DE19834772C2 - Fiber-plastic composite components with inserts - Google Patents

Description

The invention relates to the design and manufacture of inserts provided fiber-plastic composite components according to the preamble of Claim 1.

Plastic components with continuous fiber reinforcement are firmly in the today Development of mechanically highly stressed components established. specially in the field of the application of lightweight structures, for example in These are vehicle construction and especially in the aerospace industry It is impossible to imagine fiber plastic composites without it. You convince with her low weight with good mechanical properties.

Especially in the case of classic mechanical engineering and the supplier industry Significant number range from small series to exclusive special series with up to some 10,000 units per year, the resin injection technology has (Resin Transfer Molding, RTM) as very flexible, with little Investment volume and therefore especially for the small and medium-sized industry established as a very interesting manufacturing process. RTM is the generic term for a whole range of innovative variants of the Resin injection technology, but they all work according to the same scheme.

It is crucial that the reinforcement, i.e. the continuous fibers, only in the closed tool come into contact with the plastic. This enables prefabrication of the reinforcement structure, as this is outside the Tool had no contact with the plastic and therefore as normal Textile structure viewed and can also be processed.

The connection technology of continuously fiber-reinforced plastic components (continuous fibers, woven fabrics, random fiber mats, scrims, knitted fabrics, etc.) with duromer matrices (cross-linking hardening and therefore no longer meltable polymers) to other components (usually metallic structures) is insufficiently developed. It can be drilled, riveted, screwed or glued, although this is in no case a material-specific connection technology. For example, high perforations in bolt connections can cause the plastic matrix to creep. The reinforcing fibers used are cut through the drilling of holes and thus lose their effectiveness, since the forces have to be transmitted to undamaged fibers through the remaining plastic matrix due to shear loads. Since welding is not available as a connection technology, as is the case with purely metallic or thermoplastic components, the integration of connecting elements such as screwable inserts, sockets, through holes or bearing points in the not yet impregnated reinforcement structure is used as a solution (see Fig. 2b). Inserts ( 1 ) serving as force introduction elements are placed in or between the individual reinforcement layers ( 3 ). After the resin injection, the fiber-plastic composite component is formed by the hardening of the resin (matrix). Here, matrix-rich zones ( 5 ) occur during the transition from the connecting element into the fiber composite structure, which leads to problems. FIG. 2b shows that arise in these matrix-rich areas according to the load voltage spikes lead to microcracking and ultimately delamination (6), that a separation of the reinforcing layers have the effect of each other, which is reflected in unsatisfactory mechanical strength properties (B. Ferret, M. Anduze, C. Nardari: Metal inserts in structural composite materials manufactured by RTM.Composites Part A 29A pp. 693-700, 1998).

If fiber-reinforced materials are used continuously (e.g. woven fabrics, scrims, knitted fabrics, mats, etc.), this inevitably results in a layered structure, i.e. a laminate of individual reinforcement layers or reinforcement textiles. Here, the use of conventional insert technology has clear disadvantages (see Fig. 2b and Fig. 2c):

• - The inserts ( 1 ) act as foreign bodies, since these are a factor of 4 to 10 thicker than the individual reinforcement layers ( 3 );
• - Matrix accumulations ( 5 ) form, in which microcracks form, which then lead to delamination;
• - There is usually an extreme jump in stiffness metallic insert to the surrounding fiber composite structure;
• - The flow of force from the insert into the component is not optimal, since it becomes one large part must be transmitted by thrust;
• - At a moment introduction (M) forces arise perpendicular to the individual reinforcement layers ( 3 ), which must be absorbed by the much weaker matrix ( 4 ) and thus increase the risk of micro-cracking with subsequent delamination ( 6 );
• Since the inserts have to be inserted between the reinforcement layers, creates a high handling effort and thus very high Tool loading times, which in turn means low output Results in components per tool;
• - The quality of the positioning of the insert within the Reinforcement structure and thus also within the component is by a manual loading not very high;

The publication EP 0 594 131 A1 describes the production of a fiber-reinforced Plastic body disclosed, in which steel inserts are integrated become. The essentially U-shaped inserts project transversely Tabs with which they are attached to spars to be wrapped with fiber tapes be plugged on. After the inserts have been replaced by another fiber ribbon on half shells are attached and so prepared workpiece inserted in a mold where there is curable Plastic is soaked. The wrapping of the inserts with the fiber tapes should increase the strength of certain parts of the finished plastic body and absorb the forces acting on the inserts. On the other hand, they should Fiber tapes do not immovable the inserts before soaking with plastic hold on, but allow small movements, because the exact Positioning the inserts in relation to a foam body and the Half shells with the help of centering pins. The fiber tapes can be in  Direction of action of the force attack to be expected. The this increases the strength of the inserts within the plastic body only after completion, d. H. after soaking and curing the Plastic achieved. Because the fiber bands allow the inserts to move must be able to position them with centering pins these do not counteract possible delamination. In addition, the Use of positioning aids such as centering pins very technically consuming. Another disadvantage arises from the fact that the Wrapping with tapes can only be done on spar-like structures.

The invention has for its object to provide fiber-plastic composite components with inserts inserted within the fiber reinforcement structure, in which forces acting on the insert can be introduced into the fiber composite structure in a manner appropriate to the material, ie without the risk of delamination. The object is achieved by the characterizing features of the technical claim 1 and the method claim 8 .

The insert is inserted between individual reinforcement layers and together with sewn to the individual reinforcement layers. The needle sticks through that in the Flange of the insert provided holes or holes. The insert is fixed by the sewing thread and non-positively with the Individual reinforcement layers connected, i.e. sewn on. Sewing on can refer only to a part of the reinforcement layers or the whole Include laminate height. The insert can also have two perforated, mutually have spaced flanges so that the flanges Grip reinforcement structure and this through the holes of the flanges is sewn on. Sewing on creates a force-locking function between the reinforcing textiles surrounding the insert, so that the insert is held non-positively between the reinforcement layers. The Risk of delamination is eliminated as the reinforcing sewing threads are directed towards the force, i.e. perpendicular to the sewn reinforcement textiles and so on can optimally absorb the forces introduced. This effect is intensified,  if reinforcing threads, preferably made of carbon, glass or Aramid fibers are used as sewing threads. The inserts can made of any material, preferably metal, plastic or ceramic his.

Another advantage can be an optimization with regard to a application-related geometric formation of the insert can be achieved, for example by extending the foot of the insert in the direction of the force, to get a better lever arm for force absorption.

The insert can be made according to the respective requirements or Forces to be introduced must be threaded, an internal one geometric training, e.g. B. bore with or without cone, or form a massive block.

Depending on the application, the flange of the insert can be used as a solid part Bores or be made by a grid-like structure.

Sewing on an insert can be carried out in such a way that an optimized Force flow from the insert into the laminate. For this purpose, the sewing threads form the Force flow in the component after. In addition, the power dissipation in the Reinforcement structure by over the edge of the insert or the flanges outgoing seam sections can be improved.

By choosing the seam type, both the amount of sewing or Reinforcement thread, as well as the location of the reinforcement thread, e.g. B. stretched position of the needle thread on the top of the material can be influenced.

Further advantages of the invention result from the fact that the sewing the positioning accuracy is significantly increased and by automated sewing process, which is essential for structural components Reproducibility is guaranteed. The entire reinforcement textile can be used as  complex preform (preform, reinforcement textile with sewn inserts) in the tool can be inserted, resulting in significantly shorter cycle times and thus leads to a significantly increased economy.

A quality assurance system can ensure the successful sewing process with everyone essential parameters (number of stitches, thread forces, etc.) document what also the use of this technology safety-relevant structural components is possible.

The invention is explained using three exemplary embodiments. Show it:

FIG. 1a is a plan view of a fiber-plastic composite component with a sewn insert according to the first embodiment;

Figure 1b is a sectional view along line AA of Figure 1a with a first variant for the formation of yarn seams..;

1c is a sectional view along line AA of Figure 1a with a second variant for the formation of yarn seams..;

Figure 2a is a plan view of a fiber-plastic composite component with an inserted insert according to the prior art; FIG.

FIG. 2b shows a sectional view along line AA of Figure 2a with matrix-rich zones.

2c is a sectional view along line AA of Figure 2a with a Delaminationsriß, starting from the matrix-rich zones..;

Figure 3a is a plan view of a fiber-plastic composite component with a sewn insert according to the second embodiment.

Figure 3b is a sectional view along line AA of Figure 3a with a first variant for forming the thread and stitching of the insert foot..;

3c is a sectional view along line AA of Figure 3a with a second variant for forming the thread and stitching of the insert foot..;

4a is a plan view of a fiber-plastic composite component with a sewn insert according to the third embodiment.

Figure 4b is a sectional view along line AA of Figure 4a with a variant to form the thread stitches, especially the needle thread..;

FIG. 5a is a top view of a first insert variant;

Fig. 5b is a sectional view along line AA of Fig. 5a;

Fig. 5c is a plan view of a geometric variation of the Fig. 5a;

FIG. 6a is a plan view of a second insert variant;

Fig. 6b is a sectional view along line AA of Fig. 6a;

Fig. 6c is a plan view of a geometric variation of the Fig. 6a;

FIG. 7a is a plan view of a third insert variant;

Fig. 7b is a sectional view along line AA of Fig. 7a;

Fig. 7c shows a plan view of a geometric variation of the FIG. 7a;

In FIGS. 1a, 1b and 1c is an insert (1) with threaded blind with base plate, composite component fiber-reinforced plastic, which consists of individual reinforcement layers (3) and a plastic matrix (4) shown in a. According to the invention, the insert has been non-positively connected to the individual reinforcement layers using a thread seam ( 9 ) before the component manufacturing process (resin injection method). The thread seam ( 9 ) is expediently produced by sewing, the needle penetrating holes ( 8 ) of the insert flange ( 7 ) and outside the insert into the individual reinforcement layers, thus forming a clamp around the individual reinforcement layers sewn to the insert. Fig. 1b shows that the sewing includes only a part of the individual reinforcement layers or that, as shown in Fig. 1c, the insert is sewn to all reinforcement layers.

FIGS. 3a, 3b and 3c show a further embodiment of the invention in which a portion of the Insertflansches (7) is extended so that the picked up by the insert forces and moments generated by an elongated lever arm (10) smaller in the thread seams voltages.

FIGS. 4a and 4b show a further embodiment in which the thread seams are aligned along the flux lines in the component. By choosing appropriate sewing process parameters when sewing on the insert, an extended position of a sewing thread ( 12 ) can be forced.

FIGS. 5a to 5c, 6a to 6c and 7a to 7c show further embodiments and variants of annähbaren inserts. In FIGS. 5a to 5c an insert (13) is shown, which has two spaced flanges (14), so that the individual reinforcement layers may be sewn between these flanges. According to the explanations for FIG. 3a, the flanges can have both local extensions ( 16 ) or individually. In order to be able to introduce external forces into the inserts, the insert ( 13 ; 17 ; 21 ) can have an internal thread ( Fig. 5b), a simple hole, possibly expanded by a cone ( Fig. 6b), or simply solid ( Fig. 7b) be formed.

Claims (12)

1. Fiber-plastic composite component with inserts used within the fiber reinforcement structure and serving as load introduction elements, characterized in that the inserts ( 1 ; 13 ; 17 ; 21 ) are also embedded in the plastic matrix ( 4 ) by thread seams ( 9 ; 12 ) the fiber reinforcement structure ( 2 ) consisting of individual reinforcement layers ( 3 ) are firmly connected. 2. Fiber-plastic composite components according to claim 1, in which the inserts ( 1 ; 13 ; 17 ; 21 ) have a laterally projecting flange ( 7 ; 18 ; 22 ), characterized in that the flange ( 7 ; 18th , 22 ) is arranged between the individual reinforcement layers ( 3 ) and has holes ( 8 ; 19 ; 23 ) for receiving the sewing threads ( 9 ; 12 ). 3. fiber-plastic composite components according to claim 1, wherein the inserts ( 13 ) have two mutually spaced bottle ( 14 ), characterized in that the flanges ( 14 ) encompass the outer sides of the reinforcing structure ( 2 ) and holes ( 15 ) to hold the sewing threads. 4. fiber-plastic composite components according to claim 2 or 3, characterized in that the flanges ( 7 ; 14 ; 18 ; 22 ) for a better moment in the area of the greatest stress an approach ( 10 ; 16 ; 20 ; 24 ) exhibit. 5. Fiber-plastic composite components according to one or more of claims 2 to 4, characterized in that the flanges ( 7 ; 10 ; 14 ; 16 ; 18 ; 20 ; 22 ; 24 ) are formed like a grid. 6. Fiber-plastic composite components according to one or more of claims 1 to 5, characterized in that the seam sections ( 9 ; 12 ) for better derivation of the inserted via the inserts ( 1 ; 13 ; 17 ; 21 ) forces parallel to Power flow are arranged. 7. fiber-plastic composite components according to one or more of claims 1 to 6, characterized in that for better force derivation in the reinforcing structure ( 2 ) additional, over the edge of the inserts ( 1 ; 13 ; 17 ; 21 ) or . The flanges ( 7 ; 10 ; 14 ; 16 ; 18 ; 20 ; 22 ; 24 ) outgoing seam sections ( 12 ) are formed. 8. A method for producing fiber-plastic composite components according to claim 1, characterized in that the inserts ( 1 ; 13 ; 17 ; 21 ) are sewn onto the reinforcing structure ( 2 ) in a work step preceding the component manufacturing process. 9. The method according to claim 8, characterized in that when using inserts ( 1 ; 17 ; 21 ) with a laterally projecting flange ( 7 ; 10 ; 18 ; 20 ; 22 ; 24 ) placed between the individual reinforcement layers ( 3 ) becomes. 10. The method according to claim 8, characterized in that when using inserts ( 13 ) with two mutually spaced flanges ( 14 ), the reinforcing structure ( 2 ) is arranged between the flanges ( 14 ). 11. The method according to any one of claims 8 to 10, characterized in that for better derivation of the forces directed via the insert ( 1 ; 13 ; 17 ; 21 ), the direction of the seam is selected such that the parallel to the plane of the reinforcing structure ( 2nd ) running seam sections ( 9 ; 12 ) are aligned parallel to the power flow. 12. The method according to one or more of claims 8 to 11, characterized in that the seam sections ( 9 ; 12 ) for better force dissipation in the reinforcing structure ( 2 ) over the edge of the insert ( 1 ; 13 ; 17 ; 21 ) or the flanges ( 7 ; 10 ; 14 ; 16 ; 18 ; 20 ; 22 ; 24 ) can be extended.