DE102014008644A1 - Process for producing a hollow body from a fiber composite plastic - Google Patents

Abstract

The invention relates to a method for producing a hollow body (1) from a fiber composite plastic, in which a preform (11) which is constructed from a core body (12) and a semifinished fiber product (7) enveloping the core body (12) is inserted into a molding tool (11). 25) is inserted and then in an infiltration process, the core body (12) enveloping semi-finished fiber product (7) is impregnated with a liquid starting component of a matrix material (9). According to the invention, the core body (12) of the preform (11) has a hose element, in particular a pressure hose (19), in which a collapsible solid (15) is arranged, which in the process progress between a cross-sectional widened shape contour (17) and a cross-section reduced contour (FIG. 31) is changed.

Description

The invention relates to a method for producing a hollow body from a fiber composite plastic according to the preamble of claim 1 and a preform for such a method according to the preamble of claim 14.

For the production of fiber composite plastic components, braided semifinished fiber products can be used, which allow low-defect Preformherstellung and thus an overall cost-effective production.

In a generic method, a preform, consisting of a core body and of a core body enveloping semi-finished fiber, inserted into a mold. Subsequently, the mold is closed and carried out an infiltration process in which the core body enveloping semi-finished fiber is impregnated with a liquid starting component of a matrix material. By way of example, the core body can be a pressure hose which can be subjected to a gas overpressure during the infiltration process, whereby the pressure hose presses the semifinished fiber product against a shaping surface of the molding tool that imitates the outer end contour of the hollow body in negative mold. After consolidation of the matrix material, the pressure hose is relieved of pressure and the mold is opened. Then the pressure hose is removed from the cavity of the hollow body. Such a method is known from DE 2007 027 755 A1 known.

The preparation of the above-mentioned preform can be carried out in common practice in a winding process or in a braiding process, in which continuous fibers are deposited in different fiber orientations contour adapted to the core body, that is brought in close gap-free contact with the outer shape contour of the core body. In a braiding process, the core body is braided circumferentially with a fiber structure.

In the production of a hollow body with complex component geometry, such a winding or braiding process is problematic for the following reason: For example, the hollow body may have an undercut with a concave wall section, which is also found in the shape contour of the core body. In a conventional winding or braiding process, however, the applied fiber structure can not follow the contoured contour of the concave wall surface of the core body. Rather, the applied fiber structure would span over the concave wall section of the shaped body with the formation of a gap.

The object of the invention is to provide a method for producing a hollow body from a fiber composite plastic, in which even complex component geometries, for example undercuts or pointed structures, can be reliably produced.

The object is solved by the features of claim 1 or claim 14. Preferred embodiments of the invention are disclosed in the subclaims.

According to the characterizing part of claim 1, the core body of the preform has a tubular element, is arranged in the collapsible solid. The collapsible solid arranged in the tubular element can, with suitable activation, for example by a negative pressure, be adjusted in the course of the process to be process-adapted between a cross-sectional widened shape contour and a cross-section-reduced contour. According to the invention, therefore, a change in cross-section of the hose element can no longer be achieved by varying a gas internal pressure in the hose element, as is standard practice, for example, in a hose blowing method. In such a common Schlauchblasverfahren usually only round shape contours of the core body can be generated, but not more complex geometries that already come close to a complex component geometry of the hollow body final contour.

Depending on the course of the process, the collapsible solid of the core body can be activated in order to take its cross-section-reduced contour and thus come out of engagement with the inner wall of the hollow body produced.

For producing the preform, continuous fibers can, for example, be wound on the core body in a winding process or in a braiding process, the collapsible solid in its cross-sectional widened shape contour being sufficiently component-rigid in order to withstand the fiber tension applied during the braiding or winding process. The fiber structure is not applied directly to the collapsible solid, but rather with the interposition of the pressure element, in particular a pressure hose, applied to the collapsible solid. In the prior art, it is common practice to fill the pressure element of the core body in the winding or braiding process with a gas, such as air, whereby the hose internal pressure is increased. In such a pressurization with internal gas pressure, however, no more complex component geometries can be imitated on the core body. In contrast, the collapsible solid of the core body can readily be adapted at least to the final contour of the hollow body. Only restriction is that only one Undercut with concave wall section on the collapsible solid is to be avoided.

After the preparation of the preform, the collapsible solid can be spent by appropriate activation in its cross-section reduced contour. In this case, the semifinished product surrounding the core body is no longer in close, gap-free contact with the core body, but rather in loose contact with the cross-section reduced core body. As a result, the now largely semi-rigid semifinished fiber product can be simply draped in the correct position in the cavity of the molding tool. Subsequently, the cavity of the mold is closed and the pressure hose of the core body can be acted upon by a gas overpressure. As a result, the preferably elastically stretchable pressure hose presses the semifinished fiber product in the correct position against the molding surface of the molding tool, which corresponds to the hollow body end contour.

Preferably, the pressure hose may have a pressure connection which is coupled to an external pressure source, by means of which the pressure hose can be supplied with the gas overpressure. In a preferred variant, the pressure source in a dual function can also be used to activate the collapsible solid, that is, to initiate the collapse of the solid from its cross-sectional widened shape contour into its cross-section-reduced contour. This can be done by applying a gas negative pressure. Such a negative pressure application is particularly applicable when the collapsible solid is a closed-cell foam material with gas inclusions.

Preferably, the collapsible solid of the core body is thus provided after its winding or braiding process and before the implementation of the infiltration process, in particular before inserting the preform in the mold, with its cross-section reduced contour. In addition to the application of gas negative pressure, the collapsible solid can additionally or alternatively also be collapsed into its cross-section-reduced contour by application of heat.

In order to facilitate the handling of the core body in the manufacture of the preform and / or when placing the preform in the mold, the core body may have a component-rigid inner core, such as a dimensionally stable rod, which is coated by the collapsible solid. Accordingly, the core body can be constructed in three parts, namely with the component-rigid inner core, the collapsible solid and the outside hose member.

The above method may in particular also for the production of a hollow body having an undercut with an outer concave wall portion. In this case, the initially cross-sectional widened shape contour of the collapsible solid of the core body can already be adjusted to the final contour, but without the undercut. The unwound length of the cross-sectional widened core body shape contour can substantially coincide with the unwound length of the hollow body end contour in order to provide sufficient fiber material during draping in the mold.

By already close to final contour close adaptation of the shape contour of the molding a Drapiervorgang is simplified, in comparison to a nichtkontontum close adapted core body assembly in which much more complicated Drapiervorgänge in the cavity of the mold are required, with the risk that optionally the fiber structure of the semifinished fiber is excessively impaired.

After Drapiervorgang the cavity of the mold is closed and there is a loading of the hose member with an internal pressure, by means of which the hose member is reliably pressed into the, the undercut reproducing partial chamber of the mold cavity.

An essential aspect of the invention relates to the fact that - compared to a conventional internal pressure application - the hose element does not have to be filled with a gas in the production of the preform in order to provide the shape contour of the core body. Rather, the shape contour of the core body is provided by the collapsible solid, with the much more complex component geometries can be simulated close to the final contour.

In contrast to the prior art thus takes place a loading of the pressure hose with a gas internal pressure only in the implementation of the infiltration process, but not in the production of the preform. The pressure connection of the pressure hose can be used preferably not only for the pressure increase in the infiltration process, but rather also for a pressure reduction, with which the collapsible solid is reduced cross-section in order to simplify the insertion process into the mold cavity.

The advantageous embodiments and / or developments of the invention explained above and / or reproduced in the subclaims can - except, for example, in the case of clear dependencies or incompatible alternatives - be used individually or in any combination with each other.

The invention and its advantageous embodiments and further developments and advantages thereof are explained in more detail below with reference to drawings.

Show it:

1 in a cross-sectional view of a hollow body of a fiber composite plastic; and

2 to 8th each views, by means of which the method for producing the hollow body is illustrated.

In the 1 is a hollow body 1 shown in a cross-sectional view. Consequently, the hollow body 1 a closed interior 3 and a consistently constant material thickness. The hollow body 1 also has an undercut 5 with a concave wall section. The hollow body 1 is made of a fiber composite plastic, in which an indicated in crosshatch semi-finished fiber 7 with a dotted indicated matrix material 9 is infiltrated.

The hollow body 1 is done using a preform 11 made, as in the 5 is shown. According to the 5 is the preform 11 constructed in four parts, with an inner core 13 , a foam material 15 , a pressure hose 19 and the semifinished fiber product 7 , The inner core 13 is an example of a component-rigid metal rod, which is the handling of the preform 11 in the, in 2 to 8th simplified process chain shown. The inner core 13 sheathing foam material 15 defines a contour on the outside 17 , on the interposition of the pressure hose 19 the still dry semi-finished fiber 7 wound or braided. The semifinished fiber product 7 will be in one, in the 4 indicated braiding process under fiber tension on the core body 12 brought in the continuous fibers 14 be braided circumferentially in different orientations.

In the production of the core body 12 is in accordance with the 2 first the inner core 13 with the foam material 15 jacketed. This can be done by way of example in a foaming system. The foam material 15 is already with a, ajar to the hollow body end contour shape contour 17 executed, but without undercut. The unwound length of the mold contour 17 This corresponds essentially to the unwound length of the hollow body end contour.

Subsequently, according to the 3 the pressure hose 19 over the shape contour 17 of the foam material 15 of the core body 12 drawn. Subsequently, in the braiding process, the semi-finished fiber 7 on the core body 12 braided.

The preform made in this way 11 is then according to the 7 in a cavity 23 a mold 25 inserted. To simplify the loading process, according to the 5 even before the insertion process ( 7 ) the pressure hose 19 at its pressure connection 27 with an external pressure source 29 coupled and subjected to a gas negative pressure. This causes the foam material 15 from his to the 2 to 5 shown cross-sectional shape contour 17 in a cross-section reduced contour 31 collapses, as in the 6 is indicated. In that, in the 6 shown state is thus the core body 12 no longer in a close gap-free plant with the braided semifinished fiber product 7 but rather only in loose connection with corresponding free spaces within the semi-rigid semifinished fiber product 7 , In this way, during the loading process according to the 7 the semifinished fiber product 7 Process-technically simple in the mold cavity 23 to be draped in the correct position.

The loading process ( 7 ) is additionally simplified by the fact that by means of the foam material 15 of the core body 12 the preform 11 already produced close to final contour, whereby an optionally the fiber structure of the semifinished fiber product 7 impairing, extensive Drapiervorgang is avoided.

After the insertion and draping of the preform 11 in the tool cavity 23 this will be closed ( 8th ). Then again the external pressure source 29 activated to the pressure hose 19 to fill with gas and to increase accordingly the internal pressure in the pressure hose. As a result, the pressure hose presses 19 the semifinished fiber product 7 reliable against the mold surface 33 of the mold 25 ,

Subsequently, an infiltration process takes place, in which via an injection line 35 the liquid starting component of the matrix material 9 into the still dry semifinished fiber product 7 is infiltrated. After curing of the matrix material 9 and after a pressure relief of the pressure hose 19 becomes the mold 25 opened and the finished hollow body 1 taken. The core body 12 then gets out of the cavity 3 of the hollow body 1 away.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2007027755 A1 [0003]

Claims (14)

Method for producing a hollow body ( 1 ) made of a fiber-reinforced plastic, in which a preform ( 11 ), which consists of a core body ( 12 ) and one the core body ( 12 ) enveloping semi-finished fiber products ( 7 ) is built into a mold ( 25 ) and then in an infiltration process the core body ( 12 ) enveloping semi-finished fiber products ( 7 ) with a liquid starting component of a matrix material ( 9 ) is impregnated, characterized in that the core body ( 12 ) of the preform ( 11 ) a hose element, in particular a pressure hose ( 19 ), in which a collapsible solid ( 15 ) is arranged, which in the course of the process between a cross-sectional widened shape contour ( 17 ) and a cross-section reduced contour ( 31 ) is changed. Process according to claim 1, characterized in that the collapsible solid ( 15 ) with its cross-sectional widened shape contour ( 17 ) in the production of the preform ( 11 ) and that the semi-finished fiber product ( 7 ) the core body ( 12 ) of the preform ( 11 ) with the hose element ( 19 ) is wrapped. Method according to claim 1 or 2, characterized in that the pressure hose ( 19 ) of the core body ( 12 ) can be acted upon with a gas internal pressure, and that the infiltration process with a in the pressure hose ( 19 ) prevailing overpressure with which the pressure hose ( 19 ) the semi-finished fiber product ( 7 ) against the molding surface ( 33 ) of the molding tool ( 25 ), which corresponds to the hollow body end contour. A method according to claim 1, 2 or 3, characterized in that prior to carrying out the infiltration process, in particular before inserting the preform ( 11 ) in the mold ( 25 ), the collapsible solid ( 15 ) of the core body ( 12 ) from its cross-sectional shape contour ( 17 ) in its cross-section reduced contour ( 31 ) is changed. Method according to one of the preceding claims, characterized in that the collapsible solid ( 15 ) by applying a gas negative pressure and / or by applying heat from its cross-sectional widened shape contour ( 17 ) in its cross-section reduced contour ( 31 ) collapsed. Method according to one of the preceding claims, characterized in that the core body ( 12 ) a component-rigid inner core ( 13 ) formed by the collapsible solid ( 15 ) is sheathed. Method according to one of the preceding claims, characterized in that the end contour of the hollow body ( 1 ) at least one undercut ( 5 ) having a concave wall portion, and that in particular the cross-sectional widened shape contour ( 17 ) of the collapsible solid ( 15 ) close to the final contour, but without the undercut ( 5 ), is adjusted. A method according to claim 7, characterized in that the unwound length of the cross-sectional widened shape contour ( 17 ) substantially coincides with the unwound length of the hollow body end contour. Method according to one of the preceding claims, characterized in that the collapsible solid ( 15 ) is a particular closed-cell foam material with gas inclusions. Method according to one of the preceding claims, characterized in that the core body ( 12 ) after the completion of the hollow body ( 1 ), in particular under gas pressure relief, from the hollow body ( 1 ) Will get removed. Method according to one of the preceding claims, characterized in that the core body ( 12 ) in a winding process or a braiding process with the semifinished fiber product ( 7 ), in which the core body ( 12 ) is covered circumferentially with a fiber structure. Method according to one of claims 3 to 11, characterized in that the pressure hose ( 19 ) of the core body ( 12 ) a gas connection ( 27 ) for coupling to an external pressure source ( 29 ) having. Method according to claim 12, characterized in that the gas connection ( 27 ) of the pressure hose ( 19 ) is provided both for the application of positive pressure and negative pressure. Preform for a process for producing a hollow body ( 1 ) made of a fiber composite plastic, which preform ( 11 ) from a core body ( 12 ) and from one, the core body ( 12 ) enveloping semi-finished fiber products ( 7 ), characterized in that the core body ( 12 ) of the preform ( 11 ) a hose element, in particular a pressure hose ( 19 ), in which a collapsible solid ( 15 ) is arranged, which in the course of the process between a cross-sectional widened shape contour ( 17 ) and a cross-section reduced contour ( 31 ) is changeable.

Images