PSI - Issue 68

Marko Delić et al. / Procedia Structural Integrity 68 (2025) 741– 745 Marko Delić et al. / Structural Integrity Procedia 00 (2025) 000–000

743

3

To check reproducibility, three samples were made for each experiment. The samples after testing is shown in Figure 1b. The used infill patterns are shown in Figure 1a.

Fig. 1. (a) Used infill patterns – rectangular and hexagonal (b) samples after experiment

3. Results analysis The results of the experiment are shown in table 2. The table shows the mean values of the obtained results. The S/W ratio was introduced as an additional result indicator. The S/W ratio represents the ratio of the compressive stress value and the mass of the part. The stress – strain diagram are shown in Figure 2. Figure 2a shows the stress – strain diagram for samples printed with rectangular infill pattern, and Figure 2b shows the stress – strain diagram for samples with hexagonal infill pattern. Although the samples were made according to the same standard, i.e. they have the same dimensions and it was possible to show the compression diagram as a compression force - stroke, it was still decided to show the results in the form of compressive stress - strain for easier analysis of the results and comparison with other researches.

Table 2. Experiment results

Experiment designation

Compressive stress, MPa

Strain, mm

Mass, g

S/W ratio

Rec 10 Rec 40 Rec 70 Hex 10 Hex 40 Hex 70

13,95 36,76 74,81 14,17 23,99 41,30

1,31

1,27

10,98 17,50 26,24

12,81 12,71

2,1

2,85

1,73 2,97

1,3

10,9

1,87

12,83 17,96

10,29

2,3

In the case of samples printed with rectangular infill pattern and filling density of 10%, there is a drop in the value of the compressive stress after reaching the maximum force, i.e. compressive strength. This phenomenon is explained by the low value of the infill density, so due to the significant hollow space inside the sample, the internal structure breaks and significant strain occurs. In samples with higher values of infill density, there is a significant increase in compressive strength. Experiments with samples that have infill densities of 40% and 70% showed significantly higher compressive stress values. The results of the experiments unequivocally show that in the case of samples with a rectangular infill pattern, increasing the value of the infill density leads to an increase in the value of compressive stress. The experiments were stopped at approximately 12.7 mm in these two cases because there does not make sense in continuing the experiment because the value of the compressive stress would continuously increase. This assumption is derived from the fact that thermoplastic material is kneading. The compressive streсс value for the sample with a infill density of 10% is 13.95 MPa, with a filling density of 40% it is 36 MPa and with a infill density of 70% even 74.81 MPa.