Method for joule heating diffusion bonded honeycomb core

A method of manufacturing a honeycomb core, the method comprising the steps of:

• printing a pattern of spaced apart strips of a stop-off material to surfaces of a plurality of sheets of metal at locations where diffusion bonding is not desired, wherein the printing step includes the sub-steps of:
• printing a first strip having at least one of a first width, spacing, shape, and size;
• and
• printing a second strip having at least one of a second width, spacing, shape, and size different than the first width, spacing, shape, or size of the first strip so that the pattern of strips includes at least two different widths, spacings, shapes, or sizes;
• stacking the sheets of metal together in a sequence for forming the honeycomb core;
• pressing the sheets of metal together between two press plates comprising conductive material;
• applying electric current to the conductive material of the press plates, such that current flows through a thickness of the sheets of metal and such that the sheets of metal are diffusion bonded to each other at locations absent the stop-off material;
• and
• expanding the sheets of metal into the honeycomb core after the locations absent the stop-off material are diffusion bonded with adjacent ones of the sheets of metal so that the at least two different widths, spacings, shapes, or sizes effects at least one of selective contouring of the honeycomb core and at least two different densities of honeycomb core cells.