PSI - Issue 28

P. Santos et al. / Procedia Structural Integrity 28 (2020) 1816–1826 P. Santos/ Structural Integrity Procedia 00 (2019) 000–000

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viscoelastic behaviour compared to the glass fibres, which explains the observed creep behaviour. In this context, the fibre/matrix interface is also very important because the bonds’ breakage and their propagation control the creep displacement (Park and Balatinecz 1998; Georgiopoulos et al. 2015). Finally, regarding the hybrid laminates, the creep displacement after 180 min is greater with the highest content of glass fibres. In relation to full carbon fibres, for example, the displacement value is 0.6% and 2.7% higher for 6C+2G and 4C+4G laminates, respectively, evidencing the most sensitive behaviour of the glass fibres to the creep relaxation.

1,08

1.070

8G

1.068

1.058 1.066

D/D 0

4C+4G

1,06

1.057

1.056

1.038

6C+2G

1,04

1.036

1.032 1.034

1.029

8C

1,02

1.027

1,00

0

40

80 120 160 200

Time [min]

Fig. 7. Creep behaviour for all laminates studied.

4. Conclusions This study analysed the hybridization effect on viscoelastic behaviour. For this purpose, experimental tests were performed involving glass and carbon fibres and the results compared to those obtained with full glass fibre and full carbon laminates. It was possible to conclude that the maximum bending stress and bending stiffness are obtained for full carbon composites and the lowest value for full glass fibre laminates. For hybrid laminates, the presence of glass fibres decreases the bending properties and this decrease increases with the glass fibre content. Independently of the material, higher strain rates promote higher maximum bending stresses and bending modulus. From the stress relaxation tests and for all laminates, it was noticed that the stress decreases over the time. While the full carbon composites are less sensitive to the stress relaxation behaviour, the opposite occurred for full glass fibre composites. Regarding the hybrid laminates, the stress relaxation is greater with the highest content of glass fibers. In terms of creep behaviour, the displacement increases with the time, and higher content of glass fibers are responsible for higher creep displacements. Acknowledgements This work was supported by the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF).