Some structures in nature have great strength and stiffness relative to material used due to their spherical or dome-shaped design.

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“Cylinders curve in one direction, circumferentially–their lengthwise curvature is zero. Here we’re talking about structures with their surfaces curved in two directions; and, as pointed out earlier (and implicit in Laplace’s law), that double curvature gives greater strength and stiffness for a given investment of material. Maximization of internal volume for a given surface compounds the material economy–for that nothing beats a sphere, and a slight egg-shapedness (spheroidicity) doesn’t make things much worse

Nature puts this shape to use in a number of places. Our skulls are nearly spherical domes–and the light and thin bone needs only minimal internal bracing. Similarly, a turtle’s shell is a light, strong dome, as are the shells of many bivalve and gastropod mollusks; the thoraces of many insects, spiders, and crustaceans; the eggs of birds; and nut shells. Smashing the wall of a coconut takes quite an effort, and the resulting pieces don’t weigh a lot. Still, domes have several disabilities. Localized loads can be troublesome, and resistance to local penetration may demand enough material to offset most of their cheap resistance to uniform transmural pressure differences.” (Vogel 2003:440-441)

Comparative Biomechanics: Life's Physical World, Second EditionJune 17, 2013
Steven Vogel

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