Patent Application
20230243077
The invention relates to a method and a device for producing an annular multiaxial laid fabric and to an annular object produced therewith.
Multiaxial laid fabrics are used in particular in the production of composite fibre materials. In this case, these multiaxial laid fabrics are incorporated as reinforcement in a polymer matrix, where the polymer matrix can consist of polyester resin or epoxy resin, for example. To form a multiaxial laid fabric, parallel threads are laid one on top of the other in at least a lower thread layer and an upper thread layer, where the orientation of the threads in the lower thread layer differs from the orientation of the threads in the upper thread layer. After the two thread layers have been laid one on top of the other, the threads of the lower thread layer and the threads of the upper thread layer are joined to each other at points. For example, the threads can be stitch bonded, stapled or else thermally bonded to each other. In the following, “thread” is understood to mean a linear product of textile character, such as a yarn, filament or ribbon. The threads of the laid fabric can consist, for example, of carbon, glass or ceramic. Synthetic fibres, such as aramid or polyamide fibres, are also used.
DE 197 26 831 C5 discloses a multiaxial machine for forming a multiaxial laid fabric. This multiaxial machine has two mutually spaced, elongated transport elements, which are formed with fixing elements, the transport direction of which runs in the longitudinal direction of the multiaxial laid fabric produced. The transport elements in this case are in the form of driven transport chains. First, a lower thread layer in the form of an endless thread array is laid on the transport chains using a first thread-laying unit, which is guided on a feed gantry transverse to the transport direction of the transport chains, the laid thread array being laid around rows of needles, pins or hooks (fixing elements) attached to the transport chains. The feed gantry is movable at an adjustable speed along the movement direction of the transport chains. The speed of the thread-laying unit guided on the feed gantry is also adjustable. The orientation of the threads of the laid thread array relative to the transport direction of the transport chains can be defined via the interplay between the transport speed of the transport chains, the speed of movement of the feed gantry, and the speed of movement of the thread-laying unit. The threads can be oriented such that, between the threads and the transport direction of the multiaxial laid fabric produced, there is an angle of 0 degrees (threads are parallel to the transport direction), an angle of 90 degrees (threads are at a right angle to the transport direction) or an angle between 0 degrees and 90 degrees. An upper thread layer is then laid in an analogous manner on the lower thread layer, the orientation of the threads of the upper thread layer differing from the orientation of the threads of the lower thread layer. Further thread layers can be laid on the upper thread layer, depending on the application. Furthermore, inlays, such as films, foams or textiles, can be laid between thread layers lying one on top of the other. Once the desired number of thread layers has been laid, the threads of the thread layers are joined at least locally to one another using a fixing unit and then wound up into rolls.
A similar multiaxial machine is known from DE 10 2007 024 124 B3, in which the fixing unit is a stitching machine that stitches the threads of the thread layers with a stitch-bonding thread.
With the multiaxial machines known from the prior art, multiaxial laid fabrics have been produced continuously in rolls until now. If the multiaxial laid fabrics are to be used a fibre reinforcement in curved or annular structures, they must be curved accordingly. This requires a tight curve, in particular for completely closed annular structures. However, this results in twisting and displacement of the thread layers relative to one another. Furthermore, a butt joint or overlap is formed, which must be separately closed. It is disadvantageous that inhomogeneities are produced in the multiaxial laid fabric owing to the twisting and displacement of the thread layers and the subsequently closed butt joint or overlap, which can ultimately have a negative influence on the load-bearing capacity of the annular structures.
A first embodiment of the invention is a method for producing an annular multiaxial laid fabric (2), which is constructed from at least two thread layers (2a, 2b) laid one on top of the other, the method comprising the following steps: laying of a lower thread layer (2a) in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, around the entire circumference of two mutually spaced ring elements (3), the thread array or the single thread, or the thread-array sections or the single-thread sections, of the lower thread layer being held temporarily, after laying, by thread-holding elements (4) arranged around the ring circumference, and the threads of the thread array or the thread-array sections or the single thread or the single-thread sections of the lower thread layer (2a) forming an angle (α) within the range greater than 0 degrees up to 90 degrees to the circumferential direction (8) of the ring elements (3); laying of a upper thread layer (2b) in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, around the entire circumference of the two mutually spaced ring elements (3), the thread array or the single thread, or the thread-array sections or the single-thread sections, of the upper thread layer (2b) being held temporarily, after laying, by the thread-holding elements (4) arranged around the ring circumference, and the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the upper thread layer (2b) forming an angle (β) greater than 0 degrees to the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the lower thread layer (2a); fixing the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the lower thread layer (2a) at points to the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the upper thread layer (2b) by means of a fixing unit (10) around the circumference of the first and upper thread layers (2a, 2b) laid in a ring; detaching the first and upper thread layers (2a, 2b) from the thread-holding elements (4); and removing the annular multiaxial laid fabric (2) from the mutually spaced ring elements (3).
A second embodiment of the invention is a method according to the first embodiment, characterised in that at least one further thread layer (2c, 2b) in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, is laid around the entire circumference of the two mutually spaced ring elements (3) between the first and upper thread layers (2a, 2b), the thread array or the single thread, or the thread-array sections or the single-thread sections, of the further thread layer (2c, 2b) being held temporarily, after laying, by the thread-holding elements (4) arranged around the ring circumference (3), and the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the further thread layer (2c, 2b) forming an angle greater than 0 degrees to the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the first and upper thread layers (2a, 2b).
A third embodiment of the invention is a method according to the second embodiment, characterised in that two or more further thread layers (2c, 2d) are laid between the first and upper thread layers (2a, 2b), the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the further thread layer (2c, 2d) forming an angle greater than 0 degrees to the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the respectively adjacent thread layers (2a, 2b, 2c, 2d).
A fourth embodiment of the invention is a method according to any one of the first through third embodiments, characterised in that the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the lower thread layer (2a) and/or the upper thread layer (2b) and/or the further thread layer (2c, 2d) and/or the further thread layers (2c, 2d) are formed from identical or differing materials.
A fifth embodiment of the invention is a method according to any one of the first through fourth embodiments, characterised in that the threads within one of the thread arrays or thread array sections are formed from identical or differing materials.
A six embodiment of the invention is a method according to any one of the first through fifth embodiments, characterised in that, for the fixing of the thread layers (2a, 2b, 2c, 2d) at points, the threads are stitch-bonded with a stitch-bonding thread or stapled with staple elements or thermally fixed.
A seventh embodiment of the invention is a method according to any one of the first through sixth embodiments, characterised in that, after the lower thread layer (2a) has been laid, or after the further thread layer (2c, 2d) has been laid, or after the upper thread layer (2b) has been laid, a flat layer material (13) or a filler-thread layer is laid around the entire circumference.
An eighth embodiment of the invention is a method according to the seventh embodiment, characterised in that the flat layer material (13) is a separating film and/or a nonwoven fabric and/or a spacer fabric.
A ninth embodiment of the invention is a method according to any one of the first through eighth embodiments, characterised in that, after the threads of the thread layers (2a, 2b, 2c, 2d) have been fixed at points, a polymeric matrix material is applied to an inner side of the annular multiaxial laid fabric (2) and/or an outer side of the annular multiaxial laid fabric (2).
A tenth embodiment of the invention is a multiaxial machine (1) for producing an annular multiaxial laid fabric (2), characterised in that the multiaxial machine (1) has two mutually spaced ring elements (3), which are fixed in position relative to each other and have thread-holding elements (4), arranged around the ring circumference; at least one first thread-laying unit (6), which is guided on a first feed gantry (5) and is supplied by a first thread feed, for laying at least a lower thread layer (2a) and a upper thread layer (2b) in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, on the two mutually spaced ring elements (3); and a fixing unit (10) for locally fixing the threads of the first and upper thread layers (2a, 2b) laid on the ring elements; and that the first thread-laying unit (6) is movable on the first feed gantry (5) to and fro between the ring elements (3) transverse to the circumferential direction (8) of the ring elements (3); and that the first feed gantry (5) and the ring elements (3) which are fixed in position relative to each other can be rotated relative to each other in the circumferential direction (8).
An eleventh of the invention is a multiaxial machine (1) according to the tenth embodiment, characterised in that it has at least one second thread-laying unit, which is guided on a second feed gantry and is supplied by a second thread feed, for laying a further thread layer (2c, 2d) in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, on the two mutually spaced ring elements, and that the second thread-laying unit is movable on the second feed gantry to and fro between the ring elements (3) transverse to the circumferential direction (8) of the ring elements (3), and that the second feed gantry and the ring elements (3) which are fixed in position relative to each other can be rotated relative to each other in the circumferential direction (8).
A twelfth embodiment of the invention is a multiaxial machine (1) according to the tenth or eleventh embodiment, characterised in that an outer contour of the two ring elements (3) is congruent or that an outer contour of one ring element (3) is larger than an outer contour of the other ring element (3).
A thirteenth embodiment of the invention is a multiaxial machine (1) according to any one of tenth through twelfth embodiments, characterised in that it has a feed device (12) for feeding and laying a flat layer material (13) on the thread layer (2a, 2b) and/or the further thread layer (2c, 2d).
A fourteenth embodiment of the invention is a multiaxial machine (1) according to any one of tenth through thirteenth embodiments, characterised in that the fixing unit (19) is a stapling unit, a stitch-bonding unit or a heating unit.
A fifteenth embodiment of the invention is a multiaxial machine (1) according to any one of the tenth through fourteenth embodiments, characterised in that a supporting element (14) for supporting the lower thread layer (2a) laid on the ring elements (3) is provided between the two mutually spaced ring elements (3) at least in some sections around the ring circumference.
A sixteenth embodiment of the invention is a multiaxial machine (1) according to the fifteenth embodiment, characterised in that the supporting element (14) is a strip element which runs in at least some sections around the ring circumference.
A seventeenth embodiment of the invention is a multiaxial machine (1) according to any one of tenth through sixteenth embodiments, characterised in that the ring elements (3) have a circular or oval or elliptical outer contour.
An eighteenth embodiment of the invention is a multiaxial machine (1) according to any one of tenth through sixteenth embodiments, characterised in that the ring elements (3) have an outer contour in the shape of a regular polygon.
A nineteenth embodiment of the invention is a multiaxial machine (1) according to any one of the tenth through eighteenth embodiments, characterised in that the thread-holding elements (4) are needles which in each case of each of the ring elements (3) form a crown of needles along the ring elements (3), or that the thread-holding elements (4) are clamping elements arranged along the ring elements (3).
A twentieth embodiment of the invention is an annular object, characterised in that it contains an annular multiaxial laid fabric (2) produced by a method according to any one of the first through ninth embodiments.
A twenty-first embodiment of the invention is an annular object according to the twentieth embodiment, characterised in that the threads of the lower thread layer (2a) and/or of the upper thread layer (2b) and/or of the further thread layer (2c, 2d) and/or of the further thread layers (2c, 2d) and/or the flat layer material (13) are formed from polyamide or aromatic polyamide or polyethylene terephthalate or regenerated cellulose or metal or carbon or glass or ultra-high molecular weight polyethylene or polypropylene or polyacrylonitrile or PBO (poly(p-phenylene-2,6-benzobisoxazole)) or PBI (polybenzimidazole) or PPS (polyphenylene sulphide) or organic fibres or combinations thereof.
A twenty-second embodiment of the invention is an annular object according to the twentieth or twenty-first embodiment, characterised in that said object is a vehicle tyre, and that the annular multiaxial laid fabric (2) is integrated into the tyre casing.
Embodiments of the invention are explained herein by means of the drawings below. In the figures:
The object of the invention is therefore to create a method and a device for forming a multiaxial laid fabric for annular structures which has no twisting or displacement of the thread layers. Furthermore, it should no longer be necessary to close a butt join or overlap separately to form a closed ring of the multiaxial laid fabric.
According to the invention, this is achieved with a method having the features of Claim 1. Advantageous embodiments of the method can be found in Claims 2 to 9. The method comprises the following steps:
With the method, the thread layers are already brought into their shape intended for the subsequent product by laying them around the entire circumference of the ring elements before fixing the threads. Curving of thread layers already fixed to one another is no longer necessary, and therefore twisting and displacement of the thread layers by curving are avoided. Since the thread layers are laid on the ring elements in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, there is also no butt joint or overlap needing to be subsequently closed, in contrast to the subsequent curving of the thread layers. With the laying of the thread layers with different thread orientations, an annular multiaxial laid fabric is formed.
Between the lower thread layer and the upper thread layer, a further thread layer or further thread layers in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, can be laid around the entire circumference of the two mutually spaced ring elements and held with the thread-holding elements, the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the further thread layer forming an angle greater than 0 degrees to the threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the respectively adjacent thread layers. The multiaxial laid fabric can be constructed according to the requirements of each case in terms of stability, tensile strength, flexibility, etc., via the number of the further thread layers and the orientation of the threads of the further thread layers.
The threads of the thread array or the single thread, or the thread-array sections or the single-thread sections, of the lower thread layer and/or the upper thread layer and/or the further thread layers can be formed from identical or differing materials. The threads inside each of the thread arrays can also be formed from identical or differing materials (hybrid fibre bundles). By suitable selection and/or combination of materials, the multiaxial laid fabric can be further adapted to the requirements of each case in terms of stability, tensile strength, flexibility, etc.
For the fixing of the thread layers at points, the threads are, for example, stitch bonded with a stitching thread, or stapled with staple elements, or thermally fixed.
When the thread layers are laid, a flat layer material or a standing-thread layer can be laid around the entire circumference between parts of the thread layers. This layer material can provide further functional properties in the multiaxial laid fabric. The flat layer material can, for example, be a separating film and/or a nonwoven fabric and/or a spacer fabric. The filler threads are laid in such a manner that they are oriented parallel to the ring circumferential direction.
In one advantageous embodiment, before the fixed thread layers are detached from the thread-holding elements of the ring elements, a polymeric matrix material is applied to an inner side of the annular multiaxial laid fabric and/or to an outer side of the annular multiaxial laid fabric. The mechanical properties can thereby be adapted further to the respective application of the annular multiaxial laid fabric.
Furthermore, a multiaxial machine having the features of Claim 10 is proposed for producing an annular multiaxial laid fabric using the method according to the invention. Advantageous embodiments are disclosed in Claims 11 to 18. The multiaxial machine has two mutually spaced ring elements, which are fixed in position relative to each other and have thread-holding elements arranged around the ring circumference; at least one first thread-laying unit, which is guided on a first feed gantry and fed by a first thread feed, for laying a thread layer in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections on the two mutually spaced ring elements; and a fixing unit for locally fixing the threads of the thread layers laid on the ring elements. The first thread-laying unit is movable on the first feed gantry to and fro between the ring elements transverse to the circumferential direction of the ring elements. The first feed gantry and the ring elements, which are fixed in position relative to each other, can be rotated relative to each other in the circumferential direction.
In a further embodiment, the multiaxial machine has at least one second thread-laying unit, which is guided on a second feed gantry and supplied by a second thread feed, for laying a further thread layer in the form of an endless thread array or an endless single thread, or in the form of thread-array sections or single-thread sections, on the two mutually spaced ring elements. The second thread-laying unit is movable on the second feed gantry to and fro between the ring elements transverse to the circumferential direction of the ring elements. The second feed gantry and the ring elements, which are fixed in position relative to each other, can be rotated relative to each other in the circumferential direction.
It is proposed that an outer contour of the two ring elements be congruent or that an outer contour of one ring element be larger than an outer contour of the other ring element.
Furthermore, the multiaxial machine has a feed device for feeding and laying a flat layer material on the thread layer or on the further thread layer.
It is proposed that the fixing unit be a stapling unit, a stitch-bonding unit or a heating unit.
One embodiment provides for the ring elements to have a circular or oval or elliptical outer contour. In principle, it is also not excluded that one of the ring elements has, for example, a circular outer contour and the other ring element has, for example, an elliptical outer contour.
One embodiment provides for the ring elements to have an outer contour in the shape of a regular polygon.
With circular ring elements, it is preferred if the lower thread layer is laid with an angle of 90 degrees between the threads of the thread array or the thread-array sections, or the single thread or the single-thread sections, of the first layer, and the circumferential direction of the ring elements. Laying in this manner best transfers the round outer contour of the ring elements to the inner contour of the lower thread layer. With the laying of the thread layers on ring elements with identical outer contours, a multiaxial annular laid fabric in the form of a cylinder is produced. If the outer contours of the ring elements differ in extent, a multiaxial annular laid fabric in the form of a truncated cone is produced. The smaller the angle between the threads of the thread array or the thread-array sections, or the single thread or the single-thread sections, of the lower thread layer and the circumferential direction of the ring elements, the more the inner contour of the lower thread layer laid on the ring elements deviates from the outer contour of the ring elements in the region between the rings, but this is not necessarily disadvantageous, depending on the application.
In one advantageous embodiment, a supporting element for supporting the lower thread layer laid on the ring elements is provided between the two mutually spaced ring elements at least in some sections around the ring circumference. By means of said supporting element, the desired inner contour of the annular multiaxial laid fabric is maintained when the thread layers are laid, in particular if the lower thread layer is laid on circular ring elements at an angle of less than 90 degrees to the ring circumferential direction.
It is proposed that the supporting element be a strip element which runs in at least some sections around the ring circumference. This strip element is arranged on an inner side of the annular multiaxial laid fabric being formed.
In one advantageous embodiment, the thread-holding elements are needles that, together, form a crown of needles around the ring elements. During laying, the thread array or the single thread is laid around these needles, so that a fixing of the thread to the ring elements is achieved therewith. In an alternative embodiment, the thread-holding elements are clamping elements, which are arranged along the ring elements and fix the threads or the thread sections.
Also claimed is an annular object having an annular multiaxial laid fabric produced by the method according to the invention.
It is proposed that the threads of the lower thread layer and/or of the upper thread layer and/or of the further thread layer and/or of the further thread layers and/or the flat layer material be formed from polyamide or aromatic polyamide or polyethylene terephthalate or regenerated cellulose or metal or carbon or glass or ultra-high molecular weight polyethylene or polypropylene or polyacrylonitrile or PBO (poly(p-phenylene-2,6-benzobisoxazole)) or PBI (polybenzimidazole) or PPS (polyphenylene sulphide) or organic fibres or combinations thereof.
One embodiment provides for the annular object to be a vehicle tyre and for the annular multiaxial laid fabric to be integrated into the tyre casing.
According to the invention, at least a lower thread layer 2a (
By means of a further revolution, an upper thread layer 2b is analogously laid around the entire circumference of the two mutually spaced ring elements 3. By changing the speed of movement of the thread-laying unit 6 along the feed gantry 5 and/or the mutual rotation of the feed gantry 5 and the ring elements 3, the orientation of the threads of the upper thread layer 2b is changed relative to the threads of the lower thread layer 2a, and therefore the laying of the lower thread layer 2a and the upper thread layer 2b is multiaxial. The threads of the thread array of the upper thread layer 2b form an angle β (
After the lower thread layer 2a and the upper thread layer 2b have been laid, the threads of the lower thread layer 2a are fixed at points to the threads of the upper thread layer 2b around the entire circumference. To this end, the multiaxial machine 1 has a fixing unit 10. The fixing unit 10 can be, for example, a stapling unit or a stitch-bonding unit or a heating unit, without the invention being limited thereto. With a stapling unit, the threads of the thread layers are attached at points with staple elements. If the fixing unit is in the form of a heating unit, heat is input at points into the thread layers 2a, 2b and causes (with suitable selection of the thread materials) melting of the threads at points. On cooling, there are then integral bonds at points between the threads of the thread layers 2a, 2b. If the fixing unit 10 is in the form of a stitch-bonding unit, the threads of the thread layers 2a, 2b are connected to one another at points by means of a stitch-bonding thread.
In an embodiment which is not shown, the multiaxial machine 1 has at least one further thread-laying unit (analogous to the first thread-laying unit 6), which is guided on a further feed gantry and is supplied by a further thread feed. Here too, the further thread-laying unit is movable to and fro between the ring elements 3 on the further feed gantry transverse to the circumferential direction 8 of the ring elements 3, and the further feed gantry and the ring elements 3 are rotatable relative to each other in the circumferential direction. For example, the lower thread layer 2a is laid with the first thread-laying unit 6, and the upper thread layer 2b or a further thread layer is laid with the further thread-laying unit. The advantage in this case is that both thread-laying units can be arranged at an offset around the circumference of the ring elements 3, and both thread layers can be laid virtually simultaneously, with fewer than two complete mutual rotations of the feed gantry 5 and the ring elements 3 being sufficient to lay both thread layers 2a, 2b, which ultimately increases the speed for laying the thread layers 2a, 2b.
To form the multiaxial laid fabric 2, the lower thread layer 2a and the upper thread layer 2b are laid and fixed to each other. Furthermore, one or more further thread layers can also be laid between the lower thread layer 2a and the upper thread layer 2b.
After the threads have been connected at points, the thread layers 2a, 2b (and any further thread layers) are detached from the thread-holding elements 4 (for example, the thread-holding elements in the form of needles are retracted, or the threads are cut off the needles). The annular multiaxial laid fabric 2 so formed is then removed from the mutually spaced ring elements 3 (for example, pushed down from the ring elements 3 in an axial direction).
The multiaxial machine 1 in
Furthermore, the multiaxial machine 1 shown in
In the embodiment shown, the outer contours of the ring elements 3 are circular. The multiaxial machine 1 according to the invention is not limited to this embodiment, however. For example, the ring elements 3 can also have an oval or elliptical contour or an outer contour in the shape of a regular polygon. Furthermore, the rotational axes 9 of the two ring elements 3 in the embodiment shown in
The invention is not limited to thread-holding elements 4 in the form of needles. For example, the thread-holding elements 4 can also be in the form of clamping elements.
As an alternative to a thread array, it is also possible to lay an endless single thread around the entire circumference, in which case, however, more laying sub-steps are necessary for laying around the entire circumference when compared with laying a thread array. Likewise, single-thread sections or thread-array sections can also be laid on the two ring elements 3 instead of laying an endless thread array or an endless single thread. The single-thread sections or the thread-array sections can be cut from an endless thread or an endless thread array during laying. The single-thread sections or the thread-array sections can also be supplied pre-cut to the length matching the ring spacing and laid on the ring elements 3.
The threads of the thread array or the single thread of the lower thread layer 2a and/or the upper thread layer 2b and/or the further thread layer and/or the further thread layers can be formed from identical or differing materials. Furthermore, the threads within the thread arrays can also be formed from identical or differing materials (hybrid fibre bundle).
The method described can be used to produce multiaxial laid fabric 2 with a closed ring shape. Preferably, the method is used to produce multi-layered multiaxial laid structures having additional flat layers, preferably spacer textiles and preferably spacer fabrics. All organic or inorganic endless fibres, such as polyester, polyethylene, polyamide, carbon, glass, basalt, aramid, cellulose, are used as thread materials for the weft and filler threads; polyester, polypropylene and polyamide are preferably used for the stitch-bonding thread. Metallic threads or strands consisting of steel or aluminium are also used as filler-thread materials.
A typical variant is the laying of multiaxial thread layers of glass fibres in a first step, laying a spacer fabric consisting of polyester in a thickness of 2-20 mm, preferably 5-12 mm, in particular 8 mm, in a second step, and again laying multiaxial thread layers of glass fibres in a third step. Preferably, the upper and lower thread layers are identical in terms of the number of layers, weight per unit area and fibre type and are mirror-symmetrical to the spacer fabric layer in terms of their fibre orientation.
An advantage of this structure is that the butt joint of the spacer fabric, at which the two end faces of the spacer fabric meet in the ring shape and which actually forms a weak point in the overall textile structure on mechanical loading, no longer has any negative effects thanks to the subsequent stitch-bonding of the entire layer structure. Further advantageous properties of the annular structure produced in this manner result when the multiaxial thread layers on the inside and outside of the annular structure and the outsides of the spacer fabric, with the exception of the loop piles 13a of the spacer fabric, are then embedded in a polymeric matrix material and thus form a material bond. In one extension of the method according to the invention, after the threads of the thread layers have been fixed at points, a polymeric matrix material 21 is applied to an inner side of the annular multiaxial laid fabric and/or an outer side of the annular multiaxial laid fabric using an application device 20 (see
With the method according to the invention, multi-layered multiaxial ring structures are produced, which can be used to produce various annular objects. One possible annular object can be a motor-vehicle tyre (an airless, lightweight tyre, for example), in which the annular multiaxial laid fabric 2 is integrated into the tyre casing. Particularly in this intended use, the embedding of the upper or lower thread layers of the annular multiaxial laid fabric in a polymeric matrix material is advantageous. On one hand, the necessary fibre-reinforcement effect is produced. On the other, good material bonding is achieved to the tyre casing formed from synthetic rubber or natural rubber using a vulcanisation process. A low-viscosity reactive mixture or molten thermoplastic, for example, can be used for the embedding of the thread layers. However, it must be ensured, depending on the structure of the textile layer structure, that only a defined number of layers is impregnated by the plastic in the thickness direction. Particular in the preferred textile layer structure with a spacer fabric as the middle layer and outer layers of multiaxial laid fabrics, in order to maintain its textile deformation properties under compressive stress, the spacer fabric should not be impregnated. To this end, the loop piles of the spacer fabric must not be embedded, which can be ensured by inlaying separating films during the laying process. Preferably, thin polymer films are used, which can be pierced during stitch-bonding or stapling of the thread layers. Depending on the matrix material used, different thermoplastic films can be used, which enter into a good integral bond with the matrix. These can be films based for example on PP, PE, nylon 6, nylon 6,6, TPU [thermoplastic polyurethane], PLA [polylactic acid]. The stitch-bonding of the film to the textile layers also proves advantageous in this case, since the stitch-bonding thread has flow channels through the film in the thickness direction which fill easily with the matrix owing to the capillary forces and thus locally fixes the film well to the surrounding textile layers.
The threads of the lower thread layer 2a and/or of the upper thread layer 2b and/or of the further thread layer and/or of the further thread layers and/or the flat layer material 13 are preferably formed from polyamide or aromatic polyamide or polyethylene terephthalate or regenerated cellulose or metal or carbon or glass or ultra-high molecular weight polyethylene or polypropylene or polyacrylonitrile or PBO (poly(p-phenylene-2,6-benzobisoxazole)) or PBI (polybenzimidazole) or PPS (polyphenylene sulphide) or organic fibres or combinations thereof.
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