Abstract:The equivalent in-plane elastic moduli of hexagonal honeycombs have determinate solution. Compared to the in-plane properties, only the lower and upper bounds are obtained for equivalent transverse shear modulus. Due to the lack of determinate solution, it will bring many troubles for practical engineering applications. For this reason, this paper deals with the calculation of the transverse shear modulus of a honeycomb sandwich panel, under the influence of the thin face panel. Based on the Y-shaped representative unit cell, then the upper bound of hexagonal honeycomb is obtained when the ratio of the thickness of central wall to inclined wall is 1:1 and 2:1. The result shows that it is equal to the lower limit of Gibson and Kelsey’s formula. Finally, both the experimental data and finite element analysis show that the proposed theoretical solution can predict the equivalent shear modulus of honeycomb cores with good accuracy.