A Simplified Impact Damping Model for Honeycomb Sandwich Using Discrete Element Method and Experimental Data

Abstract

Honeycomb sandwich laminates with aluminum and carbon fiber reinforce polymer (CFRP) face—sheets are widely used in spacecraft structures and aerospace industries. The damping behavior of such structures is reported to improve when the granular particles, called damping particles, are inserted in the honeycomb cells. The discrete element method (DEM) has been successfully used and found to give a reasonably accurate estimate of the impact damping. In DEM formulation, Newton’s laws of motion are used to obtain the equations of motions of each damping particle considering the contact forces from immediate neighboring particles and other sources, if any. The use of DEM for the real structure where the number of particles is of order 108 or more is inefficient and impractical to perform optimization. In this paper, a damping model dissipating equivalent energy is presented for a system consisting of a small honeycomb sandwich coupon filled with damping particles and has resonance frequencies beyond the bandwidth of the model. The coupon is subjected to a range of harmonic excitations (varying frequency and amplitude). The energy dissipated by the damping particles is estimated by DEM. The normal and tangential components of contact forces are modeled using Hertz’s nonlinear dissipative and Coulomb’s laws of friction, respectively. Then the parameters of the equivalent damper are obtained which dissipates the same energy. The damping model presented incorporates the effect of fill fraction, particle size, and material, as well as the amplitude and frequency of excitation. The comparisons of the DEM model for some of the load cases are done with the experimental data showing reasonably good agreement. The model presented could be readily incorporated in the FEM model like zero-stiffness proof-mass actuator, and the effect of impact damping can be studied without actually solving the DEM governing the motions of the particles.