DE102004003749A1 - Cylindrical fiber reinforced hollow plastic product manufacture involves winding impregnated fiber onto mandrel, wrapping in fiber braid, placing in RTM tool cavity and injecting resin - Google Patents

Abstract

A laminate comprising resin impregnated fibers(10) is wound onto a mandrel(20) and a fiber braid tube is applied over the laminate. The mandrel is placed in a RTM(resin transfer molding) tool and resin is injected injected. After gelation and curing the molding is removed from the tool and the mandrel withdrawn from the hollow product. Axial tension applied to the braid presses radially on the laminate so that the braid also becomes impregnated before placing the mandrel in the RTM cavity. Injected resin is the same as the resin used to impregnate the laminate. The tool has a feed and outlet points and can also be pressurized and heated. Independent claims are included for: a) process equipment which includes an RTM tool with two halves, one half designed to hold a mandrel(20) with a wound laminate and braid(30) pressed onto it. The long sides of the tool cavity are parallel with the sides of recesses which hold the mandrel; b) a cylindrical hollow product of fiber reinforced plastic with an internal wound fiber layer and an outer braided layer.

Description

The The invention relates to a method for producing a cylindrical hollow body made of fiber-reinforced Plastic.

The The invention further relates to a device for producing a cylindrical hollow body made of fiber-reinforced Plastic.

The The invention further relates to a method according to the invention and / or the device produced hollow body.

Around the efficiency from boosting machinery and engines, it is among other measures often a desired goal, to let them run faster. An example is the field of high-frequency electric motors to call. In this area, it does not pose a problem electrically Motors to operate in the Hz range. Become however conventional Materials used, problems occur at various points the strength and stiffness of the materials. From certain Component dimensions can the mechanical components can not stand the high speeds anymore, which to a failure of the components due to the self-loading of the materials leads.

Around To reduce the stresses, it is known critical components fiber reinforced To support plastics. These fiber reinforced Plastics have very high specific strength and stiffness values up to 5 times over the values of metallic materials. By the combination of different materials or by substitution The metallic materials through fiber reinforced plastics can thus much higher Turning frequencies are realized, as with conventional Materials is the case.

at the known components made of fiber-reinforced plastics It is primarily tubular Components, for example, to reinforce metallic or magnetic materials are used. You can further used to substitute these materials.

For example permanent magnet motors are increasingly used in high-frequency electric motors, where the permanent magnets placed on the metallic rotor core become. The magnets can be glued or clamped. The permanent magnets are also by a likewise pressed or glued tube made of fiber-reinforced Plastic, which is typically carbon fiber reinforced plastic (CFK) is armored. Due to the high specific strength and stiffness values of CFRP pipes are not the magnets under frequency loaded so high that they burst or detach from the rotor.

One Another area of application for CFRP pipes is turbomolecular pumps in which in the so-called Holwegstufe a pipe element with very high frequency. Would this component made of metallic materials, would be the radial strains so big that the necessary gaps could no longer be met. From a certain material-dependent frequency that would be Pipe element burst due to self-loading and the vacuum pump to destroy. It is known to use at this point CFRP pipes through their higher Strength and stiffness values corresponding to high speeds allow the performance the pump can be increased.

at the described fiber reinforced plastic pipes it depends primarily on high radial mechanical values, because the respective component is primarily loaded by centrifugal force. At the same time very high dimensional accuracies are required because the component is always installed with very small gaps and greater dimensional inaccuracy due to the centrifugal force lead to imbalances. For this reason, it is necessary to use the fiber reinforced pipes always with very high concentricity and dimensional tolerances to manufacture. These are in most cases only by editing the fiber reinforced Reachable pipes. By processing the pipes arise, however Problems only with considerable effort through further processing solved can be. In some cases the problems remain unresolved.

issues during processing, for example, the result is that the fibers the CFRP pipes, which are primarily in the circumferential direction, in the external machining be cut. As the tubes almost always in the winding process produced, the fibers have no crossing points. The on the surface cut fibers can so come out of the laminate at too high a load and lead to failure of the component.

Another problem arises from the static charge of the fiber reinforced pipes. Specifically, CFRP tubes involve the problem of carbon fiber conductivity in that the charge can be conducted across the fiber when the surface is machined and the conductive fibers are ground. Due to the small distance of the CFRP pipe to the surrounding metal part, discharges can occur which lead to local destruction and thus to the weakening of the laminate can. When machining surfaces, especially CFRP pipes, problems arise that can only be compensated by further measures.

From the European patent EP 0 643 248 B1 For example, it is known to solve these problems in high-frequency rotors by a specific layer structure of a fiber-reinforced hollow body. In this case, an inner layer is provided which has been prepared by winding a prepreg consisting of a fibrous layer as a matrix which has been impregnated with a resin. Another outer layer is made by wrapping a layer or band of thermoplastic resin around the inner layer, the two layers being bonded to a unified body by thermosetting and thermocompression. In addition, a metal layer is deposited on the outer layer without current, which is connected to the outer layer.

task The invention is a method for producing a cylindrical hollow body made of fiber-reinforced Plastic with high dimensional accuracy which does not require mechanical post-processing of the inner and outer surface of the Body requires.

task The invention further provides an apparatus for carrying out the Provide method.

A Another object of the invention is to provide a cylindrical hollow body fiber reinforced plastic with high dimensional accuracy to provide the inner and outer surfaces. The hollow body should be especially for suitable for use in the high frequency range and at high load no fiber drops cause.

According to the invention this Task by the features of independent claims 1, 5 and 10 solved. Advantageous developments of the invention can be found in the subclaims.

The The invention provides a method for producing a cylindrical hollow body made of fiber-reinforced Plastic, in which first a base laminate impregnated with resin Fibers is wound on a winding mandrel. About the base laminate thus formed a fiber braided hose is pulled and pressed. The pressing on the braided hose on the base laminate is preferably carried out by axial pull.

To the laminate is not wrapped in the usual way for curing a hardening furnace curious, but directly further processed. The winding mandrel is according to the invention together with the base laminate and the fiber braided hose into an RTM tool introduced and resin injected into the tool. Within the RTM tool The resin system is gelled and cured under pressure and heat.

thereupon the tool is opened and the winding mandrel taken with the formed hollow body. After cooling the Winding mandrel he is removed from the cylindrical hollow body.

In a particularly preferred embodiment of the invention, the same resin is injected into the RTM tool, which was used to wind the base laminate.

The Base laminate and the braided hose on the mandrel be preferably wet introduced into the RTM tool.

The The invention further comprises an apparatus for producing a cylindrical hollow body made fiber reinforced Plastic. The device is an RTM tool with two mold halves, wherein the inner shape of the tool is designed so that in it Mandrel with a wound base laminate and a pressed on Braided hose is receivable. The long sides of the inner mold, which the outer surface of the later hollow body depicting, are parallel to the long sides arranged, which receive the mandrel laterally.

The Device suitably includes Sealing elements for sealing the two tool halves against each other and an inlet and a drain for injecting resin into the Tool. Furthermore, the device has means for pressurizing and heating up. Due to the special design of the device it is particularly suitable for carrying out the method described for producing a cylindrical hollow body.

The invention further comprises a hollow fiber-reinforced plastic hollow body having an inner winding layer and an outer braid layer. The hollow body was preferably produced by the described method. The hollow body thus produced has a smooth inner and outer surface, and the surfaces are very good coaxial with each other. The required dimensions are so accurate to produce that no mechanical post-processing of the surfaces is required. Thus, the problems mentioned during processing can be avoided and a hollow body can be provided which is very well suited for use in the high-frequency range net. The insert is additionally facilitated by the fact that the outer layer of the laminate consists of a braided tube which has points of intersection of the fibers. Due to the crossing points, detachment of the individual fibers from the surface is no longer possible.

Further Advantages, special features and expedient developments of the invention emerge from the dependent claims and the following description of preferred embodiments based on the pictures.

From the pictures shows:

1 the winding process of a fiber on a winding mandrel;

2 a mandrel with applied braid hose; and

3 the introduction of the winding mandrel in a RTM tool.

In a particularly preferred embodiment of the invention, as in known pipes, a base laminate of fibers is produced on a winding machine. Such a winding process is schematically in 1 shown. This will be the fibers 10 with the fiber orientation (radial and axial) on a mandrel 20 wound, as it provides the component design. The winding process is preferably carried out "wet", ie directly with the resin-impregnated fiber, but it can also be carried out without impregnation with a resin, in which case the resin is introduced into the system at a later time.

After the winding process, the winding mandrel 20 not stretched as in the prior art in a curing oven and the laminate thereby cured, but the winding mandrel is further processed directly. On the wound base laminate while a fiber braid hose 30 pulled in 2 is shown. The braided hose is expediently pressed by axial tension firmly on the winding laminate. Preferably, in this case a braided hose made of the same or higher quality fiber is used. The length of the braided hose in the tensioned state preferably corresponds to that of the base laminate.

The mandrel 20 with the applied wet layers is then placed in a RTM tool (Resin Transfer Molding Tool), as shown schematically in FIG 3 is shown. This tool 40 is preferably divided into an upper half and a lower half, so that the mandrel can be inserted with little effort. The inner shape 50 of the tool is designed so that in it the winding mandrel is receivable together with the wound base laminate and the pressed braid hose. The mandrel is thereby introduced into the inner mold such that the inner and outer surfaces of the hollow body to be produced later run as parallel as possible to one another. To achieve this, the inner mold is formed so that its longitudinal sides 60 and 61 , which depict the outer surface of the later hollow body, parallel to the longitudinal sides 70 and 71 are arranged, which the winding mandrel 20 pick up laterally. The introduction of the mandrel between the long sides 70 and 71 thus takes place as accurately as possible. Due to this special design of the RTM tool, the outer contour of the pipe to be produced is centered directly to the inner contour of the winding tube.

The RTM tool is combined with sealing elements 80 closed by merging the lower and upper mold halves. To avoid trapping air when inserting the mandrel into the tool, the RTM tool is rinsed with the same resin system as used in the winding process prior to curing. If the base laminate was wound dry, the first impregnation with resin takes place in this case. For this purpose, the resin is pressed by an injection pump through a hose in the RTM tool until it exits bubbles on a second hose at the other end of the tool. This ensures that the entire interior shape 50 of the tool is filled with resin.

The Resin system is after the injection process by applying pressure on both hoses compressed, so that the shrinkage of the resin system is compensated. The pressure is preferably of the order of 5-7 bar, especially at 6 bar. Subsequently, the resin system is through Heating the RTM tool gelled and hardened. After curing the Laminates the tool is opened and the mandrel removed from the tool. The fiber reinforced tube can after cooling of the winding mandrel are deported from the same. For further processing of the pipe it only needs to be worked on length, what no further problems.

10

Fiber, waterproof

20

mandrel

30

Geflechtschlauch

40

RTM tool

50

interior shape of the tool

60 61

long sides for imaging the outer surfaces of the

hollow body

70 71

long sides for lateral recording of

mandrel

80

poetry

Claims (10)

Method for producing a cylindrical hollow body ( 50 ) made of fiber-reinforced plastic, characterized by the following steps - winding a base laminate of resin-impregnated fibers ( 10 ) on a mandrel ( 20 ); - applying a fiber braided hose ( 30 ) on the base laminate; - introducing the winding mandrel ( 20 ) with the base laminate and the fiber braided hose ( 30 ) into an RTM tool ( 40 ); Injecting resin into the RTM tool ( 40 ); Gelling and curing the resin system within the RTM tool ( 40 ) under pressure and heat; - opening and removing the winding mandrel ( 20 ) with the hollow body ( 50 ) from the RTM tool ( 40 ); and - removing the winding mandrel ( 20 ) from the cylindrical hollow body. A method according to claim 1, characterized in that the same resin in the RTM tool ( 40 ) which is used to wind the base laminate. Method according to one or both of claims 1 and 2, characterized in that the base laminate and the braided hose wet on the mandrel into the RTM tool. Method according to one or more of the preceding Claims, characterized in that the braided hose by axial Train is pressed onto the base laminate. Device for producing a cylindrical hollow body ( 50 ) made of fiber-reinforced plastic, characterized in that the device is an RTM tool ( 40 ) with two mold halves, wherein the inner mold ( 50 ) of the tool is designed so that in it a winding mandrel ( 20 ) with a wound base laminate and a pressed-on braided hose ( 30 ) is receivable, and that the longitudinal sides ( 60 ; 61 ) of the inner mold, which the outer surface of the later hollow body ( 50 ), parallel to the long sides ( 70 ; 71 ) are arranged, which the mandrel ( 20 ) pick up laterally. Device according to claim 5, characterized in that it comprises sealing elements ( 80 ) for sealing the two tool halves against each other. Device according to one or both of claims 5 and 6, characterized in that it is for injecting resin in the tool comprises an inlet and a drain. Device according to one or more of the preceding claims 5 to 7, characterized in that they are suitable for carrying out a Method according to one or more of claims 1 to 4 is suitable. Device according to one or more of the preceding Claims, characterized in that it comprises means for pressurizing and heating. Cylindrical hollow body made of fiber-reinforced plastic, characterized in that it comprises an inner winding layer and an outer braid layer and according to a method according to one or more of claims 1 to 4 was produced.