  A displacement-based, geometrically nonlinear finite element model is
developed for lattice core sandwich panels modeled as 2-D equivalent
single-layer (ESL), first-order shear deformation theory (FSDT) micropolar
plates. The nonlinearity is due to the moderate macrorotations of the plate
which are modeled by including the von Karman strains in the micropolar strain
measures. Weak form Galerkin method with linear Lagrange interpolations is used
to develop the displacement-based finite element model. Selective reduced
integration is used to eliminate shear locking and membrane locking. The novel
finite element model is used to study the nonlinear bending and linear free
vibrations of web-core and pyramid core sandwich panels. Clamped and free edge
boundary conditions are considered for the first time for the 2-D micropolar
ESL-FSDT plate theory. The present 2-D finite element results are in good
agreement with the corresponding detailed 3-D FE results for the lattice core
sandwich panels. The 2-D element provides computationally cost-effective
solutions; in a nonlinear bending example, the number of elements required for
the 2-D micropolar plate is of the order 10^3, whereas for the corresponding
3-D model the order is 10^5.
