Experimental and Numerical Analysis of Pressure Waves Propagation in a Viscoelastic Hopkinson Bar

In this paper, the viscoelastic behaviour of PET is assessed in order to study the wave propagation in long SHPB made of polymeric materials. First, an analytical formulation and a numerical FE model were set up and validated using viscoelastic parameters borrowed from literature. However, for a correct description of the attenuation factor and the complex wave number of the real PET material, the storage and loss moduli as functions of the frequency must be known. For this reason, DTMA tests have been conducted at different temperatures and frequency; the experimental curves have been shifted, extrapolating the storage and loss master functions up to 100 kHz, and used for identifying the stiffness and damping parameters of a generalized Maxwell model. Then, these parameters were implemented into the numerical model for simulating the wave propagation in long bars. The numerical results are compared with the real wave signals measured from experiments performed on a SHPB made of the same PET material.