Quasi-Static Indentation Behavior of Honeycomb Sandwich Materials and Its Application in Impact Simulations

Both the crushing and indentation behaviors of sandwich materials are important aspects in failure analysis and energy absorption. In this paper, the core crushing strength of honeycomb materials from the experiment is briefly introduced, and the indentation of sandwich structures is studied in detail. Using the beam on elastic-plastic foundation models, theoretical formulations for predicting indentation behavior of sandwich materials are proposed, from which the mechanical response of elastic-plastic sandwich beams are obtained. Three stages of failure are clearly depicted by the global stiffness changes in the load versus displacement curve of elastic-plastic beams. The models are compared with the available experimental data and numerical simulation, and relatively close agreements are achieved. The compliance and compliance gradient derived form the indentation models are then incorporated with the equation of motion of the projectile to study impact response of elastic-plastic beams, and the impact energy dissipation due to the plasticity of elastic-plastic sandwich beam is uniquely recovered from the derived damping ratio. The beam on elastic-plastic foundation models proposed can be used to predict the indentation behavior of honeycomb sandwich materials, and the unique incorporation of the compliance and compliance gradient of the elastic-plastic sandwich beams in the standard mass-spring model can be utilized to characterize the effect of core compression and plasticity in the impact process.