Abstract
We have designed a new type of composite materials which not only has a Young's modulus much larger than the Voigt limit, but also is always nearly isotropic. Moreover, its Poisson's ratio can be designed at a desired value, e.g. positive, or negative, or zero. We have also demonstrated that structural hierarchy can help to enhance the stiffness of this type of composite materials. The results obtained in this paper provide a very useful insight into the development of new functional materials and structures.