Structural dependency of three-dimensionally periodic porous materials on elastic properties

The relationships between elastic properties and structures in three-dimensionally periodic porous materials, comprising a periodic array of truncated spheres of air with interconnection pathways embedded in a solid matrix, were investigated both numerically and experimentally. Finite elemental analysis was conducted for the face-centered-cubic (fcc) structure of the air-sphere model, as well as the solid-rod-connected model for comparison. The advantage of the air-sphere periodic structure, having greater rigidity than the solid-rod-connected structure for the same volume fraction, has been emphasized. The calculation results indicated that Young's modulus was consistently larger for the air-sphere model regardless of the size of the interconnection pathways of neighboring air spheres. Additionally, the interconnections were beneficial in lowering the internal stresses. However, it was necessary to focus on the interconnection size to avoid the excessive stress concentration compared with the stress in the solid-rod-connected structure. Polymer-inverted porous structures of fcc particle arrays with a solid volume fraction of 26.0% were fabricated by the combination of sintering self-assembled, monosized copper particles and replication. Their measured Young's moduli agreed well with the numerical results, confirming the advantage of greater rigidity.