FR2948586A1 - Bi-material sheet for motor vehicle i.e. car, has reinforcing wires extending along length of sheet, and space delimited transversely by two lateral sides face-to-face with two adjacent reinforcement wires filled by material - Google Patents

Abstract

The sheet (10) has a bi-material matrix (M) made of a material and series of parallel longitudinal reinforcing wires (R) that extend along the length of the sheet, which are transversely spaced from each other and made of another material. Each reinforcing wire is transversely bound on each side by vertical edge (16) of a concave profile, where section of wire is transverse by a plane orthogonal to the longitudinal direction of the sheet. A space (22) is delimited transversely by two lateral sides face-to-face with adjacent reinforcement wires filled by the former material. An independent claim is also included for a method for manufacturing a bi-material sheet.

Description

1 sheet of bi-material material and method of manufacturing such a sheet

TECHNICAL FIELD OF THE INVENTION The invention relates to a sheet of bi-material material, also called bi-material composite sheet. The invention particularly relates to a composite sheet made of two metallic materials, such as, for example, steel and aluminum. The invention also relates to a method of manufacturing a composite sheet.

BACKGROUND OF THE INVENTION The choice of a sheet material, for example the choice of a sheet in the field of mass production of automobiles, always results from a compromise between the strength of the material chosen, its weight, its thickness which can also have an influence on the industrial means for its implementation, and of course the price of the material. In the case of a mass-produced motor vehicle, the reduction in the total weight of the vehicle immediately has the effect of causing a reduction in the energy consumption necessary for its propulsion, whatever its mode of propulsion and the nature of the vehicle. the source of energy used for its propulsion. The reduction in weight still allows a gain in acceleration, a reduction in the braking distance and a saving in material purchase, as well as a gain in energy for the transformation of the material used. It is therefore a constant goal to be able to reduce the amount of material used, and in particular the amount of sheet by reducing for example the thickness of the sheet metal used. However, such a reduction in thickness should not affect the strength of the sheet material used. Moreover, as regards the body forming a rigid structure of a vehicle, the nature and strength of the sheets used should be able to vary according to their uses, and in particular the parts or areas of the vehicle in which they are used, for example between the front and the back of the vehicle, the sides, the flag, etc. To obtain each of the desired resistances, it is necessary to vary the strength of the material used, for example by the choice of a specific metal material or alloy and / or, for a given alloy, to vary the thickness. All of these techniques are known, but they lead to significant problems inherent in the purchase, storage, handling and implementation of many different materials, which has a significant financial impact. For example, for a given vehicle, it is necessary to have five different types of steel in different thicknesses, the supply of such multiple materials requiring delays of the order of twelve to eighteen months, with corresponding storage of different materials for a period of about four months. It is an object of the invention to provide a new sheet material which, in the case of a metal sheet, could be made from a single standard steel type, supplied in a standard thickness, while allowing have sheets of materials with different strength characteristics, especially depending on the part to be manufactured, while reducing inventory. 3 BRIEF SUMMARY OF THE INVENTION

For this purpose, the invention proposes a sheet of bi-material material comprising a matrix of a first material and a series of parallel longitudinal reinforcing elements which extend along the length of the sheet, which are spaced transversely from each other. others and which are made of a second material, sheet in which: - each reinforcing element is a wire whose section, by a transverse plane orthogonal to the longitudinal direction of the sheet, is delimited transversely on each side by a vertical edge concave profile; the space delimited transversely by two lateral faces facing two adjacent reinforcing threads is filled with said first material. According to other characteristics of the sheet: the profile of the section by a transverse plane of a reinforcing thread is, for example, symmetrical with respect to a median vertical plane; The profile of the section by a transverse plane of a reinforcing thread is, for example, symmetrical with respect to a median horizontal plane; the transverse plane section of each reinforcing wire is delimited transversely by a vertical "V" shaped edge; - The sheet comprises at least one outer skin which is made in said first material and which delimits the corresponding outer face of the sheet; the sheet comprises two opposite outer skins, each of which is made in said first material and each of which delimits one of the two opposite outer faces of the sheet; Said first material is aluminum or an aluminum alloy, and said second material is a steel. The invention also proposes a method for manufacturing a sheet according to the invention, characterized in that it consists in: - A) producing a network of a series of parallel longitudinal reinforcing threads which are transversely spaced apart from each other; others; B) bringing at least one layer made in said first material into contact with the upper faces of said reinforcing son; - C) penetrate the material constituting said layer in the spaces delimited transversely by the lateral faces vis-à-vis the adjacent reinforcing son, so as to fill said first material and to secure the matrix and the son reinforcement by a crimping effect. According to other characteristics of the process: - it consists in: B) bringing a layer made in said first material in contact with the upper faces of said reinforcing threads and simultaneously bringing at least one other layer, made in said first material, in contact with the lower faces of said reinforcing threads; C) simultaneously penetrating the constituent material of said one and other layers into said spaces; Said first material is penetrated into said spaces by rolling of the layer. Other features and advantages of the invention will appear on reading the following description, given by way of non-limiting example, for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a schematic cross-sectional view of an exemplary embodiment of a sheet of bi-material material according to the invention; FIG. 2 is a diagram on a larger scale illustrating, in cross sectional section, the principle used for producing the sheet illustrated in FIG. 1; and FIG. 3 is a partial schematic perspective view illustrating more completely the method according to the invention and its implementation. In the following description, the terms Vertical, Horizontal, Longitudinal, and Transversal will be used in a nonlimiting manner, and without reference to Earth's gravity, in particular by reference to the triad V, L, T indicated in the figures. FIG. 1 shows a section of a sheet of material 10 which is delimited vertically by a horizontal upper face 12 and a horizontal parallel bottom face 14. In the embodiment shown in FIG. sheet 10 has a general design symmetry with respect to a median horizontal plane PHM. The thickness "E" of the sheet is referred to as the distance which, in cross-section along the plane of FIG. 1, separates the two opposite faces 12 and 14. The sheet 10 is essentially constituted by an "M" matrix. in a first material and by a series of parallel longitudinal reinforcing elements "R" each of which is a reinforcing thread which extends along the length of the sheet, which are spaced transversely from each other and which are made of a second matter. In the example illustrated in the figures, the first material is aluminum or an aluminum alloy and the reinforcing son R are made of steel. In the exemplary embodiment shown in the figures, all the reinforcing threads R are identical, and are distributed transversely in a regular manner according to a pitch "P". Alternatively, the pitch between different wires may vary depending on the desired results. In section through the transverse plane of FIG. 1 (plane V, T), and solely by way of example, each reinforcement thread R has a double symmetry of design, on the one hand, with respect to the median horizontal plane PHM and on the other hand, with respect to a median vertical plane PVM. In the example, all the threads are identical. Of course, the profile can vary in dimensions from one wire to another, especially the io height / width ratio. As can be seen in particular schematically in Figure 3, each reinforcing element R is in the form of a reinforcing wire R which extends in the longitudinal direction L and whose section is that illustrated in 15 detail in particular in Figure 1. The profile of the cross section of a reinforcing wire R is delimited by two parallel vertical side faces 16, and is defined vertically by two opposite generally upper horizontal faces 18 and lower 20 respectively. In section, and as shown in FIG. 1, each lateral face 16 corresponds to a vertical edge 16 which is a concave profile edge which here is open V-shaped with its tip located at the plane PHM. Each side face 16 is thus a curved or hollow, concave surface. In cross section, each of the upper 18 and lower 20 horizontal faces present here, by way of example, a slightly curved convex profile. Expressed otherwise, the cross section of each reinforcing wire R has a diabolo shape consisting of two cone frustums opposite by their narrow apices. 7 two side faces vis-à-vis 16 of two adjacent reinforcement son R delimit between them a space 22 which is filled by the first material constituting the matrix M of the sheet 10. The parallel reinforcing son R are here again symmetrically distributed in the thickness E of the sheet 10 which comprises, at the top and at the bottom, ie on either side of the upper and lower faces 18 of the reinforcing threads R, an upper outer skin 22 and a lower outer skin 24, each of which is made of the constituent material of the matrix M 10 and each of which delimits the upper outer face 12 and the lower face 14 of the sheet 10, respectively. The opposite outer skins 22 and 24 extend transversely over the entire width of the sheet and longitudinally along the entire length of the sheet 10. The presence of the outer skins of course allows all types of subsequent protective coatings and / or paint . Due to the concave profiles vis-à-vis the side faces 16 of the reinforcing son R, the material constituting the matrix M is "trapped" between the reinforcing son R and the assembly is thus secured by an effect of crimping which is obtained during the manufacture of the sheet 10 according to a method an example of which will now be described. For the production of a sheet 10 according to, for example, a bi-aluminum-steel sheet, a network of a series of reinforcing wires R, each of which, for example, in section transverse, the profile contour illustrated in Figures 1 and 2. The reinforcing wire R can be made beforehand by known means for example by means of a die or by rolling a steel wire of round initial section. The network of parallel and transversely spaced R wires in a determined pitch (regular or otherwise) - for example according to the pitch "P" - can be achieved by feeding a series of wires from a series of coils of wire R, or the son can be produced in situ as the production of the sheet 10, upstream of the assembly means of the two materials by crimping.

Prior to the crimping assembly, the reinforcing threads R must be held relative to one another in the desired final position by means of positioning and guiding means which are not shown in the figures. The matrix M, for example made of aluminum, is produced here from two layers, each in sheet, upper CS and lower Cl of thickness "e" determined. By way of example, the two layers C1 and CS are here identical and of the same thickness "e". As a variant, the thicknesses of the two layers may be different from one another. The crimping assembly operation consists in causing the constituent material of the two layers CS and Cl to penetrate into the spaces 22 delimited transversely by the lateral faces. 16 adjacent reinforcing threads R to fill these spaces 22 with the first material (in this case aluminum) constituting the layers CS and Cl which will thus become the material of the matrix M of the sheet 10 after assembly. As can be seen with reference to FIG. 3, in which, for the sake of clarity, only the lower layer C and a single rolling roll or roll 26 are shown, the opposing inner faces facing one another. two opposing layers C are brought into contact with the upper and lower faces 20 opposite the reinforcing threads R, then the two opposed upper rollers 26-S (not shown) and lower 26-I causes by clamping effect and rolling progressive penetration of the constituent material of the upper layers CS (not shown) and lower Cl in the spaces 22.

The axis of the rolls is here of transverse orientation perpendicular to the longitudinal direction of advance of the sheet but, alternatively, the axis of the rolls could be parallel to the direction L.

The final thickness E of the sheet 10 to be obtained depends, of course, on the vertical gap height between the opposite cylindrical faces of the two cylinders. Thus, by rolling effect, the material of the two opposite layers CS and Cl penetrates simultaneously into the spaces 22 and a portion of this manner remains up and down on either side of the threads to form the skins 22. and 24. The domed profile of the upper 18 and lower 20 horizontal faces of the reinforcing yarns facilitates penetration and advancement of the matrix material between the reinforcing yarns.

Once the assembly is completed, the assembly is secured because of the crimping effect of the material of the matrix M in the spaces 22 between the side faces 16 of the reinforcement thread R. The design of the sheet of material bi-materials or composite sheet allows a great modularity as to the characteristics of the sheet that can be obtained. It is in particular possible to vary the number and the spacing of the reinforcement threads R, the section of each reinforcing thread, the thicknesses of the outer skins, these being extremely reduced. In addition, the thicknesses of the two skins 25 may be different from each other. It is of course also possible to vary the nature of each of the materials, and in particular the constituent steel reinforcement son R when such a material is used in combination with a matrix M aluminum or aluminum alloy.

By way of example, for a piece of aluminum origin, for example aluminum 2024, whose strength is equal to 40 kilograms per square millimeter, it may be desired to reduce the thickness and increase the resistance. For example, the thickness can be reduced by about 40% while increasing the strength by about 30% and further achieving a weight gain. For this purpose, it is necessary to provide the insertion of 5 reinforcing son R which will be crimped into the matrix M which is originally made from two layers of foil aluminum as just described and Explain. For example, for a test specimen whose width is equal to 25 mm, the strength can be increased for the same weight, by decreasing the thickness. If the thickness of the specimen is equal to twice 0.7mm - ie 1.4mm, its section is equal to 35mm2, ie a tensile strength of the specimen equal to 1400kg (40kg / mm2 X 35mm2 = 1.400, 00 kg).

For a density of 2.77, the weight of a test piece about 100 mm in length is about 9.7 grams. If a new thickness of 1 mm, ie a section of 25 mm 2, is chosen, it is decided to reinforce this 1 mm thick sheet by eighteen reinforcement wires each having an average cross section of approximately 0.32 mm 2. (0.4mm x 0.8mm), the eighteen reinforcement wires have a cross section of 5.76mm2. The new tensile strength of the specimen is equal to 1036 kg because of the presence of the reinforcing threads (for an average tensile strength of steel equal to 180 kg / mm 2, to which must be added 769 kg of the presence of aluminum whose effective cross-sectional area is 25mm2 minus 5.76mm2, or 19.24mm2 (19.24mm2 x 40kg / mm2 = 769.00kg) .The new tensile strength of the specimen is thus then equal to 1805kg instead of 1400kg and the new thickness is 1mm instead of 1.4mm.The weight of the new bi-material sheet is almost unchanged and substantially equal to 9.7 grams.

2948586 It is also possible, with identical resistance, to choose to gain weight. The implementation of rolling crimping can be carried out cold, or it can be preceded by a preheating of the two outer layers of aluminum. The design according to the invention greatly facilitates the subsequent implementation of the sheet thus produced according to the applications. Thus, it is possible to distribute the reinforcing threads and to choose their constituent material according to the shape and dimensions of a coin to be stamped in such a material. The second constituent material reinforcement son R may also vary from one wire to another. It is also possible later to heat the sheet 15 according to the invention for its implementation in complex shapes, for example to make parts in the form of shell. The design of the aluminum matrix material allows a foundry complex shaping with reinforcement son that remain embedded and crimped in the matrix.

The invention is of course not limited to the choice of two metallic materials such as aluminum and steel.

Claims (10)

REVENDICATIONS1. Sheet (10) of bi-material material comprising a matrix (M) of a first material and a series of parallel longitudinal reinforcing elements (R) which extend along the length of the sheet, which are spaced transversely from each other other (P) and which are made of a second material, sheet in which: - each reinforcing element is a wire (R) whose section, by a transverse plane orthogonal to the longitudinal direction of the sheet, is delimited transversely of each side by a vertical edge (16) of concave profile; - The space (22) defined transversely by two side faces vis-à-vis (16) of two adjacent reinforcing son (R) is filled with said first material. 2. Sheet according to claim 1, characterized in that the profile of the section by a transverse plane of a reinforcing wire (R) is symmetrical with respect to a median vertical plane (PVM). 3. Sheet according to claim 1, characterized in that the profile of the section by a transverse plane of a reinforcing wire (R) is symmetrical with respect to a median horizontal plane (PHM). 4. Sheet according to claim 1, characterized in that the section by a transverse plane of each reinforcing wire (R) is delimited transversely by a vertical edge (16) shaped "V" 5. Sheet according to claim 1, characterized in that it comprises at least one outer skin (22, 24) made in said first material which defines the outer face (12, 14) corresponding to the sheet. 6. Sheet according to claim 5, characterized in that it comprises two opposite outer skins (22, 24), each of which is made in said first material and each of which delimits one of the two opposite outer faces (12, 14) of the sheet (10). 13 7. Sheet according to claim 1, characterized in that said first material is aluminum or an aluminum alloy, and in that said second material is a steel. 8. A method of manufacturing a sheet according to any one of the preceding claims, characterized in that it consists in: - A) making a network of a series of parallel longitudinal reinforcing son (R) which are spaced transversely one another ; - B) bringing at least one layer (CS) made in said first material in contact with the upper faces (18) of said reinforcing son (R); - C) penetrate the constituent material of said layer (CS) in the spaces (22) transversely delimited by the side faces vis-à-vis (16) of the adjacent reinforcement son (R), so as to fill them with said first material and to secure the matrix and the reinforcing son by a crimping effect. 9. A method according to claim 8, characterized in that it consists in: - B) bringing a layer (CS) made in said first material in contact with the upper faces (18) of said reinforcement son and simultaneously bring another layer (C1), made in said first material, in contact with the lower faces (20) of said reinforcing wires; - C) simultaneously penetrate the constituent material of said one (CS) and other (Cl) layers in said spaces (22). 10. Method according to any one of claims 8 or 9, characterized in that said first material is penetrated into said spaces by rolling of the layer.