DE102018102061B3 - Extrusion apparatus and method for producing carbon fiber reinforced plastic semi-finished products - Google Patents

Abstract

A description is given of an extrusion device (100) for the production of carbon-fiber-reinforced plastic semi-finished products, comprising a housing (1) which has an entrance area (2) and an exit area (3), characterized in that in the housing (1) a device for producing a In addition, a method for the production of carbon fiber reinforced plastic semi-finished products is described, wherein the following steps are carried out successively: a) providing an inventive extrusion device (100) and a composite compound (10) b) initiation of the composite (C) generating an electric field; d) discharging the resulting semi-finished plastic product via the exit region (3) of the housing (1) for further processing ,

Description

The present invention relates to an extrusion apparatus and a method for producing carbon fiber reinforced plastic semi-finished products.

To improve the mechanical properties of extrusion-produced plastic semi-finished products, the compounds used are often enriched with carbon fibers. However, the orientation of the introduced fibers is currently influenced solely by the flow processes resulting from the extrusion, which results in an indefinite distribution of the fibers. This leads to irregularities in the mechanical properties of extruded components. In addition, further potentials of the carbon fibers, such as the electrical conductivity and the enormous thermal conductivity, can not be exploited.

Currently used extrusion systems determine the flow processes of the plasticized fiber-reinforced composite compound by additionally introduced flow channels, which specifically influence the fiber orientation. However, the fibers can be oriented parallel to the profile plane or during pipe extrusion in a helix arrangement parallel to the pipe axis. This also results in an undefined orientation of the fibers due to the different flow velocities in the edge regions and in the center of the flow of the plasticized composite compounds, whereby a consistent component quality can not be ensured.

The publication "Method for manufacturing plastic tubes for heat exchangers containing graphite fillers" (DOI: http://dx.doi.org/10.4421/PAPDEOTT002961) discloses the production of highly heat-conductive plastic pipes by extrusion, wherein the orientation of the carbon fibers perpendicular to the flow direction through the use of special fillers and the geometry of the flow channel in the extrusion die is achieved.

The object of the present invention is therefore to overcome the disadvantages of the prior art and to provide a device by means of which the orientation of carbon fibers in plastic semifinished products can be influenced in a targeted manner.

The object is achieved by the provision of an extrusion device for the production of carbon fiber reinforced plastic semi-finished products according to the features of the main claim. Advantageous embodiments of the device according to the invention are characterized in the dependent subclaims.

The subject of the present invention is an extrusion device 100 for the production of carbon fiber reinforced plastic semi-finished products, consisting of a housing 1 which is an entrance area 2 and an exit area 3 wherein, in the housing 1 a device for generating an electric field 4 is arranged.

Particularly preferred is an extrusion device according to the invention 100 , wherein the carbon fiber reinforced plastic semi-finished products are tubular or planar.

Preferred is an extrusion device according to the invention 100 wherein the device for generating an electric field 4 two electrodes 40 . 41 having.

Also preferred is an extrusion device according to the invention 100 , where the electrodes 40 . 41 are formed annular or planar.

Particularly preferred is an extrusion device according to the invention 100 , where the electrodes 40 . 41 are arranged concentrically or parallel to each other and an annular or planar gap 42 between the electrodes 40 . 41 form.

In addition, an extrusion device according to the invention 100 in which one electrode is the positive pole and the other electrode is the negative pole.

Further, an extrusion device according to the invention 100 preferred, wherein the device for generating an electric field 4 in the exit area 3 of the housing 1 is arranged.

Preferred is an extrusion device according to the invention 100 , wherein in the housing 1 continue a repressive thorn 5 is arranged.

Particularly preferred is an extrusion device according to the invention 100 , wherein the displacement mandrel 5 is formed rotationally symmetrical and to the housing 1 is arranged so spaced, so that between the housing interior and the displacement mandrel 5 an annular gap 6 is trained.

In particular, an extrusion device 100 preferred, wherein the displacement mandrel 5 from the entrance area 2 to the exit area 3 extends.

In addition, an extrusion device according to the invention 100 preferred, wherein the housing 1 furthermore a mandrel holding tool 8th having, which partly within the displacement mandrel 5 is arranged.

Furthermore, an extrusion device according to the invention is preferred, wherein the mandrel holding tool 8th an exit 9 which, within the displacement mandrel 5 is arranged and up to the exit area 3 of the housing 1 extends.

Also preferred is an extrusion device according to the invention 100 , where the case 1 at least one temperature sensor 7 having.

1. a) Bereitstellung einer erfindungsgemäßen Extrusionsvorrichtung 100 und eines Verbund-Compounds 10;
2. b) Einleitung des Verbund-Compounds 10 über den Eingangsbereich 2 des Gehäuses 1 in die Extrusionsvorrichtung 100,
3. c) Erzeugung eines elektrischen Feldes;
4. d) Austragen des entstandenen Kunststoffhalbzeugs über den Ausgangsbereich 3 des Gehäuses 1 zur weiteren Verarbeitung.

A further subject of the present invention is also a process for the production of carbon fiber-reinforced plastic semi-finished products, wherein the following steps are carried out successively:

1. a) providing an extrusion device according to the invention 100 and a compound compound 10 ;
2. b) Initiation of the compound compound 10 over the entrance area 2 of the housing 1 in the extrusion device 100 .
3. c) generating an electric field;
4. d) discharging the resulting plastic semi-finished product over the exit area 3 of the housing 1 for further processing.

Preferred is a method according to the invention, wherein the composite compound 10 after step b) by means of a displacement mandrel 5 transformed into an annular gap flow.

In particular, a method according to the invention is preferred, wherein the melt of the composite compound 10 by means of at least one temperature sensor 7 homogeneously tempered.

Furthermore, a method according to the invention is preferred, wherein before step d) supporting air 11 in the extrusion device 100 introduces.

For the purposes of the present invention, tubular plastic semifinished products are preferably CFRP pipes.

For the purposes of the present invention, the housing is an at least partially closed container, whereby the flow in the extrusion device is influenced.

Furthermore, for the purposes of the present invention, a voltage of at least 50 V is applied to the electrodes of the device for generating an electric field. The person skilled in the art knows that the field strength of the electric field generated depends on the applied current intensity. Advantageously, the orientation of the carbon fibers within the extrusion apparatus according to the invention can be controlled by means of the field strength. The skilled person can determine the appropriate voltage and field strength by a few simple experiments, so as to effect the desired orientation of the carbon fibers.

Furthermore, carbon fiber-reinforced plastic semi-finished products in the context of the present invention consist of a composite compound. The composite compound consists of high-modulus carbon fibers, which are fixed by a thermoplastic-based plastic matrix in a granulated compound. In particular, plastics based on polytetrafluoroethylene (PTFE) are used as the matrix base material because of their thermal and chemical properties.

An advantage of the use of high-modulus carbon fibers is that in addition to high thermal conductivity and high specific strength and stiffness properties, good electrical conductivity in the fiber direction furthermore has a negative thermal expansion. The highest thermal conductivities at 1200 W / m * K have so-called "ultra high modulus" (UHM) special carbon fibers.

In contrast to metallic materials in which the heat conduction behaves isotropically, the thermal conductivity of the carbon fibers is generally strongly anisotropic and highest in the fiber direction. UHM fibers are made from polyacrylonitrile (50%) or pitch (> 80%) due to the high carbon yield. The high thermal conductivity results from a special graphitization during the manufacturing process at temperatures up to 3000 ° C. As a result, the preorientation of the graphite planes in the direction of the fiber axis is increased, so that a strongly anisotropic material behavior is produced by means of the covalent crystal bonds. As a result, the heat conduction, depending on the degree of anisotropy transverse to the fiber direction max. 17 W / m * K. In combination, the thermal conductivity is reduced depending on the fiber content. For example, in a unidirectional laminate construction with 60% fiber volume content and 40% plastic matrix, a thermal conductivity in the fiber direction of more than 750 W / m * K can be achieved.

An advantage of the extrusion apparatus according to the invention and the method according to the invention carried out by the extrusion apparatus according to the invention is that an electric field is induced by applying an electrical voltage unit in the extrusion device, can be aligned defined on the field lines, the carbon fibers over the path of least resistance. This allows the specific Strength and stiffness properties targeted at places of highest force application as well as the high electrical conductivity in printed circuit boards and the enormous thermal conductivity of carbon fibers are exploited by a defined orientation with a high normal content to the profile plane or tube axis.

It is furthermore advantageous that by means of the extrusion device according to the invention, the extrusion systems known in the prior art can be improved in a simple manner.

It is also advantageous that the carbon fiber reinforced tubular semi-finished plastics produced by means of the extrusion apparatus according to the invention and by means of the method according to the invention can be used in a wide range of applications. Possible areas of application include the manufacturing industry and heavy industry, for example mechanical engineering, power plant technology, thermotechnology, automotive engineering, electrical engineering, chemical products). Particularly in the field of thermotechnology, the targeted orientation of highly heat-conductive carbon fibers can be used for efficient heat recovery and cooling systems, which are in high demand for the years 2020 and 2030 due to the third EU core target "Climate change and sustainable energy management".

• 1 eine Längsschnittansicht einer Ausführungsform der erfindungsgemäßen Extrusionsvorrichtung;
• 2 eine perspektivische Darstellung eines Teilschnitts durch die Ausführungsform der 1;
• 3 eine Längsschnittansicht einer Extrusionsvorrichtung;
• 4 eine perspektivische Darstellung eines Teilschnitts eines CFK-Rohres;
• 5 eine perspektivische Darstellung durch die Ausführungsform der 4; und
• 6 die Wärmeleitfähigkeit von Kohlenstofffasern, Kunststoffen, Keramik und Metallen im Vergleich.

The present invention will be explained in more detail with the accompanying drawings. It shows:

• 1 a longitudinal sectional view of an embodiment of the extrusion device according to the invention;
• 2 a perspective view of a partial section through the embodiment of 1 ;
• 3 a longitudinal sectional view of an extrusion device;
• 4 a perspective view of a partial section of a CFRP pipe;
• 5 a perspective view of the embodiment of the 4 ; and
• 6 the thermal conductivity of carbon fibers, plastics, ceramics and metals in comparison.

The invention will now be described in detail and with reference to the accompanying drawings.

1 shows a longitudinal sectional view of an embodiment of the extrusion device according to the invention 100 , The extrusion device 100 consists of a housing 1 which is an entrance area 2 and an exit area 3 includes. Accordingly, the interior of the housing 1 the extrusion device 100 at least partially isolated from the environment.

In the interior of the housing 1 is a repressive thorn 5 arranged. The Displacement Spike 5 extends from the entrance area 2 to the exit area 3 of the housing 1 , Together with the interior of the housing forms the displacement mandrel 5 an annular gap 6 out. About the entrance area 2 of the housing 1 is in the extrusion device 100 a compound compound 10 brought in. The compound compound 10 consists of high-modulus carbon fibers, preferably UHM carbon fibers, which are fixed by a thermoplastic-based plastic matrix in a granulated compound. In particular, plastics based on polytetrafluoroethylene (PTFE) are used as the matrix base material on the basis of their thermal and chemical properties.

By means of the displacement mandrel 5 becomes the introduced composite compound 10 in the annular gap 6 initiated. Thus, the composite compound 10 formed into an annular gap flow and over the annular gap 6 targeted in a gap 42 transferred between two electrodes 40 . 41 a device for generating an electric field 4 is trained.

The device for generating an electric field 4 is preferably in the exit area 3 of the housing 1 arranged. The device for generating an electric field 4 has two electrodes 40 . 41 on, where one electrode is the positive pole and the other electrode is the negative pole. By applying an electrical voltage, an electric field is induced, at whose field line the compound in the compound 10 contained carbon fibers via the path of least resistance with a high normal proportion to the axis of the extrusion device 100 align. Preferably, the carbon fibers are directed from the positive pole to the negative pole.

Furthermore, the housing has 1 a spike holding tool 8th which is at least partially within the displacement mandrel 5 is arranged. The spine holding tool 8th indicates an exit 9 on, which is inside the repressor 5 is arranged. The exit 9 extends to the exit area 3 of the housing 1 , About the spine holding tool 8th becomes support air 11 in the extrusion device 100 initiated and about the exit 9 to the exit area 3 of the housing 1 guided. The supporting air ensures a stabilization of the inner contour of the extrusion device 100 produced carbon fiber reinforced plastic semi-finished product.

Furthermore, in the housing 1 the extrusion device 100 at least one temperature sensor 7 arranged. In the in 1 embodiment shown are two temperature sensors 7 shown, with a temperature sensor 7 in the entrance area 2 and the other temperature sensor 7 in the exit region of the extrusion device 100 is arranged. The temperature sensors 7 determine the homogeneous temperature control of the melt of the compound compound 10 ,

2 shows a perspective view of a partial section through the embodiment of 1 , In this view is shown that the housing 1 the extrusion device 100 is preferably designed as a tube. Furthermore, in the present embodiment, the displacement mandrel 5 formed rotationally symmetrical. Furthermore, it is shown that the two electrodes 40 . 41 the device for generating an electric field are tubular. The electrodes 40 . 41 are arranged concentrically with each other, whereby the electrodes 40 . 41 an annular gap 42 form. The gap 42 is connected to the annular gap (not shown) of the extrusion device, which is between the displacement mandrel 5 and the housing interior is formed. In this view, it is shown that the internal electrode 41 on the outside of the displacement mandrel 5 is arranged and the outer electrode 40 on the inside of the case 1 is arranged. Preferably, the internal electrode 41 the positive pole and the outside electrode 40 the negative pole. In this case, once an electrical voltage is applied, the carbon fibers align from the plus pole to the minus pole along the field line.

3 shows a longitudinal section of an extrusion device, which is integrated within an extrusion process. Before the extrusion device according to the invention 100 is an extruder 101 with a twin screw 1001 arranged. The extruder 101 has a variety of heating elements 1003 as well as a funnel 1002 , about the carbon fibers 1004 in the extruder 101 be introduced. In the twin screw 1001 become the carbon fibers 1004 with a present matrix material to the composite compound 10 combined. The compound compound produced in the extruder 10 is then, as described above, in the inventive extrusion device 100 introduced to align the carbon fibers on the electric field. Subsequently, the viscous plastic semi-finished product over the outlet region of the housing of the extrusion device 101 in a calibration unit 102 discharged. In the calibration unit 102 the outer diameter of the plastic semi-finished product is determined. Thus, through a coupled analysis of the electrical flow field of the computational fluid dynamics and the thermal-electrical behavior, the properties of the plasticized composite compound 10 determined during the extrusion process and dimensioned the extrusion device. In order to produce particularly high-quality plastic semi-finished products, the extrusion device according to the invention 100 a process monitoring (internal cavity pressure, temperature, voltage), a homogeneous heat distribution (arrangement of heating elements) as well as a corresponding regulation for the safe process control as well as a control of the tempering and tension on.

4 shows a schematic representation of a partial section of a CFRP tube, which can be produced by means of the extrusion apparatus according to the invention and the inventive method. By means of the extrusion device according to the invention, the orientation of the highly heat-conductive carbon fibers with a high normal content within the composite compound (not shown) can be aligned specifically along the tube axis. Thus, thin-walled (t = 1.5 mm) CFRP tubes can be produced, which can be used in highly efficient tube heat transfer systems.

In 5 is a perspective view of the CFRP tube of 4 shown. In this illustration, it is once again clear how the orientation of the carbon fibers (thin black rods) with a high normal content are aligned along the tube axis by means of the extrusion device according to the invention.

6 shows the comparison of the thermal conductivity (W / m * K) of carbon fibers, plastics, ceramics and metals. From this comparison, it becomes clear that plastics such as PVDF or PP can conduct virtually no heat, whereas metals such as aluminum and copper can indeed conduct heat. Aluminum has a thermal conductivity of 235 W / m * K, and copper has a heat conduction nearly twice as high as that of aluminum. However, the highest thermal conductivity at 1200 W / m * K is due to the UHM special carbon fibers, whose heat conduction is 3 times higher than that of pure copper and 2700 times higher compared to PP and PTFE.

By means of the extrusion apparatus according to the invention or the method according to the invention can thus be a highly efficient and chemically resistant tube heat transfer system of thin-walled (t = <1.5 mm), highly thermally conductive CFRP pipes, through the targeted use of high anisotropic heat conduction of UHM carbon fibers (p = 2.2 g / cm ³ ; λ = 1200 W / m * K). By a special orientation of the fibers with a high normal content to the tube axis, the enormous thermal conductivity of the carbon fiber reinforced plastic (p = 2.0 g / cm ³ , λ = 750 W / m * K) in the fiber direction and high strength is utilized and stiffness of the tubes achieved. This can reduce the heat transfer area. This results in a considerable reduction in production time and manufacturing costs. In addition, the use of UHM fibers due to their negative coefficient of thermal expansion (<-0.1 * 10 ^-6 / K) minimizes the thermal expansion of the pipe, which can be substituted costly strain absorption systems and the risk of pipe buckling and leakage can be significantly reduced. In addition, there is a tremendous reduction in system weight as well as a significant resistance to chemical and media stresses through the use of a thermoplastic matrix. For this purpose, plastics based on polytetrafluoroethylene (PTFE) are taken into account as the matrix base material, which have already been used for the production of tubular heat exchangers in terms of their thermal and chemical properties for several years.

LIST OF REFERENCE NUMBERS

1

casing

2

entrance area

3

output range

4

Device for generating an electric field

40

electrode

41

electrode

42

gap

5

displacement Dorn

6

annular gap

7

temperature sensors

8th

Dorn holding tool

9

exit

10

Composite compound

11

support air

100

extrusion device

101

extruder

1001

twin screw

1002

funnel

1003

heating element

1004

Carbon fiber

102

calibration

Claims (17)

Extrusion device (100) for the production of carbon fiber-reinforced plastic semi-finished products, comprising a housing (1) having an entrance area (2) and an exit area (3), characterized in that in the housing (1) an apparatus for generating an electric field (1) 4) is arranged. Extrusion device (100), according to Claim 1 , characterized in that the carbon fiber reinforced plastic semi-finished products are tubular or planar. Extrusion device (100), according to Claim 1 or 2 , characterized in that the device for generating an electric field (4) comprises two electrodes (40, 41). Extrusion device (100), according to Claim 3 , characterized in that the electrodes (40, 41) are annular or planar. Extrusion device (100), according to Claim 4 , characterized in that the electrodes (40, 41) are arranged concentrically or parallel to one another and form an annular or planar gap (42) between the electrodes (40, 41). Extrusion device (100), according to one of Claims 3 to 5 , characterized in that one electrode is the positive pole and the other electrode is the negative pole. Extrusion device (100) according to one of the preceding claims, characterized in that the device for generating an electric field (4) in the output region (3) of the housing (1) is arranged. Extrusion device (100) according to one of the preceding claims, characterized in that in the housing (1) further comprises a displacement mandrel (5) is arranged. Extrusion device (100), according to Claim 8 , characterized in that the displacement mandrel (5) is rotationally symmetrical and is arranged spaced from the housing (1) such that an annular gap (6) is formed between the housing interior and the displacement mandrel (5). Extrusion device (100), according to Claim 8 or 9 , characterized in that the displacement mandrel (5) extends from the input area (2) to the exit area (3). Extrusion device (100), according to one of Claims 8 to 10 , characterized in that the housing (1) further comprises a mandrel holding tool (8) which is partially disposed within the displacement mandrel (5). Extrusion device (100), according to Claim 11 , characterized in that the mandrel holding tool (8) has an outlet (9) which is disposed within the displacement mandrel (5) and extends to the exit region (3) of the housing (1). Extrusion device (100) according to one of the preceding claims, characterized in that the housing (1) further comprises at least one temperature sensor (7). Process for the production of carbon fiber reinforced plastic semi-finished products, wherein the following steps are carried out successively: a) Provision of an extrusion device (100) according to one of the Claims 1 to 13 , and a composite compound (10); b) introducing the composite compound (10) into the extrusion device (100) via the entrance area (2) of the housing (1), c) generating an electric field; d) discharging the resulting plastic semi-finished product over the exit region (3) of the housing (1) for further processing. Method according to Claim 14 , characterized in that one transforms the composite compound (10) after step b) by means of a displacement mandrel (5) in an annular gap flow. Method according to Claim 14 or 15 , characterized in that the melt of the composite compound (10) by means of at least one temperature sensor (7) homogeneously tempered. Method according to one of Claims 14 to 16 , characterized in that before step d) supporting air (11) in the extrusion device (100) introduces.

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