Moisture Ageing Weakens Epoxy Composites and Shifts Vibration Response

Moisture exposure measurably weakened three types of fibre-reinforced epoxy composites in a laboratory ageing study, with glass-fibre epoxy showing the greatest deterioration in tensile performance despite absorbing less water than the other materials. The study examined Basalt/Epoxy, Glass/Epoxy and Basalt–Glass/Epoxy hybrid laminates after 80 days in seawater, tap water or distilled water. The researchers fabricated the laminates using vacuum bagging, a process intended to provide uniform fibre–matrix volume fractions.

Each specimen was then exposed to one of the three water environments. The experiment assessed how moisture ingress affected tensile behaviour, including failure stress and modulus, and the composites’ response to free vibration. Water uptake followed a Fickian diffusion pattern.

Seawater produced the highest diffusion coefficients, which the authors associated with matrix breakdown and osmotic influences. Tensile tests showed decreases in failure stress and modulus for all three materials after ageing. Glass/Epoxy absorbed less moisture but experienced the most notable tensile degradation, indicating that weakening of the fibre–matrix interfacial bond may be more consequential than total water uptake alone.

Free-vibration tests showed a related change: natural frequency diminished as moisture uptake increased specimen mass, while damping factors rose after ageing. The Basalt–Glass/Epoxy hybrid laminates exhibited moderate tensile and vibrational characteristics and maintained mechanical performance better under harsh exposure conditions.

Subject of Research: Effects of 80-day moisture ageing on the mechanical and vibrational properties of basalt, glass and hybrid epoxy composites

Article Title: The influence of moisture ingression on mechanical and vibrational properties of basalt, glass, and hybrid fiber-epoxy composites

Article References: Pai, D., John, J. J., Hegde, S., Thara Reshma, I. V., & Padmaraj, N. H. (2026). The influence of moisture ingression on mechanical and vibrational properties of basalt, glass, and hybrid fiber-epoxy composites. PLOS One, 21(10), e0360755. https://doi.org/10.1371/journal.pone.0360755

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360755

Keywords: basalt fibre, glass fibre, hybrid composites, moisture ageing, epoxy laminates, tensile properties, free vibration, water diffusion, fibre–matrix interface, laboratory study, influence, moisture