What coconuts can teach us about building design

Coconuts are designed to withstand the heavy impact of falling from the top of trees that can grow to 30 metres tall. And the design solutions they have developed to do so, have inspired engineers working on ways to protect buildings from earthquakes and other natural disasters.

To protect the internal seed, the coconut has a complex structure of three layers that help stop the ripe fruit splitting open when it hits the ground. 

There is the outer brown, leathery exocarp, a fibrous mesocarp and a tough inner endocarp surrounding the pulp which contains the developing seedling.

Researchers at the Plant Biomechanics Group of the University of Freiburg have been looking at ways this structure could be applied in architecture.

The structures in the coconut are all about energy absorption, plant biomechanist Stefanie Schmier said.

Within the endocarp layer there is a distinct, ladder-like design, which is thought to help withstand bending forces. Each cell is surrounded by several lignified rings, joined together by parallel bridges. 

“The endocarp seems to dissipate energy via crack deflection,” says Schmier.

“This means that any newly developed cracks created by the impact don’t run directly through the hard shell.”

The researchers believe the angle of the bundles helps divert the trajectory of the cracks. The longer a crack has to travel within the endocarp, the more likely it is that it will stop before it reaches the other side.

This structure could be applied to the arrangement of textile fibres within functionally graded concrete, to enable crack deflection in buildings, the researchers say. 

“This combination of lightweight structuring with high energy dissipation capacity is of increasing interest to protect buildings against earthquakes, rock fall and other natural or manmade hazards,” says Schmier.