FEM analysis of transverse creep in honeycomb structures

The results of an analysis of creep deformation in hexagonal and circular honeycomb structures using an elastic–plastic finite element method are reported here. Representative unit cells of transverse sections of the honeycomb structures were subjected to compression loading, with the wall material assumed to undergo creep following a power law of the form e ˙ = K σ n . It is shown that, in spite of using a steady-state law, the honeycomb shows primary and tertiary creep stages, arising from inhomogeneous deformation and geometrical effects, respectively. When the creep law is modified to include work-hardening of the wall material, the onset of the tertiary-like stage is delayed. It is also found that a circular honeycomb is stronger than a hexagonal honeycomb of similar relative density due to constraints within the structure. External constraints, such as those which may arise from friction with external surfaces, are also shown to lead to strengthening by producing triaxial compressive stresses within the cell walls.