Patent ID: 6848233

Claim:
A composite aluminium panel comprising two parallel plates and/or sheets secured to the peaks and troughs of a corrugated aluminium stiffener sheet by means of welding between the parallel plates and/or sheets, wherein the corrugated aluminium stiffener sheet is made from an aluminium alloy rolled sheet of composition (in weight percent): Mg 1.5-6.0 Mn 0.3-1.4 Zn 0.4-1.2 Fe up to 0.5 Si up to 0.5 Zr up to 0.30 optionally, at least one member of the group consisting of: Cr 0.05-0.30 Ti 0.01-0.20 V 0.05-0.25 Ag 0.05-0.40 Cu up to 0.40 other elements up to 0.05 each, 0.15 total Al balance and having in an H-condition or in an O-condition a ratio of PS/UTS in the range of 0.4 to 0.9 and having good roll formability, wherein the corrugated aluminium stiffener sheet has a thickness in the range of up to 3.0 mm.