Patent Application
20230330952
The present invention relates to a method of manufacturing a composite component with continuous fibre reinforcement and having a hole to be used e.g. for joining the component with another component. In particular, it relates to such a component in which the hole is reinforced in such a way that localized forces applied to the hole are distributed to a region around the hole.
Fibre composite materials are used in many applications including for sports gear, cars, boats, wind turbine blades etc. These materials have a unique performance when it comes to lightweight load-carrying structural components as the material can be tailored to specific needs. However, beside their superior mechanical performance, they perform weakly when concentrated loads are to be introduced. Therefore, adhesive bonding is the preferred joining technique as the load can hereby be transferred over a larger area. Unfortunately, this method of joining limits e.g. the ability to substitute worn out components with new ones, and costly local repairs are therefore often performed to extend the lifetime of the structure.
An alternative is to use joining by bolt or rivet connections. This allows for some disassembly, but it requires excessive composite material to secure a sufficient load introduction. Such excessive amount of material is disadvantageous due to the added weight and volume as well as added cost. Furthermore, if the holes for the assembly are obtained by drilling, there is a risk of introducing damage and weak points in the material during the drilling.
It is an object of the present invention to provide a method of manufacturing a fibre-reinforced component with which it is prepared for assembly with another component in a way that allows for disassembly without damaging the component.
It is another object of the present invention to provide a method of manufacturing a fibre-reinforced component with which it is prepared for assembly with another component in a way that allows for a higher load carrying capacity for a given amount of material than with known methods of joining.
It is another object of the present invention to provide a method of manufacturing a fibre-reinforced component with which it is prepared for assembly with another component in a way that lowers the risk of failure of the component due to damage induced during the joining than with known methods of joining. Such damage could e.g. be induced with a known method requiring drilling of holes to be joined with bolts.
It is an object of at least some embodiments of the invention to provide a method of manufacturing a fibre-reinforced component with which it is prepared for assembly with another component in a way which is more reliable and/or more efficient than with known methods of joining.
It is a further object of the present invention to provide an alternative to the prior art.
In particular, it may be seen as an object of the present invention to provide a method of manufacturing a fibre reinforced composite component that solves the above mentioned problems of the prior art.
Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a method of manufacturing a composite component with continuous fibre reinforcement and having a reinforced hole, the method comprising:
The reinforced hole in the composite component being manufactured will typically be circular. However, other shapes, such as elliptical, oblong, or rectangular, are also covered by the scope of protection. The first and second holes will typically have the same geometrical shape, such as circular or elliptical, but in principle it will also be able to use a reinforcing member with a circumferential member having e.g. a circular first hole and an elliptical outer shape matching an elliptical second hole in the layered arrangement of the continuous reinforcement.
By “in engagement with”, in relation to the mutual arrangement of the element fibres and the circumferential member, is preferably meant that a force applied to the circumferential member can be transferred to the element fibres due to the engagement. At the time when the reinforcing element has still not been arranged in the position of use, the engagement may mainly be based on frictional forces or on the respective geometrical designs of the circumferential member and the element fibres. The element fibres can e.g. be arranged within the first hole in the circumferential member so that in the manufactured component, the element fibres are arranged through the first hole in the circumferential member while having the element fibres extending away from the first hole in the circumferential member; examples will be shown in the figures. However, the element fibres may also be arranged in further holes or slits provided in the circumferential member. Such arrangements imply that the reinforcing element can be prepared beforehand as a ready-to-use element which facilitates the manufacturing process compared to a process in which fibres used to reinforce a hole are to be arranged, e.g. as individual strands, during the manufacturing of the composite component. Thus, the use of a reinforcing element as in the present invention may result in a more efficient and reliable manufacturing process.
The word “element” in relation to “element fibres” is used because these fibres are related to the reinforcing element and to distinguish them from the continuous fibres forming part of the surrounding composite material.
By “sandwiching engagement” is preferably meant that the element fibres are arranged with at least one layer of the continuous reinforcement on each side thereof. Examples will be shown in the figures.
By such a manufacturing method, it is possible to obtain a composite component that can be joined to e.g. another component via the hole in a manner that forms a stronger and more fatigue resistant connection than without such reinforcement of the hole and thereby contribute to a more reliable and fail safe connection/joint. This is because external forces applied to the hole, typically locally, can be distributed over a larger region of the composite component thereby lowering the risk of local stresses exceeding a critical value. This is even more the case because a compressive and local stress is transferred into a tensile stress, and fibres used for composite materials typically have a larger tensile strength compared to their compressive strength.
The element fibres may e.g. extend radially away from a central axis of the hole. However, for some applications and loading situations, it may also be relevant to let the element fibres extend e.g. tangentially to the circumference of the hole as that would be more advantageous for taking-up in-plane torsional loading of the component during use.
Another advantage of the invention is that by reinforcing the hole by use of a reinforcing element designed and incorporated for that purpose, the other fibre reinforcement of the component can be optimised with respect to other forces to be carried during use of the component, as this other fibre reinforcement no longer needs to be arranged in a manner related to the transfer of forces from the hole.
A composite component manufactured in accordance with the present invention may e.g. find use in relation to wind turbine blades, such as for root end to hub reinforcement and for joining of blade sections. As an example, the possibility of using wind turbine blades that are made from more parts that can be assembled and used without compromising the strength requirements will make it easier to transport the blades to the site of use before assembly.
Within the car industry, components made in accordance with the invention may e.g. be used when there is a need for the joining of various metallic parts, such as suspension, bumper, motor, and seats, to a composite monocoque part. In fact, the invention is considered useful within a large number of industries including for the boat, train, and aviation industries.
In some embodiments of the invention, the element fibres are provided in a configuration selected from bundle, band, and/or stretchable sleeve. When they are provided as bundles or bands, these will typically be arranged at different parts of the circumferential members so that they extend in different directions. They may be evenly distributed around the circumferential member. Alternatively, more fibres may be arranged at some points than at others depending on an expected loading of the reinforced hole during use. The element fibres may also be provided as two or more stretchable sleeves arranged inside each other as will be shown in the figures. A stretchable sleeve typically comprises fibres that are connected, such as interwoven, in a loose and thereby stretchable tubular configuration. The connection, such as interweaving, provides some mutual support to the fibres whereby it may be easier to arrange and keep them in the desired positions until they are fixated by the solidified matrix. A further advantage of a sleeve is that it can hereby be easier to ensure an even distribution of the element fibres, so that an applied outer force can be redistributed into a larger region around the hole. The magnitude of stress concentrations from the external force will then be lowered due to the redistribution obtained by the element fibers.
The layered arrangement of the continuous fibre reinforcement may be provided by a winding process, a fibre placement process, or a tape laying process. In a winding process, the fibres are typically wound around a rotating mandrel. In such embodiments, a part of the wound fibres is considered as a layer even though it has been arranged over a period of time and not as a separate unit as would be the case for a fibre mat.
Alternatively, the layered arrangement of the continuous fibre reinforcement may be provided by stacking of fibre mats. Such fibre mats could be provided as dry mats or as pre-impregnated mats. They would typically be arranged in a mould for the provision of the outer shape of the component. The arrangement of the fibre mats can be performed manually or by an automated or semi-automated process.
In embodiments of the invention, wherein the layered arrangement of the continuous fibre reinforcement is provided by stacking of fibre mats, the method may further comprise the following steps:
As an alternative to such a method, the stacking process may be so that element fibres are arranged at the surface of the final component. It is also possible to have the first and second parts of the element fibres arranged next to each other, i.e. without fibre mats there between.
Alternatively to what has been described above, the first aspect of the invention may be obtained by providing a method of manufacturing a composite component with continuous fibre reinforcement and having a reinforced hole, the method comprising the following steps:
By “tailored fibre placement” is meant a textile manufacturing technique based on the principle of sewing, knitting or crochet for a continuous placement of fibrous material for composite components. The fibrous material is fixed with an upper and lower stitching thread on a base material, which in this case is the arrangement of fibre mats. By such a process, a part of the continuous fibre reinforcement can be placed near net-shape in curvilinear patterns upon a base material in order to create stress adapted composite components.
Such a way of performing the invention is mainly relevant in relation to methods wherein the layered arrangement of the continuous fibre reinforcement is provided by stacking of fibre mats, since the tailored fibre placement is typically provided in a manner that is not appropriate to combine with the presence of a mandrel as is normally used for the winding process.
The step of arranging the at least one second fibre mat on the at least one first fibre mat with the second holes aligned may be performed so that the circumferential member of the reinforcing element is sandwiched between the fibre mats.
In any of the embodiments as described above, the circumferential member may be a solid ring. Alternatively, the circumferential member can e.g. be continuous fibres wound around the element fibres. At least for some embodiments, a solid ring, such as a metal ring, will facilitate the arrangement of the continuous fibre reinforcement. In the case of fibre mats provided with second holes, they can be arranged around the solid ring which will ensure that they stay aligned throughout the manufacturing process. A solid ring is also considered to be more suitable for ensuring an even distribution of the forces applied during use. Furthermore, a metal ring can be used to improve the fatigue strength, if it is made in a material with sufficiently high fracture toughness to suppress any fatigue crack growth. The fatigue properties may be further improved by using a ring with low surface roughness. Furthermore, a well-defined interface between the bolt to be used for the joining and the rim of the hole minimizes the risk of crushing the laminate due to local high contact pressure or wear, or due to friction between the bolt and the laminate, i.e. adhesive wear due to sliding.
The method may further comprise using a guide mandrel to keep the second holes of the layered arrangement of continuous fibre reinforcement and the first hole of the at least one reinforcing element aligned during the manufacturing. The circumferential member will then be arranged in alignment with the guide mandrel as will be shown in the figures. What is here referred to as “guide mandrel” could be an element that is to remain in place as part of the final component. It could e.g. be a shaft, a bearing, or a tube. Alternatively, the guide mandrel could be removed after the solidification of the matrix material.
When a guide mandrel is used, the circumferential member may be in the form of continuous fibres wound several times around the guide mandrel, e.g. around a sleeve of element fibres.
In any of the embodiments as mentioned above, the reinforcing element may further be provided with a circumferential insert having an inner surface forming the edge of the reinforced hole and an outer surface for supporting the circumferential member. Hereby it will be easy to ensure that a required dimensional tolerance of the hole is obtained as that will be determined by the insert. It will also be a good way to ensure that the reinforced hole has a smooth surface which can improve the fatigue performance of the composite component, as it can be less prone to crack initiation caused by loading being applied to the surface of the hole, i.e. the inner surface of the insert, during use of the composite component.
The outer surface of the circumferential insert may e.g. have a recess adapted to receive and hold the circumferential member in place. Hereby it will be easier to keep the different parts aligned in the correct mutual positions during the manufacturing process. An example of a possible design will be shown in the figures.
In embodiments having a circumferential insert, it may be provided as two halves which are inserted from opposite sides of the reinforced hole being formed and joined to form a subsequently coherent insert. At least for some geometries that may facilitate the arrangement of the insert.
At least for some of the embodiments mentioned above, the method may further comprise the step of stitching the element fibres and the fibres of the continuous fibre reinforcement made by tailored fibre placement together after all the fibres and the reinforcement have been arranged. Hereby the risk of delamination can be lowered.
In any of the embodiments as described above, a stack of reinforcing elements may be used for the provision of the reinforced hole. This may be particularly relevant for components having large thicknesses.
A second aspect of the invention relates to a composite component being manufactured by any of the embodiments of the invention according to the first aspect of the invention.
A third aspect of the invention relates to a reinforcing element for use in a method according to the first aspect of the invention, the reinforcing element comprising:
In such a reinforcing element, the circumferential member may be a solid ring, and the reinforcing element may further comprise a circumferential insert having an inner surface adapted to form an edge of a hole to be reinforced by the reinforcing element and an outer surface for supporting the circumferential member. Such a circumferential insert may e.g. be made from metal or polymer.
In a reinforcing element comprising a circumferential insert, the outer surface of the circumferential insert may have a recess adapted to receive and hold the circumferential member in place.
The first, second and third aspects of the present invention may each be combined with any of the other aspects. Furthermore, the two overall different ways of performing a method according to the first aspect of the invention can also be combined. In such a combining method, first at least one reinforcing element comprising element fibres is arranged in engagement with a stack of fibre mats. Then additional reinforcement is arranged by use of tailored fibre placement to provide further routes for the transfer of stresses from the hole into the surrounding material.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
The method of manufacturing a composite component according to the invention as well as a reinforcing element for use in such a method will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.
As described above, the present invention relates to a composite component with continuous fibre reinforcement and having a hole to be used e.g. for the assembly of the component with another component. During use of the component, many kinds of loading situations can give rise to a concentrated loading on the edge of the hole. Due to the inner structure of the composite material, such concentrated loading may cause damage, such as delamination or crack growth.
The method includes incorporating at least one reinforcing element into the component in order to obtain a reinforced hole. In some embodiments of the invention, such a reinforcing element comprises a circumferential member with a through-going first hole and a plurality of continuous element fibres extending away from the circumferential member while being in engagement with the circumferential member.
A method of manufacturing a composite component with a reinforced hole will now be described with reference to the features shown in
The method as shown in
An alternative to the above-described incorporation of a reinforcing element 1 comprising element fibres 3 is schematically shown in
In any of the methods as described above, the arrangement of the continuous fibres 7 may include the use a guide mandrel 11 to keep the second holes 8 of the layered arrangement of continuous fibre reinforcement 7 and the first hole 9 of the at least one reinforcing element 1 aligned during the manufacturing whereby better tolerances can be obtained. An example of the use of such a guide mandrel 11 is shown schematically in
As mentioned above, it will be possible to use a stack of reinforcing elements 1 for the provision of the reinforced hole.
the load-carrying area is now located below the hole, and the stresses are reduced and distributed over a larger area. Thus, the stresses are well below the ultimate stress which is in the range of 280 MPa for the current laminate. These findings are also supported by the experimental data in
Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Furthermore, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2020 70590 | Sep 2020 | DK | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DK2021/050280 | 9/13/2021 | WO |
