DE10005202A1 - Fiber reinforcement preforms oriented for particular applications are assembled by securing fiber bundles into place by stitching - Google Patents

Abstract

Fiber bundles or rovings (1) are placed on a conveyor (4) with the required fiber orientation by a handling device (2). The fibers are secured in position by seams at successive stitching stations (5,6). Sandwich structures incorporating fabrics (8), films, honeycombs, foams can be built up to deal with expected forces in any direction.

Description

The invention relates to a method for producing a novel textile reinforcement Semi-finished product class according to the preamble of claim 1.

For the production of continuous fiber reinforced fiber-plastic composite components (FKV) the reinforcing fibers are generally in the form of a flat textile semi-finished product brought in. An increase in efficiency in the production of components from continuous fiber strengthened plastics is improved technologies for manufacturing the textile Reinforcement structures achieved. The technology used to manufacture fiber Semifinished is for the later achievable strength, or utilization of the fiber own crucial. The semi-finished products to be produced in this way must, on the one hand, be different ne can have fiber orientations, and on the other hand compatible with the matrix his. If fabrics are used as reinforcement semi-finished products, in the composite for example, only 50-60% of the possible strength of a precisely aligned fiber be fathered. This results in the demand for semi-finished products that are precisely aligned Have fibers.

Judging from the existing manufacturing processes for the production of continuous fiber reinforced FKV, so there are individual requirements for the semi-finished textile, which results from the processing process and the component-specific requirements surrender. This leads to the demand for process and component-oriented confection dated fiber semi-finished products. Conventional processing methods for such plant fabrics are based on the use of given textile structures. The way to Lö solution to component and process-specific problems and requirements via an adjustment the semi-finished textile has not yet been used. The present method represents one consistent solution for the production of semi-finished fiber products, which are made of special Derive processing requirements (e.g. optimal binding architecture adapted sewing process) and at the same time meet the requirements of different components len. Such semi-finished products are referred to below as "Manufacturing Process Adapted Re inforcements (MPAR) ".

Textile, pre-assembled semi-finished products

Fibers are known to be load-bearing (component-oriented, load-bearing and confectionary tioned) and one-dimensional in a subsequent knitting process, d. H. in a Direction to sew together (laid-open specification DE 196 24 912 A1 and Offenle publication DE 197 26 831 A1 and Hörsting, K .; Huster, M .: Targetting cost reduction by FEA-designed reinforcement textiles. Proceedings 'ECCM-8', Naples / June 1998, pp. 635- 643). Such flat textile semi-finished products are called ready-made fabrics. Furthermore, there is a further one in the sense of assembling reinforcement structures Processing of these assembled multi-axial fabrics using conventional sewing technology complex preforms. Different types of semi-finished textile, as well Force application elements can be connected to each other (laid-open specification 196 08 127 A1). Another process for the appropriate storage of fibers and Manufacturing of component-oriented individual parts is the so-called "Tailored Fiber Place ment (TFP) "(published application DE 197 16 666 A1 and published application  DE 197 16 666 A1), which uses the embroidery technology around individual fibers in a load-bearing manner to file.

Additional blanks are required for preform production from ready-made fabrics editing required. There are fraying edges of the individual parts or he increased amount of waste. In this case, measures to avoid further fraying.

In the case of further processing of ready-made fabrics into thermoplastic FKV systems must have matrix-compatible binding threads (mesh threads, knitting threads) are set, which, however, are often caused by various sewing preparations (texturing, Stretching) is not completely included in the FKV as a matrix or fiber component. The Ver Working such threads on conventional warp knitting machines is only possible to a limited extent.

Due to the increased number of rows of stitches in the knitting process, there is also one Damage to the fibers (fiber undulations, local compacting) resulting in an ab lowering the mechanical properties of the FKV. Should such clutches in after following sewing processes to complex preforms are local Sliding consolidation to carry out shifts (e.g. fiber undulations, gels delay) in order to ensure an optimal result. This requires a further step in addition to the fabric production or the actual pre formings.

The sewing threads serve to fix the individual layers to each other. This function can Only fulfill the clutch in a dry state. After the impregnation process is over part of the stitch-forming threads is superfluous and leads to lowered mechani in-plane properties compared to UD tapes.

A process for the direct production of parts or the complete component as a pre form is the so-called TFP, whereby a carrier material must be used here. The This process uses modified embroidery technology, which is why the problem of Back of this reinforcement textile is important. Knots arise the lockstitch used, which in the individual fixation of each required rovings, are of a larger size. From these knots Flaws in the FKV are to be expected, which is in connection with the carrier material can be significant. Furthermore, multiple parts can be made in parallel, however must then be removed from the embroidery machine, and the machine then be re-equipped with new carrier material. This also requires Process a fixation of every single roving what, especially for large laminate thick, to a frequent penetration of the embroidery needles through the reinforcement structure is coming. There is no damage to the reinforcement rovings. Another The obstacles to this technology are different and not exactly predictable Component thicknesses and the calculation of such structures.

In the following, the versions are divided into thermosetting plastic and thermoplastic FKV to classify the different problems and solutions.  

Duromer FKV

In the case of processing to FKV systems with a thermoset matrix, the resin injection ontechnology (RTM) established as a very flexible manufacturing process. Here precon assembled preforms and / or textile reinforcement structures (assembled fabrics, Braids, knitted fabrics, fabrics, etc.) used as a semi-finished reinforcement.

In order to produce complex preforms, a preliminary process is used provided textile structures, used. Each individual layer of these semi-finished products is required cut separately to be assembled into thicker packages in a subsequent process (Sewing or gluing or binder technologies). All properties of this half witnesses are taken over (see above). If one follows these processes arise numerous other manufacturing steps that cover the entire process in its economy affect significantly negatively. This is especially true if the individual required layers must be fixed to each other before assembly. The handling is of immense importance here.

Edge problems that lead to defects or process errors can (e.g. race Tracking) can only be avoided by further process steps. Dry edges of textile Flat structures fray and thus prevent precise manufacturing.

Improvements in damage tolerance (crash or impact properties) are reported using Final stitching made. In this case, several jam layers are combined into packages caught and forfeited again, what is called final stitching. Such measure men significantly reduce the mechanical "in-plane" properties. In particular is this is crucial if the entire component area does not meet the increased impact Must withstand requirements, but locally the in-plane properties more decisive are.

Thermoplastic FKV

In the case of thermoplastic FKV systems, impregnation and con to consolidate the fibers with the matrix in a separate step (semi-finished product manufacture). Flat textile semi-finished products are used for this.

The ready-made scrims currently available are in terms of binding thread or bin defaden arrangement, this usually corresponds to a one-dimensional flat dimension structure, not optimized. In the case of processing matrix compatible yarns, which usually have greater fineness and diameter, is due to the very high proportion of twine considerable damage to the fibers in the plane instead.

These ready-made fabrics can be powder impregnated due to the sometimes very thick layer packages and in connection with high temperature (HT) -Ther moplastics (melting or decomposing the binding threads and the associated threads Dissolution of the fabric structure) cannot be processed.

In the case of the film stacking process, two paths can be followed. In order to keep the flow paths low, fabrics with a low basis weight (<500 g / m ² ) must be used. On the other hand, non-crimp fabrics with a high basis weight (<500 g / m ² ) can only be processed if foils are interfered with in the assembled scrim during the manufacture of the scrim. This method often fails due to the very narrow mesh bed and the limited headroom of the knitting unit and can therefore only be used with very thin foils.

The binding threads currently used conventionally meet after the semi-finished product often no function in the network. Furthermore, these binding threads are harmful in relation on the laminate qualities, because of the treatment with winding oils and lubricants, as well partly through the thread itself, foreign substances get into the composite matrix. Soften or if these threads melt too early during the production of semi-finished products, they shift the fiber layers, which leads to lowered mechanical properties. same for also for the impregnation or direct impregnation of made-up fabrics basis of hybrid threads.

Optimal processing of made-up fabrics is only possible by using special yarns (carbon, glass or aramid fibers or matrix-compatible binders den), which have the necessary temperature resistance to the fibers in the Keep impregnation or consolidation fixed.

The further processing of "TFP" semi-finished products to thermoplastic FKV is by means of Direk Timing and thermoplastic injection process possible. The advantages of the bela Proper laying of reinforcement fibers are retained, but the sewing thread is classify the proportion as critical for reasons as described above. The tools are complex due to the thickness variations, whereby the Sewing threads and the sewing threads themselves no smooth surfaces can arise. Landlord Continuous economic processes are not conceivable here.

The object of the invention is the various process steps between the textile pro zeß and the finished component preform or the thermoplastic semi-finished product (complete consolidated and impregnated plate or preform) to reduce and facilitate tern. The new process is based on the requirements for textile reinforcement structure, to use aligned, undamaged fibers, if possible, but can be further processed at the same time.

For the production of complex 3D gemotria for injection technologies, Ein individual parts are generated, which in as few very simple process steps as possible desired structure can be assembled. These are also intended to a high degree be optimized according to the load, local force transmission elements or special reinforcements have kung, or other functional elements.

It is also possible to manufacture "custom-fit" individual parts to influence the resin injection process in a targeted manner (e.g. local increase in fiber volu content) or sensors (actuators, "life-time monitoring") in the preform bring to.

A targeted production of the required component-specific individual parts (individual layers) increases the efficiency of the process, and at the same time leads to a reduction in material costs.

In the further processing to FKV with thermoplastic matrix the processing can properties, further processability and the quality of the product are improved become. The range of common semi-finished products can be used for thermoplastic FKV how the area of ready-made semi-finished products ("tailored blanks") is further developed become.

The process thus serves to reduce the costs in the production of continuous fiber reinforced components made of fiber-plastic composite (FKV) components.  

The problem is solved by means of a method of claim 1.

The advantages of the new process "Multi-dimensional process and component oriented Semi-finished product assembly "are highlighted using three parts:

Textile and pre-assembled semi-finished products

With the process for the so-called "Manufacturing Process Adapted Rein forcements (MPAR) ", flat textile reinforcement structures can be created manage without typical textile types of bindings and can still be processed. As Ar Such semi-finished products are particularly suitable for fiber-plastic composites right, because the fibers are aligned and the required fiber orientations are arbitrary are adjustable.

Due to the type of sewing technology used, it is also, in contrast to a very narrow stitch-forming bed of a knitting machine (Liba, Mayer, Malimo), possibly more dimensional, d. H. in different directions to introduce seams. That's why it is possible to continuously insert force application elements into the textile reinforcement structure tie. The force transmission elements are connected to the textile structure via reinforcement sewing threads that are used when sewing on.

By generating component-specific optimized seam geometries on the flat surface Structures are thus optimal fiber orientation while ensuring the Processability given. The process is designed for a continuous process and thus offers the possibility of individual semi-finished products using a Le program in the sense of avoiding waste. Through the The possibility of continuous production eliminates numerous handling and closing cutting steps. Handling can also be simplified by positioning etc. are provided, which greatly simplifies the following processes.

Duromer FKV

The semi-finished products who are produced by using a method according to claim 1 depending on the requirement can be cut to a simplified contour Preform assembly are brought. Advantages of the resin injection process can be seen on due to the net-shape ability (no fraying due to the seams fixing the edge) and the free adjustability of the fiber orientation can be fully exploited. The Integration of inserts and other functional elements (e.g. sensors) allows a wide range re approximation to the economy of injection molding processes. Reworking and the associated damage to the laminate does not take place. Race tracking effects can be avoided by adjusting the fiber volume content in the edge area become. By using special seam parameters (needle geometry, knotting arrangement), it is possible to introduce flow channels into the fiber preform in a targeted manner to ensure complete impregnability of the structure.

Thermoplastic FKV

Depending on the matrix, there will be sufficient temperature-resistant binding threads used, such continuously manufactured "Manufacturing Process Adapted  Reinforcements (MPAR) "using a powder impregnation unit for the production of ther plastic FKV, are used.

This also enables the processing of HT thermoplastics. By the limits the number of threads will not affect the subsequent processing and the mechanical characteristics in the plane are retained.

Due to the reduction in the number of needles and the larger headroom foils are also introduced continuously in order to shorten flow paths.

If direct impregnation techniques are used to process hybrid threads, offer the same potential as in the processing of thermoset-based FKV-Sys temen.

Example description

Embodiments of the invention are shown in the drawings and are in following in two areas, thermoset plastic and thermoplastic plastic, divided and closer described:

Show it:

Fig. 1 system for the continuous production of component and process-oriented reinforcing structure semi-finished products

Fig. 2 picture of a continuously produced semi-finished product for radome production with integrated fastening elements and local, additional reinforcements

Fig. 3 picture of a Radompreform item

Fig. 4 Integration of force applications

Fig. 5 production of semi-finished products for further processing

Description of the invention

With a device according to claim 1 ( Fig. 1), it is possible to produce prefabricated fiber semi-finished products, these are optimized with regard to fiber orientation and contour of the later component. Local reinforcements or seam insertion are carried out exactly according to the given component or process-specific requirements and conditions.

Fiber bundles or rovings ( 1 ) are deposited with a laying unit ( 2 ), see scrim production (Liba, Malimo) with different fiber orientations ( 3 ). The fiber bundle is transported to the sewing station ( 5 ) on a transport creel ( 4 ). The sewing station has at least one sewing head that can be programmed as required on the plane. The sewing speed or the movement of the sewing head are independent of the movement of the conveyor belts. In a subsequent sewing station ( 6 ) additional functional elements (e.g. force application elements) and local reinforcements are integrated. The semi-finished product produced in this way can be transported on rolls ( 7 ). Any number of laying and sewing stations can be operated in series (not just connected in series), which is why the introduction of fiber bundle coulters oriented in the production direction is possible through a preceding sewing process across the production direction. Before or after laying down the fiber bundle, additional flat reinforcements, e.g. B. sandwich elements are fed to the layer structure ( 8 ).

The following are two examples from processing technology for thermosetting or given thermoplastic FKV.

Duromer FKV Example radome preform ( Fig. 2, Fig. 3 and Fig. 4)

By using the method according to claim 1, several process steps can Production of the dry reinforcement structure can be avoided or simplified. The separate production of a semi-finished textile for preforming is not necessary. The handar Labor-intensive preparation for the production of the preforms can be automated and essential be simplified. Positioning of local, additional ver stiffeners or fasteners are found during the manufacture of semi-finished products instead of. The use of such semi-finished products also means that the fiber Plastic composites avoided.

The basic structure of the layer structure is first stored on a system ( FIG. 1) ( 3 ). The structure here corresponds to a laying unit based on the Liba principle. Fiber orientations and number of layers can be set as desired (e.g. quasi-isotropic). The geometry triekontur ( 9 ) of the radome development ( Fig. 2) is sewn onto the flat fibers ( 10 ) as often as desired. The laying down of the layer structure and the sewing are controlled relative to each other, but independently. The round outer geometry is realized by sewing heads that can be moved in the x and y axes. With the sewing head, in which individual stitches can be programmed, the fastening elements ( 11 ) are integrated, ie sewn on ( 16 ) ( FIG. 4). These inserts are positioned exactly on the deposited fibers. Another sewing head fixes local reinforcements such as braided sleeves ( 12 ), additional fiber bundles or other reinforcement structures. Outbreaks ( 13 ), such as for bolt connections, are mapped in the same process. To stiffen the structure, additional seams ( 14 ) are made in defined zones to increase the sliding resistance.

Several individual processes are replaced by this process, the process is measured tailored instead. Cutting and positioning work in preform The assembly of individual blanks is reduced to a minimum. The Ver Cut is significantly reduced by these measures, especially if an opti times the number of preforms is projected onto the laying width of the machine.

Subsequent to the sewing process, the roll with the prefabricated reinforcement half witness ( 7 ) can be rolled up, this serves for optimal handling of the component-oriented semi-finished products, a shift of the individual layers, or fraying is avoided.

After unrolling, the preforms are punched out or cut out, and the finished preform ( FIG. 3) ( 15 ) can be inserted into the tool. The preform is positioned in the tool to secure the fiber orientations via the fastening elements ( 11 ) or the local reinforcements ( 12 ). The textile reinforcement element does not wrinkle, since no bond has been made between the individual layers. The number of seams ( 14 ) is based on the necessary push resistance for preform assembly or the thermosetting process.

The component produced in this way is accurate to the final contour ( 15 ), which results from the semi-finished product manufacturing process. The process steps of post-processing are eliminated.

Thermoplastic FKV Case half shell example ( Fig. 5)

The use of a method according to claim 1 enables a component-oriented manufacture development of semi-finished fiber products for further processing into thermoplastic fiber Plastic composite. The consolidation of component-oriented semi-finished products can continue with the help of a double belt press. A continuous manufacture Thermoplastic prepregs can be processed on a powder spreading system, provided that they are tempera resistant sewing threads are used.

The basic structure ( 3 ) of the layer structure is first stored on a system ( FIG. 1). The necessary number of seams ( 18 ) for fixing the individual layers are applied by means of a sewing head. Only as many seams as are absolutely necessary are introduced. Increased z-thread portions can be introduced locally in zones at risk of impact ( 17 ). The production takes place continuously, on a defined laying width. The semi-finished product, which is still flat here, can be transported on rolls. Due to the closed area and the defined width of the semi-finished product carrier, powder impregnation or impregnation can be carried out on a double belt press.

If hybrid yarns are processed on the system ( Fig. 1), the impregnation can take place on a double belt press or by means of direct impregnation. For the direct impregnation process, the same procedure is used as for thermosetting FKV. With regard to near-net-shape technologies, from simple geometries, the same possibilities open up as for duromeric systems

Claims (7)

1. Continuous production of component- and process-oriented semi-finished fiber products starting from fiber bundles, characterized in that these fiber bundles are placed on a laying unit and fixed by any oriented seams. 2. The method according to claim 1, characterized in that the seams the component end display precisely. 3. The method according to claim 1 and 2, characterized in that Krafteinleitungsele elements can be integrated into the fiber structure. 4. The method according to claim 1, 2 and 3, characterized in that additional Ver Strengthening structures, area or area, (e.g. textile fabrics, rovings) positioned and fixed by sewing. 5. The method according to claim 1, 2, 3 and 4, characterized in that matrix systems, area or area, in the form of foils or films in the fiber structure inte be grated. 6. The method according to claim 1, 2, 3, 4 and 5, characterized in that core material fe, area or area, (e.g. honeycomb, cell and foam structures) in the company be integrated into the structure. 7. The method according to claim 1, 2, 3, 4, 5 and 6, characterized in that to the seam function adapted, different sewing threads (e.g. matrix compatible sewing threads) ver be applied. Seam functions are defined as fixation or positioning seams, lo kale or flat structure seams, process-related seams and assembly or handling useful seams.