DE102008005970A1 - Fiber-reinforced composite components e.g. shaft, manufacturing method, involves heating applied windings in subsequent process, and exerting external pressure on windings in heated condition to consolidate to composite components - Google Patents

Abstract

The method involves applying windings of a mixture of reinforcing fibers and a thermoplastic matrix on winding cores. The applied windings are heated in a subsequent process. An external pressure is exerted on the windings in a heated condition to consolidate to composite components. The windings are heated up to a melting temperature of the thermoplastic matrix. The windings are heated from outside and/or from inside. A number of winding cores is heated with the applied windings simultaneously in an oven. An independent claim is also included for a fiber-reinforced composite component comprising sections provided in circular or oval or elliptical or square or triangular or polygon cross section.

Description

The The present invention relates to a process for producing a fiber-reinforced composite component, in particular a shaft, according to the preamble of claim 1. Further The present invention relates to a manufactured by this method Composite component.

For the production of rotationally symmetrical, continuous fiber reinforced plastic components with freely selectable, load-oriented fiber orientation winding methods are nowadays advantageously used. This is the so-called wet winding process (see for example DE 28 32 662 A1 ), in which resin-impregnated semi-finished fiber products are wound on a core (the so-called winding core or mandrel), a sophisticated production process for small to medium-sized series for the production of continuous-fiber-reinforced pipes with thermosetting matrix. In the wet-winding process, the semi-finished fiber products used are impregnated exclusively with thermosetting resin systems. The disadvantage here is the relatively high price of the thermosetting matrix systems, which are also only briefly storable. Another disadvantage is that the thermosetting matrix systems must harden on the winding core. Thus, on the one hand usually a heatable, temperature-controlled winding core is required and on the other hand, the cycle time is determined by the curing process. After demolding the wound and cured tubes, the components must also be tempered to achieve sufficient crosslinking of the thermoset matrix. Since thermosets are neither weldable nor formable, the subsequently applied force discharges usually have to be pressed on and / or glued.

A method of the type mentioned is from the DE 694 20 688 T2 known, which relates to a so-called thermoplastic winding process. In the thermoplastic winding processes developed since the early 1980s, the conventional thermoset winding technology has been transferred directly to the thermoplastics. Here, a thermoplastic semifinished product - consisting of a mixture of continuous reinforcing fibers and thermoplastic matrix - supplied to the winding device and melted at the storage point with a heating source (flame, laser, infrared ..), so that a welding of the supplied material takes place with the surface. The thermoplastic winding processes could not prevail today due to their complex process control and low processing speed. Furthermore, it has been found that with this production method a sufficient quality laminate with correspondingly good surfaces is difficult to realize.

When Conclusion for the state of the art therefore remains to be noted that there is currently no manufacturing process with which a economical production of high quality, continuous fiber reinforced Shafts with thermoplastic matrix is possible.

The The problem underlying the present invention is therefore the Specification of a method of the type mentioned, with a economical production of fiber-reinforced composite components is possible. Furthermore, a composite component of the above be created type that are manufactured economically can and / or is designed effectively.

This is with respect to the method by a method of mentioned type with the characterizing features of claim 1 as well as with regard to the composite component by a composite component of the type mentioned above with the characterizing features of Claim 16 reached. The subclaims relate to preferred embodiments the invention.

According to claim 1 is provided that in a subsequent process step the applied windings are heated and that in the heated External condition exerted pressure on the windings is to consolidate them to the composite component. This will the actual winding process of the further processing by heating and exerting a pressure separately, so that the pro Compound component or shaft applied cycle time clearly can be shortened. Because the further processing steps can be used simultaneously with a larger one Number of components to be performed. Consequently, it is only the actual winding process for the cycle time crucial. As in the production process according to the invention The fiber reinforcement is dry and thus wound up very quickly it is possible to calculate the cycle time as well as the occupancy time the winding device per composite component against the significantly reduce conventional procedures. Still lies the innovation of the invention is that the after winding to be carried out processing steps, for example when using an automatic heating device, so to speak can run by itself without the assistance of operating personnel.

• • Eine schnelle und wirtschaftliche Fertigung von endlosfaserverstärkten Wellen mit thermoplastischer Matrix;
• • die Möglichkeit des Einsatzes von kostengünstigen, thermoplastischen Matrixmaterialien;
• • eine „saubere" Fertigung (keine Emissionen, Verarbeitung reizbarer Stoffe, MAK...);
• • geringe Lagerhaltungskosten (keine Kühlung, Materialtrennung erforderlich, keine Luftreinigung/Abzugsanlagen erforderlich);
• • kürzere Zykluszeiten als beim Nass- oder Thermoplastwickelverfahren;
• • ein geringerer erforderlicher Personaleinsatz;
• • kürzere Belegungszeit der Wickelvorrichtung; sowie
• • die Möglichkeit der Herstellung von Wellen mit integrierter Krafteinleitung.

The advantages of the invention over the prior art include:

• • Fast and economical production of endless fiber reinforced shafts with thermoplastic matrix;
• The possibility of using low cost thermoplastic matrix materials;
• • "clean" production (no emissions, Processing irritable substances, MAK ...);
• • low storage costs (no cooling, material separation required, no air cleaning / exhaust systems required);
• • shorter cycle times than the wet or thermoplastic winding process;
• • less required staffing;
• • shorter laying time of the winding device; such as
• • the possibility of producing shafts with integrated force introduction.

in the The following are examples of the invention Method and inventive composite components described in detail with references to the attached figures. Show in it

1 schematically the process steps of a method according to the invention;

2 the influence of the winding angle of a fiber winding on the thermal expansion coefficient in the circumferential direction of the shaft;

3 the radial impregnation pressure of a 2-layered wound shaft with +/- 15 ° winding angle and additional circumferential winding which sets itself when it heats up;

4 schematically a plurality of different producible with a method according to the invention composite components;

5 schematically a winding core for carrying out a method according to the invention with alternating cross-sectional shape.

The invention relates to a new manufacturing method for the production of continuous fiber reinforced shafts with thermoplastic matrix. With this method, whose manufacturing sequence is shown schematically in 1 is shown, an economical production of rotationally symmetrical components is possible.

in the a first process step, the so-called hybrid fibers - consisting from a mixture of continuous reinforcing fibers and thermoplastic matrix - wound on a winding core. The fibers can exactly match the later ones Load of the component are stored. Because the hybrid fibers are dry, that is without prior impregnation by a Resin bath, can be applied, with higher winding speeds as in the wet-wrap or thermoplastic described above Wrapping process to be worked. Using a ring thread eye Thus, high mass entries within a short time Time to be achieved.

in the In a second process step, the hybrid fiber winding is heated, until the thermoplastic matrix has melted. It can the Warming basically from the inside, from the outside or on both sides. Depending on the consolidation method used (see the following process step), on the one hand, a heating from the inside, for example, by a heatable winding core advantageous be; if necessary with slow rotation of the shaft to the Manufacture component as unbalance-free. on the other hand can be a heating from the outside very economical be realized by, for example, in a convection oven with Timer a larger number of wound Waves (for example, a daily production) at the same time without personnel Night is heated.

• • Über einen Schrumpfschlauch oder eine aufgewickelte Schrumpffolie, die auf der Außenseite der Welle aufgebracht wird und bei der Erwärmung infolge Wärmeschrumpf den Konsolidierungsdruck bewirkt.
• • Über einen speziell ausgelegten Lagenaufbau. Der Wärmeausdehnungskoeffizient der Faserwicklung in Umfangsrichtung der Welle sinkt mit steigendem Wickelwinkel stark ab. Der Wickelwinkel wird zwischen der axialen Richtung der Welle und der Aufbringrichtung der Faser gemessen. In 2 ist der Wärmeausdehnungskoeffizient der Faserwicklung in Umfangsrichtung der Welle in 1/°K·10^–6 in Abhängigkeit von dem Wickelwinkel ω in ° jeweils dargestellt für Glasfasern mit einer Polypropylenmatrix und für Kohlefasern mit einer Polypropylenmatrix. Wenn nun die äußere Wicklung einen höheren Wickelwinkel aufweist als die innere Wicklung, wird bei der Erwärmung der gesamten Welle die innere Wicklung bestrebt sein, sich stärker auszudehnen als die äußere Wicklung. Dadurch stellt sich der Konsolidierungsdruck von selbst ein. Er kann näherungsweise mit der Berechnungstheorie eines elastischen, zweischichtigen, zylindrischen Pressverbandes berechnet werden und liegt bei einer Faserwicklung von ±15°, auf die eine dünne Umfangswicklung (= Wickelwinkel von 90°) aufgebracht wurde, zwischen 20–50 bar. 3 zeigt für einen ersten Lagenaufbau, bei dem eine innere, 2 mm dicke Lage mit +/– 15° Wickelwinkel von einer 0,4 mm dicken Umfangswicklung umgeben ist, und für einen zweiten Lagenaufbau, bei dem eine innere, 2 mm dicke Lage mit +/– 15° Wickelwinkel von einer 0,2 mm dicken Umfangswicklung umgeben ist, den aus einer Erwärmung der Welle um 180°K resultierenden Imprägnierdruck in bar in Abhängigkeit von dem Innendurchmesser der Welle in mm. Das Material der Wicklung sind Kohlefasern in einer Polypropylenmatrix, wobei der Faservolumenanteil 50% beträgt.
• • Über eine äußere Stahlkokille, die auf die kalte Welle geschoben wird. Da Stahl einen geringeren Wärmeausdehnungskoeffizient besitzt als die meisten faserverstärkten Kunststoffe, wird bei Erwärmung der Welle die Faserwicklung bestrebt sein, sich stärker auszudehnen als die sie umgebende Stahlkokille und dadurch wird der Konsolidierungsdruck erzeugt.
• • Über eine auf der Außenseite der Welle angebrachte Vakuumfolie, die evakuiert wird und infolge des Unterdruckes den Konsolidierungsdruck bewirkt.

The actual impregnation and compression process takes place in a third process step. During consolidation, a radially inwardly directed impregnation pressure must act on the fiber winding. This is thereby compacted and all individual layers are compressed in such a way that the subsequent cooling and solidification of the matrix results in a homogeneous, virtually pore-free laminate or fiber composite component. The impregnation pressure to be applied can be achieved by one or more of the following measures:

• • Through a heat shrink tubing or wound shrink film applied to the outside of the shaft which causes consolidation pressure when heated as a result of heat shrinkage.
• • Over a specially designed layer structure. The thermal expansion coefficient of the fiber winding in the circumferential direction of the shaft drops sharply with increasing winding angle. The winding angle is measured between the axial direction of the shaft and the direction of application of the fiber. In 2 is the coefficient of thermal expansion of the fiber winding in the circumferential direction of the shaft in 1 / ° K · 10 ^-6 depending on the winding angle ω in ° each shown for glass fibers with a polypropylene matrix and for carbon fibers with a polypropylene matrix. Now, if the outer winding has a higher winding angle than the inner winding, the heating of the entire shaft, the inner winding will strive to expand more than the outer winding. As a result, the pressure to consolidate sets itself. It can be calculated approximately with the calculation theory of an elastic, two-layer, cylindrical interference fit and lies at a fiber winding of ± 15 °, to which a thin circumferential winding (= winding angle of 90 °) was applied, between 20-50 bar. 3 shows for a first layer structure, in which an inner, 2 mm thick layer with +/- 15 ° winding angle of a 0.4 mm surrounded by a thick circumferential winding, and for a second layer structure in which an inner, 2 mm thick layer with +/- 15 ° winding angle is surrounded by a 0.2 mm thick circumferential winding, the resulting from heating the shaft by 180 ° K impregnating in bar depending on the inner diameter of the shaft in mm. The material of the winding are carbon fibers in a polypropylene matrix, wherein the fiber volume fraction is 50%.
• • Over an outer steel mold, which is pushed onto the cold shaft. Since steel has a lower coefficient of thermal expansion than most fiber-reinforced plastics, when the shaft is heated, the fiber winding will tend to expand more than the surrounding steel mold, thereby creating the consolidation pressure.
• • Via a vacuum film on the outside of the shaft, which is evacuated and causes the consolidation pressure due to the negative pressure.

Of the fourth and final process step involves cooling and the removal of the now finished component. The releasability of the so produced waves depends mainly on the fiber orientation and the component geometry, but can by the structural design the winding core (for example divisible or multipart core) be simplified.

The The basic idea of the invention is, firstly, the actual Winding process (process step 1) of the further processing (process steps 2-4) and thus the per wave to be applied Cycle time significantly shorten. Because the last three Processing steps can be done simultaneously with a larger one Number of components to be performed. Consequently, it is only the actual winding process for the cycle time crucial. Since in the manufacturing method according to the invention the Fiber reinforcement dry and therefore wound up very quickly it is possible to calculate the cycle time as well as the occupancy time the winding device per component compared to the conventional Significantly reduce the process.

To the Another is the invention innovation in that the remaining process steps 2-4 in use an automatic heating device so to speak by itself without With the help of operating staff. This is special advantageous if the tools used for generating the impregnation pressure (additional winding, heat shrink tubing or the like) remain as part of the component and special take over decorative and / or mechanical tasks, for example a colored wear protection layer.

at The method according to the invention is a particular economic production possible if sufficient large timer equipped with timer (convection, Infrared, induction furnace or the like) is used. With such a furnace can, without requiring personnel will, a larger number of wound waves simultaneously heated, consolidated and then be cooled. Depending on the quantity to be produced For example, can be a daily production of wound waves over Night or a weekly production over the weekend in Oven through the process steps 2-4.

Become thermoplastic materials used as a matrix material, the one subject to strong thermo-oxidative degradation (for example, PA or PS), if necessary, the furnace can be evacuated or filled with inert gas.

• • So können beispielsweise außer einer rohrförmigen Querschnittform weitere konvexe Profile gefertigt werden, wie beispielsweise quadratische, rechteckförmige, dreieckige, polygonförmige, elliptische Profile oder dergleichen (siehe 4). Da es sich um thermoplastische Faserverbundbauteile handelt, ist außerdem ein nachträgliches Umformen und Verschweißen der Bauteile möglich, wodurch eine große Anzahl weiterer Profile herstellbar wird.
• • Mit dem erfindungsgemäßen Herstellungsverfahren können Wellen (Antriebs-, Gelenk- oder Torsionswellen) mit bereits integrierter Krafteinleitung hergestellt werden, indem die Faserwicklung auf Wickelkerne mit abschnittsweise unterschiedlicher Querschnittsform gewickelt wird. Solche Wickelkerne können zwecks besserer Entformbarkeit teilbar sein oder aus Einzelsegmenten bestehen, die gesteckt, geschraubt oder auf ähnliche Weise mit einander verbunden werden. 5 zeigt einen Wickelkern, der einen mittleren Abschnitt 1 mit kreisförmigem Querschnitt und zwei endseitige Abschnitte 2, 3 aufweist, wobei der in 5 vordere Abschnitt 2 einen quadratischen Querschnitt und der in 5 hintere Abschnitt 3 einen sechseckigen Querschnitt aufweist.
• • Für die Herstellung von Antriebswellen ist das erfindungsgemäße Verfahren besonders geeignet. Antriebswellen werden im Allgemeinen mit einem niedrigen Wickelwinkel zwischen 8° und 15° gefertigt, um die auftretenden Biegeschwingungen zu ertragen. Infolge der sehr dünnen Wanddicken sind solche Antriebswellen allerdings empfindlich gegenüber Torsionsbeulen. Das Auftreten von Torsionsbeulen wiederum kann durch Aufbringen einer dünnen, äußeren Umfangswicklung vermieden werden. Mit einem derartigen Aufbau der Faserwicklung (innen niedriger Wickelwinkel, außen Umfangswicklung) stellt sich der Konsolidierungsdruck – wie in 3 bereits gezeigt – beim Erwärmen der Welle von selbst ein. Bei zusätzlicher Verwendung eines Schrumpfschlauches, der aus gleichem Material wie die Matrix oder einem mit der Matrix mischbaren Material besteht (beispielsweise Matrix aus PP und Schrumpfschlauch aus strahlungsvernetztem PP), kann die Antriebswelle mit einer dekorativen, einfärbbaren Außenschicht versehen werden, die gleichzeitig auch als Schlagschutz- und/oder chemische Schutzschicht fungiert.

The production of continuous fiber-reinforced, wound shafts with a thermoplastic matrix is possible in various designs:

• Thus, for example, in addition to a tubular cross-sectional shape further convex profiles can be made, such as square, rectangular, triangular, polygonal, elliptical profiles or the like (see 4 ). Since it is thermoplastic fiber composite components, a subsequent forming and welding of the components is also possible, whereby a large number of other profiles can be produced.
• With the production method according to the invention, shafts (drive, joint or torsion shafts) with an already integrated introduction of force can be produced by winding the fiber winding on hubs with sections of different cross-sectional shape. Such winding cores may be divisible for the purpose of better demoldability or consist of individual segments which are inserted, screwed or connected in a similar manner with each other. 5 shows a winding core having a central portion 1 with a circular cross section and two end sections 2 . 3 having, in 5 front section 2 a square cross section and the in 5 rear section 3 has a hexagonal cross-section.
• The method according to the invention is particularly suitable for the production of drive shafts. Drive shafts are generally manufactured with a low winding angle between 8 ° and 15 ° in order to endure the bending vibrations that occur. Due to the very thin wall thicknesses, however, such drive shafts are sensitive to torsion buckles. The occurrence of torsion bumps in turn can be avoided by applying a thin, outer peripheral winding. With such a structure the fiber winding (inside low winding angle, outside circumferential winding) raises the consolidation pressure - as in 3 already shown - when heating the shaft by itself. With additional use of a shrink tube, which consists of the same material as the matrix or a miscible with the matrix material (for example matrix of PP and shrink tube of radiation crosslinked PP), the drive shaft can be provided with a decorative, dyeable outer layer, which also as impact protection - and / or chemical protective layer acts.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 2832662 A1 [0002]
• - DE 69420688 T2 [0003]

Claims (20)

A process for producing a fiber-reinforced composite component, in particular a shaft, in which a plurality of windings of a mixture of reinforcing fibers and a thermoplastic matrix are applied to a winding core in a first process step, characterized in that in a subsequent process step, the applied windings are heated and that in the heated Condition outside pressure is exerted on the windings to consolidate them to the composite component. Method according to claim 1, characterized in that that the windings up to the melting temperature of the thermoplastic Matrix be heated up. Method according to one of claims 1 or 2, characterized in that the windings from the outside and / or heated from the inside. Method according to one of claims 1 to 3, characterized in that a plurality of winding cores respectively with the windings applied simultaneously in an oven, in particular a convection oven, is heated. Method according to one of claims 1 to 4, characterized in that from the outside to the windings applied pressure is directed radially inward. Method according to one of claims 1 to 5, characterized in that from the outside to the windings applied pressure during heating by the layer structure the windings is exercised. Method according to Claim 6, characterized that the windings are applied in multiple layers to the winding core, wherein an outer layer has a lower coefficient of thermal expansion has as an inner layer. Method according to claim 7, characterized in that that an outer layer has a larger one Winding angle has as an inner layer. Method according to one of claims 1 to 8, characterized in that the outside of the windings applied pressure during the heating of a shrink tube or a shrink film is applied after application the windings are applied externally to this. Method according to one of claims 1 to 8, characterized in that the outside of the windings applied pressure during heating by a mold, In particular, a steel mold, is exercised before the heating is pushed onto the windings. Method according to one of claims 1 to 8, characterized in that the outside of the windings exerted pressure exerted by a vacuum foil being pushed onto the windings while being exercised the pressure of the space between the vacuum film and the windings is evacuated. Method according to one of claims 1 to 11, characterized in that after the consolidation of the windings cooled the composite component and removed from the winding core becomes. Method according to one of claims 1 to 12, characterized in that the winding core at least in sections a circular or an oval or an elliptical or a square or a rectangular or has a triangular or a polygonal cross-section. Method according to one of claims 1 to 13, characterized in that the winding core in different axial sections have a different cross-section, for example, force introduction sections in the produced with the winding core Integrated composite component. Method according to one of claims 1 to 14, characterized in that the winding core is divisible or made consists of connectable parts. Fiber-reinforced composite component, in particular formed as a shaft composite component, characterized that the composite component by a method according to any one of claims 1 to 15 is made. Composite component according to claim 16, characterized in that that the composite component at least partially a circular or an oval or an elliptical or a square or a rectangular or a triangular or a having polygonal cross-section. Composite component according to one of claims 16 or 17, characterized in that the composite component in different axial sections ( 1 . 2 . 3 ) has a different cross section, wherein in particular at least one of the sections ( 2 . 3 ) can serve as a force introduction section. Composite component according to one of claims 16 to 18, characterized in that the Ver bundbed component has an outer layer which consists at least partially of a shrunken shrink tube or a shrunken shrink film. Composite component according to one of Claims 16 to 19, characterized in that the composite component more Having layers of fiber windings, wherein an outer Location has a larger winding angle than an inner situation.