Study: How Coconut Shells Inspire the Development of Earthquake-Proof Building
Researchers the Plant Biomechanics Group of the University of Freiburg are looking into the specialized structure of coconut walls for inspiration in developing a building design capable of withstanding earthquakes and other natural disasters.
According to a press release, it is widely known that coconuts have complex structures of three layers to prevent the ripe fruit from splitting when they fall to the ground protecting the inner seed. These layers consist of the outer brown, leathery exocarp, a fibrous mesocarp and a tough inner endocarp.
To identify the mechanism working behind the complex structure of the coconut wall, researchers microscopy and computed tomography. Additionally, they used compression machines and an impact pendulum to determine how the protective layers disperse and absorb energy upon impact.
The researchers found out that the ladder-like design of the highly lignified stone cells of the endocarp help withstand the bending forces, dissipating energy through crack deflection. Each cell in the endocarp is surrounded by lignified rings that are joined together by parallel bridges, making newly developed cracks made by the impact not to run directly through the hard shell.
Furthermore, researchers noticed that the angle of the vascular bundles helps in diverting the trajectory of the cracks. This means that the crack will take longer time to travel within the endocarp, making it more likely to stop before reaching the other side.
"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," said biomechanist Stefanie Schmier in a statement.
Researchers believe that applying the distinct angle of the vascular bundle in the endocarp to the arrangement of textile fibers within functionally graded concrete could enable crack deflection.
The investigation of the specialized structure of coconut walls is part of the "Biological Design and Integrative Structures" and is funded by the German Research Foundation.