Semi-finished product manufactured from prepreg, three-dimensional preformed body and overmolded part

Abstract

The present invention provides a semi-product made of a prepreg, a three-dimensional preform and an overmolded part. More particularly, the present invention provides a semi-product made of a prepreg, including at least a first prepreg layer and a second prepreg layer, characterized in that a magnetic material layer is laid between the first prepreg layer and the second prepreg layer. Since the magnetic material layer is added between the prepreg layers, the produced semi-product, when being made into a three-dimensional preform and further into an overmolded part, can be well supported and positioned due to attraction to the magnetic material layer by the magnet on the die, and therefore be precisely shaped.

Claims

1. A semi-product made of a prepreg, the semi-product comprising: at least a first prepreg layer and a second prepreg layer, and a magnetic material layer between the first prepreg layer and the second prepreg layer, wherein when thermoplastic resin contained in the first prepreg layer and the second prepreg layer is softened, the magnetic material layer retains magnetic properties thereof and can be attracted by a magnet, wherein at least one prepreg layer of the first prepreg layer and the second prepreg layer has a cut-out portion, and the magnetic material layer is at least laid in at least one of the cut-out portions.

2. The semi-product according to claim 1, wherein when the thermoplastic resin contained in the first prepreg layer and the second prepreg layer is softened, the magnetic material layer remains in a solid state.

3. The semi-product according to claim 1, wherein the magnetic material layer is a magnetic metallic net, or a magnetic metallic sheet, or a combination thereof.

4. The semi-product according to claim 3, wherein a polypropylene film is between the first prepreg layer and/or the second prepreg layer and the magnetic material layer.

5. A three-dimensional preform, wherein the three-dimensional preform includes the semi-product according to claim 1.

6. An overmolded part, comprising: at least one three-dimensional preform according to claim 5; and a thermoplastic resin portion overmolded on the at least one three-dimensional preform.

7. The overmolded part according to claim 6, wherein the overmolded part is a motor vehicle component.

8. The overmolded part according to claim 7, wherein the overmolded part is a rear closing component of a motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be described in more detail hereinafter with reference to the drawings. It should be readily appreciated by those skilled in the art that the drawings described herein are for illustration purposes only and are not intended to limit the scope of the present invention in any way. Identical or like structures are indicated with identical or like reference numerals. For illustration purposes, these drawings are not necessarily drawn in proportion.

(2) FIG. 1 is a perspective view of a semi-product made of a prepreg according to an embodiment of the present invention;

(3) FIG. 2 is an exploded perspective view of the semi-product of FIG. 1;

(4) FIG. 3 contains cross-sectional views of the semi-product according to an embodiment of the present invention with or without a polypropylene film, respectively;

(5) FIG. 4 shows the process of machining the semi-products into the three-dimensional preforms according to two different embodiments of the present invention;

(6) FIG. 5 shows a forming die used in the process of FIG. 4;

(7) FIGS. 6 and 7 are respectively a cross-sectional view of the forming apparatus used in the process of FIG. 4;

(8) FIG. 8 is a perspective view of a three-dimensional preform according to an embodiment of the present invention; and

(9) FIG. 9 is a perspective view of an overmolded part of the three-dimensional preform of FIG. 8.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(10) FIG. 1 shows a perspective view of a semi-product 1 made of a prepreg according to an embodiment of the present invention. FIG. 2 better shows the structure of the semi-product 1 in an exploded view. In the embodiment, the semi-product 1 comprises a first prepreg layer 10, a second prepreg layer 12 and a magnetic material layer 14 sandwiched therebetween. It can be appreciated that the semi-product 1 can comprise more prepreg layers and/or layers of other materials. At least a portion of these layers of other materials can be attracted by a magnet, i.e., at least a portion of them are magnetic material layers, which can be determined by those skilled in the art according to specific design targets. For instance, in an embodiment, the semi-product 1 comprises a first, a second and a third prepreg layer stacked one on top of the other, and a magnetic material layer is sandwiched between every two adjacent prepreg layers. In another embodiment, the semi-product 1 comprises a first, a second and a third prepreg layer stacked one on top of the other, but a magnetic material layer is only sandwiched between the first and the second prepreg layer. It should be noted that the magnetic material layer can cover the full surface of the prepreg layers, or can be arranged discretely at one or more locations.

(11) The term prepreg represents an intermediate material commonly used for making a composite material and most often composed of a resin matrix and a reinforcement (such as fibers or fabrics) impregnated in the matrix. In the present embodiment, the first prepreg layer 10 and the second prepreg layer 12 are both composed of a thermoplastic resin matrix and a reinforcement impregnated in the matrix, and the reinforcement can be carbon and/or glass fibers or fabrics. The magnetic material layer 14 can be made of any suitable magnetic material (such as iron, cobalt, nickel and an alloy thereof) that can be attracted by a magnet. In the present embodiment, the magnetic material layer 14 is a metallic net with meshes, which reduces the weight of the final product and save production costs. It should be appreciated that the magnetic metallic net can be replaced by magnetic metallic sheets. In this case, the magnetic metallic sheets may not be interconnected into one piece, but with gaps, so as to reduce the weight of the final product and save production costs. Moreover, in the subsequent processing (such as hot stamping) of the semi-products, the adjacent layers of the prepreg resin matrixes can fuse and connect together through the meshes or gaps, thereby fixing the metallic layer between the two prepreg layers more firmly. It can be observed in the embodiment shown in FIGS. 1 and 2 that the first prepreg layer 10 has a cut-out portion 18, through which a magnetic metallic net 14 is visible, and the second prepreg layer 12 has the same shape and dimension as that of the magnetic metallic net 14. In the embodiment shown in FIG. 3, the cut-out portion 18 is provided in the second prepreg layer 12. Thus, in the subsequent processing step, the magnet on the die is arranged in such a way that the magnet is at least partially inserted into the cut-out portion of the prepreg layer of the semi-dimensional preform or the semi-product when the die is closed, so the magnet is in direct contact with the magnetic material layer at the cut-out portions in order to provide sufficiently large magnetic force to support and position the semi-product or the three-dimensional preform in a better way. Moreover, the three-dimensional preform (see FIGS. 4 to 7) made of the semi-product 1 can be at least partially supported by the material layer 14 during a heating process to well maintain its three-dimensional shape.

(12) It should be appreciated that these cut-out portions in the prepreg layer can have a simple or more complex geometrical shape. In the presence of cut-out portions, the magnetic material layer is laid at at least one cut-out portion. Of course, there may be no cut-out portions at all, and the area where the magnetic material layer is to be placed should not be limited to the above embodiments. In fact, according to the present invention, anything is possible as long as the magnetic force between the magnet and the magnetic material layer is sufficient to well support and position the semi-product or the three-dimensional preform during the processing.

(13) Moreover, as shown in FIG. 3(b), it is preferable that a polypropylene film 16 is laid between the magnetic material layer 14 and its adjacent prepreg layer 10 and/or 12. Since the polypropylene film can fill in the metallic meshes or gaps between the metallic sheets to discharge the air entrapped therein, the uniformity of the product can be improved greatly. Further, this is also advantageous for enhancing adhesion between the material layer and the prepreg layers.

(14) FIG. 4 shows the process of machining the semi-products 1 and 1 of FIG. 1 into the three-dimensional preforms 2 and 2. As shown, the difference between the semi-product 1 and the semi-product 1 lies in whether the magnetic material layer therein is a magnetic metallic net 14 or a magnetic metallic sheet 14. The three-dimensional preforms respectively obtained therefrom are denoted by 2 and 2. For showing the structure of the three-dimensional preforms 2 and 2 clearly, a portion of the second prepreg layer 12 is removed from FIG. 4.

(15) The semi-products 1 and 1 are heated before being placed into a forming die. Then, the hot semi-product 1 is placed into the forming die as shown in FIG. 5 (including a hot stamping punch 20 in FIG. 5) so that a magnet 22 on the punch 20 aligns with the cut-out portion in the prepreg layer of the semi-product where the magnetic material layer is exposed so as to support and maintain the semi-product in position with the help of a magnetic force for subsequent three-dimensional forming thereof. It should be noted that in the forming step, the magnetic material layer in the semi-products 1 and 1 is formed as well. Thereafter, the semi-products are demoulded to obtain the three-dimensional preforms 2 and 2. It should be appreciated that the three-dimensional shapes as shown in FIG. 4 are for illustration purposes only, and the three-dimensional preforms 2 and 2 can have more complex three-dimensional shapes for different applications.

(16) FIGS. 6 and 7 schematically show the cross-sectional views of the forming apparatus used in the process, wherein FIG. 6 shows a molding portion 30 of the die. It should be appreciated that the shape of the die is not limited to that shown in the drawings, and the schematic view is also applicable to the process of overmolding the three-dimensional preform. In particular, it should be noted that the magnetic metallic sheet 14 as shown in FIG. 7 is only laid at the cut-out portion in the prepreg layer while fully covering the cut-out portion, such that the magnet 22 on the molding portion is partially inserted into the cut-out portion and in direct contact with the magnetic metallic sheet 14 when the die is closed, so as to provide sufficient attraction to the semi-product or the three-dimensional preform. However, the area where the magnetic metallic sheet 14 should be placed is not limited to the embodiment.

(17) The three-dimensional preform 2 or 2 can be mechanically machined (such as contour finished or drilled) after cooling so as to make it into the one of a desired final dimension and geometrical configuration. FIG. 8 shows an example of the three-dimensional preform, wherein it is a rear reinforcement 3 of a motor vehicle, and FIG. 8 schematically shows the cut-out portions 18 which receive the magnets on the die to provide support thereto during the processing.

(18) Then, the three-dimensional preform is reheated to a temperature higher than the melting point of the prepreg resin matrix, so as to provide good adhesion between the prepreg resin matrix and the overmolded resin in the subsequent overmolding step. The hot three-dimensional preform is transferred to an overmolding die for an overmolding step therein, i.e., overmolding a thermoplastic resin portion on the three-dimensional preform (for instance, by means of injection molding). Demould to obtain a final three-dimensional component including a reinforcement (composed of the three-dimensional preform) and an overmolded resin portion. The resultant three-dimensional component can be for example a component of a motor vehicle. FIG. 9 shows an example of the three-dimensional component, wherein it is an automobile trunk closing component 4 composed of the prepreg three-dimensional preform (namely, an automobile rear reinforcement 3) having the magnetic material layer and the overmolded resin portion.

(19) The drawings and the above description describe the non-limitative particular embodiments of the present invention. Some conventional aspects have been simplified or omitted in teaching the invention principle. Those skilled in the art should know that the variations from these embodiments fall into the scope of the present invention. It should be understood by those skilled in the art that the above features can be combined in various ways to form a plurality of variations of the present invention. Thus, the present invention is not limited to the above particular embodiments, but defined by the following claims and their equivalents.