PSI - Issue 45

Thi D. Le et al. / Procedia Structural Integrity 45 (2023) 109–116 "Thi D. Le" / Structural Integrity Procedia 00 (2022) 000 – 000

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5. Parametric study on GFRP under internal pressure In this parametric study, two variables including the thickness ( t ) of glass fiber reinforced layers and fiber orientations are studied to investigate the effect of GFRP under internal pressure ranging from 2 MPa to 10 MPa. There are three different thickness (1.1 mm, 2.2 mm and 3.3 mm) whereas the fiber orientation remains unchanged. GFRP includes an internal HDPE pipe (DN80) with the internal diameter of 72.5 mm and wall thickness of 8.1 mm which is reinforced by bonding with fiber glass and then protected by an external HDPE pipe (DN100) with internal diameter of 93.3 mm and wall thickness of 10.4 mm according to Australia Standard of Polyethylene pipes for pressure applications AS/NZS 4130:2018. The length of pipe is 1000 mm with closed end caps as shown in Figure 3 (a).

Table 5. Utilizing rate in different GF thickness.

Utilizing rate - UR- (%)

Glass fibre thickness ( mm )

Pressure ( MPa)

0/90° GFRP

±45° GFRP

3.3 2.2 1.1 3.3 2.2 1.1 3.3 2.2 1.1 3.3 2.2 1.1

33

32.4 48.2

10

49.4 98.3 26.4 39.5 78.6 19.8 29.6 58.9

94

25.9 38.6 75.5 19.4 28.9 56.4

8

6

6.6 9.9

6.4 9.5

2

19.6

18.6

End cap

b

a

Figure 3. (a) FEA mesh of half-length GFRP; (b) FEA principal stress of half-length GFRP under internal pressure.

The measured elasticity modulus and yielding stress of HDPE are in Table 2 while the measured elasticity moduli, Poisson’s ratios, shear m oduli and ultimate stress are in Table 3. Finally, two different fiber orientations (0/90° and 45°) are considered in this study. The Figure 3 (b) demonstrates the principal stresses of glass fibre layers in FEA used to compare with GF ultimate stress from material tests to determine the utilizing rates (URs) as shown in table 5. Table 5 shows that all URs in glass fiber thickness of 3.3 mm is under 33%. For 2.2 mm thickness, all utilizing rates are under 50%. Lastly, with 1.1mm glass fiber thickness, utilizing rates of GFRP under internal pressure of 10 MPa are over 98% in 0/90° fiber orientation and 94% in 45° orientation. At 10 MPa, GFRP with 3.3 mm and 2.2 mm glass fiber thickness works fine under 50% UR but 1 mm thickness looks overworking. Similarly, for 6 MPa, GFRP with 3.3 mm and 2.2 mm glass fiber thickness works fine under 30% utilizing rates while 1 mm thickness utilizing rate is over 56%. Furthermore, 45° GFRPs appear working slightly better under internal pressure than 0/90° ones since their utilizing rates are marginally smaller than those of 0/90° GFRPs.