WO2006012876A1

WO2006012876A1 - Arrangement and method for anchoring fibre-reinforced connecting rods

Info

Publication number: WO2006012876A1
Application number: PCT/DE2005/001350
Authority: WO
Inventors: Werner Hufenbach; Olaf Helms
Original assignee: Technische Universität Dresden
Priority date: 2004-07-28
Filing date: 2005-07-27
Publication date: 2006-02-09
Also published as: DE102004038082A1; DE102004038082B4

Abstract

The invention relates to an arrangement for anchoring fibre-reinforced connecting rods (1), said arrangement comprising a force introducing element (2) and an expansion body that can be inserted into the force introducing element (2), the force introducing element and the expansion body being connected to an end of the connecting rod. According to the invention, the connecting rod (1) is radially expanded in the force introduction region, and the radial expansion is concentrated, compressed, and consolidated behind the expansion body, such that the expansion body and the connecting rod (1) are positively connected; and the force introducing element (2) has a funnel-like inner contour to which the extended part of the end of the connecting rod (1), created by the expansion body, is positively connected. The invention also relates to a method for producing the connection.

Description

Arrangement and method for anchoring fiber-reinforced tie rods

The invention relates to an arrangement for anchoring fiber-reinforced tie rods according to the preamble of claim 1. The invention further relates to a method for producing a connection between a tie rod and anchoring means according to the preamble of claim 3.

The invention serves for attaching a metallic force introduction element to tension struts, tie rods, tie rods and tension rods as well as shrouds and posts (collectively referred to as "tie rods") made of long- and endless-fiber-reinforced thermoplastic material decisive link to the further load-bearing structure or to a foundation.

Due to the problematic introduction of force in fiber composite rods, steel rods are predominantly used as tie rods. In areas where lightweight construction, corrosion resistance or electrical insulation properties are of critical importance, various solutions for the anchoring of fiber composite rods are known.

Axial continuous fiber reinforced plastic rods, which can be made, for example, by pultrusion, have excellent strength and stiffness properties. The technical problem is to introduce tensile forces in accordance with the material and power flow in such tie rods.

In Michaeli, Wegener: Introduction to the Technology of Fiber Composites, Chap. 6: Connection technology is the production of tie rods described as an endless loop. Here, the pull rod forms a loop around a bolt for the introduction of force. The loop may be formed as a simple loop, as a double loop or split loop.

The production of endless loops made of fiber composite material is very expensive, since a u. U. very long tool is needed. For each tie rod length a tool is needed. EP 0 001 235 A1 discloses a frictional connection between the end of a pull rod and a force introduction element. The force introduction element consists of an inner cone-shaped part, which is inserted into an outer part with a corresponding inner contour and can be clamped with this. The inner part has a stepped central bore in which the end of the drawbar is clamped.

The frictional connections tend to uncertainties due to fluctuating friction conditions and bias. Vibratory wear is possible.

From DE 39 42 535 Al a cohesive connection (adhesive connection and Vergussverankerung) for attaching a pull rod in a force introduction element is known.

In DE 100 10 564 C1 a combination of material and adhesion-forming compound (conical casting anchors) between the tie rod and force introduction element is described.

An anchorage for high performance fiber composite wires is known from EP 0 710 313 B1.

Adhesive surfaces must be available for bonding and potting anchors. These adhesive surfaces can lead to installation space problems. For a fiber composite rod with a diameter of 12 mm, the necessary adhesive length is about 500 to 700 mm.

From CH 693 102 A5 an anchoring for carbon fiber composite wires is also known. Here, a positive connection is realized by elastic spreading of a longitudinally split fiber composite rod. While the splitting of the rod end constitutes a pre-damage, the elastic spreading of the rod segments leads to an additional bending load in these segments. The object is to provide an easy to manufacture and easy to install arrangement, which consists of inexpensive produced fiber composite semi-finished products (eg pultruded rods) and easy-to-install metallic force application elements by means of a safe and reproducible method with the ends of the Drawbar can be connected. The system of drawbar and arrangement should ensure a high connection strength.

The object of the invention is achieved by an arrangement with the features mentioned in claim 1. Furthermore, the object is achieved by a method with the method steps mentioned in claim 3. Advantageous embodiments and variants are the subject of dependent subclaims.

By using fiber composite rods with a thermoplastic matrix, a far-reaching hot workability of these rods is ensured. By a form-fitting produced by hot forming technology, the tie rods made of fiber-reinforced thermoplastic at the ends with a metallic force introduction element (KEE) are connected. For an expansion body is inserted between the reinforcing fibers at the end of the rod, wherein the rod end widened and thus the cross section is increased at this point. Behind the spreader bar material is brought together again, compressed and reconsolidated, so that the spreader form fit and u. U. also cohesively embedded in the rod end. The resulting thickening on the rod end finds a positive fit in an approximately funnel-shaped inner contour of a metallic force introduction element.

Due to the generated thickening at the end of the rod creates a positive connection between the fiber composite rod and load introduction element, through the molten matrix can also create a material bond. The adapted funnel contour of the KEE also favors a flow path that is appropriate for the flow of force, so that excess stresses at the transition from the metallic to the fiber composite material are minimized. With conventional joining techniques, such as thread, bolt or joint connection, the force introduction element is connected to the adjacent load-bearing structure. The respective connection technique is taken into account in the design of the load introduction element.

The profile of the bar semi-finished product can vary depending on the application. The shape of the load introduction element must be matched to this profile. However, rods with a circular cross-section and rotationally symmetrical force introduction elements offer themselves for simple production.

By a sufficient fiber volume fraction disturbing thermoplastic typical creep, setting and source effects can be suppressed.

To carry out the method, a mounting device is suitable, the u. a. consists of a heating station and three linear actuators. The heating station causes this heating of the rod end. The linear drives each push a force introduction element, introduce an expansion body and actuate a mold for the re-formation of the rod end.

The mechanical deformation energy can be used for variants of the mounting device z. B. with pneumatic, hydraulic or electromechanical drives or manually applied.

The heating of the rod end can be done directly by heat radiation or convection or with a special heating tool by heat conduction. By heating the load introduction element or spreading z. B. by induction heating, the rod end can be heated indirectly by heat conduction.

For the production of tie rods made of fiber-reinforced plastic, low-priced pultruded fiber composite semi-finished products in standard lengths can be accessed. The metal parts are geometrically simple and therefore inexpensive. The assembly time is very short. The individual length of the drawbar is created by suitable cutting to length of the semifinished product and positioning of the load introduction elements, resulting in a special flexibility in the production of different lengths. The invention will be explained in more detail with reference to exemplary embodiments. In the drawings show:

1 shows a longitudinal section through an inventive arrangement with pull rod and mounted force introduction element and pressed-expansion body

Fig. 2 is an illustration for illustrating the method using a metallic spreader

Fig. 3 is an illustration for illustrating the method using a spreader made of reinforced thermoplastic

Fig. 4 is a schematic representation of a mounting device

In Fig. 1 is a longitudinal section through the force application zone of the drawbar system is shown with mounted force introduction element, wherein the geometry of the individual components is clear. The end of the pull rod 1 is spread in a cup-shaped manner and is enclosed by the force introduction element. The force introduction element 2 has a continuous cavity with a variable cross section. In the area of the bar entry, the cross section of the cavity corresponds to the cross section of the undeformed draw bar 1. At the other end, the cavity has an enlarged inner cross section, which corresponds approximately to two to four times the bar cross section. In between there is a transition area, which converts the two cross sections into each other. Because of the ease of manufacture, a design with circular cross sections is advantageous. The inner contour of the force introduction element is thus approximately funnel-shaped.

The expansion body 3 is designed so that the resulting annular space between the expansion body 3 and the force introduction element 2 has a cross-sectional surface area which corresponds approximately to the cross-sectional area of the undeformed tie rod 1. The cup-shaped end of the tie rod 1 then fills this annular space completely at primarily axial fiber orientation.

The force transmission is made possible for example via an external thread on the force introduction element 2. The expansion body 3 may consist of metallic material or of the rod material. If the expansion body like the rod made of fiber-reinforced thermoplastic, so there is an additional cohesive connection between spreader 4 and rod end 1 (Fig.l, single drawing B).

The individual drawings (A, B, C) shown in FIG. 2 show, by way of example and schematically, essential stages of the forming process during the use of a metallic expansion body 3. The drawbar 1 is secured in a non-positive manner in a device by means of clamping jaws 21 against axial displacement. A linearly driven carriage 17 carries a radiator 14, which is heated with a heating element 15. The force introduction element 2 is received by the radiator 14 and is coaxial to the rod 1 can be fed. The expansion body 3 and the upsetting tool 6 are also linearly driven and can be fed coaxially to Zustange 1.

According to the method, according to FIG. 2 (A), the expansion body 3 is first inserted into the force introduction element 2 with a low pre-load F _SKI in order to center the expansion body 3 in the force introduction element 2. The force introduction element 2 is heated by the heating cartridge 15 to a temperature slightly above the softening temperature of the processed thermoplastic matrix. The force introduction element 2 is pushed as shown in FIG. 2 (B) with the feed force F _KEEI over the end of the tie rod, wherein the rod end meets the centered entrained expansion body. The expansion body gives way a little further as the KEE advances, so that the annular space between the force introduction element and the expanding mandrel is released for the inflow of the thermally plasticized rod material. Spreader body and force introduction element are then further advanced synchronously with V _KEEI ^{= v} sκ2, so that sufficiently plasticized bar material protrudes beyond the spreader body.

In order to enclose the expansion body in a form-fitting manner, according to FIG. 2 (C), the rod material projecting beyond the expansion body is recompressed and put together by the compression tool with the compression force Fwzi. While the advancing force of the expansion body Fs _K2 and the compression force Fwzi are maintained, the joining zone is pre-stretched by a low preload force F _JCEE2 on the force introduction element, so that fibers can orient themselves in the direction of the stress. After cooling the system, the force introduction element is released from the radiator and the clamping device can be opened.

The individual drawings (A, B, C) shown in FIG. 3 schematically show essential stages of the method according to the invention when using a

Spreader 4 made of fiber-reinforced thermoplastic.

It is first according to FIG. 3 (A), a metallic auxiliary spreader mandrel 22 is used, which takes over the centering and Spreizaufgabe.

After the spreading of the rod end is held in accordance with FIG. 3 (B)

Spreizkörpervorschubkraft Fsκ ₂ the joining zone with the low biasing force F _KEE2 pre-stretched and cooled.

After cooling the system, the auxiliary spreader 22 is removed and the

Spreader made of fiber-reinforced thermoplastic according to FIG. 3 (C) used.

The projecting beyond the fiber-thermoplastic expansion body 4 bar material is applied after renewed thermal plastication with the upsetting tool and compacted. Through the renewed heat input of the expanding mandrel welded to the rod material.

FIG. 4 schematically shows an exemplary embodiment of a mounting device for producing drawbar systems from a fiber composite rod and metallic force introduction elements. The force introduction elements 2, spreader 3 and compression tool 6 are by three pneumatic cylinder actuators 8; 10; 13 actuated. The Spreizkörperträger 5 is guided concentrically by the upsetting tool and the associated pneumatic cylinder. The pneumatic actuators 8; 10 for spreader and compression tool and the heating module 14; 15 are mounted on a carriage 18 which is linearly guided on the base 19. The feed of the carriage is performed by the pneumatic actuator 13. The necessary after the centering return stroke of the expanding mandrel 3 or 22 can be defined by a Rückhubbegrenzung 16. LIST OF REFERENCE NUMBERS

Claims

claims

1. Arrangement for anchoring fiber-reinforced tie rods (1), comprising a force introduction element (2) and an insertable into the force introduction element (2) expansion body, which are connected by positive engagement with one end of the tie rod, characterized in that the tie rod (1) in Force introduction of the spreader radially expanded and the radial expansion behind the spreader merged, compacted and consolidated, so that the spreader and the tie rod (1) are positively connected, the force introduction element (2) has a funnel-like inner contour, with which caused by the spreader magnification the end of the tie rod (1) is positively.

2. Arrangement according to claim 1, characterized in that the expansion body made of reinforced thermoplastic and by vote on the matrix material of the tie rod (1) is a material connection between spreader and tie rod (1).

3. A method for producing a connection between a fiber-reinforced tie rods (1) and anchoring means, which consist of a force introduction element (2) and an insertable into the force introduction element (2) spreader, which are connected by positive engagement with one end of the tie rod (1), characterized in that the end of the tie rod (1) is held and brought to softening temperature, the spreader with its tip together with the force introduction element (2) to the end of the tie rod (1) fed axially and the spreader is centrally pressed, wherein the radial displaced material of the drawbar (1) in a space between the outer contour of the expansion body and the inner contour of the

Derived force application element (2), and the derived material is gathered behind the spreader and consolidated.

4. The method according to claim 3, characterized in that the force introduction element (2) is heated to a temperature slightly above the softening temperature and by the heated force introduction element (2), the softening of the end of the tie rod (1).

5. The method according to claim 3 or 4, characterized in that the expansion body at the beginning of the feed movement in entrained funnel-shaped force introduction element (2) is centered.

6. The method according to any one of claims 3 to 5, characterized in that the expansion body during further advancement of the force introduction element (2) recedes, so that the space between the force introduction element (2) and expansion body is released for the inflow of the thermally plasticized rod material.

7. The method according to any one of claims 3 to 6, characterized in that for the positive embedding of the spreader beyond the spreader protruding expanded bar material by an upsetting tool (6) merged, compacted and consolidated.

8. The method according to any one of claims 3 to 7, characterized in that while the feed force Fsκ _{2 are held} on the expansion body and the compression force F _W zi, by a low biasing force F _KEE2 on the force introduction _element (2) the joining zone is pre-stretched, so that fibers can orient in the direction of the stress.

9. The method according to any one of claims 3 to 8, characterized in that after cooling of the force introduction element (2) the holding force for the rod end is released.

10. The method according to any one of claims 3 to 9, characterized in that when using a spreader (4) based on thermoplastic first a temperature-resistant auxiliary spreader (22) with the force introduction element (2) fed to the end of the drawbar (1) and the rod material in the space forming is displaced, the auxiliary spreading body is exchanged for a spreading body (4) of reinforced thermoplastic and then the spreading body (4) is surrounded by the displaced and projecting bar material.