PSI - Issue 77

Boyu Li et al. / Procedia Structural Integrity 77 (2026) 316–322

319

4

Boyu Li et al. / Structural Integrity Procedia 00 (2026) 000 – 000

(b)

(a)

10 mm

10 mm

Still water

5 mm

Vertical Specimen

Horizontal Specimen

Fig. 1. (a) Printed PLA specimen; (b) Schematic of water ageing experiment.

During the exposure period, each specimen was removed from the tank at weekly intervals. Before weighing, surface moisture was removed to minimise measurement variability due to residual water. Weight measurements were conducted every week over a total duration of 7 weeks. The weight distribution for the specimens over the experimental period is presented in Fig. 2, with outliers indicated by plus (+) signs. These outliers may have resulted from incomplete removal of surface water before weighing. For the vertical specimens, the mean weight increased rapidly during the first week and reached its maximum in week 1. After this initial rise, the mean weight decreased and subsequently remained stable at a value close to the initial specimen weight throughout the remainder of the immersion period. The reduction in the mean weight may be due to the hydrolytic degradation of the PLA material. In contrast, the horizontally printed specimens exhibited a different trend: their mean weight reached an initial peak in week 2, followed by a decrease in the third week, which may similarly be associated with hydrolysis. The mean weight then increased again, reaching a maximum in week 4, before decreasing and stabilising in the following weeks.

Fig. 2. Distribution and mean values of specimen weight for both specimen orientations.