Poly(lactic acid) (PLA) is a representative bioplastic that has biocompatibility and biodegradability, and PLA is a promising material for various medical applications. However, as PLA becomes brittle by degradation, conventional tensile testing methods struggle to accurately evaluate its mechanical properties under such conditions. In this study, PLA specimens fabricated via injection molding were immersed in physiological saline at 37°C for up to 120 days. The degradation-induced changes in their mechanical properties were quantitatively evaluated using both tensile testing and digital image correlation (DIC). The maximum tensile stress decreased by 9.61% after 7 days of immersion compared to the non-immersed condition, followed by 11.3% after 60 days, 10.2% after 90 days, and 9.48% after 120 days. Regarding the Young’s modulus measured by crosshead displacement in tensile testing, a decrease of 36.9% was observed after 60 days, and 35.1% after 120 days, from an initial value of 1.11 GPa. On the other hand, DIC measurements showed an initial Young’s modulus of 3.32 GPa in the non-immersed state, which decreased by 30.7% after 60 days and by 41.5% after 120 days, indicating a 10.8% drop between 60 and 120 days. These results demonstrate that DIC is an effective method for accurately evaluating changes in the Young’s modulus of PLA even under progressive degradation.
ASAI et al. (Wed,) studied this question.