Abstract: A continuous process for making a core for a composite panel comprising cutting spaced apart tongues in columns from a metallic sheet, the tongues being foldable about base lines in the columns each base line being separated from the next tongue in the column by a web; folding the sheet to form a castellated structure having continuous side walls constituted by the spaces between adjacent columns of tongues with the webs of adjoining rows respectively lying in spaced apart parallel planes and oppositely folding the tongues of adjoining columns to lie alongside adjacent side walls with their extremities remote from their base lines extending in an appropriate one of the planes. The invention also includes a composite panel comprising the core covered on each side with sheet material as well as a process for making such a panel.

Abstract: Electrodes used for spot welding of aluminium workpieces are improved by a combination of steps:(a) A roughened surface is formed on the electrode tip, preferably to an average roughness depth of 12 to 30 microns.(b) also an artificial protective coating, e.g. a chromate-based coating or an anodic oxide film, is applied to the workpieces.(c) Optionally the nugget diameter in the initial welding set-up is arranged to be not more than 15% greater than the minimum acceptable.Features (a) and (b) act synergistically to increase the service life of the electrodes, typically to more than 2000 welds.