2. How can structural materials learn from natural materials?

As we saw in the previous section, natural materials feature hierarchical structural designs adapted to the many stresses they undergo. This adaptation is achieved first and foremost through slow evolution by natural selection, which has led to structures whose quantity, shape, composition and orientation of mineral reinforcements enable the material to respond optimally. The resulting materials are composites, with the organic and mineral parts blending together on the nanometer scale, a fact difficult to reproduce in synthetic materials. Each of these elements taken separately, such as the presence of a hierarchical structure, control over the shape and orientation of mineral reinforcements and the intimate blending of organic and mineral parts, is already present in synthetic materials. Metal alloys are an excellent example of hierarchical materials, with local gradients in composition,...