Strong, light-weight, fire-resistant construction panels with sandwich structure, useful e.g. in facades, consist of external sheets of aluminum and central core of closed-cell aluminum foam

摘要

In a construction panel (A) with a sandwich structure, consisting of two external sheets of aluminum (Al) and a thicker central core, the core is also of aluminum (specifically Al foam) with a uniform, closed-cell morphology and a high level of porosity, providing a homogeneous, rigid structure. Independent claims are included for: (1) the production of (A), from commercially available external sheets of thickness 0.5-0.6 mm, commercially available Al powder containing alloying elements and titanium hydride (TiH2; as foaming agent), by: (a) densifying a homogeneous mixture of the thoroughly dried Al powder and TiH2 by isostatic pressing; (b) consolidating the mixture by thermal treatment to give a solid foam precursor plate; (c) adjusting the thickness of the precursor to 5-6 mm under heating then to 1.2-2 mm in the cold; (d) annealing at 250-300[deg]C; (e) supplying fragments of the precursor to an expansion furnace at 550-650[deg]C for 3-5 minutes, to cause release of hydrogen, expansion of the Al and formation of a foam; (e) rapidly cooling to below the m.pt. of the Al alloy, the overall foam formation time being 8-10 minutes; (f) placing the foamed panel between the exterior sheets at an elevated temperature below the m.pt. and passing the assembly through a calibration unit based on spacer rods corresponding to the nominal thickness of (A), using a controlled speed carrier trolley; and (g) cooling the panel to ambient temperature; (2) a method for the production of an Al sandwich panel (A'), comprising two external sheets of Al and a central core of Al foam, starting from Al-silicon alloy powder mixed with TiH2 powder, by densifying the mixture by pressing, thermally consolidating, adjusting the thickness of the obtained precursor in two stages (under heating then in the cold), expanding the precursor in a furnace and applying an external sheet to each side of the foam, where: the external sheets consist of two layers of different thicknesses and different alloys, fixed by a metallurgical bonding source; the m.pt. of the inner layer is lower than that of the outer layer by 38-63[deg]C; and the outer layers are fed from respective reels to the inlet of the foaming furnace, which also receives the inner layer and the precursor, so that foaming is caused and the foam is produced between the exterior layers within the furnace; and (3) a ventilated architectural facade, based on sandwich panels (A''), comprising two Al (or Al alloy) external sheets attached to an intermediate core, where the core is of foamed Al (or Al alloy) metallurgically bonded to the exterior layers, such that (A'') is completely metallic and the facade is non-combustible, does not produce toxic gases and is stable up to high temperatures.