US3008551A - Structural panel construction - Google Patents

Description

Nov. 14, 1961 Filed May 29, 1958 N. E- COLE STRUCTURAL PANEL CONSTRUCTION 3 Sheets-Sheet 1 INVENTOR. NELSON E. COLE ATTORNEY Nov. 14, 1961 N. E. COLE STRUCTURAL PANEL CONSTRUCTION 5 Sheets-Sheet 2 Filed May 29, 1958 FIG. 3

INVENTOR. NELSON E. COLE FIG. 4

ATTORNEY Nov. 14, 1961 N. E. COLE STRUCTURAL PANEL CONSTRUCTION 3 Sheets-Sheet 3 Filed May 29, 1958 FIG. 6

FIG.5

INVENTOR NELSON E. COLE ATTOR NEY .terns in all directions within the panel structure.

United States This invention relates to reinforced structural sheets or panels and is particularly directed to an integral core "sandwich type panel structure.

A primary object of the invention is to provide a structural panel having a surface sheet and a core sheet member provided with a plurality of indentures split, formed and drawn out of the plane of the sheet, each indenture producing an opening of preselected geometrical configuration having straight sides and arcuate sides, the arcuate sides being drawn downwardly and inwardly to provide curved flanges and the straight sides being formed with angularly disposed web portions extending to the surface sheet and having attaching ears parallel with said surface sheet and attached thereto. The web portions are further provided with rearwardly extending wing portions also'extendi'ng to the surface sheet and being provided with attaching ears parallel to the surface sheet.

A further object of the invention is to monolithically fabricate a core panel that is partly split and formed and partly drawn in such a manner as to permit a much greater panel depth than is possible to provide with rigidized cores which are dependent upon the maximum limits of the drawing ability of the metal for their maximum panel depths. By means of the present invention the indentures are arranged to provide the least material possible near the neutral axis and the most material near the extreme outer surfaces consistent with all structural requirements for resisting tension, compression, shearing and buckling conditions without the use of supplemental core or filler material usually required in conventional types of built up sandwich panels.

Further objects and advantages of the invention will become apparent from a study of the following description when taken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of a section of a structural panel made in accordance with the present invention;

FIG. 2 is a sectional detail view taken substantially on a line 2-2 of FIG. 1;

FIG. 3 is an enlarged view of one of the indentures shown in FIG. 1;

FIG. 4 is a sectional detail view taken substantially on a -line 44 of FIG. 3;

FIG. 5 is a plan view of a section of another form of panel; and

FIG. 6 is a sectional detail view taken substantially on a line 66 of FIG. 5.

Structural panels of sandwich type have manyuses. They are frequently used in aircraft frame structures, truck and trailer bodies, ships, unitizedbuilding assemblies, container vessels, and in many other applications. They are found to be most desirable where a minimum thicknes dimension and the ultimate in high strength to weight ratio is required. They are also desirable where changing patterns and amounts of load positioning. These conditions set up an infinite number of stress pat- Various materials may be used in forming and assembling these panels, but metal, particularly the high strength metals, are most adaptable to this invention because a very high percentage of the total volume of material used is actively put, to work as stress carrying material. It is well known that material close to the neutral axis of a section carries but little tension or compression stress,

atent G a panel must resist dynamic load stresses in constantly Patented Nov. 14, 1961 ice while material near the extreme outer surface of the section picks up and carries the maximum of these stresses.

neutral axis and more material is provided near the extreme outer surfaces than in similar known structures.

Referring to FIGS. 1 to 4 of the drawings, it will be noted that the panel structure is fabricated from two comparatively thin metal sheets one of which may be a top or bottom sheet 10 and the other a core sheet 12. The core sheet 12 issplit, formed and drawn at regular or uniform intervals to provide a plurality of indentures indicated generally at 14. Each indenture 14 is formed out of the plane of sheet 12 and is generally equilateral-1y triangular in plan view around the edges where the indenture is depressed downwardly from the surface of the panel. The outline of this plan is partially defined in each indenture by the three equal straight lines 15 of a length of approximately one sixth of L which equals the length of each leg of the outside boundary of the equilateral triangle within which the indenture perimeter is confined. This indenture is also partially defined by the three equal and outwardly curved lines 16 all of which have a true radius approximately equal to one sixth of L which is one of the legs of the outside boundary of the above described equilateral triangle. Lines 15 and 16 completely define the plan view perimeter of each indenture. The plane surfaces 17 which occur alternately between the indenture areas are also defined generally by equilateral triangles with apexes which lie on common points with the apexes of the indenture bounding equilateral triangles.

Extending downwardly and inwardly from defining lines 16 to defining lines 19 (see FIG. 3) are buckling reinforcing flanges 29 which keep the panel surface adjacent to line 16 from buckling when this portion of the panel is under stress caused by compression loading conditions. This flange should extend downwardly at least a quarter or more of the total depth through the panel structure.

Extending downwardly and inwardly from defining line 15 to defining line 21 is the web core element 23 which becomes an extension between the buckling reinforcing flanges 20 and is generally bounded by lines 15, 21 and 24. This element 23 extends the action of buckling reinforcing flange 20 around the entire boundary of the ear 26 which will lie flush on the opposite panel sheet 10. 7

Line 21 and the outer surface of car 26 as defined by lines 21, 30, 31 and 33 all lie flush on the inner surface of the opposite panel 10.

To prevent buckling in the web core element 23 adjacent to line 21 a wing or diaphragm element 35 is added to either side of web core element 23 at line 24. This side wing element 35 is generally triangular in outline as defined by lines 24, 36 and 38. Attaching ear 40, as outlined by lines 36, 41, 42 and 43, joins wing 35 along line 36. The entire outer surface of attaching ear 40 is to lie flush and be coplanar with the inner surface of the 0pposite panel 10. I

Assembly of the two panels may be accomplished by fasteners through the inner ring of holes '45 and the outer ring of holes 46. Assembly of the two panels may also be accomplished by spot welding in which case the holes would be omitted and the welding spots placed in the general vicinity of hole positions 45 and 46. The assembly can also be accomplished by arc welding around the edges of the cars. In the event that other materials than metals are used such as plastics or fibrous materials, this assembly may be accomplished by high strength'adhesives or by the fastener method described above.

It is important to note that the positions of the holes 46 lie in a group which is spread out approximately as wide as the boundary defined by lines 15 and 16 on the opposite panel. This swing back in hole positions in order to give a wider spread to the outer ring of holes 46 is accomplished by the proper positioning of lines 21 and 36 in the flat blank on the surface of the panel sheet before the split indentures are formed into place.

All of the material used to obtain the web core structure and all of the other reinforcing elements necessary to complete this panel structure are formed monolithically from the surface of the outer panel sheet. None of the elements shown, except the fasteners in the holes when they are used, are made from separate material nor are they reattached in any way.

Referring again to FIG. 1 of the drawings, it will be noted that when it is desirable that the indentures be covered for certain installations, a second top or bottom panel 49 may be suitably secured to the indentured surface of the core panel 12.

Referring now to FIGS. and 6, a second form of the invention has been illustrated in which a dual core structure is provided. Instead of the single core sheet 12 of FIGS. 1 to 4, two core sheets 51 and 52 are provided and indentured so that the indentures 53 and 54 are interposed between the indentures of the other sheet. The indentures take the same form and are provided in the manner previously described, the difference being in the staggered arrangement of the indentures. It will be clear, however, that by means of this structure, additional strength and load carrying capacity is provided. It is to be noted also the indentures are partly split and formed and partly drawn from the plane of the core sheets and that each indenture extends from one core sheet to the other.

A panel structure made in accordance with this form of the invention may consist only of the double core panel or top and bottom sheets may be added to completely enclose the core sheets.

What is claimed is:

1. In a structural panel the combination comprising, a plain panel, a core panel provided with a plurality of indentures extending in a common direction from the plane of the panel, the indentures in said core panel forming a plurality of sides, some of said sides being provided with a buckling resisting web extending from the plane of said core panel to said plain panel, said buckling resisting web being provided with side wings extending from said web to said plain panel for preventing buckling of said Web.

2. In a structural panel the combination comprising, a plain panel, a core panel provided with a plurality of indentures extending in a common direction from the plane of the panel, the indentures in said core panel forming a plurality of straight sides and an equal number of arcuate sides, each straight side having an inclined web extending from the plane of said core panel to'said plain panel, and each arcuate side having an inclined flange extending from the plane of said core panel whereby said flanges and said webs resists buckling of the structural panel.

3. In a structural panel the combination comprising,

a plain panel, a core panel provided with a plurality of indentures extending in a common direction from the plane of the panel, the indentures in said core panel forming a plurality of straight sides and an equal number of arcuate sides, each straight side having an inclined web extending from the plane of said core panel to said plain panel, each arcuate side having an inclined flange extending from the plane of said core panel, and means at the end of each of said inclined webs connecting said core panel to said plain panel.

4. In a structural panel the combination comprising, a surface panel and a core panel of relatively thin sheet material, said core panel having a plurality of indentures extending in one direction from the plane of the panel, the indentures forming generally triangular openings having three straight sides and three arcuate sides, each straight side having an angularly disposed web portion extending to said surface panel, and each arcuate side having an angularly disposed arcuate flange portion extending toward said surface panel whereby said web portions andsaid flange portions resist buckling around the entire periphery of the indenture.

5. In a structural panel the combination comprising, a plain panel, a core panel provided with a plurality of indentures extending in a common direction from the plane of the panel, the indentures in said core panel forming a plurality of straight sides and an equal number of arcuate sides, at least one of said arcuatesides having a buckling resisting flange extending from the plane of said core panel and at least one of said straight sides having a buckling resisting web extending from the plane of said core panel to said plain panel, said buckling resisting Web being provided with side Wings extending from said web to said plain panel for preventing buckling of said web.

6. In a structural panel the combination comprising, a surface panel and a core panel of relatively thin sheet material, said core panel having a plurality of indentures extending in one direction from the plane of the panel, the indentures forming generally triangular openings having three straight sides and three arcuate sides, each arcuate side having an angularly disposed arcuate flange portion extending toward said surface panel and each straight side having an angularly disposed web portion extending to said surface panel, said web portions having side wings extending to said surface panel for resist ing buckling thereof.

7. In a structural panel the combination comprising, a plain back panel, a core panel provided with a plurality of indentures extending in a common direction from the plane of the panel, the indentures in said core panel forming a plurality of straight sides and an equal number of arcuate sides, each straight side having an inclined web extending from the plane of said core panel to said back panel, each inclined web being provided with a pair of side wings extending from said web to said back panel, said web and each side wing having attaching ears parallel to and in immediate contact with said back panel, and each arcuate side having an inclined flange extending from the plane of said core panel, said flange and said web resisting buckling of the structural panel.

8. In a structural panel the combination comprising, a surface panel and a'core panel of relatively thin sheet material, said core panel having a plurality of indentures extending in one direction from the plane of the panel, the indentures forming generally triangular openings having three straight sides and three arcuate sides, each straight side having an angularly disposed Web portion extending to said surface panel, each web having side wings extending to said surface panel, the web and side wings further being provided with ears parallel to and in contact with said surface panel, and each arcuate side having an angularly disposed arcuate flange portion extending toward said surface panel whereby said web portions and-said flange portions resist buckling around the entire periphery of the indenture.

9. In a panel structure the combination comprising, a pair of opposed'panels of relatively thin sheet material, each of said panels having a plurality of indentures extending toward the plane of the opposite panel, the indentures in said panels forming a plurality of straight sides and an equal number of arcuate sides, eacharcuate side having an inclined flange extending from the plane of said panels, each straight side having an inclined web extending toward the opposite panel, the webs of the indentures of each panel bearing against the opposite panel and being fastened thereto.

5 10. A panel structure according to claim 9 in which a pair of surface sheets of relatively thin material extend over the exterior sides of the core structure, and means securing said surface sheets to the core structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,576,559 Swift Mar. 16, 1926 Carns Dec. 9, 1930 Kemmer Sept. 28, 1943 Watter Mar. 12, 1946 Scurlock Sept. 6, 1949 Ackerlind Jan. 25, 1955 FOREIGN PATENTS Great Britain Sept. 15, 1921 France Oct. 11, 1945

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