Lightweight constructional element of sandwich structure

DETAILED DESCRIPTION Accordingly, it is an object of my invention is to provide a lightweight constructional element in particular for solar collectors which is relatively economical, can be easily made and has high strength.
In keeping with these objects and with other which will become apparent hereinafter, the honeycomb structure between the cover plates is formed by essentially cylindrical cans whose axes are perpendicular to the cover plates.
This provides a lightweight structural member having basic elements which do not need to be specially made but which are obtained from waste products.
In can recycling as hitherto employed only the material value of the drink cans was of interest.
However, due to their precise shape these cans, which accrue in very large quantities, have a very much higher value than that of their raw material alone.
In particular, the substantially cylindrical sheet metal cans made by extrusion of aluminium, aluminium alloys or steel have in spite of their very small wall thickness of for example 0.
07 to 0.
1 mm a very high dimensional stability in the axial direction.
This dimensional stability is increased still further in used beverage cans by the lid which is connected at its periphery to the cylindrical wall of the can by folding.
Opening the can by pulling out an opening tab does not appreciably change this very high dimensional stability.
These drink cans, connected together in as close an arrangement as possible along their lines of contact, in particular adhered together, form the cells of the honeycomb structure which in known manner is also connected by adhesion to the cover plates.
In the production of these drink cans of standardised size and form from aluminium or steel a certain percentage of rejects always occurs and hitherto these were melted down again.
These reject cans, due to their shape, can be used just like already used cans as honeycomb cells for this lightweight constructional element.
Since these reject cans are not provided with a lid it is possible to connect them together also by spot welding or riveting