PSI - Issue 35

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 35 (2022) 59–65

63

M.R. Khosravani and T. Reinicke / Structural Integrity Procedia 00 (2021) 000–000

5

Fig. 3. A fiber reinforced specimen under test conditions; prior to applying load (left), and after fracture (right).

As the physical properties of materials can be a ff ected by ambient temperature, all tensile tests were performed according to the standards for room temperature. In detail, the room conditions for tests of unreinforced and rein forced specimens were 23 ± 3 ◦ C and 50 ± 5% temperature and relative humidity, respectively. It should be noted that no specimens experienced failure at the grip area. In other words, there was no fracture outside the gauge section, therefore, all the occurred failures are valid and have been used to determine fracture load and mechanical sti ff ness of the examined specimens.

5. Results and discussion

The load-deflection curves of unreinforced and reinforced specimens are obtained from tensile tests. The exper imental data were processed based on the recommendations of the utilized standard to determine elastic modulus and maximum tensile strength. Fig. 4 shows average of force-displacement and stress-strain curves of unreinforced and reinforced specimens. Based on the experimental tests, average of fracture load in unreinforced specimens was 1474.5 N. The average of fracture load was increased to 8780.2 N in the reinforced specimens. The results reveal that fiber reinforcement increased maximum tensile strength of the 3D-printed parts. As expected, the tensile testing of 3D-printed composites indicated a substantial increase in the mechanical strength due to the introduction of fibers into the nylon matrix. In the nylon specimens (unreinforced), a ductile failure was observed. In contrast, brittle failure was occurred in all fiber reinforced specimens.

160

10000

Unreinforced Reinforced

Unreinforced Reinforced

120

7500

80

5000

Force (N)

Stress (MPa)

2500

40

0

0

0

2

4

6

0

10

15

5

Displacement (mm)

Strain (%)

Fig. 4. Average of force-displacement (left), and stress-strain (right) of examined specimens.