Modelling the Effects of Density Variations on the In-Plane Poisson's Ratios and Young's Moduli of Periodic Conventional and Re-Entrant Honeycombs-Part 1: Rib Thickness Variations

摘要

Finite Element (FE) modelling is used to investigate the effect of varying the rib thickness on the mechanical properties of conventional and re-entrant periodic honeycombs. The calculations confirm that the re-entrant honeycomb has a negative Poisson's ratio. The data show that the mechanical properties vary not only with honeycomb relative density, but also on how the relative density variation is achieved. Reducing the thickness of 'vertical' ribs, whilst maintaining, constant 'diagonal' rib thickness, does not alter the Young's modulus and Poisson's ratio in the x direction (E_x and v_(xy)), but does lead to a decrease in the magnitude of the y-directed properties (E_y and v_(yx)). Reducing the diagonal rib thickness at constant vertical rib thickness leads to a more marked decrease in E_y as well as in E_x, whereas v_(xy) and v_(yx) both increase in magnitude. An analytical model is also developed to account for different vertical and diagonal rib thicknesses, and good agreement with the FE model data is achieved. The results have implications for application in which maximising or maintaining mechanical properties with respect to relative density is important.