Patent Application
20100015405
The present invention relates to a production method for a workpiece composed of a fibre-composite material, and to a corresponding apparatus which, in particular, can carry out the production method according to the invention.
Although the present invention is described in the following text on the basis of a problem relating to the production of load-bearing structures in an aircraft, the present invention is not restricted to this but in general relates to the production of workpieces composed of fibre-composite materials, in particular elongated workpieces.
Fibre-composite materials have been proven for the production of an aircraft owing to their high tensile strength and low intrinsic weight. In addition to flat elements such as those in the outer envelope, elongated elements, for example so-called stringers, are formed from fibre-composite materials. Stringers with a constant profile cross section can be produced by means of a continuous-flow method.
Stringers with different cross sections are required in an aircraft. This requires the provision of different tools in order to facilitate the wide range of differently shaped stringers. Furthermore, stringers are required whose profile varies along the length of the stringer. Until now, stringers with a constant profile cross section have been adapted by manual work by application of additional individual layers composed of composite material, manually. The quality of stringers produced in this way is only of an average level, and the method is complex.
One object of the present invention is to provide a production method as well as an apparatus by means of which workpieces can be produced from a fibre-composite material, which can have a wide range of profile cross sections and can preferably be produced using a single tool. The production process is preferably carried out as a continuous production process.
The production method according to claim 1 of the invention provides the following steps for this purpose:
The workpiece is formed from the main material, by means of the production method.
The production method according to the invention matches the cross section of the workpiece to the cross section of a tool by means of the secondary material. The workpiece blank preferably has a constant cross section, which is predetermined by the tool, over its entire length.
The secondary material is preferably chosen such that it has similar mechanical characteristics to the pre-impregnated fibre semi-finished product, at least for the purposes of the prevailing conditions when the blank moulds are joined together, that is to say at the appropriate pressure and the appropriate temperature.
The at least two blank-mould areas can be arranged integrally on a blank mould. The blank mould can then be folded or slotted in the longitudinal direction for pressure-bonding. Each blank-mould area can likewise be arranged on an individual blank mould, that is to say each blank-mould area corresponds precisely to a blank mould.
According to one development a plurality of layers composed of a pre-impregnated fibre-composite material and/or the secondary material are applied in a third area of the support means in such a manner that no layer composed of the main material is covered by a layer composed of the secondary material. This ensures that the secondary material is arranged along the surface of the workpiece blank that is produced, and that the secondary material can subsequently be completely removed. Furthermore, this allows areas of any desired thickness or strength to be produced from the main material in the workpiece.
One refinement provides for the main material and/or the secondary material to be applied with a thickness which is in each case such that the thickness of the blank-mould areas is homogeneous.
The pre-impregnated fibre semi-finished product may be a woven fabric, a knitted fabric and/or a scrim. The fibre semi-finished product for this purpose preferably has fibres which are oriented at right angles to one another. According to one development, the scrim is formed from an even number of individual layers, in whose odd-numbered individual layers first fibres are aligned in a first direction and in whose even-numbered individual layers second fibres are aligned in a second direction, with the first direction being inclined at an angle of between 30° and 60° to the second direction. The first direction of all of the odd-numbered individual layers is the same, and the second direction in the immediately successive odd-numbered individual layers is arranged with mirror-image symmetry with respect to the first direction.
The support means may be a film.
The pre-impregnated fibre semi-finished product preferably has carbon fibres.
The secondary material may have a half-mould with glass fibres.
According to one refinement, before the pressure-bonding process, one of the first of the blank moulds is arranged parallel to a second of the blank moulds, and these two blank moulds are then pressure-bonded to one another.
One development provides for the first blank-mould area and the second blank-mould area to be pressure-bonded corresponding to a curve.
According to one refinement, the first blank-mould area is produced with a first length and the second blank-mould area is produced with a second length, with the first length corresponding to the length of the first blank-mould area after the pressure-bonding process, and with the second length corresponding to a length of the second blank-mould area after the pressure-bonding process. In the case of the curve, the distinction is therefore drawn between the first length and the second length. This results in the workpiece being produced without stresses. In particular, this avoids compression of fibres in the fibre semi-finished products.
The object stated above is also achieved by an apparatus for production of a workpiece composed of a fibre-composite material according to claim 13, having:
The moulding press may have a sequence of moulding segments which are arranged opposite one another in pairs and can be arranged along a predetermined curve for a state of the moulding press in which force is applied. The flexible arrangement of the moulding segments allows any desired curvature and shape of the workpiece along its longitudinal direction.
One development provides for at least two feed devices to be provided, which supply two blank moulds parallel to the moulding press, in which case a first speed for the first feed device and a second speed for the second feed device can be adjusted as a function of the curvature of the predetermined curve.
The invention also relates to a method for production of a plastic fibre-composite component in the form of a profile with a profile cross section which varies over the length, using the pultrusion process according to the precharacterizing clause of claim 16, and to a plastic fibre-composite component produced using the method. The invention also relates to a prefabricated scrim for carrying out a method such as this. Finally, the invention relates to a semi-finished product for production of a plastic fibre-composite component in the form of a profile with a profile cross section which varies over its length.
The so-called pultrusion process is nowadays a method of choice for the production of plastic fibre-composite components when the aim is to produce profiles with a constant profile cross section over their length. In the method, typically continuous material layers are stored wound up as a prefabricated scrim on rolls in the form of prepreg materials, a plurality of them are joined together, and they are pressure-bonded to one another under the influence of pressure and heat. The composite component obtained after solidification has high strength, and the production process costs little and is effective.
If, for example because of static requirements to which the plastic fibre-composite component is subject, there is a need for the profile cross section to vary over the length of the profile, this is conventionally produced by applying additional prepreg layers to the profile obtained after the pultrusion process, using a manual lamination process. An additional adhesive film may possibly also be required. This is a highly costly and time-consuming manufacturing process. In this case, both costs and manufacturing time are wasted not only by the manual lamination process itself but also by the prior treatment, that is required for this purpose, of the basic profile before the application of the additional fibre-composite layers. This prior treatment is carried out either by means of peel ply, which must be removed again manually from the basic profile after curing, or by grinding, waterbreak test, followed by the basic profile being dried back.
In modern aircraft construction, where fibre composites are increasingly being used not only as skin elements but also as structural components (stringers) which reinforce them, or else as bending beams, it is desirable to be able to produce plastic fibre-composite components with a profile cross section which varies over their length. By way of example, these can be used as stringers on a vertical fin whose cross-sectional thickness decreases with the aircraft vertical direction corresponding to the bending moment decreasing in this direction, or else as lateral floor supports with cross-sectional thickness increasing towards the ends, corresponding to the forces that occur.
A further object of the invention is to provide an improved method for production of a plastic fibre-composite component of the type mentioned initially. A further aim is to provide a prefabricated scrim for carrying out an improved method such as this. A final aim is to provide a semi-finished product for production of a plastic fibre-composite component in the form of a profile with a profile cross section which varies over its length.
This object is achieved by a method for production of a plastic fibre-composite component having the features of claim 16. The object is also achieved by a plastic fibre-composite component, produced using the method, according to claim 35. Another component of the solution according to the invention is a prefabricated scrim for carrying out the improved method according to claim 36. A final component of the solution according to the invention is also a semi-finished product for production of a plastic fibre-composite component having the features of claim 37.
Further advantageous embodiments and developments of the subject matter according to the invention are characterized in the respective dependent claims.
The present invention will be explained in more detail in the following text with reference to preferred embodiments and using the attached figures, in which:
a to 1d show two blank moulds for use in an embodiment for production of a workpiece;
a to 2c show a workpiece blank which is produced from the blank moulds shown in
a to 3c show a workpiece which is produced according to the first embodiment;
a to 4c show a workpiece blank which is produced according to a second embodiment;
a to 5c show a workpiece blank which is produced according to a third embodiment;
a to 7c show a workpiece blank which is produced according to the fourth embodiment;
a to 8d show cross sections through further workpiece blanks which are produced according to other embodiments;
a to 11c show a multilayer fibre-composite material for use in one of the embodiments;
a to 14c show schematic cross-sectional views of a part of a plastic fibre-composite component in the form of a profile with a profile cross section which varies over its length, which is produced by means of a pultrusion process, according to two exemplary embodiments of the invention;
a shows a schematic illustration of a pultrusion installation which is known from the prior art; and
b shows various phases in the successive formation of the desired profile from a prefabricated scrim, and
The same reference symbols in the figures denote identical or similar elements in the following text.
A first embodiment of a production method for a workpiece composed of a fibre-composite material will be explained in the following text with reference to
A first blank mould 1 is illustrated in the form of a side view and a plan view in
The main material 6 is preferably a pre-impregnated fibre semi-finished product (prepreg), for example having fibres composed of carbon. The pre-impregnated fibre semi-finished product can be applied to the surface 2 in the first area 4 by machine or in an automated form by means of a laying device, a so-called tape layer.
The secondary material 7 can be applied by a laying device in the second area 5 in the same way. A fibre semi-finished product with glass fibres is particularly suitable for use as the secondary material. In the uncured state, the main material 6 and the secondary material 7 therefore have similar ductile characteristics, which advantageously do not differ significantly for a subsequent pressing process. Furthermore, the secondary material 7 may be a rapid-curing material.
The thickness 8 of the secondary material 7 and of the main material are constant and of the same magnitude over the entire size of the blank mould 1. This results in the blank mould 1 having a planar surface 9.
c and 1d illustrate a second blank mould 10, which is likewise prefabricated from the film 3, the main material 6 and the secondary material 7. As can be seen in the plan view in
One workpiece blank 14 is formed from in each case two of the blank moulds 1, 10 described above, and is illustrated in the form of a side view and two cross-sectional views along the planes A and B in
In this exemplary embodiment, the two second blank moulds 10 are angled downwards along their longitudinal edge, that is to say in the direction of the film 3. The two second blank moulds 10 which have been profiled in this way are arranged at the rear with their surfaces 9 facing one another. The first blank moulds 1 are arranged with their surfaces 9 facing the angled longitudinal edges on the left-hand and right-hand angled longitudinal edges of the second blank moulds 10. This results in the cross section of the workpiece blank 14 with a double-T shape, as illustrated in
The blank moulds 1, 10 are now pressure-bonded to one another, so that the blank moulds 1, 10 are adhesively bonded to one another by means of the main material 6. The secondary material 7 should be chosen such that it is not connected to the material 6 in an adhesive or other manner during the pressing process. Furthermore, it is advantageous for the secondary material 7 to have the same ductile characteristics as the material 6, in order that the cross section of the workpiece blank 14 is not deformed during the pressure-bonding process.
In a modification of the first embodiment, a separating layer, for example a film, can be inserted between the secondary material 7 and the main material 6. This advantageously prevents connection of the two materials 6, 7.
In a subsequent step, the film 3 and the secondary material 7 are removed. This results in the workpiece 15 as is illustrated in conjunction with
The workpiece 15 is then cured in the normal manner. This can be done by the influence of pressure and/or heat.
In another embodiment, the tool blank 14 is cured. In this case, it has been found to be advantageous for the secondary material 7 to cure quickly, so that the time required for production of the workpiece 15 is increased only insignificantly. The cured secondary material 7 is then removed from the main material 6, which has likewise been cured.
The first embodiment as described above can be modified in many ways. In particular, all geometric shapes and cross sections of the workpiece 15 which can be thought of are possible. A plurality of different workpiece blanks are illustrated in the form of side views and corresponding cross sections in the following text. The correspondingly produced workpiece as well as the blank moulds that are required for this purpose can be derived from the appropriate figures by simple geometric considerations.
a to 4c show a workpiece blank 16c which has a thicker transversely located structure in the upper area in the cross section A than in the lower area of the same cross section. The film 3 is not shown, in order to simplify the illustration. However, in the same way as in
a to 5c show a workpiece blank 17 whose cross section has a simple T-profile. This workpiece blank 17 may be produced either by being formed from three blank moulds, or else by first of all producing a workpiece blank in the form of a double-T, as shown in
A second embodiment of the method for production of a workpiece will be explained in conjunction with
By way of example, only the main material 6 is applied to the film 3 in a second area 24 in the illustrated embodiment. The thickness of the individual layers 21, 22 and 23 is chosen such that the thickness of the blank mould 19 is constant over its entire length.
The workpiece blank 25 is produced from the blank mould 19 using a second blank mould. In this case, by way of example, the second blank mould is composed of the main material 6. The two first blank moulds 19 are angled along one edge, as is shown in
a to 8d show various cross sections which can be produced by means of the embodiments and blank moulds already described. Once again, it should be noted that the cross section of the workpiece blank may be the same in all cross sections.
The two blank moulds 35, 36 are guided parallel to one another and are introduced into a pressing device 37. Once the entire blank mould 35, 36 has been arranged in the pressing device 37, the two blank moulds 35, 36 are pressure-bonded to one another by the pressing device. This results in the shape of the workpiece blank being stamped in by the pressing device.
The pressing device 37 is followed by a separating device 38. The separating device 38 removes the secondary material from the workpiece blank. For this purpose, the film 3 is removed from the workpiece blank. During this process, the secondary material 7 is preferably also detached from the workpiece blank.
The workpiece blanks shown in
The structure of the material 6 on the film 3 for one particularly preferred embodiment will be described in conjunction with
The fibres in the second individual layer 6b in turn have first fibres 41, which are arranged along the main direction. The second fibres 44 arranged on them are at an angle 45 to the main direction of the first fibres 41. The second angle 45 is preferably designed such that the third fibres 44 are arranged with mirror-image symmetry about the second fibres 42, with respect to the first fibres 41. In this case, the angle 45 has the opposite mathematical sign to the angle 43.
The sequence of the individual layers 6a, 6b of the main material 6 ensures that, when the individual blank moulds are pressure-bonded, no fibres which lie parallel to one another come to rest on top of one another. In a situation such as this, these fibres could slide into one another, which would reduce the thickness of the workpiece blank in an undesirable manner at this point.
It is self-evident that, in the case of curved workpiece blanks, the fibre materials of the inner blank mould 52 may be compressed. The inner blank mould 52 is that blank mould which has a smaller radius of curvature than the blank mould 53 located opposite it. The compression of the fibres leads to weakening of the mechanical characteristics of the completed workpiece.
This is counteracted by producing the two blank moulds 52, 53 with different lengths. The lengths of the two blank moulds 52, 53 are matched to the lengths which result along the two opposite surfaces in the finished workpiece. The inner blank mould 52 is thus shorter than the outer blank mould 53.
The production devices 50, 51 for this purpose preferably insert the two blank moulds 52, 53 into the pressing device 54 at different feed rates. This is done such that the starts and the ends of the two blank moulds 52, 53 arrive in the pressing device 54 at the same time.
The invention is not restricted to the embodiment described above.
In particular, the only necessity is for the blank moulds to have a constant thickness over their length, although their thickness can vary over the width of the blank moulds. Workpieces of different design to T-shaped or double-T-shaped workpieces can also be produced.
In the described embodiments, the blank moulds are produced as elements that are separate from one another. In one embodiment, which is not described, however, it is also possible to provide a single support means. The support means is subdivided into blank-mould areas. The dimensions of the blank-mould areas correspond essentially to those of the separate blank moulds described above. The main material and the secondary material are applied to the respective blank-mould areas in a corresponding manner to the separate blank moulds. Before pressure-bonding of the blank-mould areas to form the workpiece blank, the support means is then folded or broken along the boundaries of the blank-mould areas.
a shows a schematic illustration of a pultrusion installation 100, which is known per se from the prior art and is used to produce plastic fibre-composite components 10′; 20′ in the form of profiles. The material layers to be processed are stored in the form of prepreg materials, wound up onto rolls 110 as prefabricated scrims, are joined together in a pre-forming device 120, and are pressure-bonded to one another in a pressing tool 130, under the influence of pressure and heat. Heat treatment is carried out in a tunnel oven 140 which follows the pressing tool, in order to completely cure the fibre composite. The prefabricated scrim is drawn through the installation by a pulling device 150. The profiles are cut to the desired length in a cutting device 160.
The desired profile is formed successively in the preforming device 120 by changing the prefabricated scrims, as shown in the various phases in
The profile cross section, which varies over the length of the profile, is in each case produced by one or, in the case of the illustrated exemplary embodiments, likewise a plurality of further material layers 14′; 24′, 25′ which are applied to the basic profile and are connected to it. These have a length which occupies only a portion of the length of the profile so that this results in the desired profile cross section, which varies over its length.
These further material layers 14′; 24′, 25′ are applied to the continuous material layers 11′; 21′ which form the basic profile, together with the respective compensation layers 14a′; 24a′, 25a′ which first of all supplement the profile cross section, which is desired in the end effect and varies over the length, in that portion of the length of the profile which is not occupied by the further material layers 14′; 24′, 25′, to form a profile cross section which is constant over the length of the profile. This makes it possible to use the pultrusion process to produce a semi-finished product which has a constant cross section over its length, as is also the case with conventional pultrusion processes.
A separating layer 50′ is arranged between the compensation layers 14a′; 24a′, 25a′ and the continuous material layers 11′; 21′, which are located underneath them and form the basic profile, and the further material layers 14′; 24′, 25′, which form the profile cross section which varies over its length, when the compensation layers 14a′; 24a′, 25a′ are located above them, which makes it possible to remove the compensation layers 14a′; 24a′, 25a′ at a suitable time after the pressure-bonding process and curing, with the purpose of the compensation layers 14a′; 24a′, 25a′ being to ensure a constant cross section during the pultrusion process, although they are not intended to be a component of the final product in the form of the plastic fibre-composite component 10′; 20′ with a profile having a profile cross section which varies over its length.
The exemplary embodiments which are illustrated in
In the exemplary embodiment illustrated in
According to the exemplary embodiments illustrated in
For all of the exemplary embodiments, the separating layer 50′ may be provided in the form of an anti-adhesion powder or in the form of a separating film, or else, if required, in some other suitable manner.
The continuous material layers 11′; 21′ may be stored in the form of a prefabricated scrim wound up on one or more rolls, and may be supplied to the process for production of the composite component 10′; 20′. The further material layers 14′; 24′, 25′, which are intended to form the profile cross section which varies over the length of the profile, and the compensation layers 14a′; 24a′, 25a′ which supplement them can likewise be stored in the form of a prefabricated scrim wound up on one or more rolls, and can be supplied to the process. In this case, the further material layers 14′; 24′, 25′ on the one hand and the compensation layers 14a′; 24a′, 25a′ which supplement them on the other hand can each be supplied from different rolls. In this case, it would be necessary to ensure that the abutment points 14b′; 24b′, 25b′ between the mutually supplementing layers are positioned correctly with respect to one another.
On the other hand, the further material layers 14′; 24′, 25′ which form the varying profile cross section and the compensation layers 14a′; 24a′, 25a′ which supplement them may be wound up jointly in the form of a prefabricated scrim with a constant cross section on one roll, and may be used for the method. In addition, it is possible to provide for at least one of the continuous material layers 11′; 21′ to also be wound up on a roll together with these layers to form a prefabricated scrim with a constant cross section. In the case of profiles whose cross-sectional thickness is not excessively large, it is even possible for all of the layers, that is to say the continuous material layers 11′; 21′ as well as the further material layers 14′; 24′, 25′ which form the profile cross section which varies over its length, and the compensation layers 14a′; 24a′, 25a′ which supplement them to be wound up together in the form of a prefabricated scrim with a constant cross section on a single roll.
The prefabricated scrim may additionally contain a support film, which supports the respective layers. A support film such as this is normally detached from these various layers while these various layers which are supplied from different rolls are being drawn together, and is removed from the process.
If a separating film is used as the individual separating layer, this may either be a component of the prefabricated scrim, or may be supplied separately, in which case it is normally then also wound up on a roll.
As is shown in
The plastic fibre-composite component 10′; 20′ with a profile cross section which varies over its length, and the compensation layers 14a′; 24a′, 25a′; 40′ which supplement it form a semi-finished product, which can be transported or stored in its own right, until these two components are separated.
The plastic fibre-composite component according to the invention and its production method, as well as the said semi-finished product offer a large number of advantages over conventional methods for production of such parts using the pultrusion process, specifically a considerable saving in costs and time for production, avoidance of the need for complex application of additional reinforcing layers and possibly adhesive film onto the basic profile, including omission of prior treatment which may be necessary in this case, avoidance of any additional autoclave process for such application of additional reinforcing layers, a better laminate quality and thus better mechanical performance by the composite component obtained, and the lack of test effort for the basic profile.
The profile cross section which varies over the length also offers the production advantage of a pultrusion profile whose weight is optimized and which is matched to the load.
Traditional pultrusion profiles have been distinguished by a profile cross section which is constant over their length, and by a constant component thickness. As long as the profile cross section remains constant over the length, any form of geometry (H, T, o, X, V, M, D, etc.) can be produced. The invention is distinguished in that this basic geometry can be retained, and in that the profile cross section can be varied in its component thickness. There are essentially no restrictions to the basic geometry.
All conventional materials such as CFP, GFP, AFP, natural fibres, etc., may be used as the fibre material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 038 666.3 | Aug 2006 | DE | national |
| 10 2007 015 516.8 | Mar 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/054366 | 5/4/2007 | WO | 00 | 9/28/2009 |
| Number | Date | Country | |
|---|---|---|---|
| 60838241 | Aug 2006 | US | |
| 60881613 | Jan 2007 | US |
