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Researchers have identified moisture absorption as the biggest factor in the degradation of carbon fibre used in aircraft.
The scientists from Monash University and RMIT examined different carbon fibre laminate designs under various hot and humid conditions, and found that moisture, rather than “specific temperature or humidity”, is the “dominant factor controlling how the material degrades over time”.
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“What we found is that it’s not the exact ageing temperature or humidity that matters most, it’s how much moisture the material ultimately absorbs,” said Dr Katherine Grigoriou, from the Monash Department of Mechanical and Aerospace Engineering.
“This means that if we understand how moisture builds up inside a composite structure, we can much more reliably predict how it will perform over many years in service.
“Our results show that accelerated ageing methods can still provide reliable predictions of long-term performance, as long as the moisture content in the material is properly understood and controlled.”
Carbon fibre reinforced polymers (CFRPs) are used widely in modern aircraft like the Boeing 787 Dreamliner and Airbus A350, as they are strong, resist corrosion, and – importantly – are far lighter than materials like aluminium.
Boeing says this construction “reduces inspection requirements and downtime and helps airlines keep the airplane flying more often and more profitably”, while Airbus says CFRPs “reduce overall fuel burn and environmental impact, while increasing structural longevity”.
According to the researchers, however, the materials can “slowly absorb moisture from the environment during service, gradually weakening from within”.
“Using advanced imaging techniques, the team observed microscopic internal damage forming as the material aged, including tiny voids, cracks, and weakening of the bond between fibres and the surrounding polymer matrix,” the team wrote.
“Some fibre layouts were able to retain their strength much better, while others proved significantly more sensitive to moisture-related degradation.
“These insights could help engineers design more durable composite structures, improve maintenance strategies, and increase confidence in the long-term safety of aircraft components.
“The research highlights the importance of understanding how environmental exposure affects modern aerospace materials, particularly as aircraft increasingly rely on composite structures.”
The study has been published in the Composites Part A: Applied Science and Manufacturing journal.
