abstract
- Metamaterials are porous structures that have the potential for multifunctional applications with tailored behavior. Here, tubular metamaterials are designed considering two sources of bioinspiration. Tubes are designed as hollow cylinders with elliptical voids drawing inspiration from skeletons of cholla cacti. The pattern in which voids are distributed over the tube draws bioinspiration from the brick and mortar structure found in nacre, also known as a staggered pattern. Finite element models of bioinspired tubes are subjected to torsional loads. The effective and specific torsional stiffness of tubes with staggered and non-staggered patterns is compared to understand the role of void staggering under this loading condition. The orientation of voids is also considered as a design variable. Thus, simulations of staggered and non-staggered patterns are performed for voids with different orientations. The advantage of using a bioinspired staggered pattern is discussed considering its role on the torsional stiffness of the tubes. Simulation results showed that different staggered patterns resulted in a wider range of behavior under twist compared to the range obtained from non-staggered patterns. In that sense, effective torsional stiffness may be tailored from 0.2 to 0.6 of that of a solid tube, depending on the specific choice of void pattern and orientation. It was also found that tubes with more voids (lighter) in staggered patterns offer a higher strength-to-weight ratio than other tubes with less voids (denser) as measured by their specific stiffness. These results may help in designing lightweight drive shafts or tubular members subjected to torsion.