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

## TL;DR

This study compares how different hostile environments affect the hardness and roughness of glass/epoxy composites based on their stacking sequence.

## Contribution

The novel contribution is the analysis of how stacking sequence influences hardness and roughness changes in composites under various hostile solutions.

## Key findings

- Hardness increases up to a certain exposure time and then decreases for longer immersion times.
- Roughness increased by 44.5% in alkaline solutions and decreased by 25% in mortars after specific exposure times.
- Stacking sequence significantly influences hardness and roughness changes in composites.

## Abstract

This work aims to compare the hardness (H) and roughness (Ra) 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.