Composite panel structure with frame reinforcement

Abstract

Composite panel structure including a pair of spaced, generally parallel-planar, fibre-reinforced, facial cladding sheets, and, disposed between and thermally bonded to these sheets, core structure including interleaved, generally side-by-side-parallel, elongate, low-density core elements, and elongate, higher-density, fibre-reinforced frame elements. Each frame element includes a pair of generally orthogonally intersecting, planar facial expanses, one of which is bonded to an adjacent core element, and the other of which is bonded to one of the cladding sheets.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to prior-filed, currently co-pending U.S. patent applications, Ser. Nos. 60/878,845, filed Jan. 5, 2007 for “Strength Panel With Trans-Planar, Fibre Rib Reinforcement, and its Manufacture”, and 60/879,460, filed Jan. 8, 2007, for “Panel Structure With Angular-Form Core Reinforcement”. The entire disclosure contents of these two Provisional patent applications are hereby incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to the thermoforming, and thereby the internal and external configuring, of composite-material structural components, such as panel-like components, from selected, intercooperative thermo-compatible materials. The term “thermo-compatible” as employed herein is intended to refer to thermoformable materials which can be heat-and-pressure bonded (thermo-pressure bonded, or thermobonded) to one another through a weld-like, rather than through an independent, adhesive-like, uniting and load-transmitting interface.

More particularly, the invention concerns a composite, thermoformed panel structure which features a pair of spaced, relatively thin, high-density, thermoformable cladding sheets that lie on opposite faces of a core structure which includes plural, internal, thermoformable frame elements that extend between, and are thermobonded to, the inside face of each of these cladding sheets.

Included in the core structure, in addition to the mentioned frame elements, are plural, low-density, lightweight core elements which are interleaved with the frame elements, and which may also be made of thermoformable materials.

The frame elements and core elements are generally elongate and slender in nature, and are disposed with their long axes substantially parallel to one another. The frame elements principally possess, each, one of three different forms. In one form, their cross-sectional configuration is generally I-shaped. In another, their cross-sectional configuration is somewhat Z-shaped, including a pair of spaced, substantially parallel portions which are bridged by a central, orthogonally disposed portion. In the third, this cross-sectional configuration is generally C-shaped, and also includes a pair of spaced, substantially parallel portions which are bridged by an orthogonally disposed central portion.

What exists, therefore, in this special structural arrangement is a composite, lightweight and very strong, thermoformed panel structure. The overall volumetric bulk of this structure is made up of relatively low-density, lightweight core elements, and its robust strength resides in the weld-like operative interconnections that exist between the pair of spaced, high-density, facial, thermoformable cladding sheets, and the plural, sheet-interconnecting, high-density, thermoformable frame elements which bridge between the cladding sheets, and lie interleaved with the low-density core elements.

In such a structure, no matter what the nature might be of the included, light-density core elements, the internal frame elements act as a structural load-handling unit with the two cladding sheets through material homogenizing weld-like bonded interfaces. Where the light-density core elements are made of compatible thermoformable material, load-handling weld-like bonds also exist between the core elements, cladding sheets, and the frame elements.

These and various other useful features of the present invention will become more fully apparent as the detailed description of the invention which follows below is read in conjunction with the drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified and fragmentary schematic isometric view generally of a portion of a thermoformed composite panel structure including core elements, frame elements, and spaced cladding sheets made in accordance with a preferred embodiment of the present invention.

FIGS. 2-5, inclusive, provide fragmentary, isometric illustrations of four (of many possible) different frame elements employable in a panel structure, as such is shown in FIG. 1. These several frame elements are pictured largely isolated from adjacent panel structure componentry, except for the presence in each figure of a small portion of a cladding sheet.

FIGS. 6 and 7 fragmentarily illustrate certain suitable steps that are implementable to create one form of a panel structure such as that generally pictured in FIG. 1—this particular panel-structure form being that which is fully illustrated in FIG. 8, employing a core-frame-element configuration such as that pictured in FIG. 2.

FIGS. 9 and 10 illustrate the making (FIG. 9) of another resulting form of panel structure (FIG. 10) which utilizes frame elements like that presented in FIG. 3.

FIG. 11 illustrates a modified version of the panel-structure form which is shown in FIG. 8. In this modified form of the invention, next-adjacent core frame elements are employed in a differential spacing manner, interleaved with lightweight core elements of suitable, differing, inter-frame-element (i.e., element-to-element) dimensions.

FIGS. 12-14, inclusive, illustrate the making, and the resulting structure, of a composite panel structure utilizing frame elements as pictured in FIG. 4.

FIGS. 15 and 16 show the making, and the resulting structure, of a composite panel structure employing frame elements like that shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Beginning with FIG. 1, shown generally at 20 is a thermoformed, composite panel structure, or panel, made in accordance with a preferred embodiment of the invention. Panel 20 includes a pair of spaced, parallel-planar, opposite-surface cladding sheets 22, 24 which are bridged by, and thermally bonded to, plural, spaced, parallel, elongate frame elements (shown schematically in dashed lines) including internal frame elements 26, 28, 30, and an end, or edge, frame element 32. Interleaved with next-adjacent frame elements are plural, elongate, spaced, parallel core elements 34 (between frame elements 26, 28), 36 (between frame elements 28, 30), and 38 (between frame elements 30, 32).

Most of the volume of panel structure 20 is made up by the core elements which are formed preferably of a low-density, lightweight, thermoformable material, such as PET (polyethylene terephthalate) foam material. The PET foam material has a density of about 6-lbs/ft³. These elements may also be made, if desired, of a low-density, lightweight, non-thermoformable material, such as balsa, which has a density of about 5-12-lbs/ft³.

The cladding sheets and frame elements are made preferably from a higher-density, thermoformable, sheet-like material, such as the fibre-reinforced polymer material known as Polystrand®, produced by Polystrand, Inc. in Montrose, Colo. This material is typically supplied in sheet-like form with a nominal sheet thickness of about 0.02-inches, and with a density of about 120-lbs/ft³.

Where, as is preferred, all of the materials employed in panel structure 20 are made of thermoformable materials, appropriate heat and pressure which is employed to shape and unify the panel components will produce weld-like bonds between the cladding sheets and the frame elements, between the cladding sheets and the core elements, and between the frame elements and the core elements. In all embodiments of the invention, the bonds which exist between the cladding sheets and the frame elements, all preferably made of high-density, fibre-reinforced materials, produce, in an overall lightweight panel structure, a structure of great strength owing to the coupling of the two cladding sheets through weld-like bonds developed with the interconnecting frame elements.

Within panel structure 20, all of the internal frame elements are preferably, though not necessarily, alike in configuration and equally spaced from one another. The end, or edge, frame elements, such as element 32, are somewhat different in configuration. More will be said about these frame-element configurations and considerations later.

The cladding sheets herein are formed of plural, such as two, layers of Polystrand® material to have a substantially uniform thickness of about 0.04-inches.

The spacing existing between the cladding sheets in panel structure 20 herein is about 0.5-inches. Different values for the dimension of this spacing may, of course, be chosen if desired. The uniform, center-line-to-center-line distance between next-adjacent frame elements, as seen in FIG. 1, is about 2-inches. Here, too, different uniform spacings between these elements may be chosen, if desired. Additionally, and as will be mentioned again shortly, non-uniform frame-element-to-frame-element center-line spacings may be employed, if desired.

Looking now at FIGS. 2-5, inclusive, as was mentioned earlier herein, the frame elements proposed by the present invention may preferably take on any one of three different forms. One of these three forms is illustrated herein in two different versions.

FIG. 2 shows an elongate, I-shaped (cross-sectional) frame element 40 having a long axis 40a. Element 40 is formed of two, twin-sheet, thermally bonded layers of Polystrand® material shown at 40b, 40c in FIG. 2 to have an overall layer thickness herein of about 0.04-inches. Element 40 additionally includes four, orthogonally intersecting facial expanses 40d, 40e, 40f, 40g, with expanse 40f being shown thermally bonded to cladding sheet 24. Facial expanse 40d is thermally bonded to the other cladding sheet (not shown), and expanses 40e, 40f are thermally bonded to adjacent PET core elements (also not shown). If the core elements chosen for use are made of a non-thermoformable material, such as balsa, bonding of a frame element to a core element takes the form of resin flow from the frame-element material into pores present in the non-thermoformable material.

FIG. 3 shows at 42 another version of an I-shaped, plural-layer, Polystrand® frame element having a long axis 42a, and possessing a thickness which is about twice that of previously discussed frame element 40. Accordingly, four layers in element 42 are pictured at 42b, 42c, 42d, 42e in FIG. 3. Element 42 also includes four orthogonally intersecting facial expanses 42f, 42g, 42h, 42i, with expanse 42h being shown thermally bonded to cladding sheet 24. Facial expanse 42f is thermally bonded to the other cladding sheet (not shown). PET core elements (also not pictured) are thermally bonded to facial expanses 42g, 42i.

FIG. 4 shows at 44 a generally Z-shaped (cross-sectional) frame element having a long axis 44a. Element 44, as shown herein, has, throughout, a thickness of about 0.04-inches, and includes a planar central portion 44b which joins with two, spaced, parallel-planar extremity portions 42c, 42d that have an orthogonal (axial-view) relationship with central portion 44b. Element 44 additionally includes four orthogonally intersecting facial expanses 44e, 44f, 44g, 44h, with facial expanse 44g being shown thermally bonded to cladding sheet 24. Facial expanse 44e is thermally bonded to the other cladding sheet (not illustrated), and facial expanses 44f, 44h are thermally bonded to PET core elements (not shown).

FIG. 5 illustrates, at 46, a generally C-shaped (cross-sectional) frame element having a long axis 46a. This element, like previously described element 44, has a thickness throughout of about 0.04-inches. It includes a planar central portion 46b which joins with two, spaced, parallel-planar extremity portions 46c, 46d that have an orthogonal relationship with central portion 46b. Element 46 further includes three orthogonally intersecting facial expanses 46e, 46f, 46g, with facial expanse 46g being shown thermally bonded to cladding sheet 24. Facial expanse 46e is thermally bonded to the other cladding sheet (not illustrated), and facial expanse 46f is thermally bonded to a PET core element (not pictured).

With regard to the several frame-element configurations presented in FIGS. 2-5, inclusive, elements 40, 42, 44 are structured to be internal frame elements in a panel structure, and element 46 is structured to be an end, or edge, frame element.

FIGS. 6-8, inclusive, in sequence, illustrate the making of a composite panel structure employing I-shaped internal frame elements, like element 40 seen in FIG. 2, with FIG. 8 specifically showing a fragment of such a completed, composite panel structure. These drawing figures are substantially self-explanatory.

In FIG. 6, a large, planar PET core slab 48 having a nominal plane 48a is clad, via thermo-pressure bonding, on its opposite faces with two-sheet layer assemblies 50, 52 of Polystrand® sheet material. Slab 48, after formation, is then cross-cut along lines, such as lines 54, 56, 58 to create separated units, such as units 60, 62, 64 as seen in FIG. 7. These units are then rotated orthogonally, as shown, to create, in a nominal plane 66a, a panel-structure core assembly (66 in FIG. 8), which is then clad, via thermo-pressure bonding, with two cladding sheets 68, 70 of Polystrand® material. The resulting panel structure is shown fragmentarily at 71. Dash-double-dot lines 72, 74 in FIG. 8 indicate the possibility of cladding opposite faces of a panel structure with a thicker cladding-sheet depth.

FIGS. 9 and 10 illustrate the making of a composite panel structure employing I-shaped internal frame elements like element 42 seen in FIG. 3. FIG. 10 shows a portion of a resulting completed panel structure.

The process involved here is substantially the same as the process described in relation to FIGS. 6-8, inclusive, except that, at the beginning of the process, opposite faces of a PET core slab 76 (having a nominal plane 76a) are thermally and compressively bonded with twin, two-sheet layers 78, 80 and 82, 84 of Polystrand® sheet material. Cross-cutting, cut-unit rotation, and then thermal and compressive consolidation are thereafter performed to create a finished panel structure shown fragmentarily at 86 in FIG. 10. Structure 86 possesses a nominal plane 86a.

FIG. 11 illustrates, at 88, a modified form of a panel structure like that pictured in FIGS. 6-8, inclusive, except that panel structure 88, possessing a nominal plane 88a, is defined with selectively differentiated internal centerline spacing existing between next-adjacent frame elements. These different spacings are labeled D₁, D₂, D₃ in FIG. 11.

FIGS. 12-14, inclusive, illustrate, very self-explanatorily, the making of a panel structure 90 which includes Z-shaped internal frame elements 92, 94 that are like frame element 44 seen in FIG. 4.

FIGS. 15 and 16 illustrate the making of a composite panel structure 94 which includes Z-shaped internal frame elements (such as element 96, which is like element 44 pictured in FIG. 4), and at least one C-shaped edge, or end, frame element 98 which is like frame element 46 shown in FIG. 5.

Thus, a novel and very useful composite panel structure, which is largely, if not completely, formed of thermoformable materials, has been illustrated and described. Utilizing thermoforming and compression techniques, the proposed panel is easy to fabricate in a wide range of sizes and configurations.

The low-density core elements in this panel structure furnish important dimensional stability to the structure, while at the same time, owing to the fact that, as seen in the drawing figures, they occupy most of the volume of a finished panel structure, contribute significantly to lightweightness of that structure.

Major load-handling capability of the proposed panel structure is furnished mainly by the presence of fibre-reinforced, opposite-face cladding sheets, and the additional presence and distribution of fibre-reinforced frame elements which span the space between the cladding sheets, and which are bonded to these sheets through thermoformed weld-like interfaces. These frame elements tie the cladding sheets into a cooperative load-handling system.

Those skilled in the relevant art may well recognize that variations and modifications of the proposed panel structure, not illustrated or described herein, may be made which will be clearly within the scope and spirit of this invention, and it is intended that all such variations and modifications will come within the scopes of the claims to this invention.

Claims

1. A generally planar, thermoformed, composite panel structure comprising

a pair of spaced, generally parallel-planar, fibre-reinforced, facial cladding sheets, and

disposed intermediate said cladding sheets, and thermally bonded thereto, core structure including plural, elongate, interleaved, generally side-by-side-parallel (a) core elements of one density, and (b) elongate fibre-reinforced frame elements of another density which is greater than the mentioned one density,

at least certain ones of said frame elements including at least one pair of generally orthogonally intersecting, generally planar facial expanses, one of which expanses is bonded to an adjacent core element, and the other of which expanses is thermally bonded to one of said cladding sheets.

2. The structure of claim 1, wherein each of said frame elements, as viewed along its long axis, possesses one of (a) a Z-shaped, (b) a C-shaped, and (c) an I-shaped, cross section.