Feixiang Tang

This work presents a theoretical study on the size-dependent free vibration of porous nickel-alumina functionally graded (FGM) microplates. A refined continuum model is established by integrating the modified couple stress theory (MCST) with Kirchhoff plate theory. Unlike traditional models, this framework explicitly incorporates a power-law distribution of the material length scale parameter and corrects for the physical neutral surface shift. The vibration characteristics under four distinct porosity distribution patterns (Even, X, O, and V-types) are systematically evaluated. Significantly, a counter-intuitive ‘frequency reversal phenomenon’ is revealed in the Ni-Al ₂ O ₃ system. It is found that while the uniform (Even) porosity yields higher fundamental frequencies in ceramic-rich regimes, the optimal strategy shifts to uneven distributions (specifically O-type) in metal-rich regimes. This reversal mechanism is attributed to the competition between global mass reduction and local stiffness preservation, driven by the extreme density contrast of the nickel phase. These findings provide new physical insights into the mass-stiffness coupling effect in micro-scale composites, offering theoretical guidance for high-performance MEMS resonator design.

Nanoporous gold (NPG), characterized by a bicontinuous network of nanoscale solid ligaments and pore channels, exhibits exceptional physical and chemical properties. However, the limited strength and stiffness of traditional isotropic NPG (INPG) have constrained its engineering applications. To effectively enhance the mechanical properties of NPG, this work proposes an innovative anisotropic NPG (ANPG) architecture featuring unidirectional ligament orientation. By controlling spinodal decomposition parameters, ANPG models with preferentially aligned ligaments and INPG with random ligament orientation are constructed, spanning relative densities from 0.30 to 0.50. The ligament length and diameter of ANPG along the out-of-plane direction are twice those along other directions. Molecular dynamics simulations of tensile tests show that ANPG exhibits superior out-of-plane Young’s modulus and yield strength but reduced fracture strain compared to INPG. Crucially, ANPG maintains toughness comparable to INPG at relative densities below 0.4, offering an optimal strength-toughness balance for practical applications. Scaling law analysis demonstrates INPG follows classical bending-dominated Gibson-Ashby behavior, while ANPG exhibits a hybrid deformation mechanism with significant ligament stretching contribution. Atomic-scale analysis reveals that both structures develop dislocation-mediated plasticity initially, but ANPG transitions to localized ligament necking and fractures more rapidly, explaining its reduced ductility. Strain localization quantification, measured by atomic shear strain standard deviation, confirms the intensifier deformation concentration in ANPG at large plastic strain. These findings suggest anisotropic design as a powerful strategy for developing high-performance NPG for actuators, sensors, and catalytic systems where simultaneous mechanical robustness and functional performance are required.