MXPA98005597A - Reforza structural members - Google Patents

Abstract

The present invention relates to a reinforced structural member, comprising: a channel-shaped structural member terminating at free ends spaced apart from each other and interconnected by a wall having an external compression face; a reinforcing helmet having a shorter length that the length of the channel, the reinforcing hull and structural member being interconnected, a layer of structural foam disposed between a portion of the structural member and a portion of the reinforcing hull, to define a trilaminate region, the structural foam layer being attached the structural member and the hull of the reinforcement, and the trilaminate region having an arc-shaped surface, the arc-shaped surface extending in the direction of the compression face adapted to receive the impact of a collision, having the surface in the form of bow divergent inclined walls to distribute forces through a generalized area away from the pu of concentration, at the interconnection locations of the reinforcing hull and the structural member, and to maximize resistance to bending and sagging

Description

"REINFORCED STRUCTURAL MEMBERS" REFERENCE TO THE RELATED APPLICATION This request is based on the Request Provisional Serial Number 60 / 053,053, filed on July 21, 1997.

TECHNICAL FIELD The present invention relates generally to methods and apparatuses for reinforcing structural members and, more specifically relates to the local reinforcement of sections in the form of a channel subject to bending.

BACKGROUND OF THE INVENTION In a number of applications, particularly in the automotive industry, there is a need for lightweight, high strength structural members. Even when structural members having these characteristics can be easily obtained through the use of different metal alloys, for example, titanium alloys and the like, lightweight, high strength alloys are generally prohibitive in cost in automotive applications, where the weight reductions are tightly balanced against the cost of materials. In addition, reinforcement techniques that can easily adapt to the existing geometries of structural parts are required, thus eliminating the need for fundamental design changes and providing a means by which subnormal design performance can be remedied. That is, in many cases design deficiencies are discovered after the design of the vehicle has reached the stage in which radical changes are no longer feasible. In addition, a significant amount of emphasis has been placed on the performance characteristics of structural components in the form of channels that find forces that produce bending. For example, many side impact beams designed for motor vehicle doors have a channel-shaped cavity. In addition, many functional bumpers are channel-shaped. These channel-shaped sections are very susceptible to bending forces originating in or concentrated in the center of the beam section. Even when filling the entire section with plastic foam significantly increases the stiffness of the section (at least when using high density foams), this technique can also significantly increase the mass and therefore the weight of the piece which, as stated, is undesirable in most applications. In addition, filling a section entirely with foam can contribute significantly to the cost. Finally, a large foam core often creates an unwanted heat sink. And even when increasing the metal thickness of the section or adding localized metal reinforcements will increase the stiffness, as the thickness of the metal increases, it becomes more difficult to form the part due to the limitations of the metal forming machines. . A number of approaches have been proposed to deal with the problem of reinforcing the channel-shaped sections subjected to bending as alternatives to high cost alloys, thick metal sections and large foam cores. For example, a side impact beam for a vehicle door has been proposed which comprises a metal member in the form of an open channel having a longitudinal cavity which is filled with a thermosetting or thermoplastic resin based core. The core is placed in the center of the beam section. The core may include hollow glass microspheres in order to decrease the density and hence the weight.

A reinforcement insert comprising a pre-molded effort has been proposed. The reinforcement is formed of a plurality of granules containing a thermosetting resin and a swelling agent. The pre-molded member expands and is cured at the site in a structural member. A composite tubular door beam reinforced with a synthetic foam core located in the center of the tube section has also been described in the art. The nucleus based on Resin occupies no more than a third of the tube's perforation. Tube-in-tube structures having high stiffness-to-mass ratios have also been proposed in which two nested tubes have a layer of foam placed in the annular conduit between the tubes. A local reinforcement in the nature of foamable resin placed in a carrier has also been described. The carrier is placed in the channel of a hollow structural member after which the resin expands. Therefore, it would be desirable to provide a low cost technique for reinforcing a section in the form of a channel subjected to flexion without significantly increasing the mass. It would also be desirable to provide a method for reinforcing an existing channel-shaped section that does not require any fundamental design changes to the member. The present invention provides hollow sections having increased strength with moderate increases in mass, all without the use of high volumes of expensive resins. The present invention also provides a method for reinforcing the existing structural parts without redesigning the geometry of the part. It has been found that the present invention increases the stiffness and strength of the section in the channel-shaped sections in a highly efficient manner.

COMPENDIUM OF THE INVENTION In one aspect, the present invention provides a reinforced channel-shaped member having a thin local reinforcing hull separated from the channel-shaped member by a layer of structural foam. In the reinforced section an arc extends in an opposite direction, that of the force to which the member is subjected, that is, the arc projects in the direction of the compression face of the channel-shaped member. The arch may be present as the channel-shaped member, the reinforcing helmet or both the channel-shaped member and the helmet. A portion of the hull is preferably brought into contact with the channel-shaped member and fixed thereto by spot welding or other attachment means. The combination of the arch and the structural foam supports the load, stabilizes the walls of the member in the form of a channel and distributes the force through a generalized area away from the points of concentration in the welds. In one aspect, the reinforcing hull and structural foam are preferably limited to no more than about one-third of the length of the channel-shaped member and are essentially placed in the center of the channel-like length of the member. In one aspect, the helmet is placed in the channel of the channel-shaped member and in another, the helmet forms a cap on the outside of the channel-shaped member. The hull is preferably made of high strength steel that allows the low strength steel to be used as the structural member. Also, in the applications in which the main structural member is made of high strength steel, the hull can comprise a mild steel or aluminum. In yet another aspect, the present invention provides a method for reinforcing a structural part that includes the steps of forming a structural foam layer at a local reinforcement site in a structural member in channel form. A reinforcing helmet is placed in the center of the channel portion of the member and preferably extends to no more than one third of the length of the channel member. The structural foam is placed on a surface of the hull which is then brought into contact and attached to the member in the form of a channel. These and other advantages and objects of the present invention will be more fully described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a reinforced bumper illustrating the position of a reinforcing helmet in the center of the arched section. Figure 2 is a cross section through the lines 2-2 of Figure 1. Figure 3 is a cross-section of another embodiment of the present invention illustrating a "D" reinforcing hull placed in the cavity of a section of the hollow bumper and separated from the bumper section by a layer of structural foam. Figure 4 is a cross section of another embodiment of the present invention illustrating a reinforcing helmet having a "D" shaped configuration; the reinforcement helmet is placed in the cavity of a hollow section of the bumper having a double arch with an intervention layer of structural foam.

Figure 5 is a cross-section of another embodiment of the present invention illustrating a localized arc-shaped reinforcement positioned in the channel of a section of the bumper with an intervention layer of structural foam. Figure 6 is a cross section of another embodiment of the present invention illustrating a "D" shaped reinforcing hull placed in a rectangular bumper section and separated by segmented regions of the structural foam. Figure 7 is a cross-section of another embodiment of the present invention illustrating an arc-shaped bumper having a rectangular reinforcing hull placed thereon as a lid with an intervention layer of structural foam. Figure 8 is a cross section of a double arch bumper section with an arc-shaped reinforcing cap. Figure 9 is a perspective view of a reinforced door beam illustrating the position of the reinforcing hull at the center of the rectangular section. Figure 10 is a cross section through lines 10-10 of Figure 9. Figure 11 is a cross section of another embodiment of the present invention illustrating an arched door beam with an arched reinforcing hull with an intervention layer. of structural foam.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES OF THE INVENTION Referring now to Figure 1 of the drawings, the reinforced automotive bumper 20 is shown having a section 22 of the bumper of the nature of a longitudinal structure defining the channel, which has a length considerably greater than its width. Each edge of the vertical planar wall 24 is constrained by the sides 26. Each side 26 has a flange 28 that extends above the open channel 30. The wall 24 defines an outer surface or compression face 32 and a side face of the inner channel or surface 34. It will be appreciated by those skilled in the art that the compression face 32 receives the compact in a collision and is therefore the region in which flexion is induced. Positioned in the center of the section of the bumper section 22, ie, generally positioned centrally between the ends 36 and 38, there is seen a reinforcing helmet assembly 40 having an arcuate reinforcing hull 42 and a foam layer 44 intervention. If the location of the maximum deformation is not in the central location, the reinforcement helmet assembly will properly be off-center at the location of the maximum deformation. The arcuate hull 42 has a pair of flanges 45 that lie above and contact the flanges 28 of the bumper section 22. The arcuate hull has an arc portion 46 extending in the direction of the wall 38 of the bumper section 22. For the purposes of this application the terms "arched" and "arc" will include not only a traditional "U" shaped bow, but also a "D" shape an example of which will be illustrated more fully below. The arch is also intended to include forms of M or V o. The structural member and the reinforcing helmet can be metal die-cut parts or can be metal formed by rolling. Referring now to Figure 2 of the drawings, the relationship of arched hull subassembly 40 and bumper section 22 is shown more clearly. The arcuate hull has a surface 48 that remains in contact and is bonded or bonded to the foam layer 44. Again, the arc portion 46 of the hull 42 extends in the direction of the wall 38 and therefore extends toward the compression face 32 of the bumper section 22. The foam layer 44 is also in contact with and is bonded to the face 34 of the wall 38 as well as the inner surface 50 of the side wall, thereby fixing the helmet 42 rigidly to the bumper section 22, forming a tri-construction. -laminate. In addition, the flanges 45 are fixed to the flanges 28 by means of welds even when fastening means such as mechanical fasteners or high strength adhesive may be appropriate in a specific application. The length "L" of the arched shell subassembly 40 is preferably equal to or less than one third of the length "L" of the bumper section 22. The width "" of the channel 52 defined by the arc portion 46 of the hull 42, preferably is at least 75 percent of the width "" of the channel 30 of the section 22 of the bumper. The depth "D" of the hull 42 extending towards the channel 30 is preferably at least 75 percent of the depth "D" of the channel 30. Bell-shaped arcs or "D" shapes have a relationship of elevation (D) to section (W) of about .5: 1.0 to about 1.0: 1.0 are especially preferred. As best illustrated in Figure 2 of the drawings, the hull 42 is of a relatively thin metal thickness compared to that of the bumper section 22. The metal used to form the hull 42 and section 22 will typically be steel or aluminum. For example, DI 140 shaped steel between 0.8 and 1.4 millimeters is particularly preferred for hull 42. (And note that even when metal is preferred, other materials may be suitable in a particular application). One of the advantages of the present invention is the ability to use relatively low strength steel for the bumper section 22, while reinforcing the structure with a hull 42 of lightweight high strength steel. Providing an arc 46 in the direction of the compression face 32; an intervention layer of adhesive foam 44 which is bonded to the helmet 42 and to section 22; and welding by spot welding (or otherwise fixing) the helmet 42 to the section 22, the reinforced bumper 20 provides maximum resistance to bending with minimum weight and cost. The combination of the arc 46 and the foam 44 in compression reinforces the bumper section 22 for a considerable reduction in warpage. It will be understood that the foam layer 44 essentially covers the entire surface 48 of the helmet 42. The foam 4 is preferably a resin-based material incorporating hollow glass microspheres to reduce the density. With specific reference now to the composition of the foam layer 44, the density of the material should preferably be from 320 grams per cubic centimeter to about 640 grams per cubic centimeters to minimize weight. The melting temperature, the heat distortion temperature and the temperature at which chemical disintegration occurs must also be sufficiently high such that the foam layer 44 maintains its structure at elevated temperatures typically found in paint ovens and the like. . Therefore, the foam 44 must be able to withstand temperatures in excess of 200 ° C and preferably 175 ° C for short periods of time. The foam layer 4 has a thickness of preferably 2 to 8 millimeters around the arch. In a particularly preferred embodiment, the foam layer 44 includes a synthetic resin, glass microspheres, a swelling agent and a filter. The foam 4 preferably expands in place between the hull 42 and the section 22, and are prepared by mixing the following materials together. A synthetic resin comprising from about 50 percent to about 80 percent by weight, and most preferably from about 60 percent to about 75 percent by weight of the mixture used to form the foam 44. The glass microspheres comprise from about 10 percent to about 40 percent by weight, and more preferably from about 15 percent to about 25 percent by weight of the mixture. A swelling agent comprises from about 1 percent to about 10 percent by weight, and more preferably from about 2 percent to about 6 percent by weight of the mixture. The layer 44 could initially be applied in unexpanded form, either to the hull 42 or to the section 22 and then expanded in intimate contact with the other member and thus be ligated to both members 22 and 42. When the foam is thermally expandable and the Structural member is a piece of the vehicle, the paint furnace must be used to initiate expansion of the foam, without requiring a separate heating step. Various fillers or fillers may be included (such as fuming silica, calcium carbonate, ground glass fiber and crushed glass). A filler or filler comprises from about 1 percent to about 10 percent by weight and preferably from about 3 percent to about 8 percent by weight of the mixture used to form the foam 44. Preferred synthetic resins to be used in the present invention include thermosetting resins such as epoxy resins, vinyl ester resins, thermosetting polyester resins and urethane resins. The scope of the present invention is not intended to be limited by the molecular weight of the resin and the appropriate weights will be understood by those skilled in the art based on the present disclosure. When the resin is a thermosetting resin, various accelerators such as imidazoles and "DMP 30" and curing agents, preferably di-cyanamide, may also be included to improve the cure rate. A functional amount of the accelerator is typically from about 1 percent to about 3 percent of the weight of the resin, with a corresponding reduction in the resin, the microspheres or the filler or filler material. Similarly, the amount of the curing agent used is typically from about 2 percent to about 8 percent of the weight of the resin, with a corresponding reduction in the microsphere resin or filler or filler. Effective amounts of processing aids, stabilizers, colorants, ultraviolet light absorbing agents and the like may also be included in the layer. Thermoplastic materials may also be appropriate in some applications. In the following tables, preferred formulations to be used to form foam 44 have been described. All percentages in the present exhibit are percentages by weight unless specifically designated otherwise. INGREDIENTS PERCENTAGE IN WEIGHT FORMULA I Part An Epoxy of Bisphenol A 10% Nipol Liquid 89, Healing Di-c and 7% Accelerator EMI-24 1% Microspheres B38 14? = FORMULA II Part Resin Side "Healing Side" B 'Two Epoxy Resin 74' Aliphatic Amine 65. Cellogen Inflator 6 '? Tixotrope 8% Tixotrope 4 '. K20 Microspheres 27% K20 16s Microspheres In addition to the structure illustrated in Figures 1 and 2 of the drawings, the present invention provides a number of other configurations encompassing the inventive concepts of the present invention as a motor vehicle bumper. More specifically, and now referring to Figure 3 of the drawings, the structural member or the main bumper section 54 is shown having flanges 56 that are welded to the local reinforcement hull 58. The structural foam 60 is shown by ligating the helmet 58 in place in the channel defined by the section 54 of the bumper. In Figure 4, the bumper section 62 has a double arc portion 64 having two arcs 66 and 68. The structural foam layer 70 is placed in the channel defined by the section 62. As with the structure described in FIG. Figure 4, the hull 72 is in a "D" shape and is fixed to the flanges 74. In Figure 5, the hull 76 having an arc configuration is used in combination with a section 78 of the double-bow main bumper. The helmet 76 has a pair of flanges 80 which are fixed to the corresponding flanges 82 of the bumper section 78. Figure 6 is a modification of the structure illustrated in Figure 3, with the foam layer being segmented, i.e. provided with separate linear rows or tape 84. Referring now to Figure 7 of the drawings, the reinforcing helmet 86 forms an outer lid in the bumper section 88. The bumper section 88 has an arch configuration and is provided with flanges 90 which are fixed to the ends 92 of the hull 86. The foam layer 94 is seen in the channel defined by the hull 86. In Figure 8, the section 94 of bumper has a double arc structure 96 and is separated from the cap 98 or arc-reinforced hull by a layer 100 of foam. - 1! In addition to the reinforced bumpers, the present invention is useful for reinforcing the side beams of the door. Referring now to Figure 9 of the drawings, the side impact beam 102 is generally shown having a beam section 104 defining the arch 106. As seen in Figures 9 and 10, the lid or helmet 108 The reinforcement layer is provided and fixed (preferably by spot welding) to the beam section 104 on the flanges 110 and 112. A foam intervening layer is placed between the inner surfaces 114 of the cover 108, and the surface 116 external beam 104. Alternatively, the lid and the beam section could be inverted; that is, the piece 108 could be the beam and the piece 104 an internal lid. It should be understood that this investment could be achieved in all preferred designs including those described in connection with the bumper. Figure 11 of the drawings shows yet another configuration in which two complementary arcs are nested one inside the other. The piece 118 can form either the lid or the main beam body with the piece 120 forming the corresponding hull or beam. The foam 122 is shown placed between the parts 118 and 120, in the manner described above. In yet another aspect, the present invention provides a method for reinforcing a structural part that includes the steps of forming a structural foam layer at a local reinforcement site in a channel-like structural member. A reinforcing helmet is placed in the center of the channel portion of the member and preferably extends to no more than one third of the length of the channel-shaped member. The structural foam is placed on a surface of the hull which is then contacted and ligated with the channel-shaped member. Even though the invention has been described mainly in relation to vehicle partsIt will be understood that the invention can be implemented as part of other products such as airplanes, ships, bicycles or virtually anything that requires energy for movement. Similarly, the invention can be used with stationary or static structures, such as constructions, to provide a rigid support when subjected to vibration such as from an earthquake or simply to provide light weight support for structures subjected to loads. . Further, even though the invention has been described primarily with respect to thermally expandable foams and with respect to metal pieces, for example, the structural member and the hull, other materials may be used. For example, the foam could be any suitable known expandable foam that is chemically activated towards expansion and forms a rigid structural foam. The helmet could be made of materials other than metal, for example, various plastics or polymeric materials or various fibrous materials of wood type that have sufficient stiffness to function as a backing or support for the foam. Even when a thermally expandable foam is used, the backing support must be able to withstand the heat encountered during thermal curing. Even when other types of foam materials are used, however, it is not necessary for the support member to be able to withstand high temperatures. Instead, the basic requirement for the support member is that it has sufficient rigidity to function in the manner intended. It is also possible, for example, to be used as hull materials that become rigid themselves during healing or additional treatment. The invention may also be practiced where the structural member is made of materials other than metal. It is preferred, however, that the materials be selected for the structural member and the hull as well as for the foam so that the unexpanded foam derived during the expansion forms an intense bond with these members resulting in a structural composition.

Claims (35)

R E I V I N D I C A C I O N E S:

1. A reinforced structural member comprising: a structural member defining a channel; a reinforcing helmet having a length less than the length of the channel; the reinforcing helmet and the structural member are interconnected; a layer of structural foam positioned between a portion of the structural member and a portion of the reinforcing hull so as to define a trilaminate ring, the structural foam layer being bonded to the structural member and the reinforcing hull; and the trilaminate region has an arc-shaped surface.

2. The reinforced structural member according to claim 1, wherein the reinforcing helmet is in the form of an arc.

3. The reinforced structural member according to claim 1, wherein the structural member is arc-shaped.

The reinforced structural member according to claim 1, wherein the reinforcing hull is in the form of an arc and the structural member is arc-shaped.

The reinforced structural member according to claim 1, wherein the reinforcing hull is embedded in the channel of the structural member.

The reinforced structural member according to claim 1, wherein the structural member has an inner surface in the channel and an outer surface and wherein the structural foam layer is placed between the reinforcing helmet and the outer surface.

The reinforced structural member according to claim 1, wherein the reinforcing hull is placed at a location of maximum deformation of the structural member.

The reinforced structural member according to claim 7, wherein the reinforcing hull is positioned at the center of the length of the structural member and has a length that is no greater than about one third of the length of the structural member.

The reinforced structural member according to claim 1, wherein the structural foam contains glass microspheres.

10. The reinforced structural member according to claim 2, wherein the reinforcing hull has a double arc shape.

The reinforced structural member according to claim 3, wherein the structural member has a double arc shape.

The reinforced structural member according to claim 1, wherein the structural foam layer has a thickness of about 2 to about 10 millimeters.

The reinforced structural member according to claim 1, wherein the structural member and the reinforcing helmet are die-cut metal or metal pieces formed by rolling.

The reinforced structural member according to claim 1, wherein the reinforcing hull is formed of high strength steel or aluminum.

15. The reinforced structural member according to claim 1, wherein the foam layer is at least two separate segments.

The reinforced structural member according to claim 1, wherein the structural foam contains from about 60 percent to about 78 percent by weight of polymer, from about 10 percent to about 30 percent by weight of glass microspheres , from about 3 percent to about 10 percent by weight of the filler or filler, and from about 2 percent to about 8 percent by weight of the swelling agent.

17. The reinforced structural member as claimed in claim 1, wherein the foam is expandable.

18. The reinforced structural member according to claim 17, wherein the foam is thermally expandable.

19. The reinforced structural member according to claim 1, wherein the structural member is a vehicle bumper.

20. The reinforced structural member according to claim 1, wherein the structural member is a side door beam of the vehicle.

21. A reinforced structural member comprising: a structural member defining an open channel; a reinforcing helmet formed of high strength steel and having a length no greater than one third of the length of the open channel; the reinforcing hull and the structural member are interconnected in such a way that the reinforcing hull is placed in the center of the section of the structural member in such a way that an interface is defined; a layer of structural foam placed between essentially the entire interface of the structural member and the reinforcing hull defining a trilaminate region, the structural foam layer being bound to the structural member and the reinforcing hull; and the trilaminate region has an arc-shaped surface.

22. The reinforced structural member according to claim 21, wherein the reinforcing hull is in the form of a bow.

23. The reinforced structural member according to claim 21, wherein the structural member is arc-shaped.

The reinforced structural member according to claim 21, wherein the foam is expandable

25. The reinforced structural member according to claim 24 wherein the foam is thermally expandable.

26. The reinforced structural member according to claim 21, wherein the structural member is a vehicle bumper.

27. The reinforced structural member according to claim 21, wherein the structural member is a side door beam of the vehicle.

28. A method for reinforcing a structural member that includes the steps of forming a structural foam layer at a local reinforcement site in a channel-like member, placing a reinforcing helmet generally at the center of the member-shaped section of the member. channel, place the structural foam layer against and tie it to a channel-shaped member and the reinforcing hull, and tie the structural foam to the other channel-like member and the reinforcing hull to create a trilaminate region having a surface in the form of an arch.

29. The method of claim 28, which includes fitting into the reinforcing hull in the channel-shaped member.

30. The method of claim 29, which includes mounting the reinforcing helmet to the exterior of and around the channel-shaped member.

31. The method of claim 28, wherein the structural member is a vehicle bumper.

32. The method of claim 28, wherein the structural member is a side beam of the vehicle door.

The method of claim 28, wherein the foam is an expandable foam and bonding the foam to the other channel member and the reinforcing hull during expansion of the foam.

34. The method of claim 33, wherein the structural member is a vehicle part and the foam is expanded by thermal activation.

35. The method of claim 34, wherein thermal activation occurs in a paint furnace.