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Hygrothermal Durability of CNT-Modified Recycled Carbon Fiber/Epoxy Laminates: Moisture Diffusion and Mechanical Property Retention

Anchal Sharma, Sunny Zafar

Abstract


The growing use of carbon fiber-reinforced polymer composites has increased the need for effective recycling and high-value reuse of recovered carbon fibers. This study investigates the influence of direct carbon nanotube (CNT) growth on the seawater hygrothermal durability of recycled carbon fiber/epoxy laminates. Carbon fibers were recovered through microwave-assisted chemical recycling, modified by microwave-assisted carbon nanotube growth, and remanufactured using vacuum-assisted resin infusion followed by microwave curing. The novelty of the present work lies in integrating microwave-assisted carbon fiber recovery, direct CNT growth, VARIMC remanufacturing, and seawater hygrothermal durability assessment within a unified recycling-to-reuse framework. The unmodified and carbon nanotube-modified laminates were exposed to accelerated seawater ageing, followed by moisture diffusion, tensile, impact, and fracture-surface analyses. Carbon nanotube modification reduced the equilibrium moisture uptake from 1.20 to 0.72 mass% and decreased the diffusion coefficient from 3.09 × 10⁻¹³ to 2.31 × 10⁻¹³ m²/s. After ageing, the tensile strength decreased from 412.3 to 336.6 MPa for the unmodified laminate and from 509.7 to 460.8 MPa for the modified laminate, corresponding to strength retentions of 81.64% and 90.41%, respectively. The impact strength retention also increased from 42.83% to 69.78% after carbon nanotube modification. Fracture-surface observations indicated improved fiber–matrix adhesion, crack bridging, and greater energy dissipation in the modified laminates. These results demonstrate that carbon nanotube modification can improve the moisture resistance and mechanical durability of recycled carbon fiber composites for marine structures, offshore components, wind energy systems, and lightweight automotive applications.

Keywords



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DOI: 10.14416/j.asep.2026.09.006

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