The utilization of synthetic materials stimulates environmental concerns, and researchers worldwide are effectively reacting to environmental concerns by transitioning towards biodegradable and sustainable materials. Natural fibers like jute and sisal have been being utilized for ages in several applications, such as ropes, building materials, particle boards, etc. The absence of essential information in preparing the natural-fiber-reinforced materials is still a challenge for future applications. Chemical treatments and surface modifications can improve the quality of the natural fibers. Natural-fiber-based composites are a potential candidate for many lightweight engineering applications with significant mechanical properties. In the view of the progressive literature reported in the field, this work aims to present the significance of natural fibers, their composites, and the main factors influencing these materials for various applications (automotive industry, for instance). Secondly, we aim to address different surface modifications and chemical treatments on natural fibers and finally provide an overview of natural fiber reinforced polymer composites’ potential applications.

Metals are known for high ductility and have, been used to design and fabricate structural components for many years. However, composite materials are taking over traditional materials owing to their significant mechanical properties. Fiber-reinforced composites exhibit lower ductility and failure strain, resulting in brittle failure, limiting their application where high ductility is desired. In this study, an effort has been made to design, fabricate, and test continuous fiber-reinforced composites with improved ductility. A comparative analysis was performed for optimizing the failure strain of different woven fiber-reinforced composite materials under both on-axis (0°/90°) and off-axis (±45°) loading. The materials include carbon/epoxy, E-glass/epoxy, and jute/epoxy composite. The tests were performed according to ASTM D3039 standard. The strength of all tested composites in on-axis and off-axis loading was obtained from tensile test results. But failure strain was limited in on-axis loading. Interestingly, glass/epoxy composite showed improved failure strain, by 90%, without much loss in tensile strength in off-axis loading than on-axis loading. The jute fiber revealed limited tensile strength and failure strain in both loading conditions.

There is an urgent need to recycle glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites due to environmental challenges caused by incineration and traditional landfilling. This review incorporates an overview of the latest knowledge on the recycling techniques for different GFRP and CFRP composites. The applications of these chopped fibers are limited due to significant depreciation in their mechanical properties after recycling. The high-value applications of the composites remanufactured through recycled fibers are outlined. This review also incorporates the present challenges and modern trends in the recycling of fiber-reinforced composites. It is expected that further innovations in recycling technologies will be helpful to establish a circular economy and sustainable benign environment. Graphical abstract

A salinity gradient solar pond (SGSP) is capable of storing a significant quantity of heat for an extended period of time. It is a great option for providing hot water at a reduced energy cost. Additionally, SGSP is used in low-temperature industrial applications such as saltwater desalination, space heating, and power generation. Solar pond thermal performance is dependent on a variety of operational variables, including the soil conditions, the climate of the particular site, the thickness of the solar pond layers, the depth of the water table, and the salt content of the pond. As such, this study examines the thermal performance of a solar pond under a variety of operational conditions. The solar pond model is used to test the thermal performance by simulating two-dimensional heat and mass transport equations. The equations are solved using the finite difference technique utilizing MATLAB® scripts. Salt distributions and temperature profiles are computed for a variety of factors influencing SGSP’s thermal performance. The main distinguishing variables influencing the thermal performance of SGSP are soil conditions, such as soil texture, types, the moisture level in soil, and water table depth. The final findings indicated that the fine sand dry soil performed better than the other soil types owing to its poor heat conductivity. The economic results indicated that the period of return (POR) of the intended system is around 2 years. The solar pond construction costs such as excavation, transportation, salt and lining, were considered based on the local prices. This modeled study extracted the greatest possible energy is 110W/m², with the fine sand dry at 62.48°C lowest temperature. This study suggested that the climatic conditions of Lahore is better than climatic conditions of Islamabad. Additionally, deeper water tables are suggested for improved thermal performance of the pond.