Usage of composites with natural fiber reinforcement is drastically increasing in recent times because of their low density, biodegradable nature, and low cost. However, natural fibers have certain core problems such as poor adhesion between the fiber and matrix and a relatively high degree of moisture absorption. Alkaline treatment of natural fibers is aimed at improving the adhesive strength so that effective stress transferability takes place in the composite. In the present work, Cordia-Dichotoma fibers were treated with sodium hydroxide (NaOH) and composites were prepared with different weight ratios of these fibers reinforced with epoxy. The prepared composites were tested for their tensile and flexural strengths (mechanical properties). Besides, for a comprehensive material characterization, IR spectroscopy (FT-IR), scanning electron microscope, and thermogravimetric analysis were carried out. This work investigates the influence of aforementioned NaOH treatment on thermal, mechanical, and morphological properties of the composite material.

Nowadays, research attention on composite materials accentuates where not only was their unique attributes agglomerated-alleviated weight and density, elevated impact and specific strengths, but also on where their bio-degradability and eco-friendliness transpires. In these, the alkali treated composites, to meet the needs of the aforementioned attributes and economy, with significant applicability in the market avenues. Hence, the present experimental study endeavors on investigating the effect of alkali treatment on mechanical and thermal properties of Tapsi fiber-reinforced polymer composites. Further, their characterization was done using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. From the results, it is found that 15 gms Tapsi fiber reinforced with NaOH treated specimens exhibited 43.02 MPa and 160 MPa of tensile and flexural strengths, respectively, which is notable and 10 gms Tapsi fiber reinforced with NaOH treated specimens revealed more thermal stability. The results are witnessed that showcase the effect of alkali treatment on the aforementioned properties through different characterization techniques.

A percentage of natural fibers is used for developing a composite, the materials are quite increasing in recent trends, and they can be a potential replacement of synthetic fibers in the reinforcement phase of hybrid composite. In this research, the combination of natural fibers and synthetic fibers can be used as reinforcement, and epoxy polymer can be used as matrix material. The fibers of Kevlar and Napier grass are reinforced with epoxy matrix to develop a new composite by using conventional hand layup fabrication process and to quantify the effect of this hybrid composite laminate, with five different sequences following. To identify the mechanical properties of this hybrid composite through tensile, flexural, compression strength, impact strength, and hardness tests, among all five samples, sample A was given the maximum mechanical strength, such that the tensile strength is 210 MPa, flexural strength is 165 MPa, the impact energy absorption is 23 J, the average is 40% over the other samples, and, at the same time, the compression strength of sample E is 19 MPa, revealing the negative influence of hybrid composite. The SEM morphology was carried out to identify the failure mode of the hybrid composites.

Automotive industry attention in using date palm fiber as an internal material has been sparked by its use as a polymer reinforced composite. Date palm fiber-reinforced aliphatic epoxy composites for semistructural applications are the key goals of this work. To make the various composites, they used a combination of manual lay-up and adhesive bonding. Date palm fiber/bamboo hybrid composite and uncontaminated composites were tested through density, tensile, flexural, and impact tests and also studied the effects of swelling, water absorption, and physical performance in greater depth. According to studies, hybrid composites constructed from date palm fiber and bamboo had the best mechanical properties. The date palm/bamboo hybrid composite was created to impact the toughness of 12.72 J/m in tensile, flexural strength, and impact toughness measurements. The reduced swelling and water absorption were 27.66 percent and 15.37 percent, respectively, when testing a date palm fiber/bamboo hybrid composite. Density ranged from 1.15 g/cm³ to 1.25 g/cm³ for bamboo fiber composite material and from 1.23 to 1.27 g/cm³ for date palm fiber/bamboo composite material. High flexural strength is achieved by the bamboo composite specimen (bamboo: 6.18 MPa), followed by (PDF-/: 61.12 MPa, date palm fiber-AA/: 61.08 MPa, date palm fiber-/: 60.82 MPa, and date palm fiber-/: 61.47 MPa), and the PDF composite specimens (date palm fiber-/: 61.112). Hybridized materials (date palm fiber/bamboo fiber) with a 50 : 50 ratio had higher impact strength.

Phase change material (PCM) based thermal energy storage (TES) systems are gaining increasing importance in recent years in order to reduce the gap between energy supply and demand in solar thermal applications. The present work investigates the effect of PCM capsule material on the performance of TES system during charging and discharging processes. The TES unit contains paraffin as PCM filled in spherical capsules and is integrated with flat plate solar collector. Water is used as sensible heat material as well as heat transfer fluid (HTF). The PCM capsules are of 68 mm diameter and are made using three different materials, namely, (i) high density polyethylene (HDPE), (ii) aluminum (Al), and (iii) mild steel (MS). The experimental investigation showed that the charging and recovery of stored energy are less affected by the spherical capsules material. The variables, like charging time and discharging quantity, are varied around 5% for the different capsule materials. Even though aluminum thermal conductivity is much higher than HDPE and mild steel, its influence on the performance of TES system is very low due to the very high internal heat resistance of PCM material stored in the spherical capsules.