DE102016120703A1 - Method and device for producing three-dimensional molded parts from a fiber-reinforced thermoplastic strip - Google Patents

Abstract

The invention relates to a method and an apparatus for producing three-dimensional molded parts from a fiber-reinforced thermoplastic tape. In order to accomplish a load path-optimized construction of the three-dimensional molded part with minimum use of material and energy, the method according to the invention comprises the following steps: Step A: Provision of a pressing tool (2) with a channel (3) which is located between a die (2a) and a male part (2b) of the pressing tool (2) runs exactly or substantially in the plane of movement (B) of the pressing tool (2); Step B: arranging the thermoplastic strip (1) along the channel (3) in the opened pressing tool (2); Heating the thermoplastic strip (1), preferably until shortly below the melting temperature, step D: closing the pressing tool (2) to form the three-dimensional molded part from the heated thermoplastic strip (1) within the channel (3) of three-dimensional molded parts made of a fiber-reinforced thermoplastic strip (1), the pressing tool (2) having a channel (3) which between a die (2a) and a male part (2b) of the pressing tool (2) runs exactly or essentially in the plane of movement (B) of the pressing tool (2), the channel (3) preferably being the vector of the projected load path of the three-dimensional one to be formed Shaped part in the plane of movement (B) of the pressing tool (2).

Description

The invention relates to a method and an apparatus for producing three-dimensional molded parts from a fiber-reinforced thermoplastic tape.

• - Verstärkungsfasern sind in der Fläche gerichtet (vorwiegend unidirektionale Ausrichtung in 0° oder bidirektionale Ausrichtung in 0/90° bzw. -45/+45°) und folgen so nicht dem exakten Pfad der Last,
• - eine Schichtung mehrerer winklig zueinander gestapelter Organobleche trägt die Last in der Struktur ab, führt aber zur Überdimensionierung,
• - ein überwiegender Teil der verarbeiteten Verstärkungsfasern in der Leichtbaustruktur nimmt keine Lasten auf,
• - beim endkonturnahen Zuschnitt des lastpfadgerechten Lagenaufbaus fällt ein erheblicher Anteil (bis zu 10%) Abfall an,
• - sehr großer Energiebedarf beim Konsolidieren und beim Vorheizen der Preform durch hohe Verluste infolge Konvektion sowie Abstrahlung und
• - zusätzlicher Energiebedarf in der mobilen Anwendung durch Überdimensionierung.

In the mass production of lightweight structures mainly fiber reinforced plastics are used because their anisotropic properties allow a load path optimized design. In this case, semi-finished reinforcements (predominantly of glass, carbon or aramid) are fabricated into textile fabrics (predominantly scrim, fabric, knitted fabric) and impregnated with a thermoplastic matrix. These so-called organic sheet semi-finished products are layered according to a load path-optimized layer structure and cut to final contour. Subsequently, the edged layer structure is consolidated under pressure and temperature to form a preform. Such preforms are adapted in their fiber orientation and their surface formation to the lightweight structure to be produced and are heated before the final shaping process in a preheating station (mainly infrared, contact heating or heating furnace) until shortly before their melting temperature. The heated preform is then placed in the press tool and formed under pressure to the lightweight structure. The main technical problems underlying the invention are:

• - Reinforcing fibers are directed in the surface (mainly unidirectional alignment in 0 ° or bidirectional alignment in 0/90 ° or -45 / + 45 °) and thus do not follow the exact path of the load,
• a layering of a plurality of organoplates stacked at an angle to one another bears the load in the structure, but leads to overdimensioning,
• a majority of the processed reinforcing fibers in the lightweight structure do not take up loads,
• - the near-net shape cutting of the load path-compliant layer structure accounts for a significant proportion (up to 10%) waste,
• - Very high energy consumption during consolidation and preheating of the preform due to high losses due to convection and radiation and
• - Additional energy requirements in the mobile application due to oversizing.

In the field of continuous fiber reinforced thermoplastic structures, there is no technology that solves the above problems holistically.

The Automated Tape Laying (ATL) technology allows the unidirectional storage of continuous fiber reinforced thermoplastic tapes by means of laying robots on a tool mold. A preheating station (laser, infrared, contact heating) on the laying head heats the tape online until shortly before the melting temperature and places it under pressure on the mold. A blanking device in the laying head allows the endkontaunahe trimming of the tape. Row-wise and layer-wise, such flat structures are constructed whose fiber orientation is oriented along the load path. Corresponding to the problem described above with regard to the unidirectional alignment of the fibers, no exact alignment of the fibers along the load path takes place here as well. Only the near-net shape storage of reinforcement tapes causes no costly material waste.

At the Institute of Plastics Engineering of the University of Stuttgart, a technology was developed in 2011, which is described in the German patent application DE 10 2011 054 287 A1 is described and realized the preheating on the electrical resistance of CFRP organo sheets. In this case, unidirectional organic sheets are deposited in the mold and fixed in the edge region by means of electrode clamps and energized. After the organic sheet is heated by resistance heating, the mold closes, thus forming the lightweight structure. Since the technology is based on organo sheets whose reinforcing fibers are oriented in the surface, a load path-oriented position of the fibers is also not given here.

In the production of high-performance thermoset composite structures, fibers are deposited using the tailored-fiber-placement process in a manner that meets the requirements of the adhesive technology on a textile substrate. The deposited fiber follows exactly the path of the load. The preform thus produced is then placed in a mold and impregnated with epoxy resin. Since the resin must cure after impregnation, long cycle times are required, which means that no large-scale production can be realized.

The invention is based on the object to provide a method and apparatus for resource-optimized production of three-dimensional moldings to accomplish a load path optimized design of the three-dimensional molding with minimal use of materials and energy.

• - Schritt A: Bereitstellen eines Presswerkzeugs mit einem Kanal, welcher zwischen einer Matrize und einer Patrize des Presswerkzeugs exakt oder im Wesentlichen in der Bewegungsebene des Presswerkzeugs verläuft;
• - Schritt B: Anordnen des Thermoplastbandes entlang des Kanals im geöffneten Presswerkzeug;
• - Schritt C: Erwärmen des Thermoplastbandes, vorzugsweise bis kurz unter die Schmelztemperatur;
• - Schritt D: Schließen des Presswerkzeugs zur Formung des dreidimensionalen Formteils aus dem erwärmten Thermoplastband innerhalb des Kanals.

The object of the invention is achieved by a method for the production of three-dimensional molded parts from a fiber-reinforced thermoplastic tape, comprising the steps:

• - Step A: Providing a pressing tool with a channel which runs between a die and a male of the pressing tool exactly or substantially in the plane of movement of the pressing tool;
• Step B: placing the thermoplastic tape along the channel in the open die;
• - Step C: heating the thermoplastic tape, preferably to just below the melting temperature;
• Step D: closing the pressing tool to form the three-dimensional molding from the heated thermoplastic tape within the channel.

The inventive method allows for the first time the consolidation of a fiber-reinforced thermoplastic tape, in particular a continuous fiber reinforced Organotapes, along the vector of the real acting load path in a 3D molded part. Due to the construction of the 3D molded part on the final contour, on the one hand, there is no waste during final trimming of the structure and, on the other hand, cost-intensive materials (CFRP organotapes) are only used where fiber reinforcement is necessary. The structure structure can thus be optimized adapted to the acting loads in the component, which precludes a previously required oversizing. This allows the development of structures in which the maximum lightweight potential is exploited on the basis of fiber-reinforced thermoplastic tapes, in particular of thermoplastic continuous fiber-reinforced organotapes. This results in a high degree of resource efficiency (energy and material) in the mobile end use due to maximum weight savings.

The technical field of application of the present invention is the production of complex lightweight structures in the automotive, aircraft and mechanical engineering, in particular in the production of force introduction and force dissipation elements or in the structure of structural structures.

terms and definitions

Thermoplastic tape

The term thermoplastic tape refers to a fiber-reinforced plastic tape having a thermoplastic matrix or a matrix of a bi-stage resin which behaves thermoplastic and thermosetting up to a limit temperature, the tape preferably having a constant cross section over its entire length. In the undeformed initial state, the cross section of the thermoplastic strip is referred to as the starting cross section. The cross section of the molded part produced from the thermoplastic strip, however, is referred to as the end cross section. The starting cross-section and the end cross-section are preferably the same in terms of area, but differ with regard to the cross-sectional profile. The cross-sectional profile of the starting cross section is preferably flat, preferably rectangular, wherein the longer side of the cross section, for example, at least 5 times larger than the shorter side of the cross section. As a result, the thermoplastic band is bendable in particular over the shorter side of the cross section. The thermoplastic band is preferably reinforced with continuous fibers of glass, aramid or carbon, which preferably extend exactly or substantially in the longitudinal direction of the band. It is also within the scope of the invention that the fibers form a surface textile in the form of a woven, laid or knitted fabric, wherein preferably the main direction of the fibers extends in the longitudinal direction of the band.

press tool

The pressing tool consists of at least one die ("mother shape"), which forms the negative of the outer mold for the three-dimensional molded part to be produced, and at least one male mold, which forms the corresponding counter-mold. If necessary, the die is also called lower mold or lower part, while the male mold can also be referred to as a punch or upper part. The male and female molds together define the channel for forming the three-dimensional molding and are movable in a direction of movement relative to each other, so that the channel extends in the plane of movement of the pressing tool.

Further advantageous developments of the invention are subject matter of the subclaims.

It may be advantageous if the channel of the pressing tool provided in step A images the vector of the projected load path of the three-dimensional molded part to be formed in the plane of movement of the pressing tool. This embodiment particularly favors the alignment of the fiber path along the vector of the real load path in the 3D molded part, in particular if the thermoplastic strip is reinforced with endless fibers and / or the continuous fibers extend in the longitudinal direction of the thermoplastic strip.

It may be helpful if the thermoplastic tape is placed in step B in the die of the press tool along the channel so that it completely fills the length and / or width of the channel. As a result, a particularly contour and shape-appropriate compression deformation of the thermoplastic tape is possible.

It may be useful if the thermoplastic tape is fed in step B in the direction of extension of the channel from one end of the channel to the other end of the channel, preferably from a roll, preferably automatically. Such process steps can be easily automated. The leadership of the thermoplastic tape in the direction of extent through the channel allows a particularly accurate positioning of the thermoplastic tape for the subsequent heating and compression molding, so that a particularly contour and shape-appropriate press processing of the thermoplastic tape can be done.

It may prove practical if the thermoplastic tape is cut to length in step C, connected to electrodes and heated internally by resistance heating, and / or heated from the outside by infrared radiators or hot air or the like. The intrinsic electrical conductivity of a carbon fiber reinforced thermoplastic tape or a thermoplastic tape with electrically conductive particles in the thermoplastic matrix allows its in situ heating by resistance heating. As a result, the thermoplastic tape heats up from the inside, which, in contrast to conventional heating systems (infrared, heating oven, microwave, etc.) significantly minimizes the waste heat from convection or radiation. This increases the efficiency during heating and reduces the necessary energy consumption. Due to the in-situ heating of the thermoplastic strip and its tool-integral consolidation on the final contour, a significant shortening of process times is achieved because physically separate active sites do not exist and process steps for the handling of the thermoplastic strip are eliminated.

However, it can also be advantageous if the thermoplastic tape in step A and / or in step B and / or in step C has an exactly or substantially rectangular starting cross section, wherein the starting cross section is preferably constant over the length of the thermoplastic tape. As a result, a homogeneous pressure distribution in the 3D molded part can be realized when pressing on the final contour.

It may be useful if the starting cross-section of the thermoplastic strip is deformed in step D, preferably convex and / or concave, preferably convex to the die and / or concave to the male of the pressing tool, the end cross-section of the three-dimensional molding particularly preferred with respect to Profile and / or the surface over at least a portion of its length or over its entire length is constant. In this case, only one or more sections of the thermoplastic tape can be deformed or arched or the deformation or curvature can extend over the entire length of the thermoplastic tape. Such a shaping of the end cross-section, e.g. in U-shape gives the thermoplastic tape or the resulting 3D molded part a particularly high stability.

It may be convenient if the length and / or width of the thermoplastic tape is matched to the length and / or width of the channel. Thereby, the thermoplastic tape can be laid in only one layer along the channel to completely fill the channel. In this case, the material usage of the thermoplastic tape is particularly efficient.

It may be advantageous if the thickness of the thermoplastic tape is in the range of 0.01 to 2 mm, preferably in the range of 0.2 to 1.5 mm, preferably in the range of 0.8 to 1.2 mm. Such a thermoplastic tape is sufficiently stable and flexible for the production of lightweight structures in automotive, aircraft and mechanical engineering, in particular force introduction and force dissipation elements or structures, so that the thermoplastic tape can be subjected to strong deformations in the context of compression molding.

It may prove useful if the width of the thermoplastic tape in the range of 5 to 100 mm, preferably in the range of 20 to 80 mm, preferably in the range of 30 to 80 mm. Such a thermoplastic tape covers the expected dimensions of force introduction and force dissipation elements or structures structures in automotive, aircraft and mechanical engineering sufficient.

It may be helpful if the thermoplastic band is reinforced with continuous fibers of glass and / or aramid and / or carbon, wherein the continuous fibers preferably run exactly or substantially in the longitudinal direction of the thermoplastic band. Such a thermoplastic tape is field-tested and available at low cost. The course of the continuous fibers in the longitudinal direction of the thermoplastic strip can favor their orientation along the vector of the real-acting load path in the 3D molded part to a particular degree.

A further independent aspect of the present invention relates to a pressing tool for producing three-dimensional molded parts from a fiber-reinforced thermoplastic tape, preferably according to the method according to one of the preceding embodiments, wherein the pressing tool has a channel which is exactly or substantially between a die and a male of the pressing tool in the plane of movement of the pressing tool, wherein the channel preferably the vector of the projected load path of forming three-dimensional molding in the plane of movement of the pressing tool images.

Further advantageous developments of the invention will become apparent from combinations of the features disclosed in the description as well as the claims and the drawings.

list of figures

• 1 shows in the views (a) to (c) schematically the steps A to C of the inventive method.
• 2 shows in the views (a) and (b) schematically the step D of the inventive method before and after the closing of the pressing tool, and in view (c) the molded part produced by the inventive method.

Detailed Description of the Preferred Embodiment

The preferred embodiment of the invention will be described below in detail with reference to the figures.

In a from die or lower mold or lower part 2a and male or stamp, upper or upper part 2 B existing pressing tool 2 is along a narrow channel 3 a continuous fiber reinforced thermoplastic tape (Organotape) 1 from a roll 5 through an end 3a of the canal 3 fed until the thermoplastic tape 1 the other end 3b of the canal 3 reached. Due to its thin design (up to approx. 1 mm) is the thermoplastic tape 1 in the plane perpendicular to the thickness direction flexible and can curved channels 3 in the pressing tool 2 fill out. Only perpendicular to the width alignment is the thermoplastic tape 1 rigid, since the width can have a few centimeters. This makes a channel 3 in the pressing tool 2 required, which preferably forms flat. The course of the channel 3 forms in the movement plane B of the pressing tool 2 or in the tool level of the punch 2 B the vector of the projected path of the load, in the lightweight structure to be formed 6 runs.

After the thermoplastic tape 1 the channel 3 filled, is the thermoplastic tape 1 tailored and at both ends 3a . 3b of the canal 3 with electrodes 4 fixed. About resistance heating is the thermoplastic tape 1 heated to just below the melting temperature. The resistance heating of the thermoplastic tape 1 represents in the process according to the invention an optimal heating system, but also by conventional infrared radiators or the like in the channel 3 can be realized.

Then moves perpendicular to the channel 3 a stamp 2 B , which is channel filling, into the tool die 2a and push the heated thermoplastic band 1 into the subform 2 , In this case, the geometry forms the lower mold 2a the vector of the projected path of the load in the structure to be formed 6 perpendicular to the tool normal. Because the thermoplastic tape 1 in the undeformed initial state in its length a constant output cross-section AQ has, the 3D molded part in its length and constant end cross section EQ have, in order to realize a homogeneous pressure distribution in the 3D molded part 6 during pressing on the final contour. After solidification of the thermoplastic tape 1 opens the tool 2 and the final contoured structure 6 is taken.

The 3D molded part 6 produced by the process according to the invention has an endless fiber reinforcement with a thermoplastic matrix, the structural or structurally integrated thermoplastic strip 1 a complex 3D structure with a closed and high-quality surface.

LIST OF REFERENCE NUMBERS

1

Thermoplastic tape

2

press tool

2a

die

2 B

patritze

3

channel

3a

First end of the channel

3b

Second end of the canal

4

electrodes

5

Roll of thermoplastic tape

6

Three-dimensional (3D) molded part or (lightweight) structure

AQ

Output cross-section of the thermoplastic tape

B

Movement level of the pressing tool

EQ

End cross-section of the three-dimensional molding

L

Longitudinal direction of the thermoplastic tape

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 102011054287 A1 [0005]

Claims (12)

Method for producing three-dimensional molded parts from a fiber-reinforced thermoplastic strip (1), comprising the steps: a. Step A: providing a pressing tool (2) with a channel (3) which extends between a die (2a) and a male part (2b) of the pressing tool (2) exactly or substantially in the plane of movement (B) of the pressing tool (2) ; b. Step B: arranging the thermoplastic strip (1) along the channel (3) in the opened pressing tool (2); c. Step C: Heating the thermoplastic strip (1), preferably to just below the melting temperature; d. Step D: closing the pressing tool (2) for forming the three-dimensional molding from the heated thermoplastic strip (1) within the channel (3). Method according to Claim 1 , characterized in that the channel (3) of the pressing tool (2) provided in step A images the vector of the projected load path of the three-dimensional molded part to be formed in the plane of movement (B) of the pressing tool (2). Method according to one of the preceding claims, characterized in that the thermoplastic tape (1) in step B in the die (2a) of the pressing tool (2) along the channel (3) is arranged so that it is the length and / or width of the channel (3) completely completed. Method according to one of the preceding claims, characterized in that the thermoplastic tape (1) in step B in the extension direction of the channel (3) from one end (3a) of the channel (3) supplied to the other end (3b) of the channel (3) is, preferably by a roller (5), preferably automatically. Method according to one of the preceding claims, characterized in that the thermoplastic tape (1) cut to length in step C, connected to electrodes (4) and heated by resistance heating from the inside, and / or heated by infrared radiators or hot air or the like from the outside. Method according to one of the preceding claims, characterized in that the thermoplastic strip (1) in step A and / or in step B and / or in step C has an exactly or substantially rectangular output cross-section (AQ), wherein the output cross-section (AQ) preferably over the length of the thermoplastic strip (1) is constant. Method according to one of the preceding claims, characterized in that the starting cross-section (AQ) of the thermoplastic strip (1) is deformed in step D, preferably curved convexly and / or concavely, preferably convex to the die (2a) and / or concave to the male ( 2b) of the pressing tool (2), wherein the end cross-section (EQ) of the three-dimensional molded part is particularly preferably constant with respect to the profile and / or the surface over at least part of its length or over its entire length. Method according to one of the preceding claims, characterized in that the length and / or width of the thermoplastic strip (1) is adapted to the length and / or width of the channel (3). Method according to one of the preceding claims, characterized in that the thickness of the thermoplastic strip (1) in the range of 0.01 to 2 mm, preferably in the range of 0.2 to 1.5 mm, preferably in the range of 0.8 to 1 , 2 mm. Method according to one of the preceding claims, characterized in that the width of the thermoplastic strip (1) in the range of 5 to 100 mm, preferably in the range of 20 to 80 mm, preferably in the range of 30 to 80 mm. Method according to one of the preceding claims, characterized in that the thermoplastic strip (1) is reinforced with continuous fibers of glass and / or aramid and / or carbon, wherein the continuous fibers preferably extend exactly or substantially in the longitudinal direction (L) of the thermoplastic strip (1) , Pressing tool for producing three-dimensional molded parts from a fiber-reinforced thermoplastic strip (1), preferably according to the method according to one of the preceding claims, characterized in that the pressing tool (2) has a channel (3) which is located between a die (2a) and a male part (2b) of the pressing tool (2) runs exactly or substantially in the plane of movement (B) of the pressing tool (2), the channel (3) preferably the vector of the projected load path of the three-dimensional molded part to be formed in the plane of movement (B) of the pressing tool (2) depicts.

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