Artificial and natural cellular materials exhibit stochastic porosity

Based on the foregoing, it appears that many artificial and natural cellular materials exhibit stochastic porosity, which means that they undergo bending and deformation when compressed by weight because their mechanical strength is tightly coupled with mass density. Hence, to improve the mechanical performance of conventional cellular materials, it is recommended that such materials should be well-fabricated so that they can maintain their structural architecture across different mass densities irrespective of their constituent components (Zheng et al. 1374). Accordingly, Zheng and colleagues describe a new variety of artificial cellular materials known as “ultralight mechanical metamaterials”, which have excellent mechanical performance because they retain their structural architecture across different densities. Apparently, these materials have a stretch-dominated architecture as opposed to the bend-dominated structures that are present in most conventional cellular materials (Zheng et al. 1374). In addition, these low-weight yet mechanically-efficient materials have b struts and j joints, which enable them to carry loads when compressed instead of bending as in the bend-dominated structures (refer to Appendix A). A typical example of a stretch-dominated structure contains an octet-truss unit cell, which exhibits isotopic characteristics when exposed to compressive loading. In theory, the relationship between the relative compressive stiffness and the stretch-dominated material’s yield strength is usually linear, and it is represented by these equations, E/E_s α (ρ/ρ_s) as well as σ/σ_s α (ρ/ρ_s) (Zheng et al. 1374).