Stock material or miscellaneous articles – Structurally defined web or sheet – Fold at edge
Patent
1995-07-17
1997-07-29
Ryan, Patrick
Stock material or miscellaneous articles
Structurally defined web or sheet
Fold at edge
428124, 428126, 428128, 428194, 428215, 4283135, 4283142, 4283148, 52631, 527831, B32B 900
Patent
active
056520395
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present relates to composite panels and more particularly to sandwich panels.
BACKGROUND OF THE INVENTION
The invention has been developed primarily for use in relation to display stands, display shelving and cabinets, shop fittings, interior architecture and design, interior facades, partitioning systems, and the like. It will be appreciated, however, that the invention is not limited to these particular fields of use.
Sandwich panels are well known and have found widespread use as structural materials in aeronautical and numerous other applications. The panels generally comprise a relatively thick core formed from a low density material such as foam, sandwiched between relatively thin but stronger outer skins. As is well known to those skilled in the art, such constructions have been found to produce excellent stiffness to weight characteristics.
Because of these properties, sandwich panels are generally designed for structural applications and as such, are normally intended to be as light as possible, and as stiff as possible to resist bending and buckling. In bending, most known sandwich panels tend to deform entirely elastically, or to exhibit only a relatively small amount of plastic deformation or yield before the ultimate strength of the composite material is reached, at which point either the core or one or both of the skins rupture and fail catastrophically. Thus, the panels tend to break rather than bend, when loaded beyond their limits of strength.
For this reason, most known sandwich panels have not been able to be permanently bent or cold formed into desired shapes and consequently, the manufacture of non-planar structures has required discrete panel sections to be butt-jointed, glued, or otherwise mechanically fastened to form the desired configuration. These processes are inefficient, labor intensive, time consuming and expensive. Even more importantly, however, the resultant loss of structural integrity at the joints makes largely redundant the potential strength characteristics which the sandwich panel might otherwise have been able to provide.
Some metal skinned panels have not been subject to these problems to the same extent. However, these suffer from other disadvantages in terms of excessive cost and weight. They are also subject to a tendency for the metal skins to yield under minimal surface pressure to produce visually and structurally undesirable surface distortion.
It is therefore an object of the present invention to provide a composite panel construction which overcomes or ameliorates at least some of these disadvantages of the prior art.
DISCLOSURE OF THE INVENTION
Accordingly, the invention consists in a foldable composite panel comprising an inner layer formed from a first material having a relatively high plasticity at least in compression, bonded to at least one adjacent outer layer formed from a second material having a relatively low plasticity, such that the composite panel can be permanently folded without failure at ambient temperature through an angle substantially greater than that through which the outer layer alone could be folded without failure under comparable conditions.
Without limiting the invention to any theoretical analysis, it is believed that the unexpected ability of the panel to be folded arises because on cold bending, the inner layer increases the natural bending radius and hence permits a greater angle of plastic deflection in the outer layer than would occur without the inner layer, whilst the outer layer prevents or at least delays the onset of tensile failure in the inner layer.
Preferably, the composite panel can also be permanently folded without failure through an angle substantially greater than that through which a panel of comparable thickness but composed entirely of the second material could be folded without failure under the same conditions.
Preferably, the respective plasticities of the first material and the second material permit permanent cold bending of the panel through an angle of at least 90.d
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patent: 3909995 (1975-10-01), Bainter et al.
patent: 3969868 (1976-07-01), Bainter et al.
patent: 4078959 (1978-03-01), Palfey et al.
patent: 4671985 (1987-06-01), Rodrigues et al.
patent: 5212003 (1993-05-01), Homer
Fuller Robert S.
Tremain Stephen R.
Bahta Abraham
Judson David H.
Ryan Patrick
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