In-plane impact properties of aluminum double-walled honeycomb cores

The accurate formulas for calculating the in-plane elastic moduli elastic moduli in consideration of the shear and extension deformation of cell edges and the theoretical expressions of plateau stress, densification strain and densification strain energy per unit volume of the aluminum double-walled honeycomb cores are derived. The in-plane impact finite element model of aluminum double-walled honeycomb cores with seven-by-seven cells is established, and their impact properties under the impact velocities between 3 and 252 m/s are analyzed. With the increase of impact velocity, three deformation modes in direction x₁ or x₂ are observed, and the transition velocities of deformation modes are proportional to the square root of t/l. The elastic moduli are in quadric relation to the impact velocities. The Plateau stress and densification strain energy per unit volume are proportional to the square of impact velocities, and their fitting parameters are also in quadric relation to t/l. The related empirical formulas about deformation modes, elastic modulus, plateau stress and densification strain energy per unit volume are suggested in terms of the analysis results with wall thickness from 0.05 mm to 0.3 mm.