DE102005027173B4 - Tensile strut made of fiber composite material and used in aircraft and vehicle construction - Google Patents

Abstract

A tensile compression strut made of fiber composite material for power transmission, comprising a tensile force transmission element, a pressure force transmission element and a force introduction element (3), wherein the tensile force transmission element is designed as a pull loop (1) whose inner diameter the force introduction element (3) positively contacted, characterized in that the pressure force transmission element as a pressure loop (2) is formed, the outer diameter of which is in positive contact with the force introduction element (3).

Description

The invention relates to a train-pressure strut made of fiber composite material for power transmission and their preferred use in aircraft and vehicle.

The use of high-strength fiber composites, eg. B. with carbon, glass, silicon carbide, aramid or boron fibers, and a matrix, for. As plastic, metal or ceramic, requires the use of appropriate methods for material-oriented force application. Appropriate for the material here means that the anisotropy of the material is exploited purposefully with regard to the different mechanical properties in the fiber direction and transversely thereto.

For many years, the method of loop connection for the introduction of force into tensile bar structures is already known. According to this construction method, the reinforcing fibers are looped around a bolt, so that under tensile load of the bolt there is a positive connection between reinforcing fibers and force-introducing bolt. This fiber arrangement makes optimum use of the load capacity potential of the fiber reinforcement under tensile load. The problem with this method is the introduction of compressive forces.

Technical applications, such as in DE 26 57 832 A1 or DE 29 23 535 A1 disclosed, therefore, resort to a pressure belt, which allows the corresponding corresponding hole reveal the power in the compression direction. Application examples are engine connecting rods which, in addition to a fiber-reinforced drawstring, rely on a ceramic plunger. Critical in such concepts is the combination of different materials with the resulting thermomechanical problems. Another disadvantage is that due to the only moderate Lochlaibungsfestigkeit common fiber composites a correspondingly large bolt connection is to be dimensioned so that the joint has corresponding space disadvantages and is further severely limited in terms of lightweight potential.

The object of the invention is therefore to find a strippenartiges device for mechanically highly loaded rod-like structures made of fiber composites, on the one hand, the high load capacity of the fiber composites in the fiber direction under tensile load to advantage and on the other hand allows the introduction of high pressure loads in the structure, so a lightweight construction Structural construction is achieved.

This object is achieved with the features of claim 1; Advantageous developments of the invention are described in the subclaims 2 to 9, advantageous uses emerge from the claim 10.

According to the invention, there is provided a tension-strut of a fiber composite material comprising a tensile force transmitting member, a compressive force transmitting member and a force introduction member. The tensile force transmission element is designed as a pull loop and the pressure force transmission element as a pressure loop. The force introduction element, which z. B. is made of a metallic material, the pull loop contacted form-fitting manner to the inner diameter and the pressure loop form fit to the outer diameter. The pressure loop is positioned within the pull loop such that the position of force input to which, for example, a bolt is attached as a connector to other components is between the apex of the pull loop and the apex of the pressure loop.

Advantage of the invention is that the tensile forces absorbed by the Zugschlaufe and the pressure forces can be introduced via the loop end face of the pressure loop in the pressure loop. Due to the uninterrupted fiber flow on the pressure loop, it is possible to absorb high pressure loads into the tension-compression strut.

It can be provided that the tension and / or the pressure loop of a fiber material, such. As carbon fibers, glass fibers, boron fibers, Siliziumcarbidfasern or aramid fibers are made.

In the contact region between the pull loop and the force introduction element or pressure loop and the force introduction element, a sliding film known from the prior art can be introduced. Alternatively, the force introduction element with the tension and / or pressure loop cohesively, z. B. be connected by an adhesive bond.

Another embodiment includes the cohesive connection of the tension and pressure loop, so that both loops complement each other in their function and can also take over Traganteile the respective other loop. This can be done on the one hand by an integral production of the loop body and on the other hand by a cohesive connection of the tension and pressure loops. This connection also makes it possible to increase the structural rigidity, which is advantageous in terms of stability, especially with components subjected to pressure.

One embodiment involves the combination of the pull or pressure loop with one or a plurality of shear fields such that they are arranged between the loops and the tension strut has a box shape. The parallelism of the tension and pressure loops can also be ensured by a bandage. The shear fields and / or the bandage enable the absorption of transverse or torsional loads. This is to be preferred in particular in the case of pressure-loaded or even curved loop configurations, as this can compensate for any imperfections or excessive transverse deformations. Such deformations would lead to early stability failure of the loops.

Advantageously, the pull loop, the pressure loop and the force introduction element are interconnected by optimized tolerance definition and joining in such a way that the pressure loop already under a compressive prestress and the pull loop are under a tensile prestress in the installed state. This can be achieved by z. B. Zugschlaufe, pressure loop and force introduction element are joined with an oversize, z. B. by cooling the force introduction element before joining in a liquid nitrogen bath. The preload makes it possible to compensate for any settling effects and leads to a uniform contact pattern of the loops.

A frictional connection (press fit) is preferably combined with a material connection (adhesive connection).

Advantageously, the pressure loop can also be supplemented by a clamping wedge, which is applied in a self-locking manner between the loop strands and allows additional support or even positive transverse compressive prestressing. Hereby, the carrying capacity u. a. through the targeted introduction of residual stresses further increase without having high weight penalties.

Furthermore, the force introduction element may have an additional portion inside lying in the entire curvature region of the pressure loop. This provides additional support against local bending effects. This embodiment also has the advantage that the pressure loop can absorb a supporting share over the lying on the inner edge of the loop region of the force transmission element under tensile load when z. B. the modulus of elasticity of the fibers in the Zugschlaufe is significantly lower than the modulus of elasticity of the fibers of the pressure loop. The same applies vice versa, so that according to the invention, depending on geometric requirements or load level optimal fiber utilization and thus maximum lightweight construction, can be done.

Preferably, the pressure loop and the pull loop are laterally supported in the region of the force introduction element. This increases the load capacity of the tension strut.

Advantageously, the force introduction element is designed such that the tension and pressure loops are free of bending loads.

Furthermore, the drawstring and pressure loop can be designed with different wall thicknesses. This allows the compensation of the load capacity in the event that the train strut is loaded with different load heights in the train and pressure range - but also at an equal level of pressure loads and tensile loads to meet the typically different tensile and compressive strengths of the fiber composites.

It can be provided that the fiber structure of the pull loop and pressure loop have a double-curved structure. This is made possible in the manufacture of the tension-strut by fixing in a tooling system.

Advantageously, a force introduction element with tension and pressure loop can be attached to both end regions of a bolt.

Furthermore, the tension-strut can be designed at both end regions with force introduction elements such that both the tension and the pressure loop are completely closed.

The tension strut according to the invention can u. a. used on parts of the landing gear of aircraft, on aircraft engine suspensions or on engine suspensions in vehicle construction.

The invention is explained in more detail by means of embodiments and with reference to the schematic drawings. Show this

1 : the longitudinal section of a tension-strut with drawstring and pressure bar (prior art),

2 : the longitudinal section of the arrangement of the drawstring and pressure loop on the force introduction element of the train strut,

3 : the perspective view of the train-strut with shear panels and bandage,

4 : the cross-section through the tension-strut with a pull and a pressure loop (2-loop structure),

5 : the cross-section through the tension-strut with two tension and two pressure loops (4-loop structure),

6 : the longitudinal section in the contact region of the pressure loop to the force introduction element with support on the inner diameter of the pressure loop,

7 : the longitudinal section in the contact region of the pressure loop to the force introduction element with support by clamping wedge,

8th FIG. 2: the cross-section through the tension-compression strut with the force introduction element made of split half-shells, FIG.

9 FIG. 2: the cross-section through the tension-compression strut with the force-introducing element of divided half-shells and sleeve, FIG.

10 : the cross-section through the tension-strut with the force introduction element and lateral loop support elements, and

11 : the cross section through the tension-strut with the force introduction element of split, cone-shaped half shells.

The 1 shows a known in the art tensile compression strut made of fiber composite material, this being the Zugschlaufe 1 , the pressure bridge 9 and the bolts 4 having.

In the 2 is a detail of the train-strut with the drawstring 1 , the pressure loop 2 and the force introduction element 3 shown. At the position of the force introduction at the force introduction element 3 is the bolt 4 arranged.

The 3 to 5 show the train strut in two embodiments with shear fields 8th or bandage 5 ,

In the 6 and 7 are details of the contact area of the pressure loop 2 with the force introduction element 3 shown. In the 6 is the force introduction element 3 designed such that it includes the pressure loop in the curvature region both outside and inside. In the 7 is alternatively the clamping wedge 6 introduced inside the pressure loop.

The 8th to 11 show different designs at the position of the force.

According to the 8th are the loops from each side with a half shell of the force introduction segment 3a . 3b edged. This embodiment can according to the 7 advantageous with the sleeve 7 be combined. Through the sleeve 7 is an exact guidance of the bolt (not in the 7 shown) and continue with a positive, positive or cohesive connection of the half-shells and the sleeve 7 an axial strength perpendicular to the loop direction achievable.

Furthermore, the force introduction element 3 - like in the 10 shown - also designed in one piece and by lateral loop support elements 3c . 3d be supplemented separately with the force application element 3 are connected.

By means of in the 11 illustrated embodiment may advantageously further the lateral guidance of the loops within an inlet cone on the metallic force introduction element 3 done so that an additional tension is reached.

LIST OF REFERENCE NUMBERS

1

pull tab

2

pressure loop

3

Force application element

3a, 3b

divided half shell

3c, 3d

lateral loop support element

4

bolt

5

bandage

6

clamping wedge

7

shell

8th

thrust field

9

pressure bar

Claims (10)

A tensile stress strut of fiber composite material for power transmission, comprising a tensile force transmission element, a pressure force transmission element and a force introduction element ( 3 ), wherein the traction element as a pull loop ( 1 ) is formed, the inner diameter of the force introduction element ( 3 positively contacted, characterized in that the pressure force transmission element as a pressure loop ( 2 ) is formed whose outer diameter of the force introduction element ( 3 ) contacted positively. Pull-strut according to claim 1, characterized in that the pull loop ( 1 ) and / or the pressure loop ( 2 ) are formed from carbon fibers, glass fibers, boron fibers, silicon carbide fibers or aramid fibers. Pull-strut according to claim 1 or 2, characterized in that the pull loop ( 1 ) and / or the pressure loop ( 2 ) in the contact region to the force introduction element ( 3 ) are provided with a sliding film. Pull-strut according to claim 1 or 2, characterized in that the pull loop ( 1 ) and / or the pressure loop ( 2 ) with the force introduction element ( 3 ) are cohesively connected. Pull-strut according to one of claims 1 to 4, characterized in that the pull-loop ( 1 ) and the pressure loop ( 2 ) outside the contact region to the force introduction element ( 3 ) are cohesively connected. Pull-pressure strut according to one of claims 1 to 5, characterized in that the pull loop ( 1 ) and / or the pressure loop ( 2 ) outside the contact area to the force introduction element ( 3 ) with at least one shear field ( 8th ) and / or a bandage ( 5 ) are connected. Pull-pressure strut according to one of claims 1 to 6, characterized in that the pull loop ( 1 ) with a tensile force and / the pressure loop ( 2 ) is biased with a compressive force. Pull-pressure strut according to one of claims 1 to 7, characterized in that it further comprises a clamping wedge ( 6 ), wherein the clamping wedge ( 6 ) in the interior of the pressure loop ( 2 ) is arranged. Pull-pressure strut according to one of claims 1 to 8, characterized in that the force introduction element ( 3 ) has an additional portion which serves as support on the inner diameter of the pressure loop ( 2 ) is present.  Use of the tension-strut according to one of claims 1 to 9 as a part of the landing gear of an aircraft, as part of an engine mount on the aircraft or as an engine mount in vehicle construction.

Images