Fast optimisation of honeycombs for impact protection

Cellular solids such as honeycombs are often used in impact protection systems. Those with precisely defined geometries allow responses to be programmed to specific functions, but can be costly to design. This article presents an analytical model for fast, parametric optimisation. The analytical model, and a numerical one, were validated against experimental data for three honeycomb variants, during compression tests to 80% engineering strain, and 1, 3 and 5 J impacts. The numerical model force readings remained within 5% of the experiments. A further verification of the analytical model, varying all parameters within the honeycomb geometry, was undertaken for 5 J and 15 J impacts. The analytical model predicted energy absorption at all displacement increments to be (on average) 3% higher than the numerical one. The limits of agreement(with 95% confidence) were between +9 and −15% of the numerical model. The analytical model provided solutions almost instantly, so was used in a demonstrative parametric optimisation study, for a 10 J impact. The input and output solutions were verified in the numerical model, showing a four-fold reduction in peak force (from ∼2000 to ∼500 N).