PSI - Issue 37

S. Valvez et al. / Procedia Structural Integrity 37 (2022) 738–745 S. Valvez et al. / Structural Integrity Procedia 00 (2019) 000 – 000

742

5

From Table 3, and regardless of the material, it is possible to observe that the exposure to temperature changes the dimensions of the samples and the exposure time has a significant effect on this variation. For example, considering the samples produced with PETG, the highest (+5.9%) and lowest (-2.4x10 -5 %) values of volume variation were observed for samples submitted to 130 ºC for 30 min and 240 min, respectively. Positive variations mean that the specimens have increased in size, while negative ones indicate that the specimens shrink.

Table 3. Volume variation after the annealing heat treatment.

PETG SD [mm 3 ]

CFPETG

KFPETG

Samples Group

Average [mm 3 ]

Variation [%]

Average [mm 3 ]

SD [mm 3 ]

Variation [%]

Average [mm 3 ]

SD [mm 3 ]

Variation [%]

Control

4171

38.7 50.3 25.5 35.0 46.4 35.6 93.2 34.5 45.1 62.0

-

4575.0 4732.8 4636.7 4594.6 4761.9 4476.8 4479.6 4445.1 4427.9 4296.1

21.9 38.6 37.9

-

4513.3 4689.5 4565.3 4715.8 4614.6 4460.2 4507.8 4604.1 4711.7 4642.4

47.1

-

1 2 3 4 5 6 7 8 9

4271.4 4260.9 4295.4 4313.8 4170.9 4175.2 4416.9 3998.2 4048.1

+2.4 +2.2 +3.0 +3.4 +0.1 +5.9 -4.1 -2.9

+3.4 +1.3 +0.4 +4.1 -2.1 -2.1 -2.8 -3.2 -6.1

159.0

+3.9 +1.2 +4.5 +2.2 -1.2 -0.1 +2.0 +4.4 +2.9

52.4 47.6 71.8 55.8 60.8

103.3

49.4

-2.4x10 -5

5.2

34.4 22.3 74.4 29.0

118.1

56.7 66.4

Table 4. Inverse radius of curvature (1/R) after the annealing heat treatment.

PETG

CFPETG

KFPETG

Samples Group

Average [mm]

SD [mm]

Average [mm]

SD [mm]

Average [mm]

SD [mm]

Control

0 0 0

0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0

0 0 0 0

1 2 3 4 5 6 7 8 9

4.3×10 -6 7.9×10 -6 1.3×10 -6 1.5×10 -4 1.8×10 -6 2.1×10 -6 3.5×10 -6

8.7×10 -6 8.2×10 -6 1.4×10 -6 1.2×10 -5 1.9×10 -5 1.8×10 -5 4.8×10 -5

1.1×10 -3 1.4×10 -3 1.7×10 -3 1.8×10 -3 2.1×10 -3 2.7×10 -3

1.5×10 -5 2.9×10 -5 3.7×10 -5 1.5×10 -5 2.7×10 -5 1.5×10 -5

5.1×10 -6 2.3×10 -5

1.7×10 -5 2.1×10 -5

Regarding the CFPETG material, the highest (-6.1%) and lowest (+0.4%) values of volume variation were observed for samples submitted to 130 ºC for 480 min and 90 ºC for 480 min, respectively. Finally, for KFPETG, the highest (+4.5%) and lowest (-0.1%) values of volume variation were observed for samples submitted to 90 ºC for 480 min and 110 ºC for 480 min, respectively. In this case, it is possible to notice that the inclusion of fibres into the matrix does not have a significant influence on the variation of the dimensions because, basically, all samples presented variation in volumetry. The same is not true for the inverse radius of curvature. For example, when the carbon fibres were added to the PETG only for the highest temperature (130 ºC) and longer exposure times (240 min and 480 min) the incurvature was noted. Regarding the Kevlar fibres, this evidence was only perceived for the temperatures of 110 ºC and 130 ºC and regardless the exposure time. Finally, considering only the polymer (PETG), the specimens remained straight only at the temperature of 90 °C and exposure times of 30 min and 240 min. In this context, it should be noted the fact that design considerations that do not allow changes in shape (keep its straightness) the annealing