# Nonlinear finite element analysis of lattice core sandwich beams

## TL;DR

This paper develops a nonlinear finite element model for analyzing the bending behavior of micropolar Timoshenko beams, specifically applied to various lattice core sandwich beams, capturing moderate rotations and complex core topologies.

## Contribution

It introduces a nonlinear 1-D finite element model for micropolar beams with a novel application to different lattice core sandwich structures.

## Key findings

- Good agreement with 2-D finite element results
- Effective reduction of shear and membrane locking
- Applicable to multiple lattice core topologies

## Abstract

A geometrically nonlinear finite element model is developed for the bending analysis of micropolar Timoshenko beams using the principle of virtual displacements and linear Lagrange interpolation functions. The nonlinearity enters the model via a nonlinear von K\'arm\'an strain term that allows the micropolar beam to undergo moderate rotations. The nonlinear micropolar Timoshenko beam is used as an equivalent single layer model to study four different lattice core sandwich beams. A two-scale energy method is used to derive the micropolar constitutive equations for web, hexagonal, Y-frame and corrugated core topologies. Various bending cases are studied numerically using the developed 1-D finite element model. Reduced integration techniques are used to overcome the shear and membrane locking. The present 1-D results are in good agreement with the corresponding 2-D finite element beam frame results for global bending.