Architects have known for thousands of years that an arch with
the proper curve is the strongest way to span a given space. The
inventors of corrugated fiberboard applied this same principle to
paper when they put arches in the corrugated medium. These arches
are known as flutes and when anchored to the liner board with
adhesive, they resist bending and pressure from all directions.
When a piece of combined board is placed on its end, the arches
form rigid columns, capable of supporting a great deal of weight.
When pressure is applied to the side of the board, the space in
between the flutes acts as a cushion to protect the container's
contents. The flutes also serve as an insulator, providing some
product protection from sudden temperature changes. At the same
time, the vertical liner board provides even more strength and
protects the flutes from damage.
Flutes come in several standard shapes or flute profiles (A, B,
C, E, F, etc.). A-flute was the first to be developed. B-flute was
the next and is much smaller than A-flute. C-flute followed and is
between A and B in size. It is also the most common large flute
profile. E-flute is smaller than B and F-flute is smaller yet. Due
to variances in flute sizes between manufacturers, FBA no longer
publishes flute guidelines.
In addition to these five 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, while smaller profiles provide better resistance to
process and printing crush.
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 might 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.
