The stiffness and strength of metamaterials based on the inverse opal architecture

The inverse opal architecture, a class of mechanical metamaterials recently shown to exhibit high specific strength and modulus, is further investigated here using carefully coupled experiments and finite element modeling. We demonstrate that this architecture can be exploited to achieve optimized specific strength and modulus, while simultaneously offering tunable optical bandgaps and large-area fabrication. Starting with a silica inverse opal structure and adding different thicknesses of titania (10-34 nm) the strength was gradually increased from 41 to 410 MPa and the elastic modulus from 1.7 to 8.3 GPa, within densities of 300-1000 kg m−3. Simulations confirmed that the inverse opal structure can outperform the state-of-the-art octet- and isotropic-truss designs in terms of Young's, shear and bulk modulus, as well as in structural efficiency (total stiffness). Simulations also predict stresses in the titania coating and in the silica that are on the order of the theoretical tensile yield stresses at failure, indicating that size effects controlling defect population are responsible for the high strengths.

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