General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. AbstractFused filament fabrication (FFF) 3D printing of thermoplastic polyurethanes (TPUs) offers a unique capability to manufacture tailorable, flexible cellular structures which can be designed and optimised for specific energy absorbing applications. This paper describes the first application of this methodology in the creation and experimental analysis of 3D printed cellular structures, which are capable of undergoing repeated compressions to densification without failure. A parametric study has been undertaken, capturing the energy absorbing capability of hexagonal arrays manufactured from two types of TPU, with relative densities 0.18-0.49. Arrays were subject to compressions at strain rates 0.03-0.3s -1 and were capable of absorbing energies over the range of 0.01-0.34J/cm 3 , before recovering elastically. Critically, samples attained a maximum energy absorbing 'efficiency' of 0.36, which is comparable to that of traditional expanded closed cell polyurethane foams. The energy absorption behaviour of all structures was found to be dependent on strain rate and cell orientation with respect to the compression direction. This study shows the clear potential of FFF 3D printing for the creation of a new breed of cellular architectures, which are not constrained by existing manufacturing principles, offering the designer the capability to create resilient architectures specifically tailored to operational applications and environmental conditions. Keywords: Cellular structures, thermoplastic polyurethane, 3D printing, energy absorption Introduction:

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