Analyising bending-induced double curvature in metaplates
P.J. Jager (TU Delft - Mechanical Engineering)
F. G.J. Broeren – Mentor (TU Delft - Precision and Microsystems Engineering)
Mohammad Javad Mirzaali – Graduation committee member (TU Delft - Biomaterials & Tissue Biomechanics)
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Abstract
Mechanical metamaterial plates (metaplates) can exhibit unique bending properties compared to regular plates. Where regular plates can only have anticlastic (saddle-shaped) or monoclastic (cylinder-shaped) bending-induced double curvature, metaplates can also have synclastic (dome-shaped) bending-induced double curvature. This behaviour can be controlled by altering the geometry of the unit-cell and has been linked to the unit-cell’s Poisson’s ratio. However, some metaplates exist that do not display the type of bending-induced double curvature that is expected based on their Poisson’s ratio. Recent studies have shown how Cosserat or Micropolar theory can be used to more accurately describe the bending-induced double curvature of metaplates.
In this thesis metaplates are compared using different modelling approaches. The metaplates of interest are the star-shaped unit-cell and the anti-tri-chiral unit-cell. As a starting point, the metaplates are homogenised as a Cauchy continuum and through the use of additional load cases a homogenised Cosserat continuum is created. The homogenised Cosserat continuum model is compared to both the bending behaviour of the actual metaplate and the homogenised Cauchy continuum model using Finite Element Analysis. While the developed Cosserat model displays the correct type of bending-induced double curvature, the presence of deformation defects indicate that the Cosserat model requires further refinement. Additional analysis was done in COMSOL Multiphysics to explore the influence of unit-cell parameters and boundary conditions on the bending-induced double curvature of metaplates.