Effects of temperature and strain-rate histories on the compression behavior of 3D printed PLA

Polylactic acid (PLA) specimens, 3D-printed by fused filament fabrication (FFF), were tested in compression using four distinct protocols: constant engineering strain rate (Type 1), step-wise strain rate (Type 2), interrupted constant strain rate (Type 3), and interrupted step-wise strain rate (Type 4), covering strain rates from 10 −4 to 10 −1 s −1 . Step-wise loading produces stress overshoots of up to +58% and an undershoot of −37% relative to the constant-rate reference. Interrupted loading alone, without any rate change, reproduces the same overshoot pattern, with magnitudes increasing from 9–10% at 10 −4 s −1 to 32–64% at 10 −1 s −1 , consistent with greater specimen self-heating at higher rates. When the thermal history is matched, using interrupted step-wise and interrupted constant-rate tests, the overshoot collapses to within 3% at every strain-rate transition. These results indicate that the thermomechanical history is an important parameter in the strain-rate history dependence of FFF-printed PLA in compression, with direct implications for the constitutive modeling of this material.