On the use of complex Young's modulus while processing polymeric Kolsky-Hopkinson bars' experiments

• Elastic processing of polymeric Hopkinson bars compared to viscoelastic processing.
• Elastic processing errors increase with increasing strain rate.
• Elastic processing errors increase with decreasing strain.
• Elastic processing underestimates the sensitivity of stress to strain rates.

All-polymeric Hopkinson-Kolsky bars technique was already proposed to test soft materials at intermediate and high strain rates. In this work, the accuracy of this technique, to measure forces or stresses, is investigated. Namely, the elastic processing, which is typically used for conventional bars, is compared to the viscoelastic processing that is more appropriate for polymer materials. This is motivated by the lack of details on the processing method used in the literature. While studying, aluminium honeycomb, lead, polyurea and polypropylene foams, it was demonstrated that the elastic processing can lead to significant errors mainly at small strains and high strain rates. This study emphasises the importance of using an appropriate stiffness modulus for polymeric Kolsky-Hopkinson bars.

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