Bioinspired dampers: Meniscus-inspired energy dissipation components

Nature provides examples of functionally graded porous structures that absorb energy effectively, such as the knee meniscus. The meniscus features a three-layered structure with varying porosity from the outer to inner layers. The tissue's porous spaces are fluid-saturated, facilitating energy dissipation and damping. Inspired by this architecture, two 3-layered porous geometries were designed, which consisted of thin outer layers and a thicker inner layer with higher porosity and permeability. They were created using image analysis (IA), computational fluid dynamics (CFD) simulations, and pore space segmentation (PSS). The PSS geometry shows a reduced peak pore diameter ($88\mu \text{m}$ vs $111\mu \text{m}$) and an increased density of lower throat lengths but a slightly larger throat radius compared to the CFD geometry. These differences significantly impact permeability, with PSS samples showing a peak of 1522 D versus 151 D in CFD samples. Energy dissipation capabilities were evaluated through cyclic compression experiments at varying rates and with different fluid viscosities. The dissipation energy density of the CFD geometry ($1.8\mathrm{kPa}$) was 2.5 times higher than that of the PSS geometry ($0.7\mathrm{kPa}$). Scanning Electron Microscopy (SEM) compression tests revealed deformation patterns, including crease formation, bulging, and permanent deformation.