FR3064228A1 - BUMPER BEAM FOR MOTOR VEHICLE - Google Patents

Abstract

The bumper beam (12) for a motor vehicle comprises a first zone (18) made of a reinforced polymer material comprising fibers and a second zone (20) made of a non-reinforced polymer material.

Description

Holder (s): VALEO THERMAL SYSTEMS Simplified joint-stock company.

Extension request (s)

Agent (s): VALEO SYSTEMES THERMIQUESTHS.

(34) BUMPER BEAM FOR MOTOR VEHICLE.

(3 ^) The bumper beam (12) for a motor vehicle comprises a first zone (18) made of a reinforced polymer material comprising fibers and a second zone (20) made of a non-reinforced polymer material.

FR 3 064 228 - A1

34

, 12

The invention relates to vehicles, in particular motor vehicles. The invention also relates to vehicle bumpers and more specifically to bumper beams.

It is known, in order to protect a motor vehicle during an impact, to have, on a front face and also on a rear face of the vehicle, a bumper beam. The bumper beam is further connected to a side member of the vehicle via at least two shock absorbers. During a frontal impact for example, the front bumper beam is generally directly impacted and deforms so as to absorb, with the shock absorbers, a maximum of energy so that the side member of the vehicle suffers a small proportion shock energy.

Generally, the bumper beam is made of a metallic material. This metallic material can essentially comprise steel. The disadvantage of the bumper beam is that it is relatively heavy. In addition, as the safety constraints imposed on the automotive industry increase over time, the trend is therefore to increase the weight of the bumper beam.

However, a constant objective of the automotive industry is to reduce the weight of vehicles.

Thus, the metallic material of the bumper beam may essentially comprise aluminum, which makes it possible to lighten the weight of the beam by approximately 10% to 15% compared to a beam made of steel which has the same mechanical performance.

In order to further lighten the bumper beam, it has also been envisaged to produce the bumper beam in a composite material comprising fibers. However, the bumper beam then has low shear strength.

An object of the invention is to provide a light bumper beam with suitable mechanical strength properties.

To do this, there is provided according to the invention a bumper beam for a motor vehicle, characterized in that it comprises a first zone made of a reinforced polymer material comprising fibers and a second zone made of a non-polymeric material. reinforced.

Thus, the first zone, made of a reinforced polymer material, has a low elongation at break or in other words a low capacity to elongate before breaking when it is stressed in tension.

In addition, the second zone, made of an unreinforced polymer material, has significant ductility which gives it the ability to deform, without breaking, in the event of impact; that is, to absorb an acceptable amount of energy in the event of an impact. In other words, a strong ability to deform plastically without breaking, the rupture occurring when a defect such as a crack or cavity, induced by plastic deformation, becomes critical and propagates, the second zone therefore has a strong ability to resist to this spread.

In particular, the bumper beam has good shear strength.

In addition, in the event of cracks appearing on the first zone, the second zone makes it possible to prevent the propagation of this crack and to preserve the integrity of the bumper beam.

In addition, in preferred embodiments of the invention, one and / or the other of the following arrangements may possibly be used:

the non-reinforced polymer material of the second zone is a thermoplastic polymer;

the non-reinforced polymer material of the second zone comprises polyamide and / or polypropylene;

the second zone has an elongation at break equal to at least 40%, or 50%, 60% or 80%; the bumper beam is therefore capable of absorbing a large amount of energy; more generally, the second zone can also have an elongation at break at least equal to 100%;

the reinforced polymer material of the first zone comprises a thermoplastic polymer;

the reinforced polymer material of the first zone comprises glass fibers and / or carbon fibers; when it comprises glass fibers, the first zone is less expensive, when it comprises carbon fibers, the first zone exhibits improved mechanical performance;

the reinforced polymer material of the first zone comprises continuous fibers and / or discontinuous fibers;

the first zone and the second zone have a cross section of square shape, the second zone covering the first zone; the bumper beam is therefore easier to conform; it will also be noted that the first zone can also overlap the second zone;

the first zone has a “C” shaped cross section, the second zone forms a rib for the first zone;

the first zone has a cross section of substantially hexagonal shape, the second zone extends into a space between two internal walls of the first zone;

the first zone and the second zone are in the form of at least two layers arranged alternately one on the other; the mechanical properties of the bumper beam can therefore be adjusted as desired;

the layers arranged alternately one on the other have a thickness of between 0.2 millimeter and 0.7 millimeter; in particular, the layers corresponding to the first zone may have a thickness of 0.2 millimeters and the layers corresponding to the second zone may have a thickness of 0.5 millimeters; the bumper beam is therefore mechanically reinforced; the beam comprises a third zone made of a material comprising polyamide reinforced with glass fibers and / or polypropylene reinforced with glass fibers; the bumper beam is therefore mechanically reinforced, which can in particular be useful near the headlights of the vehicle.

According to the invention, a bumper assembly is also provided for a motor vehicle comprising:

- a bumper beam as previously described, and

- at least one shock absorber intended to connect the bumper beam and one end of a side member of the motor vehicle.

Finally, according to the invention, a method of manufacturing a bumper beam as previously described is provided, comprising at least the following steps:

- the first zone is formed by pultrusion,

- the first zone is placed in a mold and the second zone is overmolded on the first zone.

Of course, the various characteristics, variants and / or embodiments of the present invention can be associated with one another in various combinations insofar as they are not incompatible or mutually exclusive of each other.

We will now describe ten embodiments of the invention using the following figures:

FIG. 1 is a schematic view of a set of bumpers according to a first embodiment of the invention seen from above when it is mounted on a front face of a motor vehicle, FIG. 2A illustrates a bumper bumpers of the bumper assembly in longitudinal section along the cutting axis AA, FIGS. 2B to 2F illustrate bumpers, seen in a configuration similar to that of FIG. 2A, according to second, third, respectively fourth, fifth and sixth embodiments, and FIGS. 3A to 3D illustrate bumpers, viewed from the front when they are mounted on a front face of a motor vehicle, according to seventh, eighth, ninth and tenth modes respectively of achievement.

A bumper assembly 10 for the front face of a motor vehicle comprises a bumper beam 12. In addition, the bumper assembly 10 comprises two energy absorbers 14 and 16 arranged near the two longitudinal ends of the bumper beam 12.

The energy absorbers 14, 16 each connect the bumper beam 12 to one end of two longitudinal members of the motor vehicle.

Thus, in the event of a frontal impact, the bumper beam 12 absorbs part of the energy of the impact and transmits part of it to the energy absorbers 14, 16 which will themselves absorb part of the energy received. to ensure that a small portion of the frontal impact energy is transmitted to the side members of the motor vehicle.

As illustrated in FIGS. 2A to 3D, the bumper beam 12 comprises a first zone 18 and a second zone 20.

In addition, as illustrated in FIGS. 2D to 2F, the bumper beam 12 can comprise a third zone 22.

The first zone 18 is made of a reinforced polymer material comprising fibers.

The second zone 20 is made of an unreinforced polymer material.

The third zone 22 is also made of a reinforced polymer material.

The reinforced polymer material of the first zone 18 comprises a thermoplastic polymer.

It is also reinforced with glass fibers.

According to a variant, the reinforced polymer material of the first zone 18 is reinforced by carbon fibers associated or not with glass fibers.

Likewise, the fibers can be continuous or discontinuous or else comprise a mixture of continuous fibers and discontinuous fibers.

The material of the first zone 18 thus forms a composite material comprising a resin in the form of a thermoplastic polymer and a fibrous reinforcement.

The first zone 18 has a relatively low elongation at break of the order of 1% to 2% and an elastic behavior.

The term “non-reinforced polymer material” designates a polymer material which does not contain fibers.

Thus, the unreinforced polymer material of the second zone 20 is in the form of a thermoplastic polymer.

It includes polyamide.

According to a variant, the non-reinforced polymer material of the second zone 20 can comprise polypropylene associated or not with polyamide.

Thus, the second zone 20 has a relatively high ductility. By ductility is meant that the second zone 20 has an elongation, in the longitudinal direction, at break equal to at least 40%, 50%, 60%, 70%, 80%, 90% or 100%. She has a plastic demeanor. The elongation at break is defined by the following equation:

A% = 100. (L _u - L _o ) / L _o , with A being the elongation at break, L _u being the ultimate length, namely the length of the bar just before the break, L _o being the initial length or the length of the bar before traction, L _o and L _u being expressed in the same unit.

The reinforced polymer material of the third zone 22 is in the form of a thermoplastic, in this case polyamide, reinforced with glass fibers. The material of the third zone 22 can also be in the form of polypropylene reinforced with glass fibers.

We will now describe, using FIGS. 2A to 3D, various configurations of the bumper beam 12. It will be noted that in these figures, separations are shown between the first 18, second 20 and third 22 zones. These separations are illustrative in order to mark the difference in material between these zones 18, 20, 22. When the invention is concretely implemented, the zones 18, 20, 22 are continuous and may not have any visible demarcation.

FIGS. 2A to 2C illustrate three configurations of the bumper beam 12 according to three different embodiments.

According to these embodiments, the bumper beam 12 comprises the first 18 and second 20 zones, but not the third zone 22.

According to the first embodiment of the invention, illustrated in particular in Figure 2A, the bumper beam 12 has a cross section of square shape. Thus, the first zone 18 and the second zone 20 both have a cross section of square shape.

As shown in FIG. 2A, the second zone 20 forms an envelope for the first zone 18 so that the second zone 20 overlaps the first zone 18, here entirely.

In addition, the first zone 18 and the second zone 20 are hollow. Thus, the bumper beam 12 is also hollow.

According to a variant not illustrated, it is the first zone 18 which overlaps the second zone 20.

According to the second embodiment of the invention, shown in FIG. 2B, the first zone 18 has a cross section substantially in the shape of a "C" or "omega", namely that the first zone 18 consists of three flat parts , a central planar part located between the two other extreme planar parts each being located at a vertical end (Z). The central flat part is connected to each extremal flat part by an inclined section so that the central flat part is offset longitudinally with respect to the two extreme flat parts.

The first zone 18 comprises a central branch 24 and two lateral branches 26, 28 which extend from two ends of the central branch 24.

The second zone 20 has a cross section of substantially conical shape and forms a rib for the first zone 18.

Obviously, the second zone may have a cross section of substantially cylindrical or evolving shape as required in mechanical strength.

As can be seen in FIG. 2B, the second zone 20 extends from the central branch 24 of the first zone 18 and forms an axis of symmetry for the first zone 18.

According to the third embodiment of the invention, illustrated in FIG. 2C, the first zone 18 has a cross section of substantially hexagonal shape and thus comprises an internal free space 29 delimited by internal walls of the first zone 18.

By comparison, the first zone 18 of the second embodiment corresponds to one half of the first zone 18 of the fifth embodiment.

The second zone 20 extends in the interior space 29 between two internal walls of the first zone 18 and has a shape analogous to that of the second embodiment.

FIGS. 2D to DF have illustrated different configurations of the bumper beam 12 according to three other embodiments. According to these embodiments, the bumper beam 12 comprises the third zone 22

According to the fourth embodiment, shown in FIG. 2D, the first zone 18 and second zone 20 each have a hollow rectangular cross section, as described for the first embodiment (FIG. 2A).

The second zone 20 overlaps the first zone 18 so as to define an interior free space 30 delimited by interior walls of the first zone 18.

The third zone 22 has a cross section of solid rectangular shape and is disposed between two interior walls of the first zone 18 in the free space 30. In other words, the second zone 20 has a cross section of substantially cylindrical shape and forms a rib for the first zone 18

According to the fifth embodiment, represented in FIG. 2E, the first zone 18 and the second zone 20 have a cross section in the shape of a "C" so that the first zone 18 covers the second zone 20, or also in the form of "Omega" as described for the second embodiment (Figure 2B).

The first zone 18 and the second zone 20 comprise a central branch respectively 24, 32 and two lateral branches respectively 26, 28 and 34, 36 which extend from two respective ends of the central branches 24, 32.

The third zone 22 has a cross section of substantially conical or cylindrical shape and forms a rib for the second zone 20.

The third zone 22 extends from the central branch 32 of the second zone 20.

According to the sixth embodiment of the invention, illustrated in FIG. 2F, the first zone 18 and the second zone 20 have a cross section of substantially hexagonal shape, the first zone 18 overlapping the second zone 20.

The bumper beam 12 includes an interior free space 31 delimited by internal walls of the second zone 20.

In addition, the third zone 22 extends in the interior space 31 between two internal walls of the second zone 20 and has a shape similar to that of the third embodiment.

FIGS. 3A to 3D show four other embodiments. The bumper beam 12 comprises the first zone 18 and the second zone 20.

According to the seventh embodiment, illustrated in FIG. 3A, the first zone 18 and the second zone 20 appear, when the motor vehicle is viewed from the front, respectively in the form of two layers superimposed on each other. In FIG. 3A, the first zone 18 is arranged on the second zone 20, in a vertical direction (Z).

According to a variant of this embodiment, it is the second zone 20 which is arranged on the first zone 18.

According to the eighth embodiment, illustrated in FIG. 3B, with reference to a vertical direction Z, the first zone 18 is in the form of a layer sandwiched by two layers which form the second zone 20.

According to the ninth embodiment, illustrated in FIG. 3C, it is the second zone 20 which is in the form of a layer sandwiched by two layers which form the first zone 18.

According to the tenth embodiment, represented in FIG. 3D, the first zone 18 and the second zone 20 are in the form of a plurality of layers arranged alternately one on the other.

In this embodiment, three layers form the first zone 18 and two layers, each arranged between two layers forming the first zone 18, form the second zone 20.

In general, the first zone 18 and the second zone 20 can be in the form of a plurality of layers superposed alternately one on the other.

In the four illustrated embodiments, the layers forming the first 18 and second 20 zones have identical longitudinal dimensions. They can also have different longitudinal dimensions.

In particular, the layers forming the second zone 20 may have lengths shorter than the lengths of the layers forming the first zone 18.

In addition, the layers forming the second zone 20 may have an identical thickness and between 0.2 millimeter and 0.7 millimeter.

The layers forming the second zone 20 may also have different thicknesses 5 from the layers forming the first zone 18. Preferably, the layers forming the first zone 18 have a thickness substantially equal to 0.2 millimeters and the layers forming the second zone 20 have a thickness substantially equal to 0.5 millimeter. This increases the ductile nature of the bumper beam 12.

We will now describe a process for manufacturing the bumper beam 12.

First, the first zone 18 is formed, for example by a pultrusion or thermoforming process.

Then, the first zone 18 is placed in a mold and the material intended to form the second zone 20 is injected into the mold so as to overmold the second zone 20 on the first zone 18.

The first zone 18 and second zone 20 can also be placed in a mold and the material intended to form the third zone 22 is injected so as to overmold the third zone 22 on the first zone 18 and third zone 22.

It is also possible to separately form the first zone 18, second zone 20 and third zone 22 and fix them to each other, for example by gluing.

Of course, many modifications can be made to the invention without departing from the scope thereof.

The third zone 22 may in particular be arranged in the form of layers 25 alternately disposed between two layers contributing to forming the first zone 18 and second zone 20.

In addition, the bumper beam 12 can have only a second zone 20 and / or third zone 22 over a portion of its length.

Claims (10)

Claims 1. Bumper beam (12) for a motor vehicle characterized in that it comprises a first zone (18) made of a reinforced polymer material comprising fibers and a second zone (20) made of a non-polymeric material reinforced. 2. Bumper beam (12) according to the preceding claim, in which the unreinforced polymer material of the second zone (20) is a thermoplastic polymer. 3. Bumper beam (12) according to any one of the preceding claims, in which the second zone (20) has an elongation at break equal to at least 40%, or 50%, 60% or 80 %. 4. Bumper beam (12) according to the preceding claim, in which the reinforced polymer material of the first zone (18) comprises a thermoplastic polymer. 5. Bumper beam (12) according to any one of the preceding claims, in which the reinforced polymer material of the first zone (18) comprises continuous fibers and / or staple fibers. 6. Bumper beam (12) according to any one of the preceding claims, in which the first zone (18) and the second zone (20) have a cross section of square shape, the second zone (20) covering the first zone. 7. Bumper beam (12) according to any one of claims 1 to 5, in which the first zone (18) has a “C” shaped cross section, the second zone (20) forms a rib for the first zone (18). 8. Bumper beam (12) according to any one of claims 1 to 5, wherein the first zone (18) has a cross section of substantially hexagonal shape, the second zone (20) extends in a space between two internal walls of the first zone (18). 9. Bumper beam (12) according to any one of the preceding claims, comprising a third zone (22) made of a material comprising polyamide reinforced with glass fibers and / or polypropylene reinforced with glass fibers . 5 10. A method of manufacturing a bumper beam (12) according to any one of claims 1 to 9, comprising at least the following steps: - the first zone (18) is formed by pultrusion, - The first zone (18) is placed in a mold and the second zone (20) is overmolded on the first zone (18). 1/2