CN114559716A

CN114559716A - Fiber composite laminate and method for manufacturing the same

Info

Publication number: CN114559716A
Application number: CN202111407915.0A
Authority: CN
Inventors: 弗朗西斯科·意达里阿诺; 阿尔贝托·吉雷利康索拉罗; 亚历山大·巴赫; 尤尔根·韦泽曼
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2020-11-27
Filing date: 2021-11-24
Publication date: 2022-05-31
Also published as: DE102020214936A1

Abstract

The invention provides a fibre composite laminate 1 having a central layer 2, intermediate layers 3, 3a, 3b, and outer layers 4, 4a, 4b arranged on the opposite side of the intermediate layers 3, 3a, 3b to the central layer 2. The central layer 2 comprises a composite material comprising carbon fibres 5 and a synthetic matrix 6, the intermediate layers 3, 3a, 3b comprise a composite material comprising carbon fibres 5 and/or glass fibres 7, and a synthetic matrix 6 comprising graphene nanoparticles 8, and the outer layers 4, 4a, 4b comprise a composite material comprising glass fibres 7 and a synthetic matrix 6. Furthermore, the invention provides a leaf spring 10 and a coil spring comprising the fibre composite laminate 1, a vehicle, and a method for producing a fibre composite laminate 1 comprising the fibre composite laminate.

Description

Fiber composite laminate and method for manufacturing the same

Technical Field

The present invention relates to a fiber composite laminated material and a manufacturing method thereof, and a leaf spring, a coil spring and a vehicle.

Background

The advantage of a leaf spring made of fibre-reinforced plastic is that it is light and has very good fatigue and corrosion resistance properties. Thus, for example in vehicles, they may replace conventional steel leaf springs. Glass-fiber-reinforced plastics (GFRP) are particularly suitable for leaf springs produced from fiber-reinforced plastics, since Glass-fiber-reinforced plastics have better elongation and are less expensive than carbon-fiber-reinforced plastics (CFRP).

However, compared to steel, fiber-reinforced plastics have the disadvantage of lower rigidity, so that geometric adjustments of the component, for example in the form of a cross-sectional change, are often required to meet the requirements of component rigidity.

In the more extensive design of leaf springs, leaf springs made of fibre-reinforced plastic are one way to compensate for the reduction in transverse stiffness. However, since the space is limited at the mounting portion of the leaf spring, it is often the case that leaf springs of different sizes cannot be mounted.

Another possibility is to use different fibers with different properties. It is thus possible to combine fibres of higher stiffness, such as carbon fibres, with fibres of lower stiffness, such as glass fibres, by superimposing the different fibres on each other to obtain a structure of one or more layers. This makes it possible to find a compromise between cost and mechanical properties. For example, DE 10139780a1 discloses a leaf spring with glass fibers and carbon fibers.

DE 102009058170a1 discloses a layered structure, adapted for design and cost reasons, which can increase the lateral stiffness with little effect on the vertical stiffness, providing a stiffer carbon fiber layer in the central plane and glass fibers in the outer plane, resulting in a kind of glass fiber-carbon fiber-glass fiber structure.

With such a layer structure, however, failure phenomena can occur at the interface of the different fibers. This may be caused by interlayer shear forces which have different effects due to the different longitudinal stiffness of the glass fibre layer and the carbon fibre layer.

When the leaf spring is stressed, the magnitude of the stress occurring in the individual layers is substantially proportional to the stiffness of the relevant layer, due to the bending moment, which results in longitudinal elongation and compression thereof.

If a leaf spring is considered as an ideal beam that is subjected to only bending forces and the whole leaf spring is made of the same material, its elongation and stress vary linearly over the whole thickness, as shown in fig. 1.

On the other hand, if the above-described glass fiber-carbon fiber-glass fiber structure is selected, interlayer shear stress caused by the difference in fiber stiffness occurs at the interface under the same conditions, as shown in fig. 2.

These interlaminar shear stresses can lead to delamination between the layers and failure of the components if the leaf springs are continuously stressed. This construction results in a limited service life of the leaf spring compared to conventional steel leaf springs.

Furthermore, DE 102015122621a1 discloses a device comprising two or more materials arranged in layers, the layers having different moduli and the layers having a decreasing modulus starting from the neutral axis. For example, a carbon fiber layer may be centrally disposed and surrounded by a glass fiber layer.

Furthermore, DE 102017122564a1 discloses a laminate having graphene layers as electrically conductive layers.

In addition, SUN, J., JI, J., CHEN Z., LIU, S., ZHAO, J. discloses that an epoxy resin composite material containing commercial graphene develops toward high toughness and high rigidity. Rscadv, 2019,9,33147-33154 discloses the use of graphene as a filler material in epoxy resins. The publication also discloses that a substrate reinforced with graphene nanoparticles has a higher tensile strength than a substrate reinforced without graphene nanoparticles.

Disclosure of Invention

On the basis of the above background, it is an object of the present invention to provide a material for a leaf spring, with which the above-mentioned disadvantages can be reduced or even avoided.

This object is achieved by the subject matter of the independent claims, the dependent claims relating to specific embodiments.

A first aspect of the invention relates to a fibre composite laminate, i.e. comprising a plurality of layers of fibre composite material joined together in layers.

The fibre composite laminate according to the invention has a central layer, an intermediate layer and an outer layer arranged on the side of the intermediate layer opposite to the central layer.

Alternatively, the fiber composite laminate may provide a symmetrical structure having a central layer, intermediate layers disposed on both sides of the central layer, and outer layers disposed on the opposite side of the intermediate layers from the central layer.

In this case, "disposed on the side of the intermediate layer opposite the central layer" means that each outer layer is connected to one of the intermediate layers on the side of the intermediate layer opposite the central layer, irrespective of the specific spatial arrangement. In other words, "on … …" does not necessarily mean "above … …," but merely indicates adjacent. Thus, the fiber composite laminate has the following structure: outer layer-middle layer-center layer-middle layer-outer layer.

The fibre composite laminate may optionally have further layers, which may be arranged between the already mentioned layers or on top of the outer layers. In one embodiment, the fiber composite laminate has only the layers explicitly mentioned according to the above structure.

Each layer of the fibre composite laminate has at least one reinforcing material in the form of fibres embedded in a matrix, in particular a synthetic matrix, the different layers differing in the use of different reinforcing fibres and/or different matrices.

Each layer may have one or more interlayers (ply). The number of interlayers depends on the preset maximum load of the fibre composite laminate. The fibers within the interlayer may preferably be continuous fibers and may be arranged unidirectionally within the interlayer or in the form of a woven or uncrimped fabric. The properties of the fiber composite laminate can be varied as desired, in particular by the size of the fibers, the arrangement within the interlayers, the fiber volume percentage and the number of interlayers within the layers. For example, the fiber volume percentage may be between 40% and 60%.

According to the invention, the central layer comprises a composite material comprising carbon fibers and a synthetic matrix. For example, the composite material of the central layer may consist of carbon fibres embedded in a synthetic matrix.

The intermediate layer comprises a composite material comprising carbon fibers and/or glass fibers, and a synthetic matrix comprising graphene nanoparticles. For example, the composite material of the intermediate layer may consist of carbon and/or glass fibers embedded in a synthetic matrix comprising graphene nanoparticles.

The outer layer comprises a composite material comprising glass fibers and a synthetic matrix. For example, the composite material of the outer layer may consist of glass fibers embedded in a synthetic matrix.

In the present invention, the term "glass fiber" refers to a material made of glass filaments. For example, the glass may be E-glass, S-glass, or R-glass.

In the present invention, the term "carbon fiber" refers to a material made of carbon filaments. For example, carbon fibers may be produced based on polyacrylonitrile or pitch.

A plurality of glass filaments or carbon filaments may form a roving with the plurality of glass filaments in the roving arranged parallel to each other. The roving may be a direct roving that is formed directly after spinning and application. Alternatively, a combination roving made of a combination of a plurality of direct rovings or multifilament yarns is also possible.

In the present invention, the term "synthetic matrix" refers to a synthetic material in which the fibers of the fiber composite laminate are or will be embedded. The synthetic matrix is preferably a thermoset matrix. For example, the synthetic matrix may be selected from a group comprising an epoxy matrix, a vinyl ester matrix, an amino resin matrix, a phenolic resin matrix, an unsaturated polyester resin matrix, and a polyurethane matrix. The synthetic matrix is preferably an epoxy matrix or a polyurethane matrix. The same synthetic matrix is preferably used for all layers. In the present invention, the term "synthetic substrate" is used as the case may be, and includes substrates in a fully cured state, a partially cured state, and a still uncured state.

In the present invention, the term "graphene" refers to a carbon modification of a two-dimensional structure (i.e., a single-layer structure). In this structure, each carbon atom is surrounded by three other carbon atoms at an angle of 120 ° to form a honeycomb structure.

In the present invention, the term "graphene nanoparticles" refers to a material made of unbound, aggregated and/or agglomerated graphene particles, wherein, in the number size distribution, at least 50% of the particles, aggregates or agglomerates have one or more external dimensions between 1nm and 100 nm. The graphene nanoparticles may preferably be in the form of nanoplatelets formed from a small number, meaning less than 10, of stacked individual graphene layers. For example, the size of a single graphene layer (the longitudinal extent of a two-dimensional single graphene layer) is between 5 and 40 μm.

In one aspect, the graphene nanoparticles are characterized by a large specific surface area, e.g., at 50m²G and 1000m²Between/g. On the other hand, graphene nanoparticles have a higher surface energy than other carbon nanoparticles (e.g., carbon nanotubes). Both properties have a positive influence on the mechanical properties of the proposed fiber composite laminate. Furthermore, by adding a small amount of graphene nanoparticles, the performance of the fiber composite laminate can be improved in a cost-effective manner. For example, the proportion of graphene nanoparticles contained in the synthetic matrix containing graphene nanoparticles may be between 0.01% and 10% by weight.

Optionally, the distribution and/or stability within the synthetic matrix may be improved, for example, by modifying the surface of the graphene nanoparticles. For example, surface modification can be performed by acid treatment and dispersion in polyvinylpyrrolidone, for example, SUN, J., JI, J., CHEN Z., LIU, S., ZHAO, J., discloses that commercial graphene-containing epoxy resin composites develop in the direction of high toughness, high rigidity. RSC adv.,2019,9, 33147-33154.

Suitable graphene nanoparticles may be prepared from graphite and may be prepared by various methods, such as chemical exfoliation, vapor deposition, oxidation, and/or sonication.

The synthetic matrix reinforced by the graphene nanoparticles may improve the ability of the laminate to absorb energy, thereby enabling the laminate to better withstand the potential for fracture of the interlayer.

In other words, the use of graphene nanoparticles increases the fracture energy, i.e. the maximum energy that a material system or laminate can absorb to achieve a progressive and detectable degradation of mechanical properties or even to achieve a catastrophic fracture. The fact is that the graphene reinforced composite material has higher elongation at break or tensile strength.

Therefore, the intermediate layer uses a synthetic matrix containing graphene nanoparticles, which may allow the performance of the fiber composite laminate to be improved, compared to a fiber composite laminate without the intermediate layer (i.e., having the structure of the background art).

The inventors have given a possible, non-limiting explanation for the beneficial properties of graphene nanoparticles, based on the fact that graphene nanoparticles, due to their large specific surface area on a microscopic level, act as a reinforcing agent for an otherwise soft matrix, thus allowing the necessary fracture energy to be increased significantly. Among other things, graphene nanoparticles improve the "support" of the fibers in the matrix.

Another aspect of the invention relates to a leaf spring having the fiber composite laminate described above. All statements in the present invention relating to the fibre composite laminate can be applied analogously to the proposed leaf spring, and the advantages of the fibre composite laminate correspond to the leaf spring.

With the leaf spring according to the invention, the maximum stress occurs in the longitudinal direction when it is subjected to the maximum permissible deflection. In order to prevent such stresses from adversely affecting the service life of the material, the invention provides an intermediate layer which is reinforced with graphene nanoparticles and which has the effect that the fibre composite laminate of the leaf spring is able to absorb higher energies.

Another aspect of the invention relates to a coil spring having the fiber composite laminate described above. All statements in the present invention relating to the fibre composite laminate are similarly applicable to the proposed coil spring, and the advantages of the fibre composite laminate correspond to those of the coil spring.

During compression, the coil springs are subjected to high torsional loads, thereby generating high shear stresses. In this case too, it is possible to provide intermediate layers reinforced with graphene nanoparticles at locations where the highest shear stress leads to a significant reduction in the service life of the component.

Another aspect of the invention relates to a vehicle having the leaf spring or coil spring described above. All statements in the present invention relating to leaf springs or coil springs are similarly applicable to the proposed vehicle. And the advantages of the plate spring or the coil spring correspond to those of the vehicle.

A vehicle is understood to mean a vehicle which is moved in any manner, for example, a land vehicle, such as a passenger car, but also a water vehicle or an aircraft.

In vehicles, there is a particularly advantageous effect, namely, a reduction in vehicle weight, due to the lighter weight of the leaf spring or coil spring, as compared to steel springs.

Another aspect of the invention relates to a method for producing the above-mentioned fibre composite laminate. Such a fiber composite laminate can be produced by the following method steps: producing a semifinished fiber base product forming the intermediate layer, the intermediate layer and the outer layer, arranging the semifinished fiber base product forming the intermediate layer on the semifinished fiber base product forming the central layer, arranging the semifinished fiber base product forming the outer layer on the side of the intermediate layer opposite to the central layer, and curing the semifinished fiber base product.

With regard to the symmetrical structure of the fiber-matrix laminated material manufactured by the present invention, the fiber-matrix semifinished products forming the intermediate layer are disposed on both sides of the fiber-matrix semifinished product forming the central layer, and the fiber-matrix semifinished products forming the outer layers are disposed on both sides of the intermediate layer opposite to the central layer.

Thus, for a symmetrical structure of the fibre matrix laminate produced according to the invention, the specific method steps are as follows: producing fiber matrix semi-finished products forming the central layer, the middle layer and the outer layer, arranging the fiber matrix semi-finished products forming the middle layer on two sides of the central layer, arranging the fiber matrix semi-finished products forming the outer layer on the other side, opposite to the middle layer, connected with the central layer, and curing the fiber matrix semi-finished products.

The term "semifinished fibre matrix" refers to a semifinished product consisting of reinforcing fibres, for example glass or carbon fibres impregnated with a synthetic matrix. For example, the fiber matrix semi-finished product may be a "prepreg".

The semifinished fibre matrix forming the central layer comprises carbon fibres impregnated with a synthetic matrix. The fibrous matrix semi-finished product forming the intermediate layer comprises carbon fibers and/or glass fibers impregnated with a synthetic matrix containing graphene nanoparticles. The semifinished fibre matrix forming the outer layer comprises glass fibres impregnated with a synthetic matrix.

The proposed method makes it possible to produce individual layers of semi-finished products, optionally also by means of a machine to produce the semi-finished products in advance, and to combine the pre-produced semi-finished products with one another later on as required. In this way, the fibre composite laminate can be produced quickly and at low cost.

Producing the intermediate layer-forming fibrous matrix blank may include impregnating carbon and/or glass fibers with a synthetic matrix containing graphene nanoparticles.

In other words, the plastic of the graphene nanoparticles and the synthetic matrix may be first mixed with each other, and then the resulting synthetic matrix containing the graphene nanoparticles may be applied to the carbon and/or glass fibers, for example, the synthetic matrix containing the graphene nanoparticles may be applied to the carbon fibers and/or glass fibers by a dipping method or a spraying method. This process variant is characterized by good dispersibility of the graphene nanoparticles in the synthetic matrix. This method can improve the reproducibility compared to the method variants described below, so that fibre composite laminates of uniform quality can be reliably produced.

Alternatively, producing the intermediate layer-forming semifinished fibrous substrate may comprise impregnating carbon or glass fibers with a synthetic matrix and then spraying with graphene nanoparticles.

In other words, the synthetic matrix may first be applied to the carbon and/or glass fibers, for example, using a dipping method or a spraying method. Subsequently, graphene nanoparticles are applied to the fibers that have been impregnated with the synthetic matrix by a spray coating process. The advantage of this variant of the method is that the graphene nanoparticles are mainly deposited at surface locations and when aligning the fiber matrix semifinished product forming the layers, the graphene nanoparticles are mainly located at the interfaces of adjacent layers. This may have a beneficial effect on the interface characteristics. Furthermore, the graphene nanoparticles may reduce consumption compared to the above method variants.

In both of the above process variants, the obtained impregnated fibers can subsequently be deposited, aligned to obtain the desired semifinished fibre matrix product.

Drawings

The invention is explained by way of example below and with reference to the preferred embodiments in the figures, the features indicated below can form an aspect of the invention either individually or in various combinations. In the figure:

FIG. 1 shows a schematic of stress in the x-direction in a prior art fiberglass laminate;

FIG. 2 shows a schematic of the stress in the x-direction in a prior art laminate of a glass fibre layer and a carbon fibre layer;

figure 3 shows a schematic of the stress in the x-direction in a fibre composite laminate with a glass fibre layer and a carbon fibre layer of a graphene nanoparticle reinforced interlayer;

FIG. 4 shows a schematic production view of an exemplary fiber matrix blank for forming an intermediate layer;

FIG. 5 shows a schematic view of an alternative method for producing an exemplary fiber matrix semi-finished product forming an intermediate layer;

FIG. 6 shows a schematic production view of an exemplary fiber matrix blank for forming a center layer;

FIG. 7 shows a schematic production diagram of an exemplary fiber matrix blank for forming an outer layer;

FIG. 8 shows a schematic view of an exemplary fiber composite laminate;

FIG. 9 shows a schematic of the change in fracture energy;

FIG. 10 shows a flow diagram of an exemplary method; and

fig. 11 shows a schematic diagram of an exemplary leaf spring and the distribution of stresses occurring therein.

Detailed Description

Figure 1 shows a stress diagram occurring under bending load for a single layer glass fibre laminate according to the prior art. Such bending load occurs, for example, if a single glass fiber laminate is used as the plate spring 10. The stress is 0Pa in the middle of the laminate, i.e., at a distance of 0m from the central plane of the laminate. Expansion occurs when positive expansion along the Z-axis occurs from the center of the laminate and compression occurs when negative expansion along the Z-axis occurs from the center of the laminate. For single ply fiberglass laminate analysis, a linear plot of stress versus laminate thickness (z-direction) was obtained.

Such a linear curve is in principle advisable, however, a single-layer glass fibre laminate is generally not suitable for use as a leaf spring 10, as explained in the foregoing.

Fig. 2 thus shows an image similar to fig. 1 of a three-layer laminate according to the prior art, comprising a central layer 2 with a carbon-fibre-reinforced synthetic matrix 6 and

outer layers

4a, 4b with a glass-fibre-reinforced synthetic matrix. In comparison with fig. 1, a linear curve of stress with laminate thickness is found only in the

layers

2, 4a, 4 b. In each case, in contrast, there is an abrupt change at the interface between the

layers

2, 4a, 4b, which can lead to interlaminar shear stresses, leading to failure of the laminate.

The fiber composite laminate 1 proposed by the embodiment of the present invention reduces the occurrence of this problem by using the

intermediate layers

3, 3a, 3b, and fig. 8 shows the structure of such an exemplary fiber composite laminate 1.

The exemplary fiber composite laminate 1 shown in fig. 8 has a central layer 2, an intermediate layer 3 disposed on the central layer 2, and an outer layer 4 disposed on the intermediate layer 3. Both the core layer 2 and the outer layer 4 consist of two interlayers, i.e. they comprise a core interlayer 2₁And 2₂And an outer interlayer 4₁And 4₂. However, the number of interlayers is not limited and a different number of interlayers may be present. Likewise, the intermediate layer 3 may have a plurality of interlayers.

The central layer 2 comprises a composite material consisting of carbon fibres 5 and a synthetic matrix 6, in the exemplary embodiment the synthetic matrix 6 is an epoxy matrix. Alternatively, a polyurethane matrix may also be used. The carbon fibres 5 are in the form of continuous fibres in which the individual filaments combine to form a roving. The arrangement of the carbon fibers 5 is unidirectional.

The intermediate layer 3 comprises a composite material comprising carbon fibres 5 and a synthetic matrix 6 comprising graphene nanoparticles 8, the synthetic matrix 6 likewise being epoxy-based. As an alternative or in addition to the carbon fibers 5, the intermediate layer may also contain glass fibers 7.

The outer layer 4 comprises a composite material consisting of glass fibres 7 and a synthetic matrix 6, the synthetic matrix 6 likewise being an epoxy matrix. The glass fibers 7 are in the form of continuous fibers, wherein the individual filaments are combined to form a roving. The arrangement of the glass fibres 7 is unidirectional, parallel to the carbon fibres in the central layer 2 and the intermediate layer 3.

Alternatively, the fibre composite laminate 1 may be of a symmetrical construction, with

intermediate layers

3a, 3b and

outer layers

4a, 4b being connected on both sides of the central layer 2 as shown in fig. 3. The explanations relating to fig. 8 may be applied to this embodiment in a corresponding manner.

Fig. 3 shows an image of a symmetrically constructed fibre composite laminate 1 similar to fig. 1 and 2, the laminate 1 having a central layer 2 consisting of a composite material comprising carbon fibres 5 and a synthetic matrix 6, and two

intermediate layers

3a, 3b of a composite material comprising carbon fibres 5 or glass fibres 7 and a synthetic matrix 6 comprising graphene nanoparticles 8, and

outer layers

4a, 4b consisting of a composite material comprising glass fibres 7 and a synthetic matrix 6. The legend shown in fig. 3 is also applicable to other images.

As shown in fig. 9, the graphene nanoparticles 8 in the

intermediate layers

3a, 3b lead to an increase in the fracture energy, thereby increasing the service life of the fiber composite laminate 1 under load. If the mixture law is used to calculate the expected tensile strength and elongation at break of the entire composite, it can be concluded that the total energy of the graphene nanoparticle reinforced composite, expressed as the area under the straight line in fig. 9, is larger.

Fig. 10 shows a production flow diagram of a fiber composite laminate 1, in a first method step S1 a fiber matrix semi-finished product 9 is produced which forms the central layer 2, the

intermediate layers

3, 3a, 3b and the

outer layers

4, 4a, 4b in the finished fiber composite laminate 1.

Here, the fiber matrix semi-finished product 9 forming the

intermediate layers

3, 3a, 3b may be produced by impregnating the carbon fibers 5 and/or the glass fibers 7 with a synthetic matrix 6 comprising graphene nanoparticles 8 or by impregnating the carbon fibers 5 or the glass fibers 7 with the synthetic matrix 6 and then spraying the graphene nanoparticles 8.

In method step S2, the fibre matrix blanks 9 are arranged one on top of the other in the desired sequence, i.e. the fibre matrix blanks 9 forming the

intermediate layers

3, 3a, 3b are arranged on the fibre matrix blanks 9 forming the central layer 2 and the fibre matrix blanks 9 forming the

outer layers

4, 4a, 4b are arranged on the fibre matrix blanks 9 forming the

intermediate layers

3, 3a, 3 b.

In a method step S3, the fiber matrix semifinished product is cured, for example by the action of high pressure and/or high temperature.

Fig. 4 to 7 schematically show the production flow of the respective fiber matrix semi-finished product 9.

Fig. 4 and 5 show two alternative methods for producing a fiber matrix semi-finished product 9, by means of which it is possible to form an

intermediate layer

3, 3a, 3b consisting of a composite material containing carbon fibers 5 and a synthetic matrix 6 containing graphene nanoparticles 8, it being possible to use glass fibers 7 instead of or in addition to the carbon fibers 5.

The method shown in fig. 4 is a single stage impregnation process, wherein a synthetic matrix 6 containing graphene nanoparticles 8 is first formed from graphene nanoparticles 8 and a synthetic matrix (e.g. epoxy) 6. For this purpose, the graphene nanoparticles 8 may be dispersed in the synthetic matrix 6 by conventional methods. The graphene nanoparticles may optionally be pretreated, e.g. surface-modified, to improve their distribution in the synthetic matrix and/or to increase the stability of the dispersion.

Subsequently, the synthetic matrix 6 comprising the graphene nanoparticles 8 is added to the carbon fibers 5 in the form of a roving, for example by spraying. Subsequently, the carbon fibers 5 are impregnated with a synthetic matrix 6 comprising graphene nanoparticles 8, deposited in the desired arrangement, and the synthetic matrix 6 is partially cross-linked, so as to obtain a prepreg material of a plate-like fibrous matrix semi-finished product 9.

Fig. 5 shows an alternative method with a two-stage impregnation process. In a first impregnation stage, the carbon fibers 5, which are present in the form of rovings, are impregnated with the synthetic matrix 6, and the fibers impregnated in this way are subsequently sprayed with the graphene nanoparticles 8. The prepreg material is then formed in such a single stage impregnation process.

Fig. 6 shows a method for producing a fibre matrix semifinished product 9, by means of which a central layer 2 can be produced, which central layer 2 consists of a composite material of carbon fibres 5 and a synthetic matrix 6. For this purpose, the carbon fibers 5 in the form of rovings are impregnated with a synthetic matrix 6. After the carbon fibres 5 impregnated with the synthetic matrix 6 have been completed, they are deposited in the desired arrangement, and the synthetic matrix 6 is partially cross-linked, so that a prepreg of a semifinished fibre matrix 9 is obtained.

Fig. 7 shows a method for producing a semifinished fibre matrix product 9, by means of which

outer layers

4, 4a, 4b can be produced, the

outer layers

4, 4a, 4b being composed of a composite material comprising glass fibres 7 and a synthetic matrix 6. For this purpose, the glass fibres 7 in the form of rovings are impregnated with the synthetic matrix 6, which, after the completion of the impregnation of the glass fibres 7 with the synthetic matrix 6, are deposited in the desired arrangement, and the synthetic matrix 6 is partially cross-linked, so that a prepreg of a semifinished fibre matrix 9 is obtained.

Fig. 11 shows a schematic view of an enlarged region a of an exemplary leaf spring 10. The leaf spring 10 has a symmetrical construction of the fibre composite laminate 1 with

intermediate layers

3a, 3b and

outer layers

4a, 4b adjoining the central layer 2 on both sides. In the exemplary embodiment, the central layer 2 and the

outer layers

4a, 4b each have three

interlayers

2₁,2₂,2₃,4₁,4 ₂,4₃,4₄,4₅,4₆And, the number of layers may be different from each other. For a more detailed explanation, reference is made to the explanation relating to fig. 3, which fig. 3 shows a similarly constructed fibre composite laminate 1.

In addition to the structure of the fiber composite laminate 1, fig. 11 also shows the distribution of stress in the fiber composite laminate 1 when the plate spring 10 is subjected to a load in the direction of the arrow. It can be seen that the

intermediate layers

3a, 3b reinforced with graphene nanoparticles can absorb a large amount of energy, and thus the fracture energy as a whole is improved.

List of reference numerals

1 fiber composite laminate

2 center layer

21,22, … 2n core layer interlayer

3. 3a, 3b intermediate layer

4. 4a, 4b outer layer

41,42, … 4n outer interlayer

5 carbon fiber

6 synthetic matrix

7 glass fiber

8 graphene nanoparticles

9 fiber matrix semi-finished product

10 leaf spring

Method steps S1 to S3

Claims

1. A fibre composite laminate (1) having a central layer (2), an intermediate layer (3, 3a, 3b) and an outer layer (4, 4a, 4b) arranged on the opposite side of the intermediate layer (3, 3a, 3b) to the central layer (2), wherein:

-the central layer (2) comprises a composite material of carbon fibres (5) and a synthetic matrix (6),

-the intermediate layer (3, 3a, 3b) comprises a composite material comprising carbon fibres (5) and/or glass fibres (7), and a synthetic matrix (6) comprising graphene nanoparticles (8), and

-the outer layer (4, 4a, 4b) comprises a composite material comprising glass fibers (7) and a synthetic matrix (6).

2. A fibre composite laminate (1) according to claim 1, wherein the intermediate layers (3a, 3b) are arranged on both sides of the central layer (2) and the outer layers (4a, 4b) are arranged on the opposite side of the intermediate layers (3a, 3b) to the central layer (2).

3. Fiber composite laminate (1) according to claim 1 or 2, wherein the proportion of the graphene nanoparticles (8) in the synthetic matrix (6) containing graphene nanoparticles ranges between 0.01% and 10% by weight.

4. Fibre composite laminate (1) according to any one of the preceding claims, wherein the synthetic matrix (6) is selected from the group comprising an epoxy matrix, a vinyl ester matrix, an amino resin matrix, a phenolic resin matrix, an unsaturated polyester resin matrix and a polyurethane matrix.

5. A leaf spring (10) having a fibre composite laminate (1) according to any one of the preceding claims.

6. A coil spring having a fibre composite laminate (1) according to any one of claims 1 to 4.

7. A vehicle having a leaf spring (10) or the wrap spring according to claim 5 or 6.

8. A method of producing a fibre composite laminate (1) according to any one of claims 1 to 4, comprising:

-S1: producing a semifinished fibre-based product (9) for forming the central layer (2), the intermediate layers (3, 3a, 3b) and the outer layers (4, 4a, 4b),

-S2: -arranging the fibre-matrix semifinished product (9) forming the intermediate layer (3, 3a, 3b) on the fibre-matrix semifinished product (9) forming the central layer (2), -arranging the fibre-matrix semifinished product (9) forming the outer layer (4, 4a, 4b) on the side of the intermediate layer (3, 3a, 3b) opposite to the central layer (2), and

-S3: curing the fiber matrix semi-finished product (9).

9. Method according to claim 8, wherein the fibre-matrix semi-finished product (9) forming the intermediate layer (3a, 3b) is arranged on both sides of the fibre-matrix semi-finished product (9) forming the central layer (2), and the fibre-matrix semi-finished product (9) forming the outer layer (4, 4a, 4b) is arranged on the side of the intermediate layer (3, 3a, 3b) opposite to the central layer (2).

10. The method according to claim 8 or 9, wherein producing the fiber matrix semi-finished product (9) forming the intermediate layer (3, 3a, 3b) comprises impregnating carbon fibers (5) and/or glass fibers (7) with a synthetic matrix (6) containing graphene nanoparticles (8).

11. The method according to claim 8 or 9, wherein producing the fibrous matrix semi-finished product (9) forming the intermediate layer (3, 3a, 3b) comprises impregnating carbon fibers (5) or the glass fibers (7) with a synthetic matrix (6) and subsequently spraying the graphene nanoparticles (8).