High strain rate behavior of graphene reinforced polyurethane composites
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] A compressive Split Hopkinson Pressure bar (SHPB) is used to investigate the dynamic mechanical behaviors of Graphene-reinforced-polyurethane composites (GR/PU) at high strain rates ranging from approximately 1500 s-1 to 5000 s-1. Four types of GR/PU composites with different GR contents: 0.25% GR, 0.5% GR. 0.75% GR and 1 % GR were prepared by the solution mixing method, and divided into two groups of unheated and post-heated specimens. Experimental results show that the GR/PU composite is a strong strain-rate-dependent material, especially in the high strain rate regime of 3000 s-1 to 5000 s-1. The dynamic mechanical properties of GR/PU composite in terms of plateau stress, peak stress, and peak load carrying capacity is better than that of pristine PU at most of applied strain rates. Among the four different GR concentrations used the 0.5%wt-GR specimen shows the maximum peak stress, and the 1%wt-GR specimen has the highest plateau stress; while no significant change in peak strain with changing GR volume fraction is obtained. Compare to unheated specimens, the plateau stress, peak stress, and peak strain of post-heated specimens are significantly higher.
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