DE102013019470A1 - Structural component with a hollow structure - Google Patents

Abstract

The invention relates to a method for producing a structural component, in particular a plastic component having at least one hollow structure (1), in which at least one lost mandrel (19) replicating the negative form of the hollow structure (1) is inserted into a forming chamber (25) of a forming tool (27) is then, and the mandrel (19) is encapsulated under pressure and heat from a liquid starting component of a plastic (14) or a light metal, after curing, the material of the mandrel (19) from the hollow structure (1) is rinsed out. According to the invention, prior to the shaping of the structural component, the mold core (19) is at least partially coated with a reinforcing layer (13) which remains integrated in the material of the structural component after shaping.

Description

The invention relates to a method for producing a structural component with a hollow structure according to claim 1, a mold core for the method according to claim 10 and a plastic component produced by the method according to claim 11.

In the automotive industry, the use of plastic components or light metal components as supporting structural elements in terms of weight reduction is desired. The plastic components or light metal components can be produced in various processes, such as an RTM process (Resin Transfer Molding), a casting process or a foaming process. In this method, a negative mold of the hollow structure replicating lost salt core is first inserted into a molding chamber of the forming tool. Subsequently, the salt core is encapsulated under pressure and heat by a liquid starting component of the plastic (or alternatively the light metal). After curing, the finished plastic component can be removed from the tool and the salt core can be rinsed out of the hollow structure of the plastic component. Such a generic method is known from EP 2 040 897 B1 known.

In automotive engineering, among other things for crash-sensitive components, such as a vehicle pillar, special requirements for component stability in the event of a side impact have to be met, which in the case of plastic components have hitherto only been possible with great manufacturing effort.

The object of the invention is to provide a method for producing a structural component having at least one hollow structure, in which the component stiffness of the structural component can be increased in a simple manufacturing technology.

The object is solved by the features of claim 1, claim 10 or claim 11. Preferred embodiments of the invention are disclosed in the subclaims.

The invention is primarily applicable in the production of a structural component made of plastic, so that below the developments of the invention are disclosed specifically based on the production of a plastic structural component. However, the same developments of the invention also apply to light metal structural components.

The invention is based on the problem that so far to increase the dimensional stability of the plastic usually its material thickness is increased, which is disadvantageous in terms of component weight, or in the manufacturing process a dimensionally stable, but usually more expensive plastic is used. Against this background is omitted according to the characterizing part of claim 1 to such measures and instead of the mold core, that is, the lost salt core, at least partially coated with an additional reinforcing layer before the plastic molding. The coated on the mandrel reinforcing layer remains integrated after plastic molding and after flushing out of the mandrel in the material of the plastic component and takes on additional reinforcing functions to increase the component stiffness of the plastic component.

The mandrel provided with the reinforcing layer can be used in various plastic molding processes. By way of example, the shaping of the plastic component can take place in a foaming process in which the liquid starting component, for example PUR, of a plastic structural foam is injected into the shaping tool and foamed. Alternatively, the shaping of the plastic component can take place in a casting process, in which the mold core inserted into the tool is encapsulated by the liquid starting component of a castable plastic. Furthermore, the molded core coated with the reinforcing layer can be used in an RTM process, in which at least one preform formed from a semifinished fiber preform is inserted into the molding chamber of the RTM tool in addition to the mold core. Subsequently, the liquid starting component of a matrix material is injected under heat and pressure into the molding chamber, whereby a fiber-reinforced plastic component is produced, in which specifically the cavity structure is additionally stiffened by means of the reinforcing layer.

The preform may be a sheet-like or three-dimensionally preformed semi-finished fiber product (for example a fiber mat, a fiber fabric, a fiber braid or the like). In the case of an RTM process, the preform is inserted into the molding chamber of the RTM tool even in the dry state, that is to say without matrix material.

Depending on the dimensional stability of the plastic component to be achieved, the reinforcing layer can have one or more reinforcing fiber layers stacked on top of one another, which can be applied to the mandrel. The reinforcing fibers in the stacked fiber layers may be arranged in the same or different fiber orientation. Optionally, the fiber layers can be applied together with a binder with which a positionally secure positioning of alignment the reinforcing fibers is ensured on the mandrel.

The reinforcing fiber layers may be applied to the mandrel in any manner. In a particularly process-reliable variant, the reinforcing fibers can be wound up as endless fibers (rovings) to form the at least one fiber layer on the mandrel acting as a mandrel. In this case, if necessary, the dry and resistant fixed continuous reinforcing fiber (such as a carbon fiber, glass fiber, Aramitfaser, etc.) due to their fiber tension sufficiently self-fixed and supported be applied to the mold core, without additional binder applied.

In addition to the reinforcing layer, it is also possible for other functional elements to be integrated in the mandrel which, if appropriate, can remain in the hollow structure of the plastic component after the mandrel material has been rinsed out. By way of example, in the material of the mold core cable strands, which serve for the power supply in the installed state of the plastic component, bulkhead parts, stiffening elements or fastening elements can be integrated.

During molding, the temperature within the mandrel is far below the forming temperature in the die-forming chamber. For this reason, more temperature-sensitive elements can be particularly preferably integrated in the mold core, which can not withstand the high molding temperature in the mold cavity.

Specifically, a stiffening element integrated in the mold chamber can have at least one contact point, which is exposed by the material of the mold core, for a perfect introduction of force. After the plastic molding, the exposed contact point of the stiffening element may be in frictional engagement with a, the hollow structure bounding inner wall of the component, whereby a reliable force is ensured in the stiffening element.

Particularly preferably, the mold core is a pressed-only salt core without expensive post-processing, with the omission of an additional solidification, for example, several hours of sintering. In this way, cavities and limitations in the plastic component can be achieved inexpensively. This results in a cost reduction by saving expensive plastic materials and accessories and a weight reduction due to the subsequent removal of the salt core.

Honeycomb structures or structures and ribs specially designed for the introduction of force can generally be produced using plastic technology. In addition, the plastic molding is also applicable to acoustic foams and other foam methods and in a composite component manufacturing. Specifically, the Schott parts can be removed together with the salt cores after plastic molding again.

On the basis of the above technology also cavities in CFRP or other plastic parts can be made and thus possibly undercuts are made inexpensively. Especially for smaller quantities can be dispensed with complicated tools. Especially in the foaming process using a PU structural foam only small forces must be absorbed by the bulkhead parts for stopping the flow front.

In the new method, cavities can be deliberately introduced into profiles and these are stiffened with the aid of the reinforcing layer. In addition, plastic parts can be ideally integrated with force-transmitting structural foams in the vehicle body and can be targeted ribbing and reinforcement with minimal foam weight (or plastic weight).

The advantageous embodiments and / or further developments of the invention explained above and / or reproduced in the dependent claims can be used individually or else in any desired combination with one another, for example, in cases of unambiguous dependencies or incompatible alternatives.

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 sectional view of a finished plastic component with two hollow structures;

2 to 4 each roughly schematic schematic representations by which a method for producing the in the 1 illustrated plastic component is illustrated; and

5 and 6 each views illustrating an alternative method for producing a plastic component.

In the 1 is an example of a finished plastic component with two hollow structures 1 . 3 shown in a schematic schematic diagram. The 1 as well as the others 2 to 6 are in view made on a simpler understanding of the invention. Therefore, the figures are only roughly simplified representations that do not reflect a realistic structure of the plastic component.

So is in the 1 the plastic component is rotationally symmetrical, with an inner cylindrical cavity structure 1 coming from a cylinder wall 5 is surrounded. In the axial direction is the cylindrical cavity structure 1 through end walls 7 limited the plastic component. Through the two end walls 7 are each flush channels 9 guided. The cavity 1 of the plastic component 1 is also made of stiffening elements 11 interspersed, each force and / or material fit in abutment with the inside of the cylinder wall 5 are. That in the 1 shown plastic component is made of a plastic, wherein to increase the component stiffness on the inside of the cylinder wall 5 additionally a reinforcing layer 13 in the plastic material 14 is integrated.

The stiffening elements 11 have passages 12 on, so that the cavity 1 when dissolving the salt core 19 completely flushed with water.

The reinforcing layer 13 is in the 1 of two stacked reinforcing fiber layers 15 . 17 is constructed. These are completely in the plastic material 14 embedded. The reinforcing fibers 19 the reinforcing fiber layers 15 . 17 may optionally be in mutually different fiber orientations.

The following is based on the 2 to 4 the process for the preparation of in the 1 shown plastic component described. Accordingly, according to the 2 the reinforcing layer 13 first on the cylindrical outer surface of a lost salt core 19 applied. The reinforcing layer 13 is in the 2 exemplified by the already mentioned above two fiber layers 15 . 17 built up. These fiber layers 15 . 17 Here, for example, in a winding process on the acting as a winding mandrel salt core 19 wound up, by means of a tensile strength continuous reinforcing fiber 18 (about a carbon fiber, glass fiber, Aramitfaser, etc.). The salt core 19 forms the negative mold of the cylindrical hollow structure 1 in the 1 shown plastic component.

In the winding process, the endless reinforcing fibers 7 in the dry state, that is, without wetted plastic material around the salt core 19 wound, stacked one above the other with the already mentioned different fiber orientations. Optionally, the fiber layers 15 . 17 be solidified with the interposition of a binder, not shown, to ensure that the fiber layers 15 . 17 remain positionally accurate and positionally accurate during the following molding process.

Like from the 2 further, the two stiffeners are 13 in the material of the salt core 19 embedded, in such a way that force introduction points 21 on the outer circumference of the salt core 19 are exposed. According to the figures, the approximately cylindrical salt core 19 on its two front sides with smaller-diameter extensions 23 extended, which the negative form of in the 1 shown flushing channels 9 form.

The salt core 19 is then according to the 3 in a mold chamber 25 a forming tool 27 inserted. Thereafter, the liquid starting component of the plastic material 14 in the molding chamber 25 injected. By way of example, the plastic material 14 be a structural foam, in a molding process in the molding chamber 25 foams under pressure and heat. In addition to the salt core 19 is in the mold chamber 25 of the foaming tool 27 another salt core 29 arranged, which the negative form of in the 1 shown hollow structure 3 (For example, a fastening contour), which in the 1 is formed on the outer circumference of the plastic component. During the foaming process, the structural foam penetrates 14 the fiber layers 15 . 17 the reinforcing layer 11 ,

After curing of the injected foam material 14 results from the 4 a composite component consisting of the finished plastic component and the still integrated therein salt cores 19 . 29 , This component composite is removed from the tool 27 taken. This is followed by demolding, in which the material of the two salt cores 19 . 29 in the demoulding direction E ( 4 ) with release of the hollow structures 1 . 3 be rinsed out.

In the above embodiment, the shaping of the plastic component takes place in a foaming process. However, the invention is not limited thereto. Rather, other suitable shaping methods can be used in conjunction with the salt core according to the invention 19 be performed. Thus, according to the 5 and 6 the one with the reinforcing layer 13 provided salt core 19 z. B. in the molding chamber 25 an RTM tool 27 inserted. In addition to the cores 19 . 29 are in the 5 two preforms formed from a semi-finished fiber product 33 inserted, both of which are structured approximately cup-shaped. The two preforms 33 (Preforms) are provided in the dry state, that is still without matrix material.

Subsequently, the liquid starting component of the matrix material 14 in the forming chamber 25 injected, causing both the preforms 33 as well as the fiber layers 15 . 17 the reinforcing layer 13 from the matrix material 14 be soaked. After curing of the matrix material 14 becomes the material of the salt cores 19 . 29 from the hollow structures 1 . 3 flushed out, which in the 5 shown plastic component results. The inner and outer contours of the in 6 plastic components shown are identical to those in the 1 shown component. In contrast to 1 is that in the 6 shown plastic component by means of the two preforms 33 fiber reinforced, whereby a further increase in the dimensional stability of the plastic component is achieved.

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

• EP 2040897 B1 [0002]

Claims (11)

Method for producing a structural component, in particular a plastic component having at least one hollow structure ( 1 ), in which at least one of the negative forms of the hollow structure ( 1 ) replicating lost mandrel ( 19 ) in a molding chamber ( 25 ) of a forming tool ( 27 ) is inserted, and then the mandrel ( 19 ) under pressure and heat from a liquid starting component of a plastic ( 14 ) or a light metal, after curing, the material of the mold core ( 19 ) from the hollow structure ( 1 ) is rinsed out, characterized in that prior to the shaping of the structural component of the mandrel ( 19 ) at least partially with a reinforcing layer ( 13 ) is coated, which remains integrated after shaping in the material of the structural component. A method according to claim 1, characterized in that the shaping of the structural component takes place in a foaming process in which the plastic or a light metal ( 14 ) is a structural foam that enters the forming tool ( 27 ) is injected and foamed. A method according to claim 1, characterized in that the shaping of the structural component takes place in a casting process, in which the plastic ( 14 ) is flowable, and the mold core ( 19 ) from the liquid starting component of the pourable plastic ( 14 ) is poured around. A method according to claim 1, characterized in that the shaping of the plastic component takes place in an RTM process in which the plastic or the light metal ( 14 ) forms a matrix material, and that in addition to the mandrel ( 19 ) at least one preform formed from a semi-finished fiber product ( 33 ) in the molding chamber ( 25 ) of the RTM tool ( 27 ) and then the liquid starting component of the matrix material in the molding chamber ( 25 ) is injected. Method according to one of the preceding claims, characterized in that for forming the reinforcing layer ( 13 ) one or more stacked reinforcing fiber layers ( 15 . 17 ) on the mandrel ( 19 ), optionally together with a binder with which the reinforcing fibers ( 18 ) positionally accurate and positionally accurate on the mold core ( 19 ) remain. Method according to claim 5, characterized in that the reinforcing fibers ( 18 ) in a winding process to form the at least one fiber layer ( 15 . 17 ) acting on the mandrel acting as a mandrel ( 19 ) are wound up. Method according to claim 5 or 6, characterized in that the at least one reinforcing fiber layer ( 15 . 17 ) in the dry state, that is without matrix material, on the mandrel ( 19 ) is applied, and that the reinforcing fiber layer ( 15 . 17 ) is impregnated only in the molding process with the liquid plastic output component or light metal output component. Method according to one of the preceding claims, characterized in that in the material of the mold core ( 19 ) at least one functional element ( 11 ), such as a bulkhead part, is integrated, and / or that the functional element ( 11 ) after rinsing out the mandrel ( 19 ) in the hollow structure ( 1 ) remains of the structural component, such as a harness for the power supply, a stiffening element or a fastener. Method according to claim 8, characterized in that the stiffening element ( 11 ) at least one force introduction point ( 21 ) formed by the material of the mandrel ( 19 ) is exposed, and after the plastic molding in frictional contact with the inside of a hollow structure ( 1 ) delimiting boundary wall ( 5 ) of the structural component. Mold core for a process for producing a plastic component with a hollow structure ( 1 ), of the mandrel ( 19 ) is simulated, according to one of the preceding claims, characterized in that the mold core ( 19 ) at least partially with a reinforcing layer ( 13 ) is coated, which is an integral part of the structural component after the plastic molding. Structural component with a hollow structure ( 1 ), which can be produced by a method according to one of claims 1 to 9, with a boundary wall ( 5 ), the hollow structure ( 1 ), characterized in that in the boundary wall ( 5 ) on the, the hollow structure ( 1 ) facing inside a reinforcing layer ( 13 ) is integrated.

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