Method for producing a component from a fibre composite, preform therefor, and component

Abstract

A method for producing a component from a fiber composite. A number of layers of a dry fibrous material are stacked to form a pile, the pile is covered by a thermoplastic film in a gas-tight manner, the inner space occupied by the pile within the film is pumped dry and the layers are fixed to form a preform that is stable during transport, the preform is reshaped, a liquid thermosetting material is inserted into the inner space by infiltration of the fibrous material, and the preform is hardened with the infiltrated fibrous material to form the finished component, the film binding permanently as the surface. The invention also relates to a component produced in such a way, and to a corresponding preform. The production method provides a process-integrated surface finishing of the fiber composite. The surface properties are created by the bound thermoplastic film.

Claims

1. A process for producing a component made of a fiber composite material wherein: (a) a number of sublayers of a dry fiber material are stacked to give a dry stack having no binder material, (b) the dry stack is placed within a thermoplastic film which is used for gastight sheathing of the dry stack, (c) an internal space occupied by the dry stack within the film is subjected to suction from a pump, the sublayers being secured to form a drapable stack that allows slipping or shearing of the fibers within the fiber material to produce a preform that is stable during transport, (d) the preform is subjected to a forming process, (e) a liquid thermoset is introduced into the internal space, resulting in saturation of the fiber material, and (f) the preform with saturated fiber material is hardened to produce the component, with durable bonding of the film forming a surface of the component.

2. The process as claimed in claim 1, wherein the liquid thermoset is introduced using a pressure difference.

3. The process as claimed in claim 1, wherein the film enters into durably strong, inseparable bonding within the component during the hardening process.

4. The process as claimed in claim 1, wherein an adhesion promoter is used to promote coherent bonding of the film within the component.

5. The process as claimed in claim 4, wherein a coating is applied by coextrusion as the adhesion promoter on an internal side of the film.

6. The process as claimed in claim 5, wherein the adhesion promoter comprises a plastic selected from the group consisting of EVA, PCB, APAO, TPE-U, TPE-E, TPE-A, EVOH, and PE, or a combination of two or more thereof.

7. The process as claimed in claim 1, wherein the internal side of the film is provided with graining in order to produce a durable bond within the component.

8. The process as claimed in claim 1, wherein, in step (d), the preform is subjected to thermoplastic deformation of the film to produce a smooth component surface.

9. The process as claimed in claim 8, wherein the thermoplastic deformation of the film, the introduction of the liquid thermoset, and the hardening of the preform with the saturated fiber material are performed together within a mold with both heat and pressure being applied to the preform.

10. The process as claimed in claim 1, wherein the dry stack is produced as a sheet.

11. The process as claimed in claim 1, wherein introduction of the thermoset, the forming process, and the hardening process take place in combination in a stamping step in a resin transfer molding process.

12. The process as claimed in claim 1, wherein the sublayers of the fiber material comprise one or more of a woven fiber fabric, a knitted fiber fabric, a fiber paper, and a nonwoven fiber fabric.

13. The process as claimed in claim 1, wherein fibers in the fiber material comprise one or more of glass fibers, carbon fibers, natural fibers, thermoplastic fibers, and aramid fibers.

14. The process as claimed in claim 1, wherein the film comprises a plastic selected from the group consisting of PMMA, PC, SAN, ASA, PVF, and PVC, or a combination of two or more thereof.

15. The process as claimed in claim 1, wherein, during one or more of the forming process and the hardening process, projecting material is removed thermomechanically.

16. The process as claimed in claim 1, wherein, by way of the thermoplastic film, in a further processing step, the component is joined thermally with another component.

17. The process as claimed in claim 1, wherein: in step (b), the dry stack of the sublayers of the dry fiber material is placed into a gastight bag formed of the thermoplastic material; in step (c), the internal space occupied by the dry stack within the gastight bag is subjected to the suction from the pump via an opening in the gastight bag, the sublayers being secured within the evacuated gastight bag to produce the preform; and in step (e), the liquid thermoset is introduced into the internal space of the preform, resulting in the saturation of the fiber material.

18. The process as claimed in claim 1, wherein: the preform that is stable during transport is produced at a first location; the preform is subjected to the forming process at a second location remote from the first location; and after producing the preform that is stable during transport, but before the preform is subjected to the forming process, the preform is transported from the first location to the second location.

19. A process for producing a component made of a fiber composite material wherein: (a) a number of sublayers of a dry fiber material are stacked to give a dry stack having no binder material, (b) the dry stack is placed within a thermoplastic film which is used for gastight sheathing of the dry stack, (c) an internal space occupied by the dry stack within the film is subjected to suction from a pump, the sublayers being secured to produce a preform that is stable during transport, (d) the preform is subjected to a forming process, (e) a liquid thermoset is introduced into the internal space, resulting in saturation of the fiber material, and (f) the preform with saturated fiber material is hardened to produce the component, with durable bonding of the film forming a surface of the component, wherein, by way of the thermoplastic film, in a further processing step, the component is joined thermally with another component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention have been explained in more detail with reference to a drawing.

(2) FIG. 1 here is a diagram of the sequence for producing a fiber composite component provided with a high-quality surface, and

(3) FIG. 2 here is a diagram of the production of a fiber composite component provided with a high-quality surface by the RTM process.

DETAILED DESCRIPTION

(4) FIG. 1 is a diagram of the production of a component provided with a high-quality surface and made of a fiber composite material. A fiber material in the form of a sheet, an example being a woven fiber fabric textile, is appropriately cut to size, and then a plurality of these fiber sheets are first stacked on top of one another in an unsecured manner as in image 1. It is also possible here to undertake a securing process, locally or sectionally, for example by needling, but drapability is retained here. The unsecured or in essence unsecured (because locally secured) and dry fiber stack is drapable in relation to the final geometry. A thermoplastic film is then used to sheath the fiber stack as in image 3. The film here by way of example takes the form of a tube and is gently brought into contact with the stack, or the stack is inserted into the film tube. The ends of the tube are welded or adhesive-bonded to one another, in such a way that a gastight sheath has been formed. The thermoplastic film used is by way of example produced as a film composite by coextrusion. In particular, an aging-resistant plastic that is impermeable to water and resistant to acid has been used on the external side of the film. An adhesion promoter has been applied on the internal side.

(5) The gastight internal space within the film is then subjected to suction from a pump as in image 6. During this process, the fiber-material stack, which is unsecured, or at most locally secured with retention of drapability, and dry, is compressed and thus dimensionally stabilized. The exterior film sheaths the stack and also provides mechanical strength, and protection from exterior influences resulting from soiling, moisture, etc. The resultant preform as in image 6 is dimensionally stable and transportable. The creation of the fiber stack required for the composite material can thus be decoupled from the subsequent shaping by a mold. The residence time in the mold has thus been reduced, thus giving an optimized and less expensive production process.

(6) A liquid thermoset is introduced into the preform as in image 8, and by way of example hardens on exposure to heat. An injection process has been indicated symbolically here, i.e. pressure is used to inject the liquid phase of the thermoset into the internal space. Uniform saturation of the fiber material with the thermoset takes place by virtue of the subatmospheric pressure in the internal space of the preform.

(7) The saturated preform is subjected to a forming process as in image 9. For this, it is by way of example inserted into the cavity of a mold. The preform, together with sheathing provided by the thermoplastic film, is subjected to a forming process under pressure to give the finished component. Heat is simultaneously introduced here, whereupon the thermoplastic film approximates the exterior geometry of the cavity, and the thermoset hardens.

(8) The hardening process in particular and by way of example causes frictional bonding of the thermoplastic film to the fiber material. The adhesion promoter applied on the internal side of the film softens by virtue of the temperature increase and penetrates into the upper fibers of the fiber material. This bonding, and the embedding of the fibers into the resin system as it hardens, creates a durably strong and inseparable bond of the thermoplastic film, as surface, to the component.

(9) The finished component produced from a fiber composite material is then obtained after demolding, as in image 10. Said component has been provided with a high-quality surface. Its surface properties are principally achieved by virtue of the sheathing of the thermoplastic film. There is no need for post-treatment through any additional process step. The component has the desired haptic properties, the desired surface structure, and the desired physical and/or chemical surface properties. In particular, it is also possible to control the color of the component advantageously by way of the thermoplastic film.

(10) FIG. 2 is a diagram of what is known as the RTM process (resin transfer molding process) for producing the component made of a fiber composite material. A dry preform 12, sheathed by film and stable during transport, is inserted here into a cavity between the two portions of a stamping press 14. The stamping press is then closed, whereupon the preform 12 is subjected to a forming process to give the topography of the desired component. The preform 12 here has not yet been saturated with a thermoset. From the preform 12 it is possible to discern a dry fiber stack 16 in the interior, and also the sheathing thermoplastic film 18 on the external side.

(11) After the stamping press 14 has been closed, with the forming process, a liquid thermoset 20 is introduced under pressure into the internal space within the film in the preform 12. To this end, by way of example compressed air 21 has been provided.

(12) The pressurized thermoset 20 flows by way of an appropriate input aperture 25 in the preform 12 into the internal space thereof, and gradually and uniformly saturates the dry fiber stack 16. At the other end of the preform 12, excess thermoset is discharged by way of a discharge aperture 26 into a receiver 27.

(13) Once the preform 12 has been saturated, the cavity of the stamping press 14 is heated, and the thermoset 20 introduced is thus hardened. However, the temperature of the cavity can also have been precontrolled in advance. The thermoplastic film 18 has by way of example been provided with graining on the internal side, for bonding as surface to the system. The thermoset 20 that has penetrated in the form of liquid phase into pores, apertures, and valleys in the film 18 hardens. Undercuts are thus formed with the thermoplastic film 18. The thermoplastic film 18 has been durably interlock-bonded to the finished component.

(14) The finished component is then removed from the stamping press 14. The desired surface properties of the fiber composite component have been established by way of the thermoplastic film 18 bonded with durable strength to the system.

KEY

(15) 1 Unsecured stacking

(16) 3 Sheathing with thermoplastic

(17) 6 Internal space subjected to suction from a pump

(18) 8 Saturation with thermoset

(19) 9 Forming process/hardening process

(20) 10 Removal of sheathed component

(21) 12 Preform

(22) 14 Stamping press

(23) 16 Dry fiber stack

(24) 18 Thermoplastic film

(25) 20 Thermoset

(26) 21 Compressed air

(27) 23 Internal space

(28) 25 Input aperture

(29) 26 Discharge aperture

(30) 27 Receiver