PSI - Issue 64

Omid Hassanshahi et al. / Procedia Structural Integrity 64 (2024) 81–88 Hassanshahi et al. / Durability of GFRP Composites Produced by Pultrusion under Thermal Environments

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results compared to transverse tensile strength results, a typical issue due to the high susceptibility of the former property and the associated test method to local geometric imperfections and material defects. With respect to the thermal cycles, two different trends were observed: while in the case of the UP series the compressive strength increase after 100 cycles (with a very high CoV of 25%) shifted to a slight degradation after 200 cycles, in the case of the VE series increased compressive strength was observed for both 100 and 200 thermal cycles. 3.3. Effects on flexural strength Fig. 5 shows the flexural strength retentions of both GFRP_UP and GFRP_VE composites. The flexural strength retention is influenced by a combination of factors related to both the matrix and fibre components. Fibres contribute to the tensile strength and stiffness in the tensile zone, while the matrix provides support and stability to the reinforcing fibres in the compressive zone, which also influences the overall performance under bending loads. Both composites (GFRP_UP and GFRP_VE) showed marginal variations of the flexural strength retention, regardless of the thermal ageing condition applied, i.e. constant temperatures and thermal cycles. Furthermore, small dispersion of results was observed in these tests, with CoV lower than 6%.

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

120%

120%

(b)

GFRP_VE

(a)

GFRP_UP

110%

110%

105.94% (2.75%)

105.33% (6.21%)

102.37% (5.22%)

101.07% (5.36%)

99.73% (4.39%)

99.88% (1.50%)

99.61% (5.28%)

99.65% (6.48%)

100%

100%

98.84% (2.47%)

98.89% (3.26%)

98.50% (3.15%)

94.34% (3.77%)

90%

90%

Flexural strength retention

Flexural strength retention

80%

80%

T20

T60

T-15

T40

TC100 TC200

T20

T60

T-15

T40

TC100 TC200

Ageing Environment

Ageing Environment

Fig. 5. Flexural strength retention: (a) GFRP_UP; (b) GFRP_VE.

3.4. Effects on in-plane shear strength The in-plane (IP) shear strength retentions are depicted in Fig. 6a and Fig. 6b for GFRP_UP and GFRP_VE composites, respectively. Despite the significant dispersion in some results, in general, all the series have shown improved IP shear strength, with relatively similar retention trends across ageing conditions, aligning with findings from transverse tensile, compressive, and flexural strength results.

0

1

2

3

4

5

6

7

0

1

2

3

4

5

6

7

130%

130%

(a)

GFRP_UP

(b)

GFRP_VE

120%

120%

116.75% (8.91%)

114.32% (6.81%)

113.96% (3.65%)

113.37% (3.41%)

112.7% (3.21%)

111.44% (4.64%)

110.01% (6.85%)

110%

110%

109.1% (3.44%)

106.59% (7.73%)

106.78% (4.45%)

105.86% (1.81%)

100.76% (4.07%)

100%

100%

90% In-plane (IP) shear strength retention

90% In-plane (IP) shear strength retention

T20

T60

T20

T60

T-15

T40

T-15

T40

TC100 TC200

TC100 TC200

Ageing Environment

Ageing Environment

Fig. 6. In-plane (IP) shear strength retention: (a) GFRP_UP; (b) GFRP_VE.