PSI - Issue 72

Božica Bojović et al. / Procedia Structural Integrity 72 (2025) 491–498

496

Despite these differences, the fractured surfaces of two-month-old specimens from both technologies show remarkable morphological similarities, as can be seen in Fig. 4. This convergence in the appearance of the fractures is expected due to the degradation processes induced by aging, such as embrittlement and loss of interfacial adhesion, which dominate over the initial differences in the compressive architecture. The microscopic observations confirm the mechanical findings and support the conclusion that material aging significantly alters the fracture properties, resulting in a more brittle failure mode for both DLP-LCD and FDM-printed PLA specimens. FDM DLP

0m

1

a)

b)

1

1m

2

c)

d)

1

2m

2

e)

f)

Fig.4. Specimen after three point bending testing: a) FDM printed 0 month old, b) DLP printed 0 month old, c) FDM printed 1 month old, d) DLP printed 1 month old, e) FDM printed 2 month old, f) DLP printed 2 months old.

Fig. 4a and 4c show FDM-printed specimens that were subjected to three-point bending immediately after fabrication and after one month of aging, respectively. In both cases, the specimens were noticeably bent without the structure failing completely. However, the two-month-old FDM specimen (Fig. 4e) shows the beginning of a crack along the bending side, indicating partial fracture under load (highlighted by the red arrow). All FDM specimens were loaded perpendicular to the filament orientation, allowing them to withstand the bending stresses without fully fracturing, with the exception of the aged specimen, which showed partial failure on the tensile side due to reduced ductility and potential weakening of the interlayers over time. In contrast, the DLP-LCD printed specimens failed completely in the bending tests, with fracture typically occurring at the center of the specimen, which corresponds to the location of maximum tensile stress.