Mechanical properties and moisture diffusion in hot-pressed jute fiber composite subjected to hygrothermal ageing

Jute fiber is one of the most extensively used eco-friendly natural fibers that are hydrophilic. The performance of natural fiber-reinforced composites is affected by the diffusion of heat and moisture from the environment in addition to the exposure time. In the present investigation, the ultimate tensile strength, displacement at fracture, and energy at yield of the jute fiber-reinforced composite under different hygrothermal (temperature and relative humidity) conditions are investigated. The samples were prepared by hand lay-up technique and the laminates were hot pressed on a hydraulic press apparatus. The specimens were further exposed to a hygrothermal environment using a humidity cabinet (with an inbuilt thermometer and hygrometer) for varied intervals of time of 4, 16, and 64 h. The longitudinal tensile stress (σ) increased at lower hot-pressing temperatures and minimum hygrothermal ageing and it decreased at a higher temperature. Upon increase in hygrothermal ageing, σ decreased at all temperatures. The energy at yield point (E) decreased significantly at lower temperatures and minimum hygrothermal ageing while minimum changes were observed at a higher hot-pressing temperature. The diffusion of moisture as a function of time and temperature explained using Fickian law. The initial region showed nearly linear variation. With continuous hygrothermal ageing, the equilibrium, considering partial pressure, was achieved between the environment and moisture inside the sample. The microstructure of the sample processed at lower hot-pressing temperatures followed by hygrothermal ageing of 16 h showed diffusion and fiber pull-out. However, at a higher temperature, matrix cracking was also observed.