By Leeanna McLean
Researchers are analyzing the integrity of coconut walls for inspiration in developing building designs that can withstand earthquakes and other natural disasters.
Coconut palms are known to grow up to 98′ high. Coconut shells consist of three layers to protect the inner seed and prevent the ripe fruit from splitting when they fall to the ground. These layers consist of the outer brown, leathery exocarp, a fibrous mesocarp and a tough inner endocarp.
Researchers from the Plant Biomechanics Group of the University of Freiburg in Germany have been working with civil engineers and material scientists to investigate how the complex structure of a coconut could be applied in architecture. The team used compression machines and an impact pendulum to determine how the protective layers disperse energy upon impact.
“By analyzing the fracture behaviour of the samples and combining this with knowledge about the shell’s anatomy gained from microscopy and computed tomography, we aimed to identify mechanically relevant structures for energy absorption,” plant biochemist Dr. Stefanie Schmier said in a press release.
The team found that the inner endocarp layer has a ladder-like vascular system, which is made up of highly lignified stone cells that help withstand bending forces.
“The endocarp seems to dissipate energy via crack deflection,” Schmier said. “This means that any newly developed cracks created by the impact do not run directly through the hard shell.”
The researchers concluded the angle of the vascular bundles helps to divert the trajectory of cracks. Hence, the longer a crack has to travel, the more likely it is to stop growing before it gets too big.
“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 man-made hazards,” noted Schmier.
So, if the distinct angle of the vascular bundle in a coconut’s endocarp could be applied to the arrangement of textile fibers within concrete, it could help enable crack deflection.