PSI - Issue 37

M.P. Silva et al. / Procedia Structural Integrity 37 (2022) 841–846 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

845

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stress level evaluated. Table 2 primarily displays the influence of impact damage on fatigue life of non immersed (control specimens) and laminates immersed (30 days).

Table 2 - Residual fatigue life for laminates immersed into different hostile solutions.

Number of cycles to failure (N f )

Test 1

Test 2

Test 3

Average 587 360 500 034

Control 480 000 Diesel 450 034 Seawater 42 793

847 587 550 023 21 401

437 542 500 045 41 037

35 077

Sulphuric acid (H 2 SO 4 ) 938

898

951

929

The comparison was made for all circumstances examined during a 30-day period, and the fatigue life obtained for each specimen is reported in table 2. The average residual fatigue life of control samples after impact is around 587360 cycles, but exposure to saltwater and sulphuric acid for 30 days promotes a reduction of around 94 and 99 percent, respectively, while the reduction for diesel solution was only 15 %. While the formation of micro-cracks in matrices is caused by the penetration of the solution into the resin (Kawada & Srivastava, 2001), the interfaces of fibres with the matrix are degraded owing to matrix dehydration and penetration. Amaro et al. (A. M. Amaro et al., 2013) attribute the decrease in fatigue life to degradation of the matrix/fibre interface as well as matrix stiffness. Multiple studies have discovered that when these solutions come into contact with the matrix, the stiffness of the matrix decreases, with the loss increasing with longer exposure times and higher solution concentrations (A. Amaro et al., 2013; A. M. Amaro et al., 2013; Mortas et al., 2014). 4. Conclusions The low-velocity impact response of a Kevlar fibre/epoxy laminate following immersion in diesel, H 2 SO 4 , and seawater was investigated in this study. It was possible to conclude that hostile conditions have a substantial influence on impact properties, with seawater and acid solution being the most aggressive. Furthermore, the exposure duration was shown to be determinant, with the impact attributes decreasing as the exposure time was increased. Finally, the degree of the damage resulted in the lowest residual fatigue life. It was able to see in sample residual fatigue life that acid solution and seawater promotes a faster fatigue degradation. Acknowledgements This research is sponsored by national funds through FCT — Fundação para a Ciência e a Tecno-logia, under the project UIDB/00285/2020. This work was also supported by the project Cen-tro-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 Centre (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). References Amaro, A. M., Reis, P. N. B., Neto, M. A., & Louro, C. (2013). Effects of alkaline and acid solutions on glass/epoxy composites. Polymer Degradation and Stability , 98 (4), 853 – 862. https://doi.org/10.1016/j.polymdegradstab.2012.12.029 Amaro, A., Reis, P., Neto, M., & Louro, C. (2013). Effect of different acid solutions on glass/epoxy composites. Journal of Reinforced Plastics and Composites , 32 (14), 1018 – 1029. https://doi.org/10.1177/0731684413483886 Fakirov, S. (2015). Composite materials – is the use of proper definitions important? Materials Today , 18 (10), 528 – 529. https://doi.org/10.1016/j.mattod.2015.10.001 Griffiths, R., & Ball, A. (2000). An assessment of the properties and degradation behaviour of glass-fibre-reinforced polyester polymer concrete. Composites Science and Technology , 60 (14), 2747 – 2753. https://doi.org/10.1016/S0266-3538(00)00147-0