DE102016015465A1 - Method for producing a sandwich component - Google Patents

Abstract

The invention relates to a method for producing a sandwich component (10) having at least two cover layers (16, 18) and at least one sandwich element (10) arranged between the cover layers (16, 18), in particular for a motor vehicle. in which the core element (14) is arranged between the fiber-reinforced thermoplastic cover layers (16, 18) of the sandwich composite and is connected at least indirectly to the cover layers (16, 18), the core element (14) being produced from a thermoplastic foam as a closed-cell foam core and subsequently is perforated, wherein at least the sandwich composite (12) is heated during manufacture to a temperature which is above the melting temperature of the thermoplastic material of the cover layers (16, 18), and wherein subsequently the heated sandwich composite (12) is formed in a cold mold and froze.

Description

The invention relates to a method for producing a sandwich component, in particular for a motor vehicle, according to the preamble of patent claim 1.

Such a method for producing a sandwich component having a sandwich component, in particular for a motor vehicle, for example, is already the DE 10 2014 005 008 A1 to be known as known. In the method, the sandwich composite has at least two fiber-reinforced thermoplastic cover layers and a core element. This means that the cover layers at least thermoplastic material, that is, a thermoplastic resin as a matrix and reinforcing fibers, which are embedded in the matrix. In the method, the core element is arranged between the fiber-reinforced thermoplastic cover layers of the sandwich composite and connected at least indirectly to the cover layers.

Object of the present invention is to develop a method of the type mentioned in such a way that the weight and cost of the sandwich component kept particularly low and excessive distortion of the sandwich component can be avoided.

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

In order to develop a method specified in the preamble of claim 1 type such that the cost and weight of the sandwich component kept particularly low and excessive distortion of the sandwich component can be avoided, it is inventively provided that the core element of a thermoplastic foam as a closed-cell foam core is produced and then perforated, wherein at least the entire sandwich composite is heated with its outer layers and the core element during manufacture to a temperature which is above the melting temperature of the thermoplastic material of the outer layers, and then the heated sandwich composite is formed in a cold mold and stiffens. The sandwich composite is thus, for example, first of all a semifinished product which is shaped in the cold mold and solidifies. The core element is an example extruded, polymeric, in particular thermoplastic, foam core, which compared to compact materials allows weight and material savings and also has an increased area moment of inertia, which leads to higher specific bending stiffnesses. The sandwich component can be used particularly advantageously for interior components which are installed in interiors of motor vehicles, in particular passenger cars.

Since the core member is formed of a thermoplastic foam, the core member has a polymeric foam structure. In addition to the chemical composition of such polymeric foam structures, these may differ from each other in terms of their respective cell size, cell distribution and cell type. With regard to the cell type, a distinction can be made between an open and a closed cell morphology and thus between an open-cell and a closed-cell structure. An open-cell structure has no cell walls, but only cell bridges, whereby an unimpeded gas exchange between individual cells of the cell structure can take place. In a closed-cell structure, ie in a closed cell or foam morphology, the individual cells are separated by cell walls. These cell walls act as diffusion barriers and thus slow down or prevent rapid gas exchange between adjacent cells. Depending on the process control and system technology, smooth and compact outer skins, for example in the form of closed edge layers, may also be produced during the production or expansion of the foam and thus the core element, which may be arranged between the respective cover layers and the core element and constitute an additional diffusion barrier to the environment ,

In the use of closed-cell foam cores as core elements for sandwich components or sandwich composites could be observed in experiments carried out that under increased, caused for example by sunlight temperature effect on the respective sandwich component to an undesirable Nachexpansion of foam cells designed as cells of the core element. An amplification of this post-expansion occurs when the closed-cell foam core additionally has smooth and compact outer skins, which can arise during the production of the core element due to the process. The post-expansion leads to changes in thickness and distortion in the sandwich component, whereby its dimensional stability or dimensional stability of a component comprising the sandwich component can no longer be guaranteed.

The perforation according to the invention, at least of the core element, it is now possible, a prevent unwanted post-expansion of the foam cells of the. Through the perforation air ducts are generated, which allow a constant pressure equalization with the environment of the core element or the sandwich component, which are prevented as a result of temperature effects occurring pressure increases and consequent cell growth.

In the or by the perforation, for example, a plurality of at least a portion of the foam core penetrating holes is produced, which, for example, completely penetrate the core element. Preferably, the holes also penetrate the possibly produced edge layers as well as the cover layers, in order to be able to reliably avoid an undesired post-expansion of the sandwich component. It is preferably provided that the plurality of holes are produced simultaneously. The holes are respective passage channels, via which, for example, a pressure equalization between the foam cells of the core element and the surroundings of the sandwich component can take place, whereby, for example, temperature-induced volume changes of the sandwich component can be avoided.

The perforation takes place for example in the normal direction of the foam core or the cover layers, whereby a particularly advantageous pressure equalization can be ensured. Preferably, the optionally already formed on this compact and preferably closed or pore-free edge layers are perforated together with the foam core to thereby reliably avoid unwanted distortion of the sandwich component can.

The perforation takes place, for example, while the core element is connected to the cover layers or subsequently. Furthermore, it is conceivable that the foam core, optionally together with the edge layers, is perforated before the core element is joined to the cover layers.

The core element is produced for example by extrusion. In this case, it is preferably provided that the perforation takes place in the hot state of the core element in direct connection to the extrusion. For example, the perforation is done by needling. Furthermore, it is conceivable to use at least one laser or another fine-blasting method in order to perforate at least the core element, in particular also the cover layers and / or the edge layers.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing. 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.

The drawing shows in:

1 a sectional view of a schematic sectional view of a sandwich component according to a first embodiment, which is produced by means of a method according to the invention;

2 a sectional view of a schematic sectional view of the sandwich component according to a second embodiment; 3 a diagram illustrating different embodiments of the method for producing the sandwich component;

4 a detail of another schematic sectional view of the sandwich component;

5 partial schematic sectional views of the sandwich component; and

6 another diagram illustrating further embodiments of the method for producing the sandwich component.

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

1 shows a whole with 10 designated sandwich component according to a first embodiment, wherein the sandwich component 10 For example, in a motor vehicle, especially a passenger car, is installed. In particular, from the sandwich component 10 made an interior component, which is installed for example in the interior of the motor vehicle. The sandwich component 10 includes a sandwich composite 12 with a core element 14 and two cover layers 16 and 18 between which the core element 14 is arranged. The core element 14 is at least indirectly with the outer layers 16 and 18 connected. The core element 14 is made of a thermoplastic foam and thus formed as a polymeric, especially thermoplastic, foam core. The respective cover layer 16 respectively 18 is designed for example as a thermoplastic or as a thermosetting cover layer. Alternatively or additionally, it is conceivable that the respective cover layer 16 respectively 18 is formed of a fiber-reinforced plastic. Thus, for example, includes the respective cover layer 16 respectively 18 a thermoplastic or thermoplastic material as a matrix and reinforcing fibers, which are the matrix, that is embedded in the thermoplastic material.

The core element 14 itself is designed as a closed-cell foam core and thus has a closed cell morphology or a closed-cell or closed-cell foam structure. As part of a process for producing the sandwich component 10 becomes the core element 14 between the cover layers 16 and 18 arranged and at least indirectly with the cover layers 16 and 18 connected. This becomes the core element 14 from a thermoplastic foam and thereby, in particular initially, produced as a closed-cell foam core. By the formation of the core element 14 as a thermoplastic foam core, the weight and the material requirements and thus the costs for producing the sandwich component 10 be kept particularly low, at the same time a particularly advantageous rigidity can be realized.

In addition, unwanted, especially temperature-related, distortions of the sandwich component 10 to avoid being the core element 14 - Especially after its production as a closed-cell foam core - perforated, as will be explained in more detail below.

In particular, it is preferably in the context of a method for producing the sandwich component 10 provided that at least the sandwich composite 12 is heated during manufacture to a temperature which is above the melting temperature of the thermoplastic material of the outer layers 16 and 18 followed by the heated sandwich composite 12 is formed in a cold mold and solidifies.

1 shows a first embodiment of the sandwich component 10 , in which 2 a second embodiment of the sandwich component 10 shows. The second embodiment differs in particular from the first embodiment in that the core element designed as a foam core 14 smooth and compact outer skins in the form of surface layers 20 and 22 having. The marginal layers 20 and 22 For example, closed and thus closed-pore layers, which are between the core element 14 and the respective cover layers 16 and 18 are arranged.

The production of the sandwich component 10 with the thermoplastic foam core takes place for example by means of pressing technology. This is the sandwich composite 12 pressed and thus produced as a pressed sandwich composite. The pressed sandwich composite 12 can be prepared for example by, for example, the thermosetting or thermoplastic, optionally made of fiber-reinforced plastic cover layers 16 and 18 with the so-called core material foam core (core element 14 ) get connected. The connection of the cover layers 16 and 18 to the core element 14 can be done via a cohesive connection mechanism, in particular by gluing, and / or by a positive connection mechanism, in particular by mechanical anchoring. Are the cover layers 16 and 18 For example, if they are formed as thermoplastic cover layers, they are, for example, when they are formed from amorphous thermoplastics, above their glass transition temperature or when they are formed from semicrystalline thermoplastics, brought about their melting temperature to the outer layers 16 and 18 for example, reshape. This means that the cover layers 16 and 18 brought to a forming temperature, in particular heated, to the outer layers 16 and 18 reshape. This forming temperature is, for example, the glass transition temperature or the melting temperature. For example, the core element also becomes 14 brought to a forming temperature to the core element 14 , in particular together with the outer layers 16 and 18 to reshape. The forming temperature of the thermoplastic foam core depends on the polymer from which the core element 14 is made. To the core element 14 Forming, in particular thermoforming, to be, becomes the core element 14 for example, heated to the glass transition temperature or beyond.

3 shows a diagram illustrating different embodiments of a method for producing the sandwich component 10 , in particular according to the first embodiment. In a first embodiment of the method, for example, initially from the core element 14 and the cover layers 16 and 18 a sandwich semi-finished product 24 made, which is the core element 14 and the cover layers 16 and 18 includes. For example, the sandwich semi-finished product 24 through the sandwich composite 12 formed or the sandwich composite 12 is initially formed as a semi-finished product, wherein the sandwich semi-finished product 24 is produced for example in a first process step. In a second process step following the first process step, the sandwich semifinished product is produced 24 (Sandwich composite 12 ), for example, to the sandwich component 10 reshaped and / or folded.

In a second embodiment of the method, this becomes the cover layers 16 and 18 and the interposed core element 14 comprehensive sandwich component 10 in one Process step produced. This becomes the core element 14 with the cover layers 16 and 18 connected while at the same time the cover layers 16 and 18 and the interposed core element 14 be transformed. This means that a connection between the cover layers 16 and 18 and the core element 14 during a simultaneous deformation of the outer layers 16 and 18 and the core element 14 , in particular in a mold, takes place.

In a third embodiment of the method, the sandwich component, also referred to as sandwich composite component, is produced 10 made in two steps. At a first, in 3 S1 denotes the steps, the cover layers 16 and 18 and the core element functioning as the core layer 14 formed separately in a respective mold. In the second step S2, a connection is then made to the already formed and thus preformed core element 14 with the already formed and thus preformed cover layers 16 and 18 to the sandwich component 10 in a corresponding mold to connect and optionally further reshape.

• – Einbringen und Plastifizierung eines schaumbildenden thermoplastischen Kunststoffs in einen Extruder
• – Einbringen eines chemischen oder physikalischen Treibmittels in den plastifizierten Kunststoff
• – Homogenisierung des Treibmittels
• – Expansion des Treibmittels nach Verlassen einer Extrusionsdüse des Extruders unter Ausbildung einer zellulären Struktur.

The example formed as a plastic foam sheet core element 14 For example, it is produced by extrusion, ie by means of an extrusion process. The extrusion process can be divided into the following steps:

• - Introduction and plasticization of a foam-forming thermoplastic in an extruder
• - Introduce a chemical or physical blowing agent in the plasticized plastic
• - Homogenization of the blowing agent
• - Expansion of the blowing agent after leaving an extrusion die of the extruder to form a cellular structure.

Such plastic foam films may be made on the basis of different thermoplastics such as from the group of polyolefins or the polyester.

By perforating at least the core element described above 14 a perforation is made. Preferably, both the core element 14 as well as the cover layers 16 and 18 perforated, with the cover layers 16 and 18 simultaneously with the core element 14 can be perforated. Indicates the sandwich component 10 the marginal layers 20 and 22 on, it is preferably provided that the marginal layers 20 and 22 perforated, wherein it is preferably provided that the core element 14 simultaneously with the surface layers 20 and 22 and simultaneously with the cover layers 16 and 18 is perforated. The perforation of the sandwich component 10 is for example in 4 shown schematically and there with 26 designated. Out 4 is evident that the perforation 26 a plurality of holes 28 which are, for example, through-holes or through-channels which cover the outer layers 16 and 18 , the core element 14 and the marginal layers 20 and 22 penetrate. In particular, the holes penetrate 28 respective, in 4 With 30 designated cells of the core element 14 or its foam structure. Over the holes 28 is, for example, the respective interior of the respective cell 30 with the environment 32 of the sandwich component 10 fluidly connected, so between the cells 30 or between their interior and the environment 32 a pressure equalization can take place.

Overall, it can be seen that the core element 14 is designed as a closed-cell core with cell walls, which serves as core material in the sandwich composite 12 acts. Optionally, but not necessarily, the core material has the compact and closed edge layers 20 and 22 on. Through the perforation 26 become the optional marginal layers 20 and 22 and the cells 30 , in particular their cell walls, pierced, such cell walls are not present in an open-cell foam core.

The core element 14 is a centrally located core layer to a particularly high area moment of inertia of the sandwich component 10 to be able to realize. Through the perforation 26 can thermally induced distortions, which, for example, from changes in volume of the core element 14 result, be avoided. As a result, the sandwich component formed as a sandwich composite component 10 be used particularly advantageous as an interior component and thus in the interior of vehicles. The perforation 26 allows pressure equalization between the environment 32 and the cells 30 or the respective interior of the cells 30 in particular by the cell walls of the cells 30 be perforated.

Preferably, the core element 14 and optionally the surface layers 20 and 22 and the cover layers 16 and 18 perforated before this to the sandwich component 10 be transformed. 5 shows an example of a cell 30 of the core element 14 , For example, prevails in the cell 30 or inside the cell 30 a pressure p ₁ . For example, with a temperature increase ΔT _pos , there is an increase in the cell 30 prevailing pressure p ₁ . Is the cell 30 not perforated and not with the hole 28 provided so expands, for example, in the cell 30 contained air, causing it to distort the core element 14 can come. In other words, when using extruded thermoplastic Foamed cores with a closed cell configuration as core material in sandwich composite components without perforation of the foam core may, under the influence of temperature, result in a reexpansion of the core element 14 or the cells 30 come, especially if the perforation 26 is not provided. The post-expansion is characterized by an expansion of trapped air and / or propellant gases in the cells 30 caused.

While with open foam cells a fast pressure equalization by the gas exchange with the environment 32 can take place, this is largely prevented in closed-cell foams, since air and / or propellant gas is enclosed by surrounding cell walls. Pressure equalization is therefore only possible via diffusion processes through cell walls, whereby these diffusion processes take place only very slowly. An additional barrier can be the process-related, compact and also referred to as edge regions edge layers 20 and 22 be generated. The thickness of the surface layers 20 and 22 is often many times larger than the thickness of the cell walls, whereby a diffusion through the diffusion barrier forming edge layers 20 and 22 only very slowly or not at all possible.

Now even with closed-cell foam cores fast gas exchange with the environment 32 to allow, comes the perforation 26 of the sandwich component 10 and in particular the closed-cell foam core (core element 14 ) for use. Does it therefore come under the influence of temperature to the expansion of one in the cell 30 trapped air fraction and / or a propellant gas, can through the holes 28 a faster, in 5 through arrows 34 illustrated pressure equalization with the environment 32 respectively. The holes 28 are thus through the perforation 26 generated channels, via which a venting of the cells 30 can be done. This can cause excessive distortion of the sandwich component 10 be avoided.

The perforation 26 sees the penetration of the cell walls and the optionally available closed boundary layers 20 and 22 of the core element 14 in front. It should be through the perforation 26 Air channels in the core material or in the sandwich composite 12 be generated. Furthermore, in addition, the cover layers 16 and 18 perforated, if this at the perforation already on the core element 14 are arranged and the sandwich composite 12 form. Through the perforation 26 For example, a vertical penetration of the core material or of the sandwich composite system is to take place at individual points or points, wherein so many perforation points or perforation points are provided that the majority of the cell walls are penetrated in the core material. A vertical penetration means that the perforation 26 always perpendicular to the top layer level, as is particularly good 4 is recognizable.

The perforation 26 can be done mechanically by the core element 14 or the sandwich composite 12 pierced for example by means of needles. For this a flat board can be equipped with several needles. As a result, a perforation device can be formed by means of which the perforation 26 will be produced. In this case, the perforation device can form an independent tool or, in a heating phase before thermoforming, at least the core element 14 and the cover layers 16 and 18 integrated into the sandwich composite component.

An alternative to a mechanical penetration is the energetic penetration, for example by a laser beam, wherein the core material can be locally melted and decomposed. A corresponding perforation device can also be a holding device, to which one or more lasers are fastened, which are the core material or the sandwich composite 12 can penetrate vertically in appropriate places.

The perforation 26 at least the core element 14 or the sandwich composite 12 Overall, during various process steps in the manufacture of the sandwich component 10 respectively. Preferably, the perforation takes place 26 before a molding process, in the context of which sandwich composite 12 to the sandwich component 10 deformed, in particular thermoformed, is.

6 shows a diagram on the basis of which different points in time to which the perforation 26 is prepared are explained. For example, the closed-cell nuclear material, which is the compact surface layers 20 and 22 may perforate after its preparation in the extrusion process, in particular before the core element 14 with the cover layers 16 and 18 is connected. The perforation 26 can take place directly after the extrusion plant, wherein the core material also has a certain residual heat from the production of the core element 14 results. Alternatively, the core material 14 be perforated at a later time after cooling to room temperature in a separate process step.

Furthermore, it is conceivable that the closed-cell core material, with or without compact edge layers 20 and 22 , as well as the outer layers at the same time 16 and 18 in the production of sandwich semi-finished products 24 be perforated. The perforation 26 takes place for example during a Preparation of a respective connection of the core element 14 with the cover layers 16 and 18 , Alternatively, the semi-finished sandwich 24 in a subsequent step, that is after the core element 14 with the cover layers 16 and 18 was connected, perforated.

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 102014005008 A1 [0002]

Claims (6)

Method for producing at least one sandwich composite ( 12 ) with at least two outer layers ( 16 . 18 ) and at least one between the cover layers ( 16 . 18 ) core element ( 14 ) sandwich component ( 10 ), in particular for a motor vehicle, in which the core element ( 14 ) between the fiber-reinforced thermoplastic outer layers ( 16 . 18 ) of the sandwich composite and at least indirectly with the outer layers ( 16 . 18 ), characterized in that the core element ( 14 ) is produced from a thermoplastic foam as a closed-cell foam core and then perforated, wherein at least the sandwich composite ( 12 ) is heated during manufacture to a temperature which is above the melting temperature of the thermoplastic material of the outer layers ( 16 . 18 ), and then the heated sandwich composite ( 12 ) is formed in a cold mold and solidifies. A method according to claim 1, characterized in that in the perforation a plurality of at least a portion of the foam core penetrating holes ( 28 ), which are produced simultaneously. A method according to claim 1 or 2, characterized in that the foam core together with the outer layers ( 16 . 18 ) is perforated. Method according to one of the preceding claims, characterized in that between the respective outer layers ( 16 . 18 ) and the interior of the core element ( 14 ) respective closed edge layers ( 20 . 22 ) of the core element ( 14 ), which together with the core element ( 14 ) are perforated. Method according to one of the preceding claims, characterized in that the core element ( 14 ) is perforated before, during or after the core element ( 14 ) with the cover layers ( 16 . 18 ) is connected. Method according to one of the preceding claims, characterized in that the core element ( 14 ) is perforated after its production in still warm, resulting from the production state.

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