PSI - Issue 26

N.A. Fountas et al. / Procedia Structural Integrity 26 (2020) 139–146 Fountas et al. / Structural Integrity Procedia 00 (2019) 000–000

142

4

The 3D CAD model of the ASTM D638-10 type I standard tensile specimen was prepared in CATIA® V5 R18 and then exported as a *.STL file for importing it to Repetier Host® environment for modelling the printing process and slicing the part with the Cura Engine® embedded module. Specimens per experimental run were fabricated using a low-cost 3D printer. All tests are carried out at the temperature 23±2 o C and relative humidity 50±5% as per ISO R291:1977 (Plastics – Standard Atmospheres for Conditioning and Testing). The material used for fabricating the parts was Polylactic Acid (PLA) 1.75 mm filament black, which is a kind of a thermoplastic polyester.

Table 2. Experimental results according to the L 16 factorial design. Experiment no. Coded parameters

Objective

A

B C D E Tensile strength (Load, kN)

1 2 3 4 5 6 7 8 9

- 1 +1 - 1 +1 - 1 +1 - 1 +1 - 1 +1 - 1 +1 - 1 +1 - 1 +1

- 1 - 1 - 1 +1 - 1 - 1 - 1 - 1 +1 - 1 - 1 - 1 +1 - 1 - 1 +1 - 1 +1 - 1 - 1 - 1 +1 - 1 +1 +1 +1 - 1 +1 +1 +1 - 1 - 1 - 1 - 1 +1 - 1 - 1 - 1 +1 +1 +1 - 1 +1 +1 +1 - 1 +1 - 1 - 1 +1 +1 +1 - 1 +1 +1 - 1 +1 +1 +1 - 1 +1 +1 +1 +1

0.6617 0.6824 0.7943 0.8028 1.2926 1.5919 1.7603 1.5193 0.8239 0.8693 0.8995 0.8525 1.7663 1.5158 1.7838 1.5674

10 11 12 13 14 15 16

With reference to the L 16 experimental design each specimen was individually printed at the middle of the printer’s working envelope to minimize the bed’s positioning error effect. PLA material was extruded through a heated nozzle with 0.2 mm diameter, at 190 o C whilst the temperature of the heated bed was kept at 65 o C. After fabrication, the specimens were dimensionally examined to ensure whether different geometric features are reasonably fabricated as per the nominal design. Tensile tests were performed using the Instron ® 4482 dual-column Universal Testing machine shown in Fig.1a. Bluehill ® 2 environment was utilized to set up the interface such as the specimen dimension and other settings related to the overall process for performing the tensile tests.

Fig. 1. (a) Instron ® 4482 testing machine; (b) Tensile test outputs from tensile tests.