MXPA99000006A - Structural member of reforz channel configuration - Google Patents

Abstract

The present invention relates to a reinforced structural member, comprising: a structural member having a non-planar wall a reinforcing laminate covering secured to the non-planar wall and having the same configuration as the non-planar wall, the covering comprising a layer of foam attached to the non-planar wall and a thin sheet made of metal or polymer / plastic bonded to the foam layer, and the coating being of a uniform thickness to provide an exposed surface of the same configuration as the non-planar wall of the member structure

Description

STRUCTURAL MEMBER OF REINFORCED CHANNEL CONFIGURATION BACKGROUND OF THE INVENTION The present invention relates generally to methods and apparatuses for reinforcing various structures and, more especially, relates to reinforced members in the form of a channel. Structural members of high strength, light weight, are required in a number of applications, for example in motor vehicles and aircraft as well as in various devices such as household appliances and the like. A number of composite materials in the passage have been proposed as structural members, such as light weight exotic alloys. In most ^ c of the applications, however, the reduction of mass must be balanced against the cost of the product to the consumer. In this way, there is a need to provide strength without significantly increasing material and labor costs. Additionally, 2 reinforcement techniques are needed which can be adapted to existing geometries in structural parts, avoiding any requirement for fundamental design changes. As examples of reinforcement techniques, the The present inventor has described a number of metal / plastic composite structures to be used to reinforce components of motor vehicles. In the patent of E.U.A. No. 4,901,500, entitled "Composite Light Weight Beam", discloses a vehicle door comprising an open channel-shaped metal member having a longitudinal cavity that is filled with a thermoplastic or thermosetting resin-based material. In the U.S. Patent,. No. 4,908,930, entitled "Method for Making a Torsion Bar", describes a hollow torsion bar reinforced by a mixture of resin with filler. The tube is cut to length and cut with a resin-based material. In the U.S. Patent A. No. 4,751,249, entitled "Reinforcement Insertion for a Structural Member with Method for Making and Using The Same", provides a previously molded reinforcement insert for structural members that is formed of a plurality of granules containing a thermosetting resin with a blowing agent. In the patent of E.U.A. No. 4,978,462, entitled, "Composite Tubular Reinforced Door Beam Reinforced with a Syntactic Foam Core in the Average Tube Extension", describes a composite door beam having a resin-based core that does not occupy more than a third part of the perforation of a metal tube.

In the Patent Application of E.U.A. No. 08 / 245,798, filed May 19, 1994, entitled "Compound Laminated Beam for Automobile Body Construction", describes a hollow laminated beam characterized by a high ratio of rigidity to mass and having an external portion that is Separates from an inner tube by a thin layer of structural foam. In co-pending US Patent Application Serial No. 08 / 245,798, filed May 19, 1994, entitled "Compound Laminated Beam for Automotive Bodywork", a W-shaped carrier insert reinforcement is described that bears a body of foam, to be used when reinforcing a hollow beam. In the United States Patent Application Serial No. 08 / 644,389, filed May 10, 1996, entitled "Internal Reinforcement for Hollow Structural Elements", the present inventor describes a beam reinforcement member in 1 that includes a layer of external foam. The beam in 1, as in the case of most of the previous reinforcements, involves a preformed structural insert that is then inserted into a hollow structural member. It is also known how to increase the strength of a laminated structure by bonding flat metal plates together using an intermediate layer of resin. For example, it is known to form a laminated metal sheet to be used as a floor panel member comprising a pair of flat metal sheets having an intermediate layer of asphalt or elastic polymer. Even when the filling of the entire section with plastic foam significantly increases the section stiffness (at least when they are used high density foams), this technique can also significantly increase the mass, and thus part of the weight, which, as shown, is an undesirable feature in most applications. In addition, filling a section • j_5 completely with foam can be prohibitively expensive and creates a large thermal sink. Y. even when increasing the metal gauge of a section or adding localized metal reinforcements will increase the stiffness, as metal thickness increases, it is more difficult form the part due to limitations of metal forming machines. Consequently, it would be desirable to provide a low cost technique for reinforcing a structural channel configuration member without increasing proportionally the mass. It would also be desirable to provide a method for reinforcing an existing channel configuration member that does not require any fundamental design changes to the member. The present invention provides channel configuration members that have increased strength with moderate increases in mass and without the use of high volumes of expensive resins. The present invention further provides a method for reinforcing existing structural parts without redesigning the geometry of the part. It has been found that the present invention increases the section stiffness and provides vibration damping in channel configuration sections in a highly efficient and reproducible manner.

COMPENDIUM OF THE INVENTION In one aspect the present invention provides a reinforced channel configuration member. The channel configuration member is preferably a stamp or the like defining a channel. The channel generally has a length that is greater than its width. The channel configuration member is typically formed of metal or plastic. A layer of expanded structural foam is disposed in the channel. The configuration of the structural foam coincides with that of the channel-shaped pattern; that is, the foam has a surface that is bonded to and conforms to the wall of the channel configuration member defining the channel and another (opposite) surface which is itself channel configuration. An insert is arranged and ligated to the structural foam layer. The geometry of the insert coincides with that of the structural foam. The insert is a thin sheet of metal or plastic and has a thickness of 0.05 to 2.54 mm.

In another aspect, two reinforced channel configuration members are formed and then joined together to form a reinforced tube. In still another aspect, the present invention provides a method for reinforcing a structural part «R including the steps of forming a laminated structure having a layer of uncured, unstressed foam-forming resin and a layer comprising a sheet metal or plastic carrier; placing the laminate on a part that has a non-planar geometry; conform the laminated Q to the geometry of the non-planar part; and thermally expand and bond the resin to the part. In one aspect, the method of the present invention reinforces a channel configuration structure through the steps of extruding a flat layer of thermally expandable structural resin on the surface of a release coating; placing a thin flat sheet on the resin to form a thin sheet / resin laminate having a release layer; Die cut the material to the configuration; remove the release coating; placing the thin sheet / resin laminate on a channel configuration structural member so that the resin layer is oriented to the part; pressing the sheet / resin laminate structure into the channel so that the resin layer contacts the part in the channel; Trim any excess thin sheet laminate / resin part; and heating the part to thermally expand the thermally expandable resin and to securely bind the resin to the thin sheet and channel configuration member. These and other advantages and objects of the present invention will now be described more fully with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a reinforced channel member made in accordance with the present invention. Figure 2 is a cross-section of a thin-film / resin two-layer laminate used in the present invention. Figure 3 is a detailed view of the reinforced channel member of Figure 1, in an intermediate construction stage with the forming tool shown in position on top of the preform. Figure 4 is a cross section along lines 4-4 of Figure 1. Figure 5 is a cross-section of two reinforced channel configuration structures made in accordance with the present invention, welded together in your eyelashes to form a reinforced tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 5 Referring now to Figure 1 of the drawings, the reinforced structure part 20 is generally shown having a stamp 21 with walls 22 and floor or bottom 23 defining channels 24 and 26. The tabs 28 are also seen, which can receive a 2Q closure plate 29 shown in shadow in Figure 4. The pattern 21 is preferably a metal stamp, but could be formed from another metal forming technique such as molding or the like or it could be formed of a material such as plastic, for example, polycarbonate. The embossing dimensions 21 can vary widely depending on the application. In the most preferred embodiment of the present invention, the stamp 21 is a structural member, eg, a radiator support structure, in a motor vehicle. The stamp 21 has a metal gauge or thickness of about 0.76 to about 3.05 millimeters. Still referring to Figure 1 of the drawings, the layer 30 of thermally expanded structural foam is shown disposed on the walls 22 and floor or bottom 23 in the channels 24 and 26. The layer 30 of thermally expanded structural foam is a structural foam which adds stiffness, resistance and vibration damping characteristics to the reinforced structural part. The layer 30 of thermally expanded structural foam expands through the use of heat, as will be more fully described below, and, in the expanded state illustrated in Figure 1, has a thickness of about 3.18 millimeters to about 9.54 millimeters and more preferably it has a thickness of about 1.59 millimeters to about 6.35 millimeters. The reinforcement or inner thin sheet 32 is disposed on the layer 30 of thermally expanded structural foam and comprises, in the most-1 O mode preferred, a thin sheet of steel, a thin sheet of aluminum or resin impregnated with glass (fiberglass), although it may be possible to use other materials in some applications. The reinforcement or sheet 32 thin internal defines its own channel, as will be described more fully in the present. In the preferred embodiment, the reinforcement or inner thin sheet 32 is provided with a plurality of perforations 33 (shown only in Figure 3) that define perforation channels 35 (shown in Figures 3 and 4). The perforations 33 serve the important function of allowing the gas to escape through the reinforcement or inner thin sheet 32 as the layer 33 expands thermally when heated. In absence of the perforations 33, the layer 30 of thermally expanded structural foam may not be properly bonded to the stamp 21 due to the formation of gas cavities. The layer 30 of thermally expanded foam or foam preferably has a thickness of about 3.18 millimeters to about 12.7 millimeters and more preferably, in automotive applications, a thickness of about 6.35 millimeters to about 9.54 millimeters. In most applications, the layer 5 of thermally expanded structural foam will extend over the entire area of the thin sheet 32; that is, it will completely separate the thin sheet 32 from the pattern 21. An important aspect of the present invention is the reduction of mass in the reinforced structural part. Also, as described in the background above, resin is a relatively expensive component and, thus, resin reduction is a desirable goal. By providing shaped or nested channel configuration structures in place as shown in Figure 1, the resin volume is reduced on a solid resin filler and the weight is reduced using a thin reinforcing sheet instead of an insert heavy heavy metal. Referring now to Figure 2 of the drawings, in accordance with the method of the present invention, the lamination preform 36 is shown having the layer 30 'of thermally expandable structural resin and the inner reinforcement or sheet 32' thin in the form of a two-layer laminate construction. The preferred method for forming the rolling preform 36 is by extruding the layer 30 'of thermally expandable structural resin onto a release paper layer such as a waxed paper. The resin / release paper sheet is then ready to receive the thin sheet 32 ', ie, the thin sheet 32' is placed on the side d? resin d? the resin / sheet of release paper, the resulting "trilaminate" is then passed through a nip roll or the like to securely bind the resin to the thin sheet. The process of forming the trilaminate is preferably carried out using a conveyor or the like. The resin / release layer / thin sheet is then cut with die to the configuration; the coating of release is removed just before use. In this preferred process, layer 30 'of thermally expandable structural resin is at a temperature of about 38 ° C to 66 ° C as it is deposited on the coating. 1, - More preferably, the thin sheet 32 'is perforated with an average of about 1 to about 2 perforations per 6.35 square centimeters with each perforation having a diameter of about 1.59 millimeters to about 4.77 millimeters. The perforations are preformed in the thin sheet 32 'prior to lamination to the resin sheet. Using the most preferred formulation for the layer 30 'of thermally expandable structural resin, the rolling preform 36 can be used up to ? f- approximately ninety days after it is manufactured.

As stated in the foregoing, the laminated preform 36 (unexpanded) has a thickness of about 3.18 millimeters to about 6.35 millimeters. Referring now to Figure 3 of the drawings, the preferred method for shaping the preform 36 laminated to the stamp 21 is through the use of the forming tool 38 shown to be placed on top of the rolling preform 36 moving in the direction of the arrow A. That is, the forming tool 38 contacts the main surface 40 of the preform 36 and presses the rolling preform 36 into the channels 24 and 26. It will be noted that, in essence, the structural foam channel 42 and the hollow to thin channel 44 are formed as best seen in Figure 4. As is also best seen in Figure 4, the layer 30 of thermally expanded structural foam and the inner reinforcement or thin sheet 32 are trimmed to below. the upper surface of the stamp 21. In Figure 5 of the drawings, two reinforced structural parts 20 are shown joined to form the tube 46 reinforced with the welded tabs 48. In this way, the present invention can also be used when tube applications are required. A number of resin-based compositions can be used to form the thermally expanded structural foam layer 30 in the present invention. Preferred compositions impart excellent strength and stiffness characteristics to the reinforced structural portion while being added only marginally to the weight. With specific reference now to the composition of thermally expanded structural foam layer 30, the density of the material should preferably be from about 240.28 grams per liter to about 800.94 grams per liter to minimize weight. The melting point, the heat distortion temperature and the temperature at which the chemical break occurs must be sufficiently high so that the layer 30 of thermally expandable structural foam maintains its structure at the elevated temperatures typically encountered in paint furnaces and the similar. Therefore, the thermally expanded foam layer 30 should be able to withstand temperatures in excess of 60 degrees Centigrade and preferably 177 degrees Centigrade for short periods without exhibiting substantial heat-induced distortion or degradation. In more detail, in a particularly preferred embodiment, the layer 30 of thermally expanded structural foam includes a synthetic resin, microspheres, a blowing agent and a filler. A synthetic resin comprises from about 40 percent to about 90 percent by weight, preferably from about 50 percent to about 80 percent by weight, and more preferably from about 50 percent to about 70 percent by weight of foam 30 'of thermally expanded structural foam. In the present invention, the foam layer 30 has a cellular structure which provides a low density, high strength material, which, in the reinforced structural part 20, provides a strong structure, however of light weight. Microspheres that are compatible with the present invention include "hollow" spheres of reinforcement or microbubbles that can be formed from either glass or plastic. The plastic microspheres can be thermosettable or thermoplastic and be expanded or non-expanded. In one embodiment, unexpanded microspheres are used which then expand to form the layer 30 of thermally expanded structural foam. Preferred microspheres are from about 10 to about 400 and preferably from about 20 to about 100 microns in diameter. The microspheres may also comprise a larger, lighter-weight material, such as macrospheres of more than 400 microns in diameter. Glass microspheres are particularly preferred. Also, a blowing agent which may be a chemical blowing agent or physical blowing agent is preferably included. The microsphere component constitutes from about 5 percent to about 50 percent by weight, preferably from about 10 percent to about 40 percent by weight, and more preferably from about 15 percent to about 40 percent by weight. hundred percent by weight of the material that forms the layer 30 'of thermally expandable structural foam. The blowing agent constitutes from about 1 percent to about 15 percent by weight, preferably from about 1 percent to about 10 percent by weight, and more 1 c preferably from about 1 percent to about 5 percent by weight of layer 30 'of thermally expandable structural resin. Suitable fillers include glass or plastic microspheres, silica fume, calcium carbonate, ground glass fiber and A strand of cut glass. Glass microspheres are particularly preferred. Other materials may be appropriate. A filler comprises from about 1 percent to about 40 percent by weight, preferably about 1 percent by weight. ?) - about 30 weight percent and more preferably about 1 percent to about 20 weight percent of the layer 30 'of thermally expandable structural resin. Preferred synthetic resins for use in the present invention include thermosetting agents such as epoxy resins, vinyl ester resins, thermosetting polyether resins, and urethane resins. It is not intended that the scope of the present invention be limited by the molecular weight of the resin. When the resin component of the liquid filler material is a thermobleable resin, various accelerators, such as "EMI-24" (imidazole accelerator) and "DMP-30", and curing agents, preferably organic peroxides such as peroxide "MEK" and "Percadox" can also be included to improve the curing regime. A functional amount of accelerator is typically from about 0.1 percent to about 4.0 percent resin by weight with a corresponding reduction in one of the other components. The effective amounts of processing aids, stabilizers, colorants, UV absorbers and the like can also be included in the layer. Thermoplastics may also be appropriate. The following tables show preferred formulations for layer 30 'of thermally expandable structural foam. It has been found that these formulations provide a thermally expanded structural foam layer that is fully expanded and cured at about 160 ° C and provides a reinforced structural part having excellent structural properties. All percentages in the present disclosure are percent by weight unless specifically designated otherwise.

Formula 1 Ingredient In Weight Polyester resin ("ARS-137-69") 80.9"Percadox 16N" 1.1"3M C15" 18 Formula II Ingredient In Weight EPON 828 54.5 Haloxi 62 7.5 Der 732 6.1 Expancel 551DU 2.0 SG Micros 8.8 3M K20 17.7 DI-CY 3.4 Formula III Weight Ingredient Polyester resin ("ARISTECH 13031") 48.8"Percadox 16N" 0.7"SG Micros" (PA IND) 50.5

Claims (23)

1. - A reinforced structural member, comprising: a structural member defining an open channel; a layer of structural foam disposed in the channel and bound to the structural member, the structural foam layer having a geometry conforming to the 10 channel configuration; and an insert disposed on the foam layer, the insert having a geometry conforming to the configuration of the foam layer.

2. The reinforced structural member according to claim 1, wherein the member 15 structural is a beam.

3, - The reinforced structural member according to claim 1, wherein the structural foam includes glass microspheres.

4. The reinforced structural member according to claim 1, wherein the insert is a thin sheet having a thickness of about 0.05 to about 0.38 millimeters.

5. The reinforced structural member of according to claim 1, wherein the cured structural foam layer has a thickness of about 3.18 millimeters to about 12.7 millimeters.

6. The reinforced structural member according to claim 1, wherein the structural member is a metal stamping.

7. The reinforced structural member according to claim 1, wherein two of the structural members are joined together in the configuration of a tube.

8. The reinforced structural member according to claim 1, wherein the structural foam contains a blowing agent.

9. A method for reinforcing a structural member, comprising the steps of: contacting a flat layer of thermally expandable structural resin with a flat thin sheet to form a two-layer laminated preform; placing the laminated preform of two layers in contact with a part defining a structural channel so that the laminated preform of two layers covers the channel; forming the two-layer preform to the channel configuration so that the thermally expandable resin portion of the resin portion of the two-layer preform is in contact with the part defining the structural channel; and heating the two-layer laminated preform and the part defining the structural channel to expand the thermally expandable resin.

10. The method for reinforcing a structural member according to claim 9, further including the step of trimming any excess of the laminated preform of two layers before the heating step,

11. The method for reinforcing a structural member of according to claim 9, wherein the structural member is a beam.

12. The method for reinforcing a structural member according to claim 9, wherein the two-layer preform is formed by extruding a layer of the thermally expandable structural resin onto a release coating and then placing the thin sheet flat on the layer. of thermally expandable structural resin.

13. The method for reinforcing a structural member according to claim 9, wherein the thin sheet has a thickness of about 0.05 to about 0.38 millimeters.

14. The method for reinforcing a structural member according to claim 9, wherein the thermally expandable resin has a thickness of about 3.18 millimeters to about 6.35 millimeters before the heating step and a thickness of about 3.18 millimeters to about 12.7 mm after the heating step.

15. The method for reinforcing a structural member according to claim 9, wherein the structural member is a metal stamp.

16. The method for reinforcing a structural member according to claim 9, wherein two of the structural members are formed and then joined together in the configuration of a tube.

17. The method for reinforcing a structural member according to claim 9, where the structural foam contains microspheres.

18. The method for reinforcing a structural member according to claim 9, wherein the thin sheet is steel or aluminum.

19. The method for reinforcing a structural member according to claim 9, wherein the thin sheet is resin filled with glass.

20. A method for reinforcing a part, comprising the steps of: extruding a layer of thermally expandable resin as a layer on the surface a release coating, placing a thin sheet on the resin to form a laminate; die cutting the laminate to a predetermined configuration; placing the laminate on a part that has a non-planar geometry; conform the laminate to the geometry of the non-planar part; and thermally expanding and bonding the resin to the non-planar part.

21. The reinforced structural member according to claim 1, wherein a closure plate is provided on the structural member that closes the channel.

22. The reinforced structural member according to claim 1, wherein the thin sheet is perforated.

23. The method for reinforcing a structure according to claim 9, further comprising the step of piercing the thin sheet.