Hardness and Roughness of Glass/Epoxy Composite Laminates Subjected to Different Hostile Solutions: A Comparative Study

This work aims to compare the hardness (H) and roughness (R_a) of glass/epoxy composites after being exposed to various hostile environments, which is possible because the constituents are always the same. Considering the stacking sequence [45₂, 90₂, -45₂, 0₂]_s, the hardness increases for all solutions up to a certain exposure time, from which it decreases for longer immersion times. For the same stacking sequence, roughness had its highest increase (around 44.5%) for the alkaline solution after 36 days of immersion, while the highest decrease (around 25%) occurred for all mortars after 30 days of exposure. For the stacking sequence [0₂, 90₂]_2s, the hardness varied in the opposite direction for acidic and alkaline solutions, observing a direct increase in H with immersion time. However, for samples immersed in oil, hardness decreased as a function of immersion time. In terms of roughness, there was a linear increase with immersion time for all samples, which increased linearly. Therefore, it can be concluded that the stacking sequence has a significant influence on hardness and roughness. Furthermore, knowledge of the variation in hardness and roughness is very important because it can be associated with the structural response of a composite exposed to hostile environments.