DE102015005504B4 - Process for producing a fiber-reinforced plastic component - Google Patents

Abstract

Method for producing a fiber-reinforced plastic component (1) in an RTM process, in which at least one semifinished fiber product (9) of dry, not yet matrix-impregnated fiber material is provided in a provision step, in a preforming step the semifinished fiber product (9) to form a preform (39 ) is deformed three-dimensional component end contour, and in an injection step, the preform (39) in a Werkzeugkavität (13) of an injection tool (15) consisting of a lower tool part (21) and an upper tool part (20) is inserted and under pressure and heat a liquid Matrix preforming component is injected into the mold cavity (13) and cured therein, the preforming step being divided into a first partial step in which the still undeformed semifinished fiber product (9) is prepositioned in the tool cavity (13) to form the preform (39), and in a second sub-step in which a starting component a s foaming material in the mold cavity (13) is foamed and the foaming foam material, the semi-finished fiber product (9) to form the three-dimensionally transformed preform (39) against the mold cavity (13) delimiting molding surface (17, 19) presses, characterized in that before Carrying out the injection step, a tool cavity height (h) is increased by raising one of the injection tool parts (20, 21) by a height offset (Δh) in order to improve the flow behavior of the matrix output component injected into the tool cavity (13).

Description

The invention relates to a method for producing a fiber-reinforced plastic component in an RTM process according to the preamble of patent claim 1.

In vehicle construction, the RTM process (resin transfer molding) can be used for mass production of high-performance components made of fiber-reinforced plastics. With the help of the RTM process, components in large quantities and high fiber volume contents can be produced reproducibly in short cycle times.

From the EP 2 524 796 A1 is an RTM process is known in which in a provision step, a planar semi-finished fiber from dry, that is not matrix-saturated fiber material is provided. The semifinished fiber product can be, for example, a fiber mat, a fiber fabric, a fiber braid, knit fabric, scrim or nonwoven fabric. In a preforming step upstream of the injection step, the still planar semi-finished fiber product is shaped three-dimensionally and component-to-product contours to form a preform. Subsequently, the injection step takes place in which the preform inserted in a mold cavity of an injection tool is impregnated under pressure and heat with a liquid matrix starting component and then cured.

In common practice, the preforming step takes place in a preforming process upstream of the injection mold, which is a press with preform tools by way of example, in which the still-dry semifinished fiber product is reshaped in three dimensions. For such a three-dimensional deformation of the semifinished fiber product, a binding is required, in which a binder is applied to the not yet matrix-impregnated semi-finished fiber product. The preforming step is thus technically complex and technically feasible.

From the DE 100 24 814 A1 a generic method for producing a fiber-reinforced plastic component is known, which is realized as a plastic component. From the DE 10 2013 114 770 A1 For example, a method of making reinforcing fiber reinforced sandwich components is known. From the DE 10 2009 034 265 A1 For example, a method for producing a plastic molded article having a foamed core and a non-foamed shell is known.

The object of the invention is to provide a method for producing a fiber-reinforced plastic component, which can be carried out with reduced compared to the prior art process engineering effort.

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

The invention is based generally on the basic idea of carrying out the preforming step and the subsequent injection step together in the injection tool, which makes it possible to dispense with a preforming system upstream of the injection tool from a process engineering point of view. Against this background, according to the characterizing part of patent claim 1, the preforming step for forming the preform is subdivided into a first preforming substep, in which the still undeformed semi-finished fiber product is prepositioned in the tool cavity of the injection tool. This is followed by a second preform sub-step, in which an initial component of a foam material is foamed in the mold cavity. The foaming foam material presses - forming a three-dimensionally transformed preform - the semi-finished fiber against the mold cavity limiting molding surface. The mold surface of the mold cavity defines a negative mold of the component contour, whereby the semifinished fiber product process is easily formed during the foaming up to the final component contour. The thus-formed preform then remains in the injection tool to perform the injection step.

In a technical implementation of the preforming step, the still undeformed semifinished fiber product is drapable, that is to say limp and substantially without inherent rigidity, inserted into the tool cavity and pre-positioned therein. The semi-finished fiber product may preferably be a drapable textile, for example a woven fabric, knitted fabric, scrim or the like. The semi-finished fiber prefabricated in the tool cavity is then foamed in the second preform sub-step to form the preform in which the preform is formed.

Preferably, the foam material of the preform can form a dimensionally stable foam core after its curing, which is integrally integrated in the preform. The foam core may preferably be designed with a sufficiently high pressure stability. As a result, a collapse of the preform is avoided due to high internal cavity pressures in the subsequent injection step and permanently ensures sufficient foam core dimensional stability.

In a further embodiment variant, the foam core may be a structural foam, in particular a plastic structural foam, whose liquid starting component is foamed under pressure and heat in the second preform sub-step. By way of example, the plastic structural foam can be made of PU, PP or PA or a 2K structural foam. In this way, a lightweight preform results, which has a significantly reduced component weight compared to a conventional fiber-reinforced plastic component. With a view to further reducing the weight, lightweight foam granules may be integrated in the structural foam, for example acrylic glass spheres, lightweight granules of foamed glass or clay, mineral foam granules, metal foam granules or the like.

During the foaming process taking place in the second preform sub-step, the injection tool parts bounding the tool cavity are pressed against one another with a predetermined pressing force. Laterally outside the tool cavity a circumferential seal is positioned between the two injection tool parts, which seals the tool cavity outwards, between opposing tool surfaces of the two injection tool parts.

After curing of the preform formed in the mold cavity, the injection step is carried out. In order to improve the flow behavior of the matrix output component injected into the mold cavity, the tool cavity height is increased in the subsequent injection step compared to the second preform substep, by slightly raising one of the two injection tool parts by a predetermined height offset. The height offset is dimensioned such that on the one hand the sealing function of the circumferential cavity seal is ensured and on the other hand a sufficiently free gap spacing is formed in the mold cavity, through which the liquid matrix output component can flow with reduced flow resistance. After curing of the matrix material, the finished plastic component can be removed from the injection tool.

The injection tool is assigned an injection unit, via which the liquid matrix output component can be fed into the mold cavity. For this purpose, an injection line integrated in the injection tool opens into the tool cavity at a gate mark. In addition, the injection tool is associated with a foaming system which is fluidly connected via a firing channel with the Werkzeugkavität. In the second preform sub-step, the liquid foam material starting component can be fed into the mold cavity via the injection channel. The injection channel of the foaming system and the injection line of the injection unit are functionally separated from each other.

With the method according to the invention, a lightweight component with a sandwich structure or a multilayer structure can preferably be produced. For this purpose, in each case a semi-finished fiber product can be prepositioned (draped) in the first preform sub-step on opposite, opposing mold surfaces. This takes place with the formation of a free space between the two semi-finished fiber products. In the second process step, the foaming process is carried out, in which the foam material starting component is injected into the free space. In this way, results in a three-layer structure with a middle foam core and opposite cover layers of each one fiber-reinforced plastic material.

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

• 1 in einer schematischen Schnittdarstellung ein faserverstärktes Kunststoffbauteil mit einer Sandwichstruktur;
• 2 bis 5 jeweils Ansichten, die die Prozessschritte zur Herstellung des in der 1 gezeigten Bauteils veranschaulichen.

Show it:

• 1 in a schematic sectional view of a fiber-reinforced plastic component with a sandwich structure;
• 2 to 5 each views that illustrate the process steps involved in making the in 1 illustrate illustrated component.

The figures are made with a view to a simple understanding of the invention. Therefore, the figures are only roughly simplified representations that no realistic structure of the plastic component 1 as well as in the 2 to 5 shown injection tool 15 play.

In the 1 is a fiber-reinforced plastic component 1 shown in one, in the 2 to 5 indicated RTM device is made. The plastic component 1 has a multilayer construction 6 on, and from a medium foam core 3 as well as two outer cover layers 5 . 7 , The foam core 3 exemplifies a plastic structural foam, while the two upper and lower cover layers 5 . 7 are each made of a fiber-reinforced plastic material. Each of the top layers 5 . 7 has a semi-finished fiber 9 on that in a plastic matrix 11 ( 5 ) is embedded.

The following is based on the 2 to 5 the process for the preparation of in the 1 The plastic semi-finished products are thus described in a first provisioning step 9 from a dry, that is not matrix-impregnated fiber material provided. The semi-finished fiber products provided 9 are in an unobstructed state in which the semi-finished fiber products 9 are still drapable, so limp and essentially without inherent rigidity. The two still drapable semi-finished fiber products 9 become a tool cavity in a first preform sub-step 13 of the injection tool 15 inserted. The two drapable semi-finished fiber products 9 will be facing each other, opposite mold surfaces 17 . 19 prepositioned the tool cavity 13 define and each opposing tool parts 20 . 21 assigned.

Like from the 2 to 5 shows, is the upper part of the tool 20 by means of a master cylinder arrangement 23 stroke adjustable, while the lower tool part 21 is stationarily positioned. In the upper part of the tool 20 is located laterally offset to the force application point of the press ram of the master cylinder assembly 23 an injection line 25 standing at a gate 27 into the tool cavity 13 empties. The injection line 25 is part of only in the 5 indicated injection unit 29 ,

In the lower part of the tool 21 is a bullet channel 31 integrated, which also in the Werkzeugkavität 13 flows and forms part of a 4 indicated foaming system 33 is. With the tool closed 15 is the tool cavity 13 to the outside by means of a circumferential sealing element 35 sealed in the 3 to 5 between facing tool surfaces 36 the upper and lower tool parts 20 . 21 is arranged.

After in the 2 pre-positioning of the presentable semi-finished fiber products 9 on the mold surfaces 17 . 19 of the injection tool 15 becomes the tool cavity 13 closed with a press force F _P. Between the two in the tool cavity 13 inserted semi-finished fiber layers 9 is in the 3 a free space 37 Are defined. In the open space 37 opens the bullet channel 31 the foaming plant 33 ,

Subsequent to the pre-positioning, a second preform partial cut is carried out, in accordance with the 4 the foaming plant 33 is activated. Then, a liquid foam material output component through the injection channel 31 in the open space 37 the tool cavity 13 shot, under pressure and heat, which foams the foam material and the two semi-finished fiber 9 forming a three-dimensionally transformed preform 39 ( 4 and 5 ) against the two molding surfaces 17 . 19 suppressed. The foam material of the foam core formed 3 is designed so that it has a sufficiently high pressure stability. This is of relevance in the subsequent injection step ( 5 ) to avoid collapse of the foam material and to ensure proper dimensional stability.

In the 5 the injection step is indicated, in which a liquid matrix-starting component via the injection line 25 into the tool cavity 13 is injected. In this way, the outer semi-finished fiber products 9 of the preform 39 impregnated with the plastic matrix. To the flow behavior of the tool cavity 13 injected matrix output component before the injection step ( 5 ) the tool cavity height h by lifting the upper tool part 21 increased by a height offset .DELTA.h, whereby the flow resistance in the Werkzeugkavität 13 reduced.

Claims (9)

Method for producing a fiber-reinforced plastic component (1) in an RTM process, in which at least one semifinished fiber product (9) of dry, not yet matrix-impregnated fiber material is provided in a provision step, in a preforming step the semifinished fiber product (9) to form a preform (39 ) is deformed three-dimensional component end contour, and in an injection step, the preform (39) in a Werkzeugkavität (13) of an injection tool (15) consisting of a lower tool part (21) and an upper tool part (20) is inserted and under pressure and heat a liquid Matrix preforming component is injected into the mold cavity (13) and cured therein, the preforming step being divided into a first partial step in which the still undeformed semifinished fiber product (9) is prepositioned in the tool cavity (13) to form the preform (39), and in a second sub-step in which a starting component a s foaming material in the mold cavity (13) is foamed and the foaming foam material, the semi-finished fiber product (9) to form the three-dimensionally transformed preform (39) against the mold cavity (13) delimiting molding surface (17, 19) presses, characterized in that before Carrying out the injection step, a tool cavity height (h) is increased by raising one of the injection tool parts (20, 21) by a height offset (Δh) in order to improve the flow behavior of the matrix output component injected into the tool cavity (13). Method according to Claim 1 , characterized in that in the first preform sub-step, the semi-finished fiber product (9) drapierfähig, that is limp in the Werkzeugkavität (13) prepositioned, and that the semi-finished fiber product (9) is prepositioned in particular in an unobstructed state. Method according to Claim 1 or 2 , characterized in that the foam material of the preform (39) forms a foam core (3) integrated in the preform (39) after curing in the second preform sub-step, which has a pressure stability in order to collapse during the To avoid injection step and to ensure dimensional stability. Method according to Claim 3 , characterized in that the foam core (3) is a structural foam, in particular a plastic structural foam whose liquid starting component is foamed under pressure and heat in the second preform sub-step, and in that the plastic structural foam is in particular a PU structural foam or a 2K Structural foam is. Method according to one of the preceding claims, characterized in that the liquid matrix starting component is injected into the mold cavity (13) at a gate (27) formed in the injection tool (15), and in that the foam material starting component is introduced into the tool cavity (13) opening Einschußkanal (31) in the Werkzeugkavität (13) is fed. Method according to one of the preceding claims, characterized in that for producing a plastic component (1) with multilayer structure (6) in the first preform sub-step on mutually facing opposite cavity molding surfaces (17, 19) semi-finished fiber products (9) are prepositioned, namely forming a free space (37) between the semifinished fiber products (9), and in the second process step the foam material output component is injected into the free space (37) and cured. Method according to Claim 3 , characterized in that the foam core (3) is a polymer foam made of thermoplastic material, in particular a plastic structural foam, which is foamed as a melt with the addition of blowing agent under pressure and heat in the second preform sub-step, and that the plastic structural foam in particular a PP , PA, PE or other thermoplastic. Method according to Claim 3 , characterized in that the foam core (3) is a cast polyamide, optionally with the addition of blowing agent, whose liquid starting components polymerize under pressure and heat in the second preform sub-step and optionally foamed. Method according to one of the preceding claims, characterized in that a dipping edge of the injection tool (15) is made of a sealing material which is resiliently mounted in the tool and thus simultaneously seals the mold.

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