Here's an interesting fact about the pomelo fruit: even though a mature fruit can weigh up to 2 kg (4.4 lb), they remain intact after falling from heights of over 10 meters (33 ft). The secret lies in the structure of their peel. Scientists have copied that structure, to produce a new type of aluminum composite that's stronger than straight aluminum.
The pomelo's peel is comprised of a "graded, fiber-reinforced foam" that incorporates a myriad of tiny impact-absorbing strut-like structures. Scientists from RWTH Aachen University and the University of Freiburg, both in Germany, took that design and applied it to the creation of a unique metal hybrid.
The center of the material is composed of pure aluminum, which is good at withstanding permanent changes in shape. The outer shell, however, is made of an aluminum-silicon alloy, which has a high tensile strength (it's difficult to break, in other words). As a result, the composite resists both deformation and breakage, better than either the pure aluminum or the alloy on their own.
It has been suggested that the metal could be particularly useful in the manufacturing of strong but lightweight safety materials, particularly in the automotive industry.