Compressive behaviour of 3D printed thermoplastic polyurethane honeycombs with graded densities

Simon R.G. Bates*, Ian R. Farrow, Richard S. Trask

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

135 Citations (Scopus)
721 Downloads (Pure)


Fused filament fabrication of thermoplastic polyurethanes (TPUs) offers a capability to manufacture tailorable, flexible honeycomb structures which can be optimised for energy absorbing applications. This work explores the effect of a range of grading methodologies on the energy absorbing and damping behaviour of flexible TPU honeycomb structures. By applying density grading, the energy absorbing and damping profiles are significantly modified from the uniform density equivalent. A 3D-printing procedure was developed which allowed the manufacture of high-quality structures, which underwent cyclic loading to densification without failure. Graded honeycomb architectures had an average relative density of 0.375 ± 0.05. After quasi-static testing, arrays were subjected to sinusoidal compression over a range of amplitudes at 0.5 Hz. By grading the structural density in different ways, mechanical damping was modified. Cyclic compressive testing also showed how strain-softening of the TPU parent material could lead to reduced damping over the course of 50 cycles. Samples were subjected to impact loading at strain-rates of up to 51 s-1 and specific impact energies of up to 270 mJ/cm3. Lower peak loads were transferred for graded samples for the most severe impact cases. This behaviour reveals the potential of density grading of TPU structures to provide superior impact protection in extreme environmental conditions.

Original languageEnglish
Pages (from-to)130-142
Number of pages13
JournalMaterials and Design
Early online date14 Nov 2018
Publication statusPublished - 15 Jan 2019


  • Additive manufacturing
  • Cellular structures
  • Functional grading
  • Thermoplastic polyurethane


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