function of increasing the stiffness can be maintained as the core of the composite element.

If both cover layers were made of the same material, forming would hardly be possible without destruction in the context of deep drawing since the cover layers could very quickly be destroyed by high local elongation.

The avoidance of high local elongation takes over the first cover layer, which is such that it allows only a small elongation at the processing temperature. The first cover layer can thus cause particularly high radial forces on the forming tool, in contrast to the second cover layer, which is not disadvantageous. Due to the high resistance to expansion of the first cover layer, during the forming process, on the one hand, material flows from respective edge regions of the composite element and, on the other hand, expansions not only occur locally, but are distributed over larger areas. If during the production of the composite element by the forming the Nachfießen of the material is not hindered and the material has enough strength, in areas of the composite element with high degree of deformation (deep drawing) sufficient material can flow and thus a local thinning can be prevented. This is made possible by the first cover layer with its lower extensibility compared to the second cover layer.

The various cover layers thus fulfill different functions during the production of the composite element during the forming process. The first cover layer supports the subsequent flow of the material and reduces local strains, while the second cover layer generates the lowest possible forces during forming, that is to say when it expands.

With the composite element, a multilayer composite is provided, which comprises at least the various cover layers and the core layer arranged between the cover layers, at which the problems of unwanted thinning and undesired compression known from the prior art can be at least substantially reduced, thereby resulting in high degrees of deformation while maintaining a high rigidity can be achieved.

Further advantages, features and details of the invention will become apparent from the the following description of a preferred embodiment and with reference to the drawing (s). The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

• 1 eine schematische Schnittansicht eines Verbundelements;
• 2 eine weitere schematische Schnittansicht des mittels eines Umformwerkzeugs an einem Umformbereich verformten Verbundelements; und
• 3 eine schematische Schnittansicht eines aus dem Stand der Technik bekannten Verbundelements.

Showing:

• 1 a schematic sectional view of a composite element;
• 2 a further schematic sectional view of the deformed by means of a forming tool at a forming area composite element; and
• 3 a schematic sectional view of a known from the prior art composite element.

In the figures, identical and functionally identical elements are provided with the same reference numerals.

1 shows a schematic sectional view of a composite element 10 for a present not further illustrated vehicle. The composite element 10 includes respective cover layers 14 . 16 made of fiber-reinforced plastic and one, between the outer layers 14 . 16 arranged and with the cover layers 14 . 16 connected core layer 18 from a plastic foam. The plastic foam is presently designed as a polyethylene terephthalate foam (PET foam). The use of the polyethylene terephthalate foam is advantageous since the thermoplastic foam core 18 As a result, plastically deformable at its processing temperature, but not yet in a molten state, while the PP portion of the cover layer is melted. This results in a softness of the foam core 18 at its processing temperature, so that different strength or extensibility of the outer layers 14 . 16 overall very well. The respective cover layers 14 . 16 and the core layer 18 form a sandwich composite 12 , The cover layers 14 . 16 are presently designed as respective nonwovens. The cover layers 14 . 16 are by means of a respective adhesive film (not shown) with the core layer 18 connected.

At least one of the cover layers 14 . 16 can be made up of a plurality of individual layers which belong to the respective cover layer 14 or to the cover layer 16 be connected exist. This is a particularly targeted adjustment of physical properties of the cover layer 14 or. 16 allows. Thus, for example, a respective mass fraction of reinforcing fibers in layers in the respective cover layer 14 or. 16 be reduced by one of the individual layers of pure matrix material (without reinforcing fibers) or compared to another of the individual layers or the other individual layers increased proportion of matrix material is formed. At least one of the individual layers can also have a different fiber length, ie longer or shorter reinforcing fibers, than other individual layers.

The first cover layer 14 In the present case, it is at least partially formed from natural fibers, synthetic fibers and additionally or alternatively from glass fibers.

The composite element 10 also has a decorative element 28 and a foam element 30 on, by means of which the decorative element 28 on the first cover layer 14 is held. The decorative element 28 may be formed as a TPO film or as a PVC film, wherein the foam element 30 a foam backing of the decorative element 28 can form.

The first cover layer 14 the cover layers 14 . 16 has fibers with a first fiber length and a lower extensibility than the second cover layer 16 the cover layers 14 . 16 which has fibers with a smaller second fiber length compared to the first fiber length.

The fibers of the first cover layer 14 are aligned unidirectionally in the present case. Alternatively, the fibers of the first cover layer 14 be designed as a fiber fabric or as a fiber grating. By introducing the unidirectionally oriented, in other words directed fibers or forming the fibers as a fiber fabric or as a fiber grating, the effect of the resistance to stretching in the first cover layer 14 be further increased. Thus, the, compared to the second cover layer 16 less extensible, so having a higher resistance, the first cover layer 14 (First nonwoven) are reinforced, resulting in the processing (forming) overall lower elongation of the sandwich composite 12 causes.

In addition, the fibers of the first cover layer 14 as compared to the fibers of the second cover layer 16 have different fiber types. Additionally or alternatively, at least some of the fibers, preferably all fibers of the first cover layer 14 Branches have. Due to the branching, a particularly large resistance of the first cover layer 14 be achieved because the fibers can get caught under load due to their branches.

2 shows a forming of the composite element 10 by means of a forming tool 40 , whereby the composite element 10 at a forming area 50 is plastically deformed. Due to the different fiber lengths that has the forming tool 40 during forming facing, first cover layer 14 a high resistance, whereas the forming tool 40 turned away during forming, second cover layer 16 has a particularly low resistance to stretching. This will be local strains of the composite element 10 even with heavy forming kept low or reduced, so that the sandwich composite 12 even with such a strong forming is maintained.

The composite element 10 In summary, allows improved deformation or deformation of sandwich components of micro sandwich, since a local thinning of the material of the composite element 10 Compared to known from the prior art composite elements can be substantially reduced. Due to the lower tensile forces in the stretchable, second cover layer 16 act during processing, so when forming the composite element 10 less normal forces on the core layer 18 , bringing a height of the core layer 18 during forming at least largely preserved. This shows the reshaped composite element 10 also in strongly deformed areas of the sandwich composite 12 a high rigidity.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102016000726 A1 [0002]
• DE 102012006609 A1 [0003]
• DE 19832721 A1 [0004]

Claims (8)

Composite element (10), in particular for a vehicle, with cover layers (14, 16) of fiber-reinforced plastic and with a core layer (18) of a plastic foam arranged between the cover layers (14, 16) and connected to the cover layers (14, 18), characterized in that a first cover layer (14) of the cover layers (14, 16) comprises fibers having a first fiber length and lower extensibility than a second cover layer (16) of the cover layers (14, 16), which has one compared to the first Fiber length smaller, second fiber length has. Composite element (10) after Claim 1 , characterized in that at least a part of the fibers of the first cover layer (14) are unidirectionally aligned or formed as a fiber fabric or as a fiber grating. Composite element (10) after Claim 1 or 2 , characterized in that at least some of the fibers of the first cover layer (14) have branches. Composite element (10) according to one of the preceding claims, characterized in that the first cover layer (14) is at least partially formed from natural fibers, synthetic fibers and / or glass fibers. Composite element (10) according to one of the preceding claims, characterized in that the composite element (10) has a decorative element (28) and a foam element (30), by means of which the decorative element (28) is held on the first cover layer (14). Composite element (10) according to one of the preceding claims, characterized in that the plastic foam of the core layer (18) is formed as a polyethylene terephthalate foam. Composite element (10) according to one of the preceding claims, characterized in that at least one of the cover layers (14, 16) contains polypropylene. Composite element (10) according to one of the preceding claims, characterized in that at least one of the cover layers (14, 16) by means of a bonding agent film with the core layer (18) is connected.

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