Method of making a structural member

A method of making an elongated beam structural member having an interior attachment structure of corrugated paperboard sheets of a first density which interior attachment structure is capable of being machined to form joints using the tubular beam structural member, comprising the steps of:

• (a) applying an adhesive coating to an exterior surface of an elongate corrugated paperboard sheet comprising at least one liner and a sheet of flutes to make a coated corrugated paperboard sheet;
• (b) repeating step (a) to assemble a stack of a plurality of said coated corrugated paperboard sheets of a first density bonded together with the coated surface of each of the corrugated paperboard sheets engaged to an adjacent sheet;
• (c) sandwiching the stack between adhesively coated fibreboard sheets having a second density greater than the first density to form a sandwiched stack;
• (d) applying at least one separation layer of a corrugated paperboard sheet to the sandwiched stack;
• (e) adding a second said stack sandwiched between adhesively coated fibreboard sheets to said separation layer to define a billet comprising at least the two stacks separated by the separation layer;
• (f) ripping the billet along a line perpendicular to the stacked corrugated paperboard sheets and spaced inwardly of a side edge of the billet to yield a core plank;
• (g) ripping said core plank along said separation layer in a direction parallel to the sheets of coated corrugated paperboard sheets to define elongate core planks having a low-density interior structure of coated corrugated paperboard sheets;
• and
• (h) cutting the elongate core planks to length to form an elongated beam structural member for making components of packaging.