Abstract: A three-dimensional composite structural panel composed of a number of parallel trusses mutually spaced by interposed insulative elements and interconnected by cross wires, is fabricated by positioning a cross wire transversely of the longitudinal runner wires of trusses after they are stacked in alternation with the insulative elements, and then welding the cross wire to the runner wires at each point of contact. Rows of electrodes, one for each side of the lattice, are mounted to simultaneously resistance weld a single cross wire at each side of the lattice to all of the trusses of a panel. All of the electrodes are pressed against the wires to be welded by means of individual fluid motors energized with a common fluid pressure and separately driving individual electrodes.

Abstract: A modular lightweight structural panel is made of a lightweight, foil-faced expanded plastic filler reinforced by wire lattice structures. A number of long, narrow pre-coated filler elements are interleaved with a number of substantially flat lattice structures to form a laminated panel subassembly with corresponding reflective surfaces of the filler elements collectively forming substantially planar surfaces of the multilayered reflective panel core. The subassembly is laterally compressed, in a direction perpendicular to the planes of laminations, to thereby force each of the lattice structures to be pressed into and partially embedded in mutually contiguous surfaces and foil edges of adjacent ones of the filler elements.