The egg is one of the unique feats of natural engineering. Its three-dimensional arch structure can support the weight of a standing human being yet it is so delicate that a baby bird can peck its way out.
Some of the questions that come to mind:
1) From an engineering standpoint; in what applications can egg-shaped structures be designed to serve special external and internal loading conditions?
2) In artificial replica, can we manipulate it strength with different materials? (the eggshell is mainly made of calcium carbonate), or does the egg's strength necessarily come from its shape, not material?
Eggs have a very fascinating microstructure. I investigated a number of different one and the overall property was that from inside you can see "prepared" notches which makes it obviously easy for the baby bird to produce a crack and "escape". This crack easily follows the grain boundaries of the lamellar calcite grains which grow mainly perpendicular to the egg surface. No idea how nature is doing this since for smaller eggs it is not that pronounced as for peacocks or ostriches. Finally, under pressure from outside extremely stable, but from inside quite weak :-).
Eggs have a very fascinating microstructure. I investigated a number of different one and the overall property was that from inside you can see "prepared" notches which makes it obviously easy for the baby bird to produce a crack and "escape". This crack easily follows the grain boundaries of the lamellar calcite grains which grow mainly perpendicular to the egg surface. No idea how nature is doing this since for smaller eggs it is not that pronounced as for peacocks or ostriches. Finally, under pressure from outside extremely stable, but from inside quite weak :-).
It looks like that the shape of an egg follows an inverse catenary curve which is a very strong construction because it distributes the load along the line of the material at every point. The force from outside is transfered to compressive force inside the material in that case. At your image the shape adjacent the egg may be the strongest.
Regarding your considerations: a) Of course there are applications already (in architecture, have a look to http://en.wikipedia.org/wiki/Catenary). And b) as mentioned, the strength comes from the shape, but the material have to withstand the resulting compressive stress and thus is also important.
Thank you Michael. I liked the wiki link that shows the egg shapes were used as “inverted catenary arches,” carrying external loads (like those under ancient roofs), or being weighted structures (for monuments, green houses and kilns (and domes?)). The first submarines actually looked like eggs in vertical positions withstanding the external hydrostatic pressures of water.
A question here comes whether the egg-shaped structures are not as efficient for withstanding internal pressures (for pressure vessels) as for external pressures (for submarines), for the same thickness and material.
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