“The most instructive experiences are those of everyday life.”—Friedrich Nietzsche
While Nietzsche’s quote seems correct, I would venture to add that some of the most instructive lessons can be learned from everyday objects. Items that most people utilize and discard without a second thought can teach us some astounding principles. One of the most common objects, both in the “real” world and the world of Destination ImagiNation™, is cardboard. It is a rather unassuming material that we use in everything from cereal boxes to shipping containers to sets (both elaborate and simple). But would you believe it if I told you that cardboard can teach us something about engineering?
While there are a few types of cardboard, we are specifically interested in corrugated cardboard. Like all other cardboards, corrugated cardboard is made from heavy paper and glue. But unlike your cereal box, 
this type consists of two flat linerboards and one wavy layer. The wavy/ fluted/arched board is sandwiched between the two flat boards. Architects have used arches for thousands of years, because the appropriately curved arch is the strongest way to span a gap. The flutes in the corrugation resist bending and pressure when glued to the linerboard due to the same principle.
The arched flutes form rigid columns that can support a great deal of weight. The strength of the board is measured in two ways, the edge crush test and the burst test. To test the edge crush strength, place a piece of cardboard on its edge (i.e. the flutes running vertically) and see how much weight it holds. A standard panel of corrugated cardboard can hold 32 lbs. The burst test sees how much pressure (pounds per square inch) is needed to bust a hole in a panel. A typical piece of corrugated cardboard can hold 200 lbs. per square inch.
The arched design provides more benefits than just strength. The flutes supply structure while the air space between the arches acts as a cushion for whatever is in the corrugated cardboard box. The empty space also serves as an insulator, because of the extended amount of time needed for heat to transfer from one side to another. Cardboard has a thermal conductivity of .5 whereas of water’s conductivity rating is 1.6. This means that water transfers heat 3 times more than cardboard.
Other factors that play into the strength of corrugated cardboard are the type of paper used, the type of corrugation, shape of the container, and use. The more dense the paper used equals the stronger the material will be. For illustration, compare normal computer paper with cardstock. The height of the flutes affects the number of flutes in an area which affects the overall strength. For example, one meter (about 3 feet) can fit one hundred and ten 5 mm tall flutes or four hundred and fifty .7 mm tall flutes. While the increased number of flutes will make the cardboard stronger, what is the possible downside of more flutes? (Think of a bed with many springs compared to a bed with fewer springs.) While flutes support cardboard rigidity, the common cardboard cube shape adds structure and support due to its corners. To test this, try to crush a single piece of cardboard versus a box. How the cardboard is being used is also important, since cardboard does not stand up well to moisture. Since damp paper loses its rigidity and wet glue loses its bonding, cardboard should not be used to contain water.
So how can you use the principles that cardboard shows us? Can you add arches to something to make it stronger? How many arches will you use? Can you add airspace to keep things cool and cushioned? Can you give an object more strength if you add corners? Can you find a way to overcome cardboard’s water problem? Try to brainstorm ideas and then write them down and save them to use in the future.
Post written by Alisha Heisterkamp, Co-Affiliate Director
Resources:
“All About Corrugated.” Corrugated Packaging. http://www.corrugated.org/Basics/AboutCorrugated.aspx
F, Dan. “Properties of Corrugated Cardbaord.” eHow. http://www.ehow.com/about_6514103_properties-cardboard.html
Procana. “What is corrugated cardboard?” Pagter Innovations. http://www.pagter.com/am/procona/procona/corrugated-cardboard.html
