Thermal Conductivity Properties and Heat Transfer Analysis of Multi-re-entrant Auxetic Honeycomb Structures

In this work, the static and transient conductivity properties of a novel centersymmetric honeycomb structure are evaluated using analytical and finite element (FE) models. The honeycomb structure features a unit cell geometry allowing in-plane auxetic (negative Poisson’s ratio) deformations, and geometry parameters to be used to design the honeycomb configurations for multifunctional applications. The equivalent thermal conductivity along the two principal directions of the multi-re-entrant unit cell is calculated using a theoretical approach based on Fourier’s law and electric-thermal analogy. To validate the theoretical models, a FE analysis has been carried out on periodic unit cells under thermal steady-state conditions, showing an excellent agreement with the theoretical results. A transient thermal analysis, considering convection and radiation, has been performed numerically to evaluate the possible use of this honeycomb configuration for sandwich panels in thermal protection systems. Parametric analysis on the thermal conductivity and maximum temperatures acquired during convection-radiation is performed vs. the nondimensional geometry parameters of the honeycomb cell. The auxetic honeycomb configurations show higher out-of-plane conductivity, strong in-plane thermal anisotropy, and the lowest peak temperatures during heat transfer between the bottom and top faces of honeycomb panels.