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The influence of water absorption on the mechanical and thermo-mechanical behaviour of carbon nanofibre (CNF) doped epoxy composites was investigated. When immersed in seawater for a long interval of 6 months, all the composite specimens endured saturation whilst weight change of composites was periodically monitored after removal of travelling specimens from a water-beaker. The equilibrium water content and the diffusion coefficient of all composites were evaluated with the help of Fick’s law of diffusion. The results demonstrated a general reduction in flexural modulus and strength, hardness, storage modulus and glass transition temperature (Tg) for seawater exposed specimens due to absorption of seawater as compared to their unexposed specimens. After-effects of water absorption such as plasticisation, swelling of epoxy polymer, interfacial damages and micro-cracks, were marked as the main reasons behind the deterioration of properties. However, among all, the least degradation in properties was observed in the nanocomposite with 0.75 wt.% CNFs loading. Such trivial degradation in properties is due to formation of strong interface of CNFs with the epoxy polymer. The experimental findings were further confirmed by the microstructures of fractured specimens using field emission scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The study of mechanical properties of carbon nanotube reinforced polymeric materials under different environmental conditions are very much essential as this material possesses potential for using it in structural parts, automobiles, marine field and so on. This study deals with the effect of moisture absorption on the mechanical and thermal properties of carbon nanotube/epoxy composites by immersing it in sea and distilled water at 30℃ temperature and at 75% Relative Humidity (RH) humidity. Composite specimens containing different wt.% of carbon nanotubes were prepared, tested and subjected to water immersion test. The flexural properties, hardness and glass transition temperature (Tg) of water-immersed specimens were evaluated and compared with unexposed specimens as per the American Society for Testing and Material (ASTM) standard. It is concluded that the water absorption brought certain loss in the mechanical properties and reduction in Tg of the composites. It was also found that moisture uptake affected both sea and distilled water samples in different ways. [ABSTRACT FROM AUTHOR]

Hygrothermic aging of epoxy and carbon nanotube (CNT)/epoxy composites (0.5, 0.75, and 1 wt.%) was studied for their application suitability in seawater environments. The specimens were emerged in seawater and kept at constant temperature of 30°C for a maximum duration of 180 days. The specimens were periodically weighed for water absorption study and tested for mechanical as well as thermal properties. All aged samples were showing some amount of degradation owing to their moistureabsorption rates. CNT composites absorbed less moisture than pure epoxy because of the presence of nanofillers. C0.75 was found to be hygrothermally more stable reflecting minimum reduction in flexural properties and glass transition temperature value, which was due to least moisture/water absorption. Deterioration of properties was significant in C1, though it was better than pure epoxy. Fractographic analysis by scanning electron microscopy (SEM) revealed interfacial debonding as the dominant failure mechanism, resulting in pull out of nanotubes. [ABSTRACT FROM AUTHOR]