DE102017115670A1 - A method of making a fiber composite part and a fiber composite part - Google Patents

Abstract

The proposal is for a part of a fiber composite material which has fibers (7) embedded in a matrix (6), wherein the matrix (6) is produced on the basis of a hardenable plastic, and in the fiber composite material an inhibiting layer (5) is formed, which contains a thermoplastic material. Further, a method for producing the part is given. The part is particularly suitable as a mold for the production of components made of fiber composites.

Description

• - in einer Urform wenigstens eine Faserschicht ausgebildet wird, die Fasern aufweist, die in ein aushärtbares duroplastisches Matrixmaterial eingebettet sind, und bei dem
• - das Matrixmaterial nachfolgend ausgehärtet wird.

The invention relates to a method for producing a part of fiber composite material, in which:

• in an original form, at least one fibrous layer is formed which comprises fibers embedded in a thermosetting thermosetting matrix material and in which
• - The matrix material is subsequently cured.

The invention further relates to a component made of a fiber composite material.

Such a method and such a part of a fiber composite material are known from DE 10 2005 023 320 A1 known. The known fiber composite material comprises at least a first layer of a thermosetting resin and at least a second layer of an elastomer, which are joined together in one operation, namely by a common heat treatment at a temperature between 120 ° C and 190 ° C. With the known fiber composite material can be produced stable vibration damping lightweight components.

Forming tools for the production of components made of fiber-reinforced plastics (FRP) have two basic tasks: the combination of fiber and matrix and thus the formation of the material itself, as well as the shaping within defined geometrical tolerances. Demands on the mold are suitable for the production of the component geometry, the tightness against liquids and gases and the resistance to cyclic temperature loads when using the mold. The molding tool is intended in particular to seal a process space which is dense both to liquids and to gases, since the matrix material provided for the component is generally liquid at the beginning of the process and is introduced into the process space via a pressure difference between the interior and the exterior of the process space Process room is injected and there impregnates the fibers. In addition, the process space is usually evacuated at least before the start of the curing cycle before injection or in components produced in the so-called prepreg process in order to avoid air pockets in the finished component. To cure the initially still liquid matrix material, the matrix material must often be subjected to a heat treatment. The temperature of the mold is a process parameter which is essential for the control of the chemical reactions and the curing of the liquid matrix material.

Forming tools for making fiber reinforced plastic components typically use two classes of materials: metals such as steel, aluminum or special nickel alloys, and fiber reinforced plastics.

• - Das Formwerkzeug und das Bauteil haben den gleichen oder zumindest einen ähnliche Wärmeausdehnungskoeffizient. Dadurch ist die Gefahr gering, dass das Bauteil auf das Formwerkzeug aufschrumpft und dann beim Entformen zerstört wird. Außerdem können prozessinduzierte Deformationen reduziert werden.
• - Bei der Temperierung des Formwerkzeugs, insbesondere auch bei ungleichmäßiger Temperierung tritt keine Verformung des Formwerkzeugs auf.
• - Aufgrund der geringen thermischen Masse des Formwerkzeugs ergeben sich hohe Aufheiz- und Abkühlraten.
• - Durch das geringe Gewicht des Formwerkzeugs ist die Handhabung einfach und der Fertigungsprozess kann verhältnismäßig schnell ablaufen.

In comparison to metal forming tools, fiber-reinforced plastic molds have the following advantages for the production of components made of fiber-reinforced plastics:

• - The mold and the component have the same or at least a similar coefficient of thermal expansion. As a result, the risk is low that the component is shrunk onto the mold and then destroyed during demolding. In addition, process-induced deformations can be reduced.
• - During the tempering of the mold, especially in uneven tempering occurs no deformation of the mold.
• - Due to the low thermal mass of the mold resulting in high heating and cooling rates.
• - Due to the low weight of the mold, handling is easy and the manufacturing process can be relatively fast.

Forming tools made of fiber composites are used only very limited in mass production despite the advantages mentioned. This is mainly due to the shorter life of the mold made of fiber composites compared to metallic molds. The process temperatures necessary to cure the matrix of the component made in the mold allow the mold made of a fiber composite to age rapidly. In particular, leaks occur. The leaks are caused by cracking in the mold. Due to the cyclic thermal and mechanical loading of the mold, microcracks occur in the matrix and at fiber-matrix interfaces. These microcracks increase to a continuous crack through the laminate of the mold. These microcracks eventually cause the mold to leak.

Further, from the publication MIN, HS; KIM, SC: Fracture toughness of polysulfone / epoxy semi-IPN with morphology spectrum; Polymer Bulletin, 1999, Vol. 42 (2), pages 221-227 known to connect thermoplastic material, namely polysulfone, with an epoxy resin, which is cured at a temperature of 150 ° C. The known Material has improved resistance to cracking.

Starting from this prior art, the invention is therefore an object of the invention to provide a simple method for the production of parts of fiber composites that inhibit the microcracking or influence the crack growth so that no continuous cracks.

The invention is further based on the object to provide a corresponding part of a fiber composite material.

These objects are achieved by a method and an apparatus having the features of the independent claims. In dependent claims advantageous embodiments and developments are given.

In the method of making a fiber composite part, a thermoplastic resin material is embedded in the fiber layer prior to curing of the matrix material. As a result, an inhibiting layer is formed in the part of fiber composite material which has a significantly higher breaking elongation than the surrounding matrix material. If a crack arrives at this inhibition layer, the energy needed to further propagate the crack is increased, thereby delaying or arresting crack growth.

In one embodiment of the method, the matrix material is introduced into the fiber layer in liquid form, and the thermoplastic material is placed in the fiber layer prior to introduction of the matrix material. This ensures that the matrix material encloses the inhibitor layer.

In a further embodiment of the method, the matrix material is cured before removal of the part from the master mold at a temperature less than or equal to 100 ° C, 60 ° C, 40 ° C, 30 ° C, 27 ° C or 25 ° C. Such a curing process is sufficient to establish a strong bond between the inhibiting layer and the adjacent matrix material. As a result, an inexpensive and easily workable material can be used for the master. With lower curing temperatures, the requirements for the material of the original form also decrease.

As far as the part requires further hardening after demolding, after removal from the master, the part may be subjected to a post cure at a temperature above the temperature used to remove the part prior to removal of the part from the master mold. The temperature used for postcuring can be, for example, at a temperature greater than 100 ° C, 150 ° C or 170 ° C.

The thermoplastic material used for the inhibition layer may be formed as a closed film, perforated film, fabric or nonwoven.

A firm connection between the inhibiting layer and the at least one adjoining fiber layer can be achieved above all when the thermoplastic material is soluble in the matrix material.

The matrix material may be, for example, an epoxy resin. The inhibiting layer may further be, for example, a thermoplastic material such as polysulfone, polyphenylsulfone, polyethersulfone, polyamide or other material which is soluble in the matrix material.

In particular, the thermoplastic material may be a nonwoven fabric made on the basis of a polyamide, which may be brought into contact with fibers of the fibrous layer by a heat treatment prior to introduction of the matrix material, whereby the fibers of the adjacent fibrous layers can be spatially stabilized.

A part of a fiber composite produced by the method can form a transition region between the inhibitor layer and the matrix. In this transition region there is a gradual transition from the matrix to the thermoplastic inhibiting layer. Inclusions of thermoplastic material and inclusions of the matrix material used for the matrix may occur in the transition region towards the matrix. By such a composite, the inhibiting layer and the at least one adjacent fiber layer are securely bonded.

Further, a plurality of inhibiting layers may be formed in the fiber composite, which are arranged at unequal intervals. In this way crack formation can be effectively suppressed already in the initial stage.

The parts produced by the method can be used in particular as molding tools for the production of components from fiber composite tools.

• 1 einen Querschnitt durch einen Faserverbundwerkstoff mit eingebetteter thermoplastischer Hemmschicht;
• 2 einen Querschnitt, der die Wirkung der eingebetteten thermoplastischen Hemmschicht gegen Rissbildung veranschaulicht; und
• 3 eine Darstellung einer Vorrichtung zur Herstellung eines Formwerkzeugs aus dem in 1 dargestellten Faserverbundwerkstoff.

Further advantages and features of the invention will become apparent from the following description, are explained in the embodiments of the invention with reference to the drawings in detail. Show it:

• 1 a cross section through a fiber composite material with embedded thermoplastic inhibiting layer;
• 2 a cross-section illustrating the effect of the embedded thermoplastic cracking inhibiting layer; and
• 3 a representation of an apparatus for producing a molding tool from the in 1 represented fiber composite material.

1 shows a cross section through a fiber composite material 1 with a protective layer 2 , two outer fiber layer 3 and an inner fiber layer 4 , Into that of the fiber layers 3 and 4 formed laminate is a flexible inhibitor layer 5 embedded in a central or eccentric thermoplastic material.

The fiber layers 3 and 4 each point into a matrix 6 embedded fibers 7 on that in the fiber layers 3 and 4 may be oriented in different preferred directions. The flexible inhibitor layer 5 is formed of a thermoplastic material which is formed as a film, as a perforated film or a textile, for example as a nonwoven or woven fabric, or as a three-dimensional printed structure.

With the fibers 7 I usually deal with carbon fibers. For the matrix 6 In particular, an amine-curing or anhydride-curing epoxy resin is used. Such epoxy resins can be present as cold-curing epoxy resins, which do not need to be heated to cure, in contrast to thermosetting epoxy resins, where the curing reaction at least temporarily requires a temperature above room temperature.

It is understood that the glass transition temperature of the matrix 6 and the inhibitor layer 5 used materials above the maximum operating temperature of one of the composite material 1 should be made part. The glass transition temperature of the matrix 6 and the inhibitor layer 5 The materials used should be at least 20 ° C above the maximum operating temperature. The glass transition temperature is suitably determined by means of the so-called dynamic-mechanical analysis.

For the inhibition layer 5 In particular, thermoplastics having a glass transition temperature which are above the maximum operating temperature of the fiber composite material are suitable 1 finished mold lies. If the mold made of the fiber composite material is used, for example, up to a temperature of 180 ° C, can for the inhibiting layer 5 a thermoplastic material having a glass transition temperature above 220 ° C can be used. The same applies to the material used for the matrix 6 is used.

The thickness of the protective layer is usually in the range of 0.05 to 0.3 mm. The fiber layers 3 and 4 often have a thickness in the range of 0.1 mm to 1 mm. The one of the fiber layers 3 and 4 formed stack usually has a thickness of up to 10 mm.

In 2 is the function of the inhibitor layer 5 illustrated. The left part of the 2 gives the conventional structure without inhibition layer 5 again, during the construction of the fiber composite material 1 in the right part of the 2 is shown.

The integrated in the laminate, flexible inhibitor layer 5 inhibits or prevents the spread of microcracks. When using the fiber composite material 1 for a mold form in the fiber composite material 1 Gradually, micro-cracks start to permeate the mold for gases and liquids. This is due to the embrittlement of the matrix caused by oxidation processes 6 and stresses in the fiber composite material 1 that occur when the fiber composite material 1 manufactured mold passes through thermal cycles. By introducing the thermoplastic inhibiting layer 4 be in a small area, the mechanical properties of the fiber composite material 1 flatly changed. The breaking elongation of the thermoplastic inhibiting layer 5 is significantly higher than the elongation at break of the matrix material 6 , Get a crack 8th to the thermoplastic inhibiting layer 5 , which increases the further propagation of the crack 8th necessary energy, which delays or stops crack growth. At a crack 9 in a conventional fiber composite, on the other hand, this is not the case and the crack 9 can penetrate the conventional fiber composite material.

With little extra effort in the production of the mold can in this way for a long time or permanently fluid-tightness of the fiber composite material 1 manufactured mold are guaranteed. As a result, the life of molds made of fiber composites is significantly increased.

• - die Hemmschicht 5 kann mit Hilfe einer durchgängigen , geschlossenen thermoplastischen Folie hergestellt sein;
• - die Hemmschicht 5 kann mit Hilfe einer perforierten thermoplastische Folie hergestellt sein, die einen Harzfluss durch die Hemmschicht 5 hindurch ermöglicht; oder
• - die Hemmschicht 5 kann von einem thermoplastischen Textil, zum Beispiel einem Gewebe oder Vlies, gebildet sein.

The integration of the thermoplastic inhibitor layer 5 into the fiber layers 3 and 4 is of the design of the inhibitor layer 5 dependent. The following embodiments of the inhibitor layer 5 are feasible:

• - the inhibitor layer 5 can be made by means of a continuous, closed thermoplastic film;
• - the inhibition layer 5 can be made by means of a perforated thermoplastic film, which allows resin flow through the inhibiting layer 5 through; or
• - the inhibition layer 5 may be formed from a thermoplastic textile, for example a woven or nonwoven fabric.

It should be noted that for the production of the inhibitor layer 5 used film has a thickness between 0.05 mm and 0.5 mm, preferably a thickness between 0.05 and 0.15 mm or a thickness of 0.1 +/- 0.02 mm. The thermoplastic textile which may be made by injection molding may have the same thickness.

Depending on the configuration of the thermoplastic inhibiting layer 4 and their chemical composition combines differently with the surrounding fiber layers 3 and 4 ,

If the inhibitor layer 5 formed by a closed thermoplastic film, must have sufficient bonding between the fiber layers 3 and 4 and the film arise so as not to significantly weaken the entire fiber composite.

One way of interfacing is adhesion. The thermoplastic film and the matrix 6 sticking during the production of the fiber composite material 1 ,

Another possibility of the connection is a connection of the two substances by the dissolution of the thermoplastic film surface by the uncrosslinked resin of the matrix 6 and the subsequent connection. When the epoxy resin crosslinks, a transition region forms between the inhibiting layer 5 and adjacent fiber layer 4 , Characteristic of this transition region are the island-like inclusions of epoxy resin on the side of the transition region facing the thermoplastic and inclusions of thermoplastic on the side of the transition region facing the epoxy resin. This mixing forms a good connection between the inhibitor layer 5 and matrix 6 , In addition, they affect the matrix 6 enclosed thermoplastic areas already in the matrix 6 as additional obstacles to the spread of cracks. The transition region also forms when the matrix 6 is made of a cold-curing epoxy resin and the fiber composite material 1 Cures at room temperature.

A very thin thermoplastic film dissolves completely in the matrix 6 and forms an inhibitory layer 5 in which the thermoplastic island-shaped in the matrix 6 is solved.

Examples of epoxy resins soluble in thermoplastics are polysulfone (PSU), polyphenylsulfone (PPSU), polyethersulfone or polyamide.

Textiles made of thermoplastic filaments are available in the ordered composite in the form of a woven fabric or in the disordered composite in the form of a nonwoven fabric. Thermoplastic nonwovens made of a polyamide, so-called binder fleeces are common tools in the manufacture of components made of a fiber composite material. By short-term melting, the fleeces can with the dry fibers 7 be connected and contribute to the fibers 7 to position and the fiber layers 3 and 4 to shape. During the formation process of the fiber composite tool, the nonwoven becomes from the surrounding matrix 6 soaked. In the finished mold remains a finely distributed thermoplastic structure, which in turn as an inhibiting layer 5 serves.

The production of a mold from the fiber composite 1 can be done in various processes, such as the so-called LCM (liquid composite molding) method, the prepreg process or the hand lamination.

3 schematically shows a device suitable for producing a mold according to the LCM method 10 , The device 10 includes a prototype 11 with an in 3 schematically illustrated profile 12 whose geometry determines the shape of the mold to be produced. On the original form 11 become the fibers of the fiber layers 3 and 4 together with the material for the thermoplastic inhibiting layer 5 dry on the protective layer 2 built up. The protective layer 12 , which is usually formed by a hardcoat, in particular by a so-called gelcoat, represents the outer skin in the finished mold. Further, additional auxiliary material layers 13 be applied. The layered layers form a stack 14 that of a cover film 15 is covered. The cover foil 15 is circumferentially by a seal 16 sealed gas-tight. In the cover foil 15 are also an inlet 17 and an outlet 18 educated.

• - Fertigung der Urform 11, üblicherweise durch spanende Bearbeitung;
• - Auftragen und Aushärten der Schutzschicht 2;
• - trockener Aufbau des Stapels 14
• - Tränkung des Stapels 14, insbesondere der Faserschichten 3 und 4 mit dem Matrixmaterial;
• - Aushärten des Matrixmaterials bei Raumtemperatur;
• - Entformung des Formwerkzeugs aus der Urform 11;
• - Nachhärten der Matrix durch eine Wärmebehandlung;
• - Endbearbeitung des Formwerkzeugs.

The manufacturing process of a molding tool produced from the fiber composite material comprises in particular the following method steps:

• - Production of the original form 11 usually by machining;
• - Applying and curing the protective layer 2 ;
• dry stack 14
• - Impregnation of the pile 14 , in particular the fiber layers 3 and 4 with the matrix material;
• - curing the matrix material at room temperature;
• - Removal of the mold from the original form 11 ;
• - post curing of the matrix by a heat treatment;
• - Finishing of the mold.

The original form 11 forms the shape of the mold and creates its geometry. For the production of the original form 11 Usually polyurethane or epoxy foam boards are machined. On this contour, the mold is subsequently made, the surface of the prototype 11 generates the contour of the mold surface.

It should be noted that for cost reasons for the production of the original form 11 Usually materials are used which are easy to work but which do not have high temperature resistance. Because of this, be for the matrix 6 also cold-curing epoxy resins are preferred. If the material used for the original form is also resistant to higher temperatures, for the matrix 6 also thermosetting epoxy resins are used.

To form the pile 14 is the prototype on the prototype first 12 applied, which forms an abrasion protection for the surface of the finished mold. After the protective layer 12 is cured, the dry fiber material of the fiber layers 3 and 4 , as well as the thermoplastic inhibiting layer 5 and the adjuvant layer 13 Applied in layers. The dry layers are covered with the gas-tight cover foil 15 covered and the edges with the seal 16 opposite the original form 11 sealed. Then the stack can 14 over the outlet 18 be evacuated. This will be the matrix 6 forming liquid resin in the pile 14 sucked and can soak it. Following this, the composite usually cures at room temperature. The mold then has sufficient strength and the mold can be removed from the master mold 11 be removed from the mold. To fully cure the matrix and thus achieve the desired mechanical properties of the mold, the mold is heat treated in an oven. The mold is gradually heated to 180 ° C and then cooled down again to room temperature. The entire heat treatment takes about a full day.

In the final step, the mold is trimmed to final contour. This projecting ridges are removed, especially in the area between the original form 11 and cover film 15 can form.

In the manufacture of a mold with integrated inhibiting layer 5 , is when filing the dry semifinished fiber products that make up the fiber layers 3 and 4 are made, the material for the inhibitory layer 5 between the semifinished product for the fiber layers 3 and 4 placed. For a flat impregnation of the stack 14 becomes the inhibitor layer 15 lapped and thus part of the network. For the LCM method described here is for the inhibitory layer 5 a perforated film or a thermoplastic textile particularly suitable. Both are permeable to resin during manufacture and thus allow complete saturation of the surrounding fibers 7 , For the production of molds from fiber composites with integrated inhibition layer 5 is compared to the prior art thus only an additional step necessary. The scope of this work depends on the size and complexity of the mold geometry.

Other methods of making a fiber composite mold are the prepreg process and the hand lay-up process. Here, the laminate is built up layer by layer. Both methods differ only insofar as in the prepreg process already impregnated with resin fiber layers are applied to each other. The material for the inhibition layer 5 is thereby inserted and connects to the surrounding resin in the further process. In these processes, the impregnation of the laminate by the thermoplastic inhibitor layer is influenced 5 locked out.

Thus, a closed thermoplastic film for forming the inhibitor layer 5 be used.

The integration of a thermoplastic inhibitor layer 5 In a fiber composite material represents a cost-effective way to increase the life of manufactured from this fiber composite molds.

Thereby, the tightness for air and resin, and the wear resistance of the surface, decoupled from each other, which is particularly important if the fiber composite material with a protective surface serving the surface protection 2 is provided because this protective layer 2 then not have to ensure the tightness. In that sense, for the protective layer 2 a material turned off for the protective function can be used.

Furthermore, no additional methods or tools for the production of the original forms 11 needed. Thus, the mold can be manufactured inexpensively with conventional devices for vacuum injection.

In order to further increase the resistance to cracking, more of the inhibiting layers can also be used in the fiber composite material 5 be provided. The inhibition layers 5 can be arranged at the same distance. In addition, it is also possible, the inhibition layers 5 at least partially at different distances to arrange. For example, the distance between the inhibiting layers 5 to a top of the fiber composite 1 be less than the distance of the inhibiting layers 5 inside the fiber composite material 1 to the formation of cracks 8th as early as possible to prevent. Furthermore, it can be provided in zones of the mold, which are exposed to a special mechanical or thermal stress, the number of inhibiting layers 5 increase locally.

The method described here is particularly suitable for the production of molds. In principle, the method can also be used to produce other parts in which it depends on a high strength and lasting tightness. Such parts may be in particular tanks for storage and storage of gases or liquids or lines for their transport.

Finally, it should be noted that features and properties that have been described in connection with a particular embodiment can also be combined with another embodiment, except where this is excluded for reasons of compatibility.

Finally, it should be noted that in the claims and in the description, the singular includes the plural unless the context indicates otherwise. In particular, when the indefinite article is used, it means both the singular and the plural.

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 102005023320 A1 [0003]

Cited non-patent literature

• MIN, H.S .; KIM, S.C .: Fracture toughness of polysulfone / epoxy semi-IPN with morphology spectrum; Polymer Bulletin, 1999, Vol. 42 (2), pages 221-227 [0008]

Claims (15)

Method for producing a part of a fiber composite material, in which: - in a master mold (11) at least one fibrous layer (3, 4) is formed which has fibers (7) embedded in a matrix (6) which is separated from a fibrous material hardenable thermosetting matrix material is formed, and in which - the matrix material is subsequently cured, characterized in that prior to curing of the matrix material to form a the crack formation in the fiber composite aggravating inhibiting layer (5) a thermoplastic material in the fiber layer (3, 4) is embedded , Process for producing a part of fiber composite material according to Claim 1 , characterized in that - the matrix material is introduced into the fiber layer (3, 4) in liquid form and that - the thermoplastic material is introduced into the fiber layer (3, 4) before the introduction of the matrix material. Process for producing a part of fiber composite material according to Claim 1 or 2 , characterized in that the matrix material is cured prior to removal of the part from the master mold (11) at a temperature less than or equal to 100 ° C, 60 ° C, 40 ° C, 30 ° C, 27 ° C or 25 ° C. Process for producing a fiber composite part according to any one of Claims 1 to 3 , characterized in that the part after removal from the master mold is subjected to a post cure at a temperature which is above the temperature used prior to removal of the part from the master mold (11) to cure the part. Process for producing a part of fiber composite material according to Claim 4 , characterized in that the part after removal from the master mold (11) is subjected to a post-curing at a temperature greater than 100 ° C, 150 ° C or 170 ° C. Process for producing a fiber composite part according to any one of Claims 1 to 5 , characterized in that the thermoplastic material is introduced as an uninterrupted film, perforated film, fabric or non-woven. Process for producing a fiber composite part according to any one of Claims 1 to 6 , characterized in that the thermoplastic material is soluble in the matrix material. Process for producing a fiber composite part according to any one of Claims 1 to 7 , characterized in that the matrix material is an epoxy resin. Process for producing a part of fiber composite material according to Claim 7 and 8th , characterized in that the thermoplastic material is a polysulfone, polyphenylsulfone, polyethersulfone or polyamide Process for producing a part of fiber composite material according to Claim 6 and 8th , characterized in that the thermoplastic plastic material is a nonwoven fabric made on the basis of a polyamide Process for producing a fiber composite part according to any one of Claims 1 to 10 , characterized in that a molding tool is produced by the method. Part of a fiber composite material having fibers (7) embedded in a matrix (6), wherein the matrix (6) is produced on the basis of a thermosetting thermosetting material, characterized in that - at least one inhibiting layer (5) is formed in the fiber composite material is that contains a thermoplastic material. Part made of a fiber composite according to Claim 12 , characterized in that the matrix material at a temperature less than or equal to 100 ° C, 60 ° C, 40 ° C, 30 ° C, 27 ° C or 25 ° C is curable. Part made of a fiber composite according to Claim 12 or 13 , characterized in that inclusions of thermoplastic material and inclusions of the matrix material used for the matrix are present in the transition region between the inhibiting layer and the matrix. Part of a fiber composite material according to one of Claims 12 to 14 , characterized in that in the fiber composite material, a plurality of inhibiting layers are formed, which are arranged at unequal intervals.

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