DE102015010305A1 - Process for the production of a fiber-matrix composite - Google Patents

Abstract

Method for producing a fiber-matrix composite (17) from at least one fiber matrix semifinished product (5) having a molding tool (1) having at least one first part form (2) and at least one second part form (3), comprising the following substeps: inserting the fiber-matrix semifinished product (5) into a gap (4) of the opened molding tool (1) arranged between the at least one first part mold (2) and the at least one second part mold (3), the fiber-matrix semifinished product (5) after insertion against the at least one first part mold (2), a first closing (10) of the molding tool (1), a first injection (11) of matrix material (7) into the gap (4), a second closing (14) to a closed mold (1). As a result of the design of the production method and in that the matrix material (7) is injected into the gap (4) through at least one injection opening (6, 6 ', 6' ') arranged in at least one second part form (3), the manufacturing method can be used Produce fiber-matrix composites (17) which have a high surface quality and which have the desired high mechanical strength and stability even with a small material thickness.

Description

The invention relates to a method for producing a fiber-matrix composite of at least one fiber-matrix semifinished product, a fiber-matrix composite produced by such a method and a mold for producing a fiber-matrix composite with such a method.

Increasingly, not only in the automotive industry, metal components are being replaced by plastic components, for example, to achieve weight reduction or cost reduction, or to consider environmental issues. In this case, such plastic components can be produced for example by injection molding, in which process a plastic melt is injected under high pressure into a mold cavity. Usually, however, due to the high viscosity of the plastic melt used, a very thin wall thickness of the plastic component can only be manufactured to a limited extent with this method. In addition, plastic components produced by injection molding do not have a very high surface quality, since the surface finish can not be produced reliably.

By means of the injection-compression molding, a further development of injection molding, or the Quellflussprägens can indeed produce plastic components that can be equipped with a good surface finish and thin walls, but due to the required for the respective plastic component mechanical strength and stability of reducing the wall thickness of the respective Plastic component limits.

To produce plastic components with high mechanical strength and stability, it is possible to form the plastic components as fiber-matrix composites. In this case, such fiber-matrix composites can be produced for example from fiber-matrix semifinished products, wherein for the production of the fiber-matrix composite, the fiber-matrix semifinished can be inserted into an intended mold and consolidated in the same. When using fiber-matrix semi-finished products, such as organic sheets, the plastic or the matrix contributes only subordinate to the mechanical stability of the finished fiber-matrix composite, as essentially the fiber layers ensure the stability of the fiber-matrix composite. Consequently, in the case of plastic components formed as a fiber-matrix composite, smaller material thicknesses can be formed than with pure plastic components, without the mechanical strength and stability suffering therefrom. However, the fiber-matrix semi-finished products used can have dimensional tolerances, such as thickness tolerances and shape tolerances, so that lower surface qualities can occur in the currently customary production methods due to lack of consolidation or due to insufficient filling of the fiber matrix semifinished product with matrix material. In addition, with the currently customary methods, thin wall thicknesses can only be displayed to a limited extent.

A method for producing a fiber-matrix composite from at least one fiber-matrix semifinished product is DE 691 31 459 T2 known. In this method, a fiber-reinforced resin layer is placed in a gap of an open mold formed by an upper and a lower mold of the mold, and the fiber-reinforced resin layer is abutted against the lower mold upon insertion. Through a hole in the resin layer, plastic is injected into the gap via the lower mold between the fiber-reinforced resin layer and the upper mold, which is subsequently spread over the surface by closing the mold between the fiber-reinforced resin layer and the upper mold. As a result, at least the surface condition of the plastic component on its side facing the upper mold can be produced with sufficiently high quality. However, this method is not suitable for plastic components that are not intended to have holes, and moreover, if the plastic injection is not precisely sized, due to loss of consolidation or material tolerances of the fiber reinforced resin layer, cavities may still remain which reduce the surface quality of the final component. In addition, with several injection sites, which are to be provided for example for very large components or unfavorable component shapes for a uniform distribution of the matrix material, several holes must be formed in the fiber-reinforced resin layer.

Accordingly, there continues to be a non-decreasing demand for processes for the production of lightweight components, in particular formed as a fiber-matrix composite, which have a high surface quality and / or thin wall thickness with high mechanical strength and stability of the component.

The present invention is concerned with the problem of specifying an improved or at least one alternative embodiment for a production method for fiber-matrix composites and suitable molds, which is characterized in particular by a high surface quality and / or thin wall thicknesses of the fiber matrix composite produced therewith. Composite distinguishes.

In one aspect of the invention, it is thus proposed that a method for producing a Fiber-matrix composite of at least one fiber-matrix semifinished product with a at least one first part mold and at least one second part mold having mold following sub-steps comprising:
inserting the fiber matrix semifinished product into a gap of the opened molding tool arranged between the at least one first part form and the at least one second part mold, wherein the fiber matrix semifinished product lies against the at least one first part mold after being inserted,
a first closing of the mold,
a first injection of matrix material into the gap,
a second closing to a closed mold,
wherein the matrix material by at least one in at least
a second part form arranged injection port is injected into the gap.

Advantageously, fiber-matrix composites can be produced by the method described above, which have a high surface quality and / or thin wall thicknesses at the same time high mechanical strength and stability. In this case, the at least one fiber-matrix semifinished product can be inserted into the opened mold in an undefined position, since the fiber-matrix semifinished product is finally positioned only in the course of the further process. This can increase the speed of the manufacturing process.

After the first closing of the molding tool, in which the molding tool is only partially and not completely closed, the gap between the at least one first part mold and the at least one second part mold can be designed such that between the at least one second part mold and the inserted fiber mold. Matrix semi-finished sufficiently free space is arranged so that any injected matrix material can be easily distributed on the inserted fiber matrix semifinished product. The distribution of matrix material injected into the gap is essentially facilitated by the fact that it can flow freely in the free space without having to be forced at least partially through the fiber-matrix semifinished product. Due to the uniform distribution of the matrix material on the fiber-matrix semifinished product an improved consolidation and a higher surface quality can be achieved.

In addition, as a result of the first injection of matrix material into the gap by the injected matrix material, the fiber-matrix semifinished product can be applied or pressed onto the at least one first part mold at least at the injection sites, so that the positioning or the abutment of the fiber-matrix semifinished product the first part form is improved. Consequently, an exact application and insertion of the fiber-matrix semifinished product into the mold can be dispensed with, since this is achieved mainly during the first injection of matrix material into the gap. An exact application of the fiber-matrix semifinished product to the first part form may be advantageous in order to avoid wrinkling and irregularities or impurities in the finished fiber-matrix composite. In this case, a low injection pressure is used during the first injection of matrix material, so that at a high bulk temperature of the matrix material, a high mass volume can be injected in a short time. This in turn promotes rapid application of the fiber-matrix semifinished product to the at least one first part form.

After the first injection, the mold is completely closed, so that the matrix material can spread due to the closing process over almost the entire fiber-matrix semi-finished product and flooded it. In this case, a high flow rate and the initial remaining free space between the fiber-matrix semifinished product and the at least one second part form enables high filling and thin flooding of the fiber-matrix semifinished product. The resulting good consolidation of the fiber-matrix semifinished product can on the one hand thin wall thicknesses and high surface quality in the finished fiber-matrix composite are produced, the finished fiber-matrix composite in the areas of thin material strength high resilience and Having stability by the fibers.

If the matrix material is injected into the gap by at least one injection opening arranged in at least one second partial mold, the matrix material can advantageously be supplied from the side where the fiber matrix semifinished product does not bear against the first partial mold or the molding tool. Consequently, it is possible to dispense with holes in the fiber-matrix semifinished product since the feed of the matrix material does not take place via the side on which the fiber-matrix semifinished product rests against the molding tool or the at least one first part mold. If the side of the fiber-matrix composite facing the second part form is also the side of a viewing region of the finished fiber-matrix composite, the desired high surface quality can be achieved by such injection of the matrix material due to the uniform distribution of the matrix material on the fiber matrix -Halbzeug be enabled.

A fiber-matrix composite essentially consists of at least one 2/3-dimensional fiber structure embedded in a matrix. In this case, the 2- / 3-dimensional fiber structure is surrounded by the matrix, which is bound by adhesives or cohesive forces to the 2- / 3-dimensional fiber structure. As materials for fiber structures can Glass fibers, carbon fibers, aramid fibers, PBO fibers, polyethylene fibers, natural fibers, basalt fibers, quartz fibers, alumina fibers, silicon carbide fibers or mixed forms are used. Duroplastics, thermoplastics, elastomers and fillers, saturated or unsaturated polyester resins, epoxy resins, vinyl ester resins or mixed forms can be used as matrix materials.

The term 2-dimensional fiber structure includes woven, knitted, knitted, nonwoven, unidirectional laid-down fibrous layers, multiaxial fabrics, mats, knits, spacer fabrics, braided sleevings, embroidery, sewing fabrics, tear-off fabrics or blends. The term 3-dimensional fiber structure also encompasses several layered 2-dimensional fiber structures. The 2-dimensional fiber structures can be designed differently. For example, it is conceivable that a unidirectional fiber layer may be followed by a nonwoven fabric as the next layer, while a fabric may terminate the 3-dimensional fiber structure. However, it is also possible to use exclusively unidirectional 2-dimensional fiber structures for constructing a 3-dimensional fiber structure. The unidirectional 2-dimensional fiber structures can be the same orientation or differently oriented with respect to their direction. In the latter case, there is a multiaxial clutch.

A fiber-matrix semifinished product is to be understood as meaning a 2/3-dimensional fiber structure which functions as a preform, preform, preform, prepreg or mixed form for a fiber-plastic composite. Organic sheets are accordingly fiber-matrix semi-finished products. From the semi-finished fiber product is produced by injections of the matrix or of the matrix material in the fiber semifinished product and by subsequent compression of the fiber-matrix composite. In this case, the fiber-matrix semifinished product may comprise plastics which act as binders, binders, impregnating agents, adhesion promoters or mixed forms. By means of, for example, these plastics, the fiber-matrix semifinished product can be kept in shape, so that displacement of the fiber structure relative to one another, for example during transport, can be largely avoided. It is also conceivable that the fiber-matrix semifinished product is formed as a fiber semifinished product without a significant proportion of matrix material.

A molding tool is understood to be a tool with which a shaping of the respectively produced component is made possible during the manufacturing process. In the present case, such a molding tool has at least one first part form and at least one second part form. In this case, during the production process or during insertion, first closing and first injection, the fiber-matrix semifinished product substantially abuts against the at least one first part form, while essentially a possible viewing region of the finished fiber-matrix composite is formed by the at least one second part form becomes. It is also possible for more than one first part form and / or more than one second part form to be provided, and even further part forms which represent further functionalities of the molding tool.

Since the at least one second part form can form the visible region of the finished fiber-matrix composite, the matrix material is advantageously fed via at least one injection opening, which is formed in the at least one second part form, to the gap of the molding tool. It is conceivable that, in the case of several second partial shapes, not all second partial shapes have an injection opening for matrix material.

In this case, the injection opening can be supplied with matrix material via channels, which are formed in the at least one second part form, wherein the channels are connected to a screw press or screw pump, which can build up the injection pressure for the matrix material.

Furthermore, after the second closing, in which the mold is completely closed, a second injection of matrix material can be carried out. As a result, the surface quality can be further improved since any cavities remaining during the second closure can be filled by injecting further matrix material. As a result, any material loss occurring during the production process can be reliably compensated, as can material tolerances of the fiber-matrix semifinished product used. In addition, a second injection of matrix material advantageously prevents weld lines and significantly improves the surface quality. In this case, a higher injection pressure is used for the complete filling of the gap with matrix material during the second injection, than with the first injection of matrix material into the gap. In addition, dimensional tolerances of the fiber-matrix semi-finished used play a minor role, even if the tool gap corresponds exactly to the nominal thickness of the fiber-matrix semifinished product used, since the flooding during the first injection and the finalizing filling during the second injection shortcomings and material tolerances in Fiber matrix semi-finished can be compensated. As a result, the process reliability is increased and the respective desired mechanical strength and stability profile can be ensured while maintaining high surface quality of the finished fiber-matrix composite.

If the second injection of matrix material is carried out via at least one injection opening arranged in at least one second partial mold, it is advantageously possible to ensure a high surface quality and a secure backfilling of cavities by injection over the side facing the viewing area, which after the first injection and the second Close still remain. In this case, the injection of matrix material can be carried out via the same injection openings of the first injection or at least partially via injection openings, via which no matrix material is supplied to the gap during the first injection. In this way, matrix material can advantageously be injected in a targeted manner in the regions during the second injection, which, for example, due to the shaping tend to cavities and thus to a poor surface quality, but are not activated or directly filled during the first injection.

If, during the first injection, a partial first opening of the molding tool is carried out, then, for example, during the first closing, the molding tool can be closed more strongly. By a stronger first closing of the molding tool, a first fitting or application of the fiber-matrix semifinished product can be made to the at least first part form, which is then continued by the first injection of matrix material and by a simultaneous opening of the molding tool. This can avoid that, for example, in a geometrically unfavorable shape by the first injection of matrix material, the fiber-matrix semifinished product is unfavorably displaced or pushed away. In this case, by opening during the injection, a sufficiently large remaining free space between the fiber-matrix semifinished product and the at least one second part form can be produced, so that sufficient matrix material can be pressed into the gap, that then optimally on the Distribute fiber matrix semifinished product and can flood it.

If the gap after the first injection has an offset, in particular of 1 to 4 mm, compared to a gap with a completely closed mold, an optimal distribution of the matrix material on the inserted fiber-matrix semifinished product can be achieved. In this case, an offset is understood to mean that stroke by which the first part shape must be adjusted relative to the at least one second part shape-or vice versa-during the second closing in order to completely close the molding tool.

If, prior to the second closing, a material supply, via which matrix material is conducted to the at least one injection opening, is sealingly closed, it can advantageously be prevented that matrix material is forced back into the material supply due to the second closing and the concomitant pressure build-up from the gap. This can counteract undesired material loss within the gap via the injection opening and due to the increased process reliability, a reproducibly good result can be achieved.

If the injection pressure during the second injection of matrix material into the gap is greater, in particular 1.5 to 8 times greater than an injection pressure during the first injection of matrix material into the gap, then a low pressure during the first injection and at high mass temperature high mass volume can be introduced into the gap in a short time and thereby an application of the fiber-matrix semifinished product to the at least one first part form can be achieved. In addition, due to the rapid filling and the high melt temperature, the flow properties of the matrix material can be improved during the subsequent second closing of the molding tool. The high injection pressure during the second injection again ensures almost complete filling of remaining cavities, in which case no high mass volume is necessary, since most of the matrix material is preferably applied to the gap during the first injection. Thus, for example, the injection openings for the first injection may be made larger than the injection openings used for the second injection.

By the second injection of matrix material into the gap, it is also possible in particular to significantly increase the consolidation of the fiber-matrix semifinished product. In this case, the term "consolidation" is understood in particular to mean a reciprocal proportion of air in the material of the fiber-matrix semifinished product. Preferably, by the second injection of matrix material, the consolidation can be increased to approximately 100%.

In another aspect, a fiber-matrix composite made by a method as described above is proposed. Due to the production by the method described above, the fiber-matrix composite can have thin wall thicknesses, with high mechanical strength and stability and / or the surface finish in the field of view of the fiber-matrix composite can have a high surface quality.

In a further aspect, a mold for producing a fiber-matrix composite is proposed according to a method as described above. By means of such Forming tool, the advantages described above can be achieved.

It show, each schematically:

1 an open mold with inserted fiber matrix semifinished product,

2 a partially closed mold,

3 a first injection of matrix material into a partially closed mold,

4 a completely closed mold,

5 a arranged in a closed mold fiber-matrix composite after a second injection of matrix material.

A mold 1 , as in 1 shown, has at least a first part shape 2 and at least a second part form 3 on. Between the first part form 2 and the second part form 3 is with the mold open 1 A gap 4 arranged in the at least one fiber-matrix semifinished product 5 can be inserted. It is also conceivable that in the gap 4 two or more fiber-matrix semi-finished products 5 are inserted, which are then interconnected by the subsequent process. By inserting the fiber-matrix semifinished product 5 so in the mold 1 positioned it after insertion on the first part mold 2 is applied.

In the second part form 3 is at least one injection port 6 . 6 ' . 6 '' provided, over the matrix material 7 . 7 ' can be injected into the gap. This is the matrix material 7 . 7 ' via supply lines 8th in the second part form 3 are formed, the injection openings 6 . 6 ' . 6 '' fed. A material feed 9 For example, it is designed as a screw press or screw pump, so that the high injection pressures required can be built up.

By a first closing 10 can with inserted fiber matrix semifinished product 5 the mold 1 be at least partially closed, as in 2 shown.

With now partially closed mold 1 will, as in 3 shown, is matrix material 7 via at least one injection opening 6 . 6 ' in the second part form 3 are formed in the gap 4 injected under low injection pressure but with high mass temperature and high mass volume. Through this first injection 11 of matrix material 7 in the gap 4 becomes the fiber matrix semifinished product 5 reinforced to the at least one first part form 2 pressed or created. Because the mold 1 , as in 2 and 3 shown is only partially closed and therefore an offset 12 of preferably 1 to 4 mm, the matrix material may be 7 simply in a free space 13 between the inserted fiber-matrix semifinished product 5 and the at least one second part form 3 accumulate and distribute.

Will now be a second close 14 according to 3 performed, in which the mold 1 until its end position 15 is completely closed, so distributes the matrix material 7 increasingly in the diminishing gap 4 primarily on the surface of the fiber-matrix semifinished product 5 , but also under filling of gaps 16 between the fiber-matrix semifinished product 5 or in the same, as in 4 shown.

To the surface quality of the finished fiber-matrix composite 17 , as in 5 shown to further improve can be injected through a second 18 of matrix material 7 ' any remaining cavities 19 , as in 4 shown even after the first injection 11 and second closing 14 still occur, can be completely filled. Because the second injection 18 under a high injection pressure, can provide an optimal surface quality of a viewing area 20 passing through the second part form 3 is formed, can be achieved, for example, as a regression of weld lines, which may occur after the second closing, can be achieved by backfilling and compression.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 69131459 T2 [0005]

Claims (9)

Process for producing a fiber-matrix composite ( 17 ) from at least one fiber-matrix semifinished product ( 5 ) with at least one first partial form ( 2 ) and at least a second partial form ( 3 ) having molding tool ( 1 ), comprising the following sub-steps: - an insertion of the fiber-matrix semifinished product ( 5 ) into one between the at least one first partial form ( 2 ) and the at least one second partial form ( 3 ) arranged gap ( 4 ) of the opened mold ( 1 ), wherein the fiber-matrix semifinished product ( 5 ) after insertion on the at least one first part form ( 2 ), - a first closing ( 10 ) of the molding tool ( 1 ), - a first injection ( 11 ) of matrix material ( 7 ) in the gap ( 4 ), the matrix material ( 7 ) Irregularities of the fiber-matrix semifinished product ( 5 ) in the hot state - a pressing step, for complete consolidation of the fiber-matrix semifinished product ( 5 ) and - a second closing ( 14 ) to a closed mold ( 1 ), characterized in that the matrix material ( 7 ) by at least one in at least a second partial form ( 3 ) arranged injection port ( 6 . 6 ' . 6 '' ) in the gap ( 4 ) is injected. Method according to claim 1, characterized in that a second injection ( 18 ) of matrix material ( 7 ' ) after the second closing ( 14 ) is carried out. Method according to one of the preceding claims, characterized in that the second injection ( 18 ) of matrix material ( 7 ' ) via at least one in at least a second partial form ( 3 ) arranged injection port ( 6 . 6 ' . 6 '' ) is made. Method according to one of the preceding claims, characterized in that a partial first opening of the molding tool ( 1 ) during the first injection ( 11 ) is carried out. Method according to one of the preceding claims, characterized in that the gap ( 4 ) after the first injection ( 11 ) a first offset ( 12 ), preferably from 1 to 4 mm, compared to a gap ( 4 ) with completely closed mold ( 1 ) having. Method according to one of the preceding claims, characterized in that before the second closing ( 14 ) a material supply ( 9 ), about the matrix material ( 7 . 7 ' ) to the at least one injection opening ( 6 . 6 ' . 6 '' ), is sealed tightly. Method according to one of the preceding claims, characterized in that an injection pressure during the second injection ( 18 ) of matrix material ( 7 ' ) in the gap ( 4 ) is greater, preferably 1.5 to 8 times greater than an injection pressure during the first injection ( 11 ) of matrix material ( 7 ' ) in the gap. Fiber matrix composite ( 17 ), prepared by a process according to any one of the preceding claims. Molding tool ( 1 ) for producing a fiber-matrix composite ( 17 ) with a method according to any one of claims 1 to 8.

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