DE102007026453A1 - Multi-cellular fiber-plastic connection structure for use as e.g. wheel axle, in aircraft landing gear, has belts provided in external wall of pipe, where belts and shear force rods are fiber-reinforced - Google Patents

Abstract

The structure has belts (2) and shear force rods (3), where the belts and the shear force rods are fiber-reinforced. The belts are provided in an external wall of a pipe, and have an enhancement with approximately 0 degrees oriented unidirectional fiber layers (6). The rods are designed as nested cells with fiber layers (5), which enclose the fiber layers of the belts in layers. The fiber layers of the rods are arranged in the wall of the pipe. An independent claim is also included for a method for producing a multi-cellular connection structure.

Description

The The invention relates to a multi-cell composite structure with cartwheel profile for axles and shafts, process for its manufacture as well as its use.

Shafts and axles, which have to absorb very high bending and torsional moments as well as lateral forces, have so far mainly been produced from metallic materials. These include wheel axles of aircraft landing gears, for which ultra-high-strength steels are used. For drive shafts, which are burdened by torsional and bending moments, different fiber composite construction methods and associated manufacturing processes are already being used. The following processes are typically used for the production of single-cell fiber composite hollow structures:
Winding technology (filament winding) is a widely used process for the production of torsionally and flexurally stressed lightweight drive shafts made of carbon fiber reinforced plastic (CFRP). Such drive shafts are typically made with cross windings of impregnated fibers on a cylindrical winding core.

at The braiding pultrusion first become fiber strands (Yarn, rovings) to a tubular textile semi-finished product then processed for shaping and consolidation with synthetic resin or thermoplastic through a ring-shaped nozzle system is pulled.

With The braiding pultrusion can be especially resistant to bending and torsion Manufacture tubular profiles.

The Hose-blowing process comes in different variants for the production of hollow structures made of fiber-reinforced Plastic used (eg the bicycle handlebar).

Are known after US 6,918,839 B2 and US 6,974,555 B2 the construction of a multi-cell drive shaft made of a fiber composite structure, the aim is to be able to transfer even when damaging one of the cells still high torsional moments. The focused damage tolerance is achieved by maintaining a closed wave cross section despite damage, which allows an undisturbed circulating shear flow.

Of the significant disadvantage of classical hollow shafts and axes of fiber composite structures with circular cross-section is in the for many Applications to low shear stiffness and shear resistance too see. By ± 45 ° -oriented fiber layers can Shear stresses caused by shear forces be recorded. Due to the material anisotropy and the uneven Distribution of shear force shear flow in hollow structures with circular cross section However, this results in a very low material utilization. At high shear force load can therefore compared with classic fiber composite hollow structures metallic hollow structures rarely achieved a weight advantage become. In addition, thin-walled hollow shafts tend and axes with circular cross section often for ovalization of the cross section in the area of load discharges such as bearings. From this can affect the bearing function as well as stability problems.

The US 6,918,839 B2 and US 6,974,555 B2 disclose multi-cell drive shafts, which serve above all the safe transmission of torsional moments even if individual cells are damaged. No information is given on the transmission of shear forces and bending moments. The described ribs are not capable of absorbing shear stresses due to shear force loads, as the two patents lack disclosure of structural and material mechanical task sharing with stressful association of fiber orientations in the ribs and in the outer shell. Suitable fiber orientations are not listed here, but which are required for a firm connection of the shear-resistant and shear-resistant ribs with the bending-resistant and rigid belt layers in the shell.

It was now the task of ultralight, elongated, externally approximately rotationally symmetrical hollow structures of a fiber-plastic composite (FKV) to find, which are suitable for transmitting both high bending moments and high shear forces, and for example in aircraft landing gear as a wheel axle at the papermaking can be used as rollers, in marine propulsion or in general mechanical engineering for cross-loaded drive shafts and hinge pins. These fiber composite hollow structures are not only intended to reduce system masses, but also to reduce mass moment of inertia, which contributes to better dynamics of drive systems. A high fatigue strength of high-performance fiber composite structures should also contribute to a long service life of the components gene.

Next the provision of a stress-oriented fiber composite lightweight construction method for axles and shafts with highest component stiffnesses and structural strengths with regard to bending, shear force and torsional stress, For this purpose, suitable axle and shaft profiles are to be determined and to determine a material and force flow appropriate fiber arrangement. In addition, there is an associated manufacturing process to design and design special production tools. With the help of the axle system in fiber composite lightweight construction particularly powerful suspension and drive components for motor vehicles, aerospace applications and industrial Applications arise.

The Task could be based on the features of the claims be solved.

there The invention relates to a multi-cell composite structure with cartwheel profile for axles and shafts with straps and push bars, where the straps and shear bars are fiber reinforced. Preferably are located in the outer tube wall straps, a gain of about 0 °, a maximum of ± 10 ° -oriented possess unidirectional (UD) fiber layers. Preferably, the Thresholds as nested cells with a reinforcement from ± 30 ° to ± 60 °, especially ± 45 ° -oriented Fiber layers constructed, the fiber layers of the push cells the Wrap the fiber layers of the belts layer by layer. In a particular embodiment of the invention are located in the pipe wall additional ± 30 ° - to ± 60 ° -, preferably ± 45 ° fiber layers. Furthermore you can there are more fiber layers in the pipe wall with an approximately 0 ° / 90 ° fiber orientation. Another embodiment involves in the push bars individual fiber layers with larger fiber angles from ± 30 ° to ± 70 °.

The The invention also relates to a method for producing the multicellular Composite structure with cartwheel profile. The production of the composite structure takes place in the resin transfer molding (RTM) process by means of a closed tool system, preferably with a tool with Dipping edge, which defines the outer contour of the composite structure, and in which the cells of the hollow structure are reusable or lost mandrels are formed.

First are the cell-shaped push bars by mounting of several braided tubes made of reinforcing fibers built on the mandrels, with slivers with unidirectional (UD), longitudinal fiber orientation, as semi-finished for the straps are integrated. As an alternative, the Form cores surrounded by winding technology with reinforcing fibers become. Thereafter, the molded cores are wrapped with fibers assembled with positioning aids and then the complete fiber preform with the mandrels for the infiltration with reaction resin in a closed vacuum-tight Mold inserted. After that, the trapped in the tool Evacuated air and injected reaction resin, then heat supplied and finally demoulded. Preferably are placed on the with positioning aids, Molded cores enveloped with fibers, further fiber layers for Reinforcement of the pipe wall applied. For rejuvenation The wall thicknesses of the fiber composite component become mandrels used with variable cross-section.

The reusable mandrels are preferably made of aluminum or steel.

lost Structured foam cores can be used in the fiber composite component remain or as soluble cores after fiber composite consolidation be washed out.

at A variant of the method is the multicellular composite structure by Laminating several shell components (modules) in an open Forming tool and then connecting the shell components using adhesive technology or rivet, screw or bolt connections constructed, wherein the shell components in each case contiguous consist of a push bar and a segment of the cylinder wall and in the area of the cylinder wall straps included.

The Invention also relates to the use of the invention Multicellular composite structure with wagon wheel profile as component for Axes and waves.

With the shear field carrier principle (cf. 1 , left) bending stresses are mainly transmitted by paired straps, which are arranged opposite each other with the greatest possible distance from the bending axis (also: neutral fiber). These straps are connected by a shear panel that absorbs shear stress induced by shear forces. Such as running as a double T-profile carrier take loads only in a load level. By several ver ver turned double T-profiles (cf. 1 , Center), in principle, differently directed loads can be recorded. Such an arrangement of double T-beams can be fused to a pipe cross-section with push bars (see. 1 , right), whereby a structure with Wagenradprofil arises. The hollow axle or hollow shaft according to the invention with carriage wheel profile is produced from a fiber-plastic composite with a high proportion of stress-oriented reinforcing fibers. Carbon fiber reinforcements are ideally used for very light, stiff and high-strength profile shafts. Glass fibers offer a low-cost alternative for highly stressed components with lower rigidity and component weight requirements. In addition, depending on the task, other fiber reinforcements such as aramid or basalt fibers can be used. In principle, thermoplastics (for example polypropylene, polyamide, polyphenylene styrene, polyether ether ketone) and thermosets (for example epoxy resins, polyether resins, phenolic resins) are suitable as matrix systems.

For axles and shafts made of fiber composite structures with carriage wheel profile, the fiber orientations are matched to the individual tasks of specific cross-sectional areas. Bending stresses are essentially taken up by belt-like about 0 °, maximum ± 10 ° -oriented unidirectional (UD) fiber layers in the outer pipe wall based on the shear field carrier. According to the bending moment curve, the belt cross sections can be varied over the component length (cf. 5 ). Shear stresses induced by shear forces are for the most part transmitted through the shear bridges of ± 30 ° to ± 60 °, preferably ± 45 ° oriented fiber layers, whereby a secure connection to the approximately 0 ° fiber reinforced belts by continuing this ± 45 ° Fiber layers is guaranteed in the pipe wall. The push bars can thus be designed as closed cells, the fiber layers of the straps being enclosed between individual fiber layers of the cells. These cells are then arranged approximately like "pieces of cake" in the circular cross section of the axis or shaft (see. 2 ). The thickness of the push bars can be adapted to the lateral force curve according to the load. Additional ± 30 ° to ± 60 °, preferably ± 45 °, fiber layers in the tube wall serve primarily to absorb torsional loads and to a lesser extent also the transmission of transverse forces. Depending on the expected component load in the pipe wall more fiber layers z. B. with about 0 ° / 90 ° fiber orientation are arranged.

Next the transmission of shear force-induced shear flows The webs also serve the stiffening of the circular Tube cross-section, which approximately in load introduction areas of an ovalization the cross section is encountered. For this purpose can individual fiber layers in the push bars with larger ones Fiber angles of ± 45 ° to ± 70 °, for example, ± 60 °, be executed.

The Resin Transfer Molding (RTM) process is predestined for the production of hollow structures with carriage wheel profile. Hereby, fiber composite hollow structures can be produced reproducibly in small to medium series. In the RTM method, the outer contour of the fiber composite structure according to the invention is predetermined with a closed tool system. The cells of the hollow structure are formed by reusable or lost mandrels. For stress-appropriate tapering of the wall thicknesses of the fiber composite component shaped cores with variable cross-section are used. Reusable mandrels are typically made of aluminum or steel. The demoldability must u. U, be ensured by a division of the nuclei (see. 6 ). Lost cores made of structural foam can remain in the fiber composite component, soluble cores are washed out after the fiber composite consolidation.

The Production of a fiber composite structure with carriage wheel profile begins with the structure of the cell-shaped push bars by mounting of several braided tubes of reinforcing fibers on the mold cores. It already slivers with unidirectional (UD), longitudinal fiber orientation integrated as a semi-finished product for the straps. Alternatively you can the mandrels also by winding technology with reinforcing fibers be surrounded. The forming cores covered with fibers become then assembled with positioning aids, so that externally an approximately rotationally symmetric Arrangement results. On this arrangement, more fiber layers be applied to reinforce the pipe wall. The complete fiber preform with mandrels is used for the infiltration with reaction resin in a closed vacuum-tight Mold inserted. A tool with dipping edge allows while closing the tool without reinforcing fibers pinch. In the RTM process, the tool included in the tool is included Air evacuated and injected reaction resin. By heat the viscosity of the resin is reduced and thus the Impregnation of semi-finished fiber accelerates. Further Heat supply then serves to stimulate the chemical curing process. After demolding of the fiber composite structure is possibly a cutting Finishing performed.

For very large wave structures, first individual push bar segments together with the associated belt segments are made individually in an open mold. These segments are then joined by riveting or gluing to a rotationally symmetric structure and bandaged with other fiber layers such as by means of winding technology.

• – eine Achse oder Welle aus einer Faserverbundstruktur mit höchster Schubfestigkeit und -steifigkeit durch integrierte Schubstege mit
• – beanspruchungsgerechten Faserorientierungen zur Übertragung von Biege-, Querkraft-, Längskraft- und Torsionsbelastungen bei einer äußerlich rotationssymmetrischen Struktur sowie
• – eine Konzeption einer Fertigungstechnik für mehrzellige Hohlstrukturen mit beanspruchungsgerechten Wandstärken und Faserorientierungen zur Verfügung gestellt.

With the invention will

• - An axle or shaft made of a fiber composite structure with maximum shear resistance and rigidity by integrated shearbars with
• - Stress-oriented fiber orientations for the transmission of bending, shear force, longitudinal force and torsional loads in an externally rotationally symmetric structure and
• - Provided a conception of a production technique for multicellular hollow structures with load-bearing wall thicknesses and fiber orientations.

By become the multicellular execution of axes and waves new application areas for fiber composite lightweight construction developed. Especially where limited space conditions in Related to heavy load concentrations so far the use high quality steels may have required with the fiber composite construction according to the invention significant weight savings are achieved.

characters

1 shows the schematic representation of structures with double-T beams and carriage wheel profile.

2 shows the cross section of the composite structure according to the invention with cart wheel profile.

3 shows the top view (open) of the composite structure according to the invention with cartwheel profile.

4 shows the longitudinal section of a wheel axle for a symmetrically constructed aircraft landing gear using the composite structure according to the invention with Wagenradprofil.

5 shows the longitudinal section of the composite structure according to the invention with cart wheel profile.

6 shows the top view (open) of the composite structure according to the invention with cart wheel profile with the associated system of mold cores.

7 shows the cross section of the composite structure according to the invention with carriage wheel profile with two-part tool.

8th shows the cross section with partial views of the composite structure according to the invention with cart wheel profile in a construction for larger fiber composite structures.

1 shows a comparison of double T-profile and carriage wheel profile for structural components that are loaded by transverse force bending. Both structures are based on the principle "shear field girders" with straps 18 and shear fields 19 based on. In contrast to classic double-T beams, structures with carriage wheel profiles are suitable for transmitting high shear forces and bending moments with different orientations.

In 2 and in 3 is the arrangement of reinforcing fibers in an axle of a composite structure with carriage profile 1 shown. Bending stresses are provided by 0 ° -oriented UD-reinforced belts 2 added. The push bars 3 are designed as nested cells, the straps being enclosed between individual fiber layers of the shear webs. Braided tubular semi-finished products with fiber angles of about ± 30 ° to ± 60 ° are predestined for reinforcing the shear bars. Depending on the requirement profile, the outer pipe wall will be provided by further 0 ° layers 6 , ± 45 ° layers 5 and 0 ° / 90 ° layers 4 strengthened.

4 schematically shows an application for an axle in fiber composite lightweight construction with wagon wheel profile 1 , Here, the fiber composite structure according to the invention serves as a wheel axle for a symmetrically constructed aircraft landing gear. The axle becomes centered in an axle carrier 12 clamped and takes over metallic bearing seats 7 . 8th the forces of the rims 10 with wheels 11 on. In this figure are also the bearings 9 to see.

In 5 is a half longitudinal section through a fiber composite structure according to the invention 1 shown. Clearly, here is the possibility of the wall thicknesses of the straps 2 and the push bars 3 adapted to the course of bending moments and transverse forces.

6 shows a fiber composite structure according to the invention with cartwheel profile 1 and an associated system of cores 13 with which the shaping of the inner component surfaces is made possible. As the cell cross-sections increase from the center of the component to the outside, the individual mandrels become 13 designed in two parts, so that the mold core halves can be removed without undercuts from the finished component in the opposite direction. An exact positioning of the cores 13 in the tool is by positioning aids 14 and positioning pins 15 guaranteed.

In 7 outlines a tooling system that allows resin infiltration and consolidation in the RTM process. The two-part tool 16 . 17 the system takes form cores 13 with the fiber semi-finished products positioned thereon. The design as a dipping edge tool simplifies the closing of the tool, without pinching reinforcing fibers. In the RTM process, the trapped air is evacuated from the vacuum-tight mold and tempered reaction resin is injected. After curing of the matrix material, the component is removed from the tool and then the individual mold core segments removed from the mold. If necessary, this is followed by a machining finish, such as turning or grinding.

8th provides a design for larger fiber composite structures with cart wheel profile 1 In this process variant, the push bars 3 in an open mold 20 constructed from ± 45 ° fiber layers, with 0 ° fiber layers for the straps 2 can be integrated. Then these modules become 21 to an externally rotationally symmetrical, multicellular structure, adhesively bonded or with the help of blind rivets. The pipe wall of this axle or shaft 1 can then be reinforced by hand lamination or winding technology further stress. Table 1: reference numerals in the figures 1 Multicellular fiber composite structure for axles and shafts 2 Straps with unidirectional 0 ° fiber reinforcement 3 Thrust webs with ± 45 ° fiber reinforcement 4 Cylinder segment with 0 ° / 90 ° fabric reinforcement 5 Cylinder segment with circulating ± 45 ° fiber reinforcement 6 Cylinder segment with 0 ° fiber reinforcement 7 Metallic bearing seat 8th Metallic bearing seat, axially adjustable 9 roller bearing 10 rim 11 tires 12 axle 13 mold core 14 Positioning aid for mold core 15 positioning 16 RTM mold, lower part 17 RTM mold, upper part 18 belt 19 thrust field 20 Open mold for the production of push bars 21 Module consisting of a single push bar with molded strap segment

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 6918839 B2 [0006, 0008]
• US 6974555 B2 [0006, 0008]

Claims (14)

Multicellular composite structure with carriage wheel profile for axles and shafts ( 1 ) with straps ( 2 ) and push bars ( 3 ), characterized in that straps ( 2 ) and push bars ( 3 ) are fiber reinforced. Multicellular composite structure according to claim 1, characterized in that in the outer tube wall straps ( 2 ), which have a gain with approximately 0 ° -oriented unidirectional (UD) fiber layers ( 2 ). Multicellular composite structure according to claim 1 and / or 2, characterized in that the shear webs ( 3 ) are constructed as nested cells with a reinforcement of ± 30 ° to ± 60 ° -oriented fiber layers, wherein the fiber layers of the thrust cells the fiber layers of the straps ( 2 ) in layers. Multicellular composite structure according to one or more of claims 1 to 3, characterized in that in the tube wall additional ± 30 ° to ± 60 ° fiber layers ( 5 ) are located. Multicellular composite structure according to one or more of claims 1 to 4, characterized in that in the tube wall further fiber layers ( 4 ) with about 0 ° / 90 ° fiber orientation. Multicellular composite structure according to one or more of claims 1 to 5, characterized that in the shearbars individual fiber layers with larger Fiber angles of ± 45 ° to ± 70 °. A process for producing the multicellular composite structure according to claim 1, characterized in that the composite structure in the resin transfer molding (RTM) process by means of a closed tool system ( 16 . 17 ), the outer contour of the composite structure ( 1 ) and in which the cells of the hollow structure are replaced by reusable or lost mandrels ( 13 ) are formed, wherein initially the cell-shaped push bars ( 3 ) by mounting a plurality of braiding tubes of reinforcing fibers on the mandrels ( 13 ), wherein fiber slivers with unidirectional (UD), longitudinal fiber orientation, as a semi-finished for the straps ( 2 ) or the mandrels ( 13 ) are surrounded by reinforcing fibers by winding technique, then the forming cores enveloped with fibers ( 13 ) with positioning aids ( 14 ), then the complete fiber preform with mandrels ( 13 ) is inserted for the infiltration of reaction resin in a closed vacuum-tight mold, then evacuated the enclosed in the tool air and pressed reaction resin, then heat is supplied, and is finally removed from the mold. Process according to claim 7, characterized in that a tool with dipping edge is used. A method according to claim 7 and / or 8, characterized in that with the positioning ( 14 ) assembled with fibers enveloped mandrels ( 13 ), further fiber layers ( 4 . 5 ) are applied to reinforce the pipe wall. Method according to one or more of claims 7 to 9, characterized in that the Rejuvenation of the wall thicknesses of the fiber composite component Form cores are used with variable cross-section. Method according to one or more of claims 7 to 10, characterized in that reusable Mold cores made of aluminum or steel. Method according to one or more of claims 7 to 11, characterized in that lost Cores made of structural foam in the fiber composite component can remain or as soluble cores after fiber composite consolidation be washed out. Method for producing the multicellular composite structure according to claim 1, characterized in that the composite structure is formed by laminating a plurality of shell components (modules) ( 21 ) in an open mold ( 20 ) and by subsequent connection of the shell components by means of adhesive technology or rivet, screw or bolt connections is constructed, wherein the shell components zusammenhän together resulting from a push bar ( 3 ) and a segment of the cylinder wall and in the region of the cylinder wall straps ( 2 ) contain. Use of the multicellular composite structure with Cartwheel profile according to claim 1 as a component for axles and waves.