DE102015120270A1 - Manufacturing method for a component having a porous fiber matrix structure - Google Patents

Abstract

The invention relates to a production method for a component (1) and in particular to a production method for a component (1) having a porous fiber matrix structure (12) and to a component (1) produced in this way with a porous fiber matrix structure (12). The manufacturing method comprises the following steps: introducing a fibrous structure into a mold, introducing a blowing agent into the mold, and curing the fibrous structure and the blowing agent. Upon curing, the blowing agent expands and forms, together with the fibrous structure, a porous fiber matrix structure (12).

Description

TECHNICAL AREA

The invention relates to a production method for a component and, in particular, to a production method for a component having a porous fiber matrix structure and to a component produced in this way with a porous fiber matrix structure.

BACKGROUND OF THE INVENTION

Composites with a hard topcoat and a lightweight core are known. However, the known composites are complex to produce and have a rather abrupt transition between the cover layer and the core, which leads to a rather abrupt change in the physical properties of the individual layers. This rather abrupt transition can be e.g. Cause shear stress and lead to failure of the component.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simplified method of manufacturing a component and, in particular, an improved component having a porous fiber matrix structure.

This object is achieved by a manufacturing method for a component and the component produced therewith having the features of the independent claims. Advantageous embodiments and further developments can be taken from the subclaims and the following description.

• – Einbringen einer Faserstruktur in eine Form,
• – Einbringen eines Treibmittels in die Form, und
• – Härten der Faserstruktur und des Treibmittels,

wobei das Treibmittel expandiert und zusammen mit der Faserstruktur eine poröse Faser-Matrixstruktur bildet. It is proposed to provide a component manufacturing method which does not necessarily include the following steps in this order:

• Introducing a fiber structure into a mold,
• - Introducing a blowing agent in the mold, and
• Hardening the fiber structure and the blowing agent,

wherein the blowing agent expands and forms a porous fiber matrix structure together with the fibrous structure.

A porous fiber matrix structure can be understood to mean a composite of the expanded blowing agent and the fibers of the fiber structure likewise expanded by the blowing agent. In other words, the result is a foamed, highly porous fiber composite component or, in other words, a fiber-reinforced foam.

The introduction of the fiber structure into the mold may be a laying out of the mold with the fiber structure. The shape may be a simple plane or at least depict a part of the component to be produced. The component can therefore have any shape, that is to be flat or more or less complexly curved or angled. Hardening involves heating with or without additional pressure. The curing can be done in an autoclave or in a closed mold under pressure. The heating may e.g. to 120 ° C to 180 ° C happen.

The fiber structure may be a fiber reinforced and especially carbon fiber reinforced plastic. For a particularly homogeneous porosity and particularly good mechanical properties of the component, the fiber structure may comprise short, randomly oriented fibers. The fibers can be recycled. The fibrous structure may be a preimpregnated prepreg or a non-preimpregnated (dry) fibrous web. The preimpregnated prepreg is provided with an impregnating component prior to introduction into the mold, and the (dry) fiber fabric is provided with an impregnating component after introduction into the mold. The impregnating component may be a resin. The impregnating component may comprise an expanding additive. The impregnating component may be thermosetting. The fiber structure can therefore be designed for temperatures between -50 ° C and 300 ° C and thus be far superior to conventional foam materials.

The propellant may be a chemical or physical propellant. It can be powdery and free-flowing or liquid. An example of a chemical blowing agent is sodium bicarbonate. By the heat during curing of the component, a volatile constituent of the blowing agent separates, which leads to the expansion or foaming of the fiber structure.

The introduction of the propellant into the mold can be a surface application of the propellant to the fiber structure or the propellant can be introduced by gravity, negative pressure or overpressure into the mold and thus into the fiber structure. The expansion of the propellant may be foaming.

The fabrication process for a device having a porous fiber matrix structure facilitates the fabrication of composites and particularly sandwich structures for e.g. the lightweight construction. In this case, even highly complex forms, such. Double curved components are produced with relatively little effort. In particular, only one production step is needed.

The manufacturing method of the invention can be implemented inter alia by two alternatives, which are presented below.

In the first alternative, the fibrous structure is a preimpregnated prepreg, the introduction of the fibrous structure into the mold is a laying out of the mold with the fibrous structure, and the introduction of the foaming agent into the mold is a planar application of the foaming agent to the fibrous structure.

By repeating the two introduction steps "introducing the fiber structure" and "introducing the propellant", a stack of alternating fiber structure layers and propellant layers can be produced. The type, amount and / or distribution of the fiber structure and / or the propellant per fiber structure layer or propellant layer can be handled variably to achieve different degrees of expansion over the height of the stack. In particular, the amount of blowing agent applied flatly to the fiber structure may differ between different fiber structure layers of the stack. In this way, e.g. more blowing agent can be applied in a middle part of the stack than in an edge region of the stack, so that this middle part expands further during hardening than the edge region. Thus, e.g. a stack with strongly porous middle part and not or hardly porous edge region are produced. In other words, the type, amount and / or distribution of the propellant in a central propellant layer in the stack may be designed for porous expansion of the fibrous structure by the propellant and the type, amount and / or distribution of the propellant in a propellant layer external to the stack may be designed for forming a non-porous or hardly porous cover layer.

The components thus produced by the method of the present invention may have a very smooth transition between on the one hand a monolithic outer layer and a very light, highly porous core. In this case, the cover layer and the core of the component can be made of the same material, which is e.g. with regard to licensing restrictions in aeronautical engineering is advantageous. The cover layer and the core of the component may have the same physical properties, e.g. no residual stresses or thermal distortion occur. The cover layer and the core of the component can be produced in a single process sequence. The cover layer may have a closed surface and a relatively high strength, rigidity and hardness. The core may have a relatively low density, hence low weight and large pores. In this way, a "bionic" structure similar to a bone with a stable outer skin and a sponge-like core can be created.

The course of the blowing agent amounts and thus the porosity over the height of the stack can be varied continuously or stepwise. With regard to the amount of blowing agent and thus the porosity of the stack may be constructed symmetrically or asymmetrically to its innermost layer.

In one embodiment, after porous expansion and curing, the fibrous structure comprises a fiber-reinforced cover layer, the outer layers in the stack comprise a fabric, scrim or unidirectional laminates, and the middle layer in the stack or core has a reinforcing fabric. The fiber-reinforced cover layer may comprise unidirectional prepreg tapes and the fabric of the outer layers may comprise twill or canvases, which by its increased fiber discharge smoothly merges into the open-pored middle layers of the core and improves the bond between the cover layer and the core. The core may comprise non-woven fibers with a high weight. The core may have isotropic properties or increased strength in the stack height direction.

In the second alternative of the manufacturing process, the fiber structure is a dry fiber fabric, the introduction of the fiber structure into the mold is a laying out of the mold with the fiber structure, and an impregnating component and the blowing agent are introduced by vacuum or overpressure into the mold and thus into the fiber structure. The dry fiber web may be a fleece, a woven fabric, a knit, a scrim, a fabric, a felt or the like. The impregnating component and the blowing agent may e.g. be sucked or injected simultaneously or successively from one side of the mold to the other by or along the dry fiber fabric. However, the impregnating component and the blowing agent can also be applied across the layers of the dry fiber fabric, e.g. be pushed or sprayed from top to bottom through the mold, or simply flow or sink through gravity. If the impregnating component and the blowing agent are introduced into the fiber structure in such a way that a uniform mixing occurs, a uniform porosity (without a cover layer with properties different from the core) is also produced.

The type, amount and / or distribution of the fiber structure in the mold can be handled variably, that is to say identical or different fiber structures can be used within the mold and distributed uniformly or differently.

In one embodiment, during the introduction of the fibrous structure, the impregnation component and the propellant, the mold has a first internal volume which is expanded to a larger, second internal volume after a predetermined time. In this case, the first internal volume is designed for forming a cover layer, and the second internal volume is designed for porous expansion of the fiber structure.

In another embodiment, the mold is not completely filled with the fibrous structure, the impregnating component and the blowing agent, cured at a first pressure for a first period of time, and cured at a second pressure lower than the first pressure for a second period of time. In this case, the first pressure is designed for forming a cover layer, and the second, lower pressure is designed for a porous expansion of the fiber structure into the remaining space of the mold.

In one embodiment, after the porous expansion and hardening, the fibrous structure has a cover layer of unidirectional, multi-axial fibers, the outer layers of the stack comprise a fabric, scrim or unidirectional laminates for improving the bonding of cover layer and core and the middle layers in the stack The core has a thick, non-woven fibers.

It is further proposed to provide a component which has been produced by the above-described manufacturing method and therefore comprises a fiber structure and a blowing agent, wherein the expanded blowing agent together with the expanded fiber structure forms a porous fiber matrix structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and applications of the present invention will become apparent from the following description of the embodiments and the figures. All described and / or illustrated features alone and in any combination form the subject matter of the invention, regardless of their composition in the individual claims or their back references. In the figures, like reference numerals represent like or similar objects.

1 shows a schematic overview of a manufacturing method for a component with a porous fiber matrix structure.

2a and Fig. b shows a cross section through such a component with a porous fiber matrix structure.

DETAILED DESCRIPTION EXPLAINED

EMBODIMENTS

• – Schritt S1, Einbringen einer Faserstruktur in eine Form,
• – Schritt S2, Einbringen eines Treibmittels in die Form, und
• – Schritt S3, Härten der Faserstruktur und des Treibmittels.

1 shows a schematic overview of a manufacturing process for a component 1 which does not necessarily include the following steps in this order:

• Step S1, introducing a fiber structure into a mold,
• Step S2, introducing a blowing agent into the mold, and
• Step S3, hardening of the fiber structure and the blowing agent.

Upon curing, the blowing agent expands and, together with the fibrous structure, forms a porous fiber matrix structure 12 , Such a porous fiber matrix structure 12 is in 2a and b shown. Under porous fiber matrix structure 12 is understood a composite of the expanded blowing agent and the fibers of the likewise expanded by the blowing agent fiber structure. This results in a foamed, highly porous fiber composite component or a fiber-reinforced foam.

The manufacturing method according to the invention simplifies the manufacture of composites and in particular of sandwich structures for e.g. the lightweight construction. In this case, highly complex forms, such as Double curved components are produced with relatively little effort. The manufacturing method of the invention can be implemented inter alia by two alternatives, which are presented below.

In the first alternative of the manufacturing process, the fiber structure is a prepreg prepreg, the introduction of the fiber structure into the mold is a laying out of the mold with the fiber structure, and the introduction of the propellant into the mold is a planar application of the propellant to the fiber structure. That in the 1 Thus, the manufacturing method shown comprises an optional pre-step S0 of preimpregnating the fiber structure.

2a and b shows a component 1 produced by the above-described manufacturing method and therefore comprising a fiber structure and a blowing agent, wherein the expanded blowing agent together with the expanded fiber structure has a porous fiber matrix structure 12 forms.

By repeating the two introduction steps "introducing the fiber structure" and "introducing the propellant", a stack of alternating fiber structure layers and propellant layers can be produced. The type, amount and / or distribution of the fiber structure and / or the propellant per fiber structure layer or propellant layer can be handled variably to achieve different degrees of expansion over the height of the stack. In particular, the amount of blowing agent applied flatly to the fiber structure may differ between different fiber structure layers of the stack. In this way, more blowing agent can be applied in a middle part of the stack than in an edge region of the stack, so that this middle part expands further during hardening than the edge region. So can a stack, as in the 2a and b, with a highly porous and therefore light central part of a porous fiber matrix structure 12 and not or hardly porous and therefore stable edge region of a cover layer 11 be generated.

The components thus produced by the method of the present invention 1 Thus, a very smooth transition between a monolithic, protective cover layer 11 and a very light, highly porous core of a porous fiber matrix structure 12 and produced in a single process. In this way, a "bionic" structure similar to a bone with a stable outer skin and a sponge-like core can be created.

In the second alternative of the manufacturing process, the fibrous structure is a dry fiber web which is introducing the fibrous structure into the mold as above, laying out the mold with the fibrous structure and an impregnating component, and the blowing agent is introduced by vacuum or overpressure into the mold and thus into the fibrous structure brought in. The impregnating component and the blowing agent may be sucked or injected from one side of the mold to the other through or along the dry fiber web. However, the impregnating component and the blowing agent can also be pressed or sprayed transversely to the layers of the dry fiber fabric, for example from top to bottom, through the mold or simply flow or sink through gravity. If the impregnating component and the blowing agent are introduced into the fiber structure in such a way that a uniform mixing occurs, a uniform porosity (without a cover layer having properties different from the core) of the porous fiber matrix structure also becomes 12 generated.

But it is also the production of a component 1 like in the 2a and b possible. In this case, during the introduction of the fiber structure, the impregnation component and the propellant, the mold has a first internal volume, which is expanded after a predetermined time to a larger, second internal volume. In this case, the first internal volume is for forming a cover layer 11 and the second internal volume is for a porous expansion of the fiber structure into a porous fiber matrix structure 12 designed. That in the 2 shown component 1 however, may also be produced by not fully filling the mold with the fibrous structure, the impregnating component and the blowing agent, curing at a first pressure for a first period of time, and curing at a second pressure lower than that during a second period of time first pressure is. In this case, the first pressure for forming a cover layer 11 and the second, lower pressure for porous expansion of the fibrous structure into the free space of the mold to form a porous fiber matrix structure 12 designed.

In addition, it should be noted that "encompassing" does not exclude other elements or steps, and "a" or "an" does not exclude a multitude. It should also be appreciated that features or steps described with reference to any of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limiting.

Claims (10)

A method of manufacturing a component ( 1 ), comprising the following steps: introducing a fiber structure into a mold, introducing a blowing agent into the mold, and hardening the fiber structure and the blowing agent, wherein the blowing agent expands and, together with the fiber structure, forms a porous fiber matrix structure 12 ).  The manufacturing method of claim 1, wherein the fibrous structure is a preimpregnated prepreg, the introduction of the fibrous structure is a laying out of the shape with the fibrous structure, and the introduction of the foaming agent is a planar application of the foaming agent to the fibrous structure.  Manufacturing method according to the preceding claim, wherein by repeating the two introduction steps, a stack of alternating fiber structure layers and propellant layers is produced, wherein the type, amount and / or distribution of the fiber structure and / or the propellant per fiber structure layer or propellant layer is variable. A manufacturing method according to the preceding claim, wherein the type, amount and / or distribution of the blowing agent in a stack in the middle blowing agent layer for a porous expanding the fiber structure is designed by the blowing agent, and the type, amount and / or distribution of the blowing agent in one in the stack outer propellant layer for forming a cover layer ( 11 ) is designed.  A manufacturing method according to the preceding claim, wherein after the porous expansion and curing the fiber structure is provided with a further fiber-reinforced cover layer and in the stack middle layers comprise a reinforcement fabric and in the stack outer layers comprise a fabric, scrims or unidirectional laminates. A manufacturing method according to any one of the preceding claims, wherein the blowing agent is a powdered, free-flowing, chemical blowing agent. The manufacturing method according to claim 1, wherein the fibrous structure is a dry fiber fabric, the introduction of the fibrous structure is a laying out of the shape with the fibrous structure, and an impregnating component and the foaming agent are introduced by vacuum or overpressure into the mold and thus into the fibrous structure.  A manufacturing method according to the preceding claim, wherein during the introduction of the fibrous structure and the propellant, the mold has a first internal volume which is expanded after a predetermined time to a larger, second internal volume, the second internal volume being adapted for porous expansion of the fibrous structure.  Production method according to one of the preceding claims, wherein the impregnating component is thermosetting. A component ( 1 ), which comprises a fibrous structure and a blowing agent, wherein the expanded blowing agent together with the expanded fibrous structure has a porous fiber matrix structure ( 12 ).

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