Effects of water, alkali solution and temperature ageing on water absorption, morphology and mechanical properties of natural FRP composites
Plant-based jute vs. mineral-based basalt
Because of the environmental, technical and economic benefits, plant-based (e.g. jute) natural and mineral-based (e.g. basalt) natural fiber reinforced polymer (FRP) composites are considered as alternatives for conventional glass FRP composites. However, the scarcity of data on the long-term durability of natural FRP composites becomes a major barrier for their wider use in different engineering areas. In this work, durability studies were performed to evaluate the effects of water and alkali solutions, and the temperature of their solutions on weight gain, tensile properties and surface morphology of jute and basalt fabric reinforced epoxy composites. In total, four types of composite specimens (i.e. untreated jute fabric/epoxy, alkali-treated jute fabric/epoxy, silane-treated jute fabric/epoxy and untreated basalt fiber/epoxy) were fabricated and exposed to different ageing conditions for 180 days. The water absorption and tensile properties of these four composite specimens were measured and compared. The results showed that in general, the weight gains of the three plant-based natural jute/epoxy specimens (i.e. from 5.0% to 8.5%) were larger than that of the mineral-based natural basalt/epoxy composite (i.e. from 1.1% to 2.2%). Both alkali and silane treatments of jute fiber reduced the water absorption and enhanced the tensile strength of the resulting jute fabric/epoxy composites. For all the four types of composites, increasing exposure temperature of the water and the alkali solutions caused the reduction in their tensile strength. The strength reduction of these four types of composites at alkali solution was larger than the reduction of the corresponding composite at the water solution. In addition, their reduction in tensile strength was more pronounced compared with that in their Young's modulus. Compared with mineral-based basalt/epoxy composites, the untreated, alkali-treated and the silane-treated plant-based jute fabric/epoxy composites showed higher tensile strength reduction retention for the considered ageing conditions. However, the basalt fiber composites had much higher modulus retention. The deterioration of the interfacial properties of these composites at different ageing conditions was confirmed by the SEM observations.