Abstract: With bending, shear and tension deformations being considered in thethin-walled beams within aluminum honeycomb cores under in-plane loadings, theanalytical formulas for the in-plane elastic moduli of the aluminum honeycombcores are derived based on Timoshenko beam theory. The finite elementsimulation methods for calculating these moduli for a representativeunit cell are proposed based on shell elements. The calculations on theelastic moduli of two kinds of aluminum honeycomb coresare carried out, respectively, by using the theoretical andfinite element methods. The agreement between the calculated results andthe experimental data has verified thetheoretical formulas and finite element simulation method.Finally, the effects of aluminum honeycomb cores' configuration parameterson their material efficiency are analyzed.