CN1422209A - Multi-dimensional tailored laminate - Google Patents

Abstract

A fibrous core material (24) is disposed between a portion of two opposed metal skins (22) and bonded thereto to form a structural laminate (20) having comparable strength to steel sheets of greater weight and having a profile which varies compositionally in different regions of the laminate.

Description

Multidimensional Custom Laminates

technical field

This invention relates to laminate structural panels, and more particularly to lightweight laminates having desirable structural properties.

Background technique

Vehicle bodies typically include metal panels selected for properties such as strength and stiffness, formability, corrosion resistance, weldability, impact resistance, etc., based on the intended location of the panels on the vehicle. In cases where the application requires multiple properties, the selected metal plate may be of a specialized alloy, conventionally heat-treated and may be joined to other metals, for example by welding or with fasteners, to provide required characteristics. Steel sheets are more widely used on motor vehicles than any other material to form panels or other structures. Those of ordinary skill in the art will appreciate that desired structural properties, such as stiffness, vary according to the particular application. When higher stiffness values are required for the plate, the thickness is usually increased. But increasing the plate thickness makes the plate or part not only heavier but also more expensive. In U.S. Patent 5,985,457, entitled STRUCTURAL PANEL WITH KRAFT PAPER CORE BETWEEN METAL SKINS ("Structural panels with kraft paper core between metal skins"), which is hereby incorporated by reference in its entirety, the inventors of this invention A structural panel is disclosed that is a laminate structure having metal skins separated by and bonded to an intervening fiber core. The laminates described here have a very high specific stiffness and are relatively light in weight. But as described here, the arrangement of the fiber core is continuous with the metal skin. In some applications, the presence of the core can interfere with forming fasteners, welds or clearance openings and methods thereof. The requirement was to provide a lightweight structural laminate that could be tailored to suit specific fastening, welding and clearance opening operations. The present invention meets these and other desired objectives.

Summary of the invention

In one aspect, there is provided a structural laminate having a compositionally varying profile along the laminate body. The laminate has first and second skins formed from sheet metal. The fiber paper core is arranged between the sheet metal skins and bonded to these skins. In one aspect, the fibrous paper core is impregnated with an adhesive resin which bonds the fibrous paper core directly to the skin. In another aspect, an adhesive layer is provided between the core material and the skin to bond the core to the skin. Along the edges of these laminates, there is a gap or space between the two metal skins; ie, the paper core does not extend completely over the edge of the steel skin in at least some places. The cross-section of the core is non-uniform, it has a profile that is "tailored" for the required use. For example, the non-uniform profile can allow fasteners or fasteners to pass through the laminate or facilitate the placement of apertures. The resulting tailor-made laminate structure is extremely lightweight compared to a single sheet of metal of similar thickness and strength.

In yet another aspect of the invention, a method of forming a tailored structural laminate is provided. The method comprises the steps of placing a fibrous core of paper material between two metal skins, the fibrous core covering an area less than the entire area of the adjacent skins, ie along the edges of the laminate as described in the preceding paragraphs at A gap or space exists between two metal skins. Pressure is applied to the purpose-built laminate to promote the bond between the core and the metal skin. In one aspect, a number of laminates are prepared which are then stacked one on top of the other and then pressed to bond the layers simultaneously.

Brief description of the drawings

Figure 1 is a cross-sectional view of a laminate of the present invention;

Figure 2 is a plan view of the laminate of Figure 1;

Figure 3 is a laminate of the present invention in another configuration;

Figure 4 is a view of a die cutter forming a laminate of the present invention;

Figure 5 shows the door panel.

Detailed Description of the Preferred Embodiment

Referring now to Figure 1 of these figures, there is shown a non-uniform or tailored laminate 20 having a metal skin 22 and an intermediate region 23 in which a fiber core 24 can be seen. As can be seen most clearly in FIG. 2 , in this embodiment the fiber core 24 is recessed from each edge 25 of the panel 20 . Thus, there is an unfilled gap or space 27 between partially opposing metal skins 22 . In this embodiment, the space is in the shape of a channel extending completely around the perimeter of the plate 20 . In plan, the area of space 27 can vary widely, but is generally at least 1 square inch. It can be seen that the composition of the plate 20 varies along the axis 21 as indicated by arrows A and B . In other words, along the path of arrow A, the board 20 is metal-spacer-metal; at arrow B, the board 20 is metal-paper-metal. It will be appreciated that the placement of gaps 27 in panel 20 will vary depending on the intended use of the laminate or component; gaps 27 may occur at one or more edges of panel 20 and may be located solely in interior regions of panel 20 (ie as a cut hole in the center of core 24 or may have an irregular shape to suit a particular application). The core 24 may be discontinuous, eg, formed into individual strips or the like.

One material for forming the fiber core 24 is fully described in the aforementioned US Patent No. 5,985,457, which is hereby incorporated by reference.

The respective layers shown in FIG. 1 will now be described. As stated, metal skin 22 is generally flat, having a flat surface on each side. Metals that may be used to form skin 22 are preferably selected from steel, aluminum, copper alloys, and combinations thereof. Most preferred are metals that provide sufficient structural and (where necessary) corrosion resistance at the lowest cost in the particular environment in which the panel 20 will be used.

In a preferred construction, skin 22 is most preferably formed of galvanized steel, and each layer 22 has a thickness of about 0.005 inches or greater, preferably between about 0.005 inches and about 0.030 inches, and more preferably from about 0.005 inches to about 0.012 inches. In one embodiment, the intermediate fibrous layer 24 preferably has a thickness of about 0.01 inches and greater, and preferably from about 0.01 inches to about 0.05 inches. Accordingly, the overall thickness of the panel 20 in one embodiment is generally between about 0.020 inches and about 0.110 inches. A plate having the dimensions stated in the description of FIG. 1 of the accompanying drawings and having the preferred layer thicknesses just described generally weighs about 40-70% of the weight of a single steel plate of similar dimensions and stiffness.

As known to those of ordinary skill in the art, steel comes in many grades according to the carbon content and other elements it contains. Broadly speaking, these grades are low carbon steel plate, medium carbon steel plate and high carbon steel plate. Preferred for use here are low carbon steels and low carbon microalloyed high strength steels (HSLA). The most preferred metal skins for use in the present invention are cold rolled steel, galvanized steel, tin plated steel and stainless steel. It may be preferred to utilize single-sided galvanized sheets, the outer surfaces of the skins 22 being galvanized surfaces and the inner surfaces of these skins being bare metal for bonding. In one embodiment, different zinc coatings are preferred, ie a thin zinc coating on the inner surface and a thicker zinc coating on the outer surface. In one embodiment, the galvanized steel sheet is cold rolled to final gauge with the zinc on the surface.

As stated, layer 24 is a fibrous material. As used herein, without limiting the scope of the invention, the term "fiber" refers to a substantially homogeneous collection of fibers (natural or synthetic) that can be formed into a board product. The most preferred fibrous material (thought to be unique among fibreboards) for use herein as layer 24 is paper. As known to those of ordinary skill in the art, paper is essentially a woven or felt-like structure of fibrous material formed into relatively thin sheets through the medium of a dilute suspension of pulp and water. It basically consists of cellulose fibers. Pulp for papermaking can be made by mechanically grinding wood or other plant material, by chemical treatment (sulfites, kraft or soda) and also by chemical treatment of cotton, flax and hemp rags, waste, straw, etc.

In the present invention, the kraft pulping method is most preferred. It is well known to those of ordinary skill in the art that kraft pulping (this process is also known as kraft pulping or alkaline pulping) forms paper of higher physical strength and bulk. A preferred paper is saturated kraft paper sold by Westvaco of Charleston, S.C.

Also, as is well known in the art, the average alignment of cellulose fibers in paper is controlled to some extent by the "machine direction" during papermaking. It is believed that the orientation of the paper in the laminate is a factor in the present invention that affects the stiffness and strength of the laminate. Most preferred are laminates wherein the machine direction of the kraft paper is a line parallel to the central axis of bending of the laminate. Another class of fiber materials used herein is plastic fiber paper.

In a preferred embodiment of the invention, layer 24 is provided as a resin-impregnated fiber material. Where layer 24 is kraft paper, the paper is impregnated with resin which is then dried. Most preferred for use herein is phenolic resin impregnated kraft paper. Polyester resin impregnation is also suitable for some applications. Methods of impregnating paper with resins are well known to those of ordinary skill in the art. A substantially preferred resin-impregnated paper is formed by soaking a base paper web in a liquid phenolic resin. Typically, multiple layers of saturated impregnated paper are laminated together to form a single layer of semi-cured impregnated paper. In preferred embodiments of the invention, the resin constitutes from about 15% to about 45% by weight of the resin-impregnated layer 24, although in particular applications outside of the ranges set forth below for the resin-containing layer 24 may be suitable or desirable. .

In most cases, thermosetting resins are preferred for use in impregnating the paper layer 24, although thermoplastic resins may also be acceptable in some applications. In the case of thermoset resins, as stated, the resin is usually cured to a semi-molten stage before forming the board 20, but the impregnated paper can be fully impregnated prior to the laminate extrusion operation (controlled heat and pressure) described below. solidify. In the case of phenolic resins, the resin cures to a semi-molten stage prior to lamination. It is then fully cured when the skin 22 and impregnated paper core 24 are laminated together using an extruder. A number of standard additives such as curing agents, fillers, etc. may be included in the resin as appropriate for certain applications.

With or without resin impregnation of the fibrous layer 24 , it is preferred or required to use a layer of adhesive to bond the skin 22 to the fibrous core 24 . Many adhesives are available for use in specific applications, including epoxies, phenolic resins, isocyanates, polyurethanes, and hot melts. A particularly preferred binder for this purpose is a nitrile phenolic resin binder sold by Ashland Chemical as "Arofene 1166". The adhesive can be applied directly to layer 24 or to metal skin 22 or both by any method. Preferably, the steel is pretreated with a conversion coating such as complex oxides or zinc phosphate to improve bond integrity and corrosion resistance.

In another embodiment, as shown in FIG. 3 , an edge strip 28 of a different material than the fiber core 24 is provided. Various materials such as thermoplastics or adhesives can be used for the edge strip 28 . The strip 28 may constitute a single strip around the outer periphery of the panel 20 .

In another embodiment, the fibrous layer 24 may have a plurality of apertures (not shown) extending therethrough; these apertures may provide an adhesive as described more fully in the aforementioned reference, U.S. Patent No. 5,985,457. "bridge".

Referring now to Figure 4 of the drawings, there is shown one method of assembling skin 22 and layer 24 using extruder 30 . Extruder 30 includes platens 32 that are moved toward each other in a conventional manner using hydraulics or the like. As more fully described in co-pending U.S. Patent Application No. 09/373,298, entitled IMPROVEDSTRUCTURAL PANEL AND METHOD OF MANUFACTURE, filed August 12, 1999 Also, the platen 32 is preferably heatable so that heat and pressure can be applied to the laminates to cure the resin and bond the adhesive, the entire contents of which are incorporated herein by reference.

Several metal/fiber/metal laminates can be laminated together and extruded as described in immediately preceding US Patent Application No. 373,298. After the extruded laminate has cooled, it is removed from the extruder and the individual plates are separated.

In some applications, the laminates of the present invention can replace metal parts that are not flat plates. Thus, as described in immediately preceding US Patent Application No. 373,298, parts with non-planar geometries can benefit from the tailor-made laminate approach of the present invention.

Such a multidimensional laminate 20 may be used as a door panel 34 shown in FIG. 5 . The body of the door panel 34, indicated generally at 36, may comprise a rigid lightweight composite material comprising an outer metal skin of steel plate and an inner core of paper of the type described herein. The door panel 34 has front and rear edge portions indicated at 38, 40 which comprise an outer skin of steel and an inner core of high strength steel suitable for welding. Adjacent the opening 42 formed in the door panel 34 to make the window, there is an area designated by reference numeral 44 which will deform to create a recess associated with a door handle (not shown) and which comprises a steel sheet outer skin and an inner core made of thermoplastic material that can withstand strains of up to 30 percent.

While particular embodiments of the present invention have been shown and described herein, it will, of course, be understood that the invention is not limited thereto since numerous modifications may be made by those of ordinary skill in the art in light of this disclosure. It is therefore intended to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

Claims (21)

1. structure sheaf casting die, it comprises:

First and second epidermises of making by metallic plate;

Be arranged on the fiber core between the described metallic plate epidermis, described fiber core is bonded on the described metallic plate epidermis;

Wherein said fiber core is less than described epidermis, thereby forms the gap between the described metal epidermis of a part.

2. structure sheaf casting die as claimed in claim 1, the area that wherein said gap contacts with described epidermis is at least 1 square inch.

3. structure sheaf casting die as claimed in claim 1, wherein the thickness of every described epidermis is approximately 0.005 inch at least.

4. structure sheaf casting die as claimed in claim 1, wherein said gap forms a passage along the whole length at least one edge of described laminate.

5. structure sheaf casting die as claimed in claim 1, wherein said gap forms passage along the whole periphery of described laminate.

6. structure sheaf casting die as claimed in claim 1, wherein said gap are filled with the material different with forming described fiber core.

7. structure sheaf casting die as claimed in claim 1, wherein said metallic plate is selected from cold-rolled steel sheet, galvanized steel plain sheet, tin plate and corrosion resistant plate.

8. structure sheaf casting die as claimed in claim 1 wherein is bonded in described fiber core on the described metallic plate epidermis with adhesive.

9. structure sheaf casting die as claimed in claim 1, wherein the thickness of every described epidermis is about 0.005 inch to about 0.030 inch.

10. structure sheaf casting die as claimed in claim 1, wherein said fiber core is flooded with resin.

11. structure sheaf casting die as claimed in claim 1, the thickness of wherein said fiber core are approximately 0.01 inch at least.

12. structure sheaf casting die as claimed in claim 1, the thickness of wherein said fiber core are about 0.01 inch to about 0.05 inch.

13. structure sheaf casting die as claimed in claim 1, wherein said laminate are a kind of structural slabs.

14. structure sheaf casting die as claimed in claim 1 also comprises the adhesive phase that is arranged between described fiber core and the every epidermis.

15. structure sheaf casting die as claimed in claim 1, wherein said fiber core is a paper.

16. structure sheaf casting die as claimed in claim 1, wherein said metallic plate epidermis is a galvanized steel plain sheet, and this steel plate comes out with lip-deep zinc is cold rolling.

17. structure sheaf casting die as claimed in claim 1, wherein said fiber core are the fleeces that polylith bonds together mutually with adhesive.

18. structure sheaf casting die as claimed in claim 1, wherein said laminate is an on-plane surface.

19. structure sheaf casting die as claimed in claim 1, wherein said metal epidermis is a steel plate, and this steel plate has carried out preliminary treatment to improve bonding integrality and corrosion resistance with conversion coating.

20. structure sheaf casting die as claimed in claim 1, wherein said metal epidermis is formed by the low-carbon microalloy high-strength steel sheet.

21. structure sheaf casting die as claimed in claim 1, the described material in the wherein said gap is a kind of thermoplastic.

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