PSI - Issue 64

H. Varela et al. / Procedia Structural Integrity 64 (2024) 1427–1434 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Outcomes of printability evaluation: a) Manual extrusion system, freshly extruded 3-layers 4x4x16 cm3 specimen, hardened 3DP and conventional specimens; b) Robotic 3DP evaluation with M1, sections of M1 filament showing fiber alignment.

Figure 4b presents 3DP with the robotic 3D printer. In this case, only M1 could be properly printed. Mortars with higher amounts of fibers produced pumping blockage and could not be printable. This issue could be probably solved it with a stronger pumping system. It was observed how fibers were aligned by the 3DP process of M1 (fig.4b), which could be beneficial for hardened mechanical properties, as explained by Hamback et al. (2016).

Conventional specimen

3DP specimen

12

2.2

8

2.0

1.6 Apparent density (g/cm 3 ) 1.8

4

0

Open porosity (%)

M0

M1

M2

M3

M0

M1

M2

M3

M4

M4

Fig. 5. Open porosity (water accessible) and apparent density of conventional and 3DP specimens.

Figure 5 presents the experimental results of open porosity accessible to water ( P op ) and apparent density ( D ap ) evaluated on conventional and 3DP specimens. SF reduced open porosity for VF of 0.5 and 1 % of long fibers (13 mm), while 1.5 % and shorter SF slightly increased P op . When 3DP specimens were compared to conventional specimens, it was observed that 3DP reduced P op in all cases, probably due to particle squeezing during extrusion according to Wolfs et al. 2019, Varela et al. (2023a) and Liu et al. (2023). According to P op , D ap was affected by SF type, amount, and casting technique. VF of 0.5 and 1 % of long fibers (13 mm), increased D ap , while 1.5 % and shorter SF slightly decreased D ap . When 3DP specimens were compared to