The role of cellular structure in creep of two-dimensional cellular solids

The creep response of cellular solids is sensitive to the details of the microstructure. Here, finite element simulations were used to model the steady state, secondary creep rate of several two-dimensional cellular solids: a Voronoi honeycomb, representing a structure with a random variation in cell shape; a plane section of a micrograph of a commercially available closed-cell aluminum foam; and the same plane section of the foam, but with the curvature of the cell walls suppressed. The solid was assumed to follow power-law creep. Both periodic boundary conditions and boundary conditions corresponding to a finite size sample were analyzed. The results of the models are compared with the analytical results for a regular hexagonal honeycomb of the same relative density. The creep rates of all of the other structures are higher than that of the regular hexagonal honeycomb. The results indicate that the details of the microstructure can have a significant effect on the creep rate, and thus the lifetime, of the cellular solid. Cell wall curvature plays the most significant role, but the distribution of cell shape and size also influences the creep rate.