CORRUGATED STRENGTH

Architects have known for thousands of years that an arch with the proper curve may support a significant amount of weight. The inventors of corrugated fiberboard applied this same principle to paper when they put arches in the corrugated medium.  The arches, known as flutes, anchored with a starch-based adhesive can resist bending and pressure from any direction.

Corrugated fiberboard may also be called combined board for it is comprised of linerboard and a heavy paper medium. Linerboard is the flat, outer surface that adheres to the medium. The medium is the wavy, fluted paper in between the liners.  Board strength will vary depending on various linerboard and medium combinations available.

1. •SINGLE FACE (fig.1): Medium glued to 1 linerboard; flutes exposed
   

2. •SINGLE WALL (fig.2): Medium between 2 linerboards
   

3. •DOUBLE WALL (fig.3): Varying mediums layered between 3 linerboards
   

4. •TRIPLE WALL (fig4): Varying mediums layered between 4 linerboards
   

FLUTE FACTS

1. •A-FLUTE was the original corrugated flute design, but is rarely used today.
   

2. •B-FLUTE was developed for canned goods.  It contains 47 flutes per sq ft., and measures 1/8” thick.
   

3. •C-FLUTE is commonly used for shipping cartons.  It contains 39 flutes per sq ft., and is 5/32” thick.
   

4. •E-FLUTE is 1/16” thick and contains 90 flutes per sq ft.
   

5. •F-FLUTE was developed for small retail packaging.  It contains 125 flutes per sq ft. and is 3/64” thick.
   

In addition to the most common profiles, new flute profiles, both larger and smaller than those listed here, are being created for more specialized boards. Generally, larger flute profiles deliver greater vertical compression strength and cushioning. Smaller flute profiles provide enhanced structural and graphics capabilities for primary (retail) packaging.

Different flute profiles can be combined in one piece of combined board. For instance, in a triple wall board, one layer of medium might be A-flute while the other two layers may be C-flute. Mixing flute profiles in this way allows designers to manipulate the compression strength, cushioning strength and total thickness of the combined board.

(The above information hase been cited from the Fibre Box Handbook 1999, distributed by Fibre Box Association)

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