PSI - Issue 68

Soran Hassanifard et al. / Procedia Structural Integrity 68 (2025) 77–83 S. Hassanifard and K. Behdinan / Structural Integrity Procedia 00 (2025) 000–000

81

5

Smax (MPa) ′ " 0º

′ " (ABS/0.1% GNP) ′ " (ABS/0.5% GNP) ′ " (ABS/1% GNP) 0º 90º 0º 90º 0º 90º

Table 2. Fatigue strength reduction factors at different load levels.

(Pure ABS)

90º

12 15 20 25

1.97 1.82 1.61 1.50

2.03 1.90 1.73 1.62

1.85 1.77 1.68 1.60

1.96 1.84 1.71 1.61

1.92 1.87 1.84 1.77

2.08

1.71 1.63 1.57 1.52

1.81 1.71 1.59 1.50

2.0

1.97 1.93

It has also been observed that material degradation occurs under cyclic loading. Fig. 2 shows the variation in elastic modulus versus the number of applied cycles for samples subjected to cyclic loads with a stress amplitude of 17.5 MPa and a stress ratio of =0. As the number of cycles increased, the Young’s modulus decreased by 4 to 15 percent before final failure, contributing to a reduction in fatigue life. A similar trend was observed across different load levels. Therefore, an averaged value of the reduced Young’s modulus for each filament was used in equations (4) and (5) to more accurately calculate the mean stress and strain amplitude.

1000 1200 1400 1600 1800 2000 2200

Pure ABS 0.1% GNPs 0.5% GNPs 1.0% GNPs

Elastic Modulus (MPa)

1

10

100

1000

10000

Number of Cycles (N)

Fig. 2. Variations in Young’s modulus versus the number of applied cycles for all filaments.

3. Results and discussion To predict fatigue life of 3D-printed samples using the modified Morrow and SWT models, the values of mean stress/maximum stress and strain amplitude are required. Fig. 3 illustrates an example of a hysteresis loop for the pure ABS 3D-printed sample at 0º raster orientation, subjected to 25 MPa stress with an equivalent " ! =1.5 .

'# &# %# $# "#

!"# !$# !%# !&# !'# #

!#(#) !#(#$ !#(#&

#

#(#& #(#$ #(#)

*+,-../M12P4

*+,P5S

Fig. 3. A loading-unloading loop for pure ABS 3D-prined sample with 0º raster angle under 25 MPa.