Dynamic compressive behaviour of auxetic and non-auxetic hexagonal honeycombs with entrapped gas. (December 2020)

• Record Type: Journal Article
• Authors: Rapaka, Sri Datta; Pandey, Manoj; Annabattula, Ratna Kumar
• Is Part Of: International journal of impact engineering. Volume 146(2020)
• Publication Date: 2020-12
• Subjects: Honeycombs -- Entrapped gas -- Dynamic stress-strain states -- Dynamic crushing strength -- Shock front; Impact -- Periodicals; Shock (Mechanics) -- Periodicals; Impact -- Périodiques; Choc (Mécanique) -- Périodiques; Impact; Shock (Mechanics); Periodicals; 620.1125
• DOI: 10.1016/j.ijimpeng.2020.103718
• Languages: English
• ISSNs: 0734-743X

Abstract

Highlights: A cell-based theoretical model to estimate the average nominal stress required to crush non-auxetic hexagonal honeycombs with entrapped gas at a constant velocity shows a good agreement with the finite element simulations. The dynamic stress-strain states for a regular hexagonal honeycomb with entrapped gas lie on a unique curve and are found to be different from the quasi-static response. In the absence of entrapped gas, the dissipation performance parameter is the highest for the honeycomb with cell angle θ = − 30 ∘, followed by θ = 30 ∘ . In the presence of entrapped gas, the non-auxetic honeycombs show higher dissipation performance parameter than the auxetic honeycombs, for the strain-rates in the shock regime. Graphical abstract: Abstract: This work aims to study the uniaxial dynamic compression response of hexagonal honeycombs with different cell morphologies in the presence of an entrapped gas. A theoretical model is proposed to estimate the dynamic crushing strength of non-auxetic honeycombs while including the effect of the entrapped gas on the crushing process. The theoretical predictions are shown to agree well with the finite element (FE) simulations. From the numerical simulations, Hugoniot relations between the shock velocity and the impact velocity are obtained for various honeycomb geometries. It has been observed that shock velocity varies almost linearly with impact velocity. Using this fundamental relation, we derive the stress-impact velocity Hugoniot from the conservation law of momentum. The dynamic stress-strain states of a regular hexagonal honeycomb obtained from the FE simulations show a good agreement with the Hugoniot predictions. It is shown that the dynamic stress-strain states for various impact velocities lie on a unique curve, which is different from the quasi-static stress-strain response. The local strains behind the shock front are significantly lowered in the presence of an entrapped gas, and the stresses behind the shock front are higher as compared to the case where there is no entrapped gas. The variation of the plateau stresses with the cell morphology has been explained, and correlated to the energy absorption capacity of the honeycombs. A new method to characterize the energy absorption capacity of honeycombs is proposed, and the performance of various honeycombs has been compared through the dissipation performance parameter.