The present work aims to study the moisture uptake and thickness swelling behaviour and its effect on tensile and flexural properties of Luffa cylindrica epoxy composite. Characterizations of the luffa fibre surface were carried out by energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Composites were casted with single, double and triple layer of Luffa cylindrica fibre reinforced with epoxy resin by general hand-layup technique. Moisture uptake tests of composites were conducted by subjecting the composite samples in three different environments such as distilled water, saltwater (5% NaCl solution) and sub-zero temperature (–25°C). The diffusivity constant, thickness swelling rate parameter (KSR) and equilibrium moisture content were found out. The result indicates that moisture absorption pattern follows the Fickian diffusion behaviour for composites in all three environments. As the fibre layer increases, the percentage of moisture uptake increased due to high cellulose content. The mechanical properties of the composites were decreased with moisture absorption. Scanning electron microscope study was carried out to study the fracture behaviour of tested samples.

In the present work, epoxy/carbon black (CB) composites were made with 1, 2, 3, 4 and 5 wt. % of CB. The tensile test, flexural test, and impact test of the epoxy/CB composites and neat epoxy were performed and, their results were compared. The results conclude that the tensile strength, flexural strength, and impact strength of the 4 wt. % of CB composites is better than the other composites and neat epoxy. Thermal graphic analysis (TGA) and differential scanning calorimeter (DSC) of the pure epoxy and composites were calculated and analyzed. The results found that the glass transition (Tg) of the neat epoxy was increased with the addition of CB content up to 4 wt. % and then it was decreased. The decomposition temperature of the composites was increased with the increased in the CB content.

Sub-zero weathered GFRP (glass fiber reinforced plastics) composites were aged in water at 60 C for different conditioning times to study fluid sorption kinetics under the influence of a thermal gradient. The effect of subsequent freezing of the conditioned samples on the retention of prior thermal history has been investigated. The variation in mechanical properties during the aging process was studied. One batch of the hydrothermally conditioned specimens was further subjected to sub-zero treatment at 20 C temperature. The samples which were subsequently frozen showed higher interlaminar shear strength (ILSS) initially, although this trend was reversed after a certain conditioning period. Thus, the present study aims to evaluate the mechanical behavior of polymer composites under the influence of extreme and complex conditions.

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Fiber-reinforced glass-epoxy composites with and without prior thermal history are subjected to hygrothermal conditioning for different exposure times. The prior thermal history is given in the form of thermal shocks and thermal spikes at three different temperatures. The effects of exposure time and prior thermal history on the moisture absorption kinetics are studied. The effects of prior conditioning parameters are also investigated. The variation of mechanical properties as a function of exposure time and prior conditioning parameters are assessed by the three-point short beam shear bend test. It has been observed that there is an initial improvement in the mechanical properties followed by a steady deterioration. Mechanical tests performed at different crosshead velocities show increasing brittleness of the composites and that is found to be a function of cross-head velocity.

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The aim of the present study is to investigate the degradation behavior of glass fiber reinforced polyester composites during hygrothermal ageing for different lengths of time after suffering thermal shocks and thermal spikes at 100, 150, and 200°C. The moisture gain kinetics and change of interlaminar shear strength (ILSS), a primary mode of analysis of interfacial strength of the composite, were evaluated. Moisture absorption, found more in spiked samples, showed initial Fickian trend but eventually changed to non-linear pattern as the exposure time increased. It has been found that the composite specimens having a history of thermal spike showed more degradation. The damage was found even more at higher temperature and at lower loading rates.

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