Düşünceli, NecmiDrozdov, Aleksey D.Theilgaard, Naseem13.07.20192019-07-1613.07.20192019-07-1620170032-38881548-2634https://doi.org/10.1002/pen.24404https://hdl.handle.net/20.500.12451/4804Experimental data are reported on poly(lactic acid) (PLA) in tensile loading-unloading tests and relaxation tests under stretching and retraction at temperatures ranging from room temperature up to 508C. Two characteristic features of the time-dependent response of PLA are revealed: (i) with a decrease in minimum stress under retraction at a fixed temperature, relaxation curves change their shape from monotonically decaying with time (simple relaxation), to non-monotonic (mixed relaxation) to monotonically increasing (inverse relaxation) and (ii) with an increase in temperature, inverse relaxation after unloading down to the zero stress evolves into mixed relaxation with a pronounced shift of the peak position to smaller relaxation times. Constitutive equations are derived for the mechanical behavior of PLA, and adjustable parameters in the stress-strain relations are found by fitting the observations. Ability of the model to predict the time-dependent response under cyclic deformation is confirmed by numerical simulation. (C) 2016 Society of Plastics Engineerseninfo:eu-repo/semantics/embargoedAccessArticle57323924710.1002/pen.24404Q2WOS:000397033700001N/A