Unidirectional carbon fiber-reinforced polymer nanocomposites were developed by adding alumina (Al2O3) and silicon carbide (SiC) nanoparticles using ultrasonication and magnetic stirring. The uniform nanoparticle dispersions were examined with a field-emission scanning electron microscope. The nano-phase matrix was then utilized to fabricate the hybrid carbon fiber-reinforced polymer nanocomposites by hand lay-up and compression molding. The weight fractions selected for Al2O3 and SiC nanoparticles were determined based on improvements in mechanical properties. Accordingly, the hybrid nanocomposites were fabricated at weight fractions of 1, 1.5, 1.75, and 2 wt.% for Al2O3. Likewise, the weight fractions selected for SiC were 1, 1.25, 1.5, and 2 wt.%. At 1.75 wt.% Al2O3 nanoparticle loading, the flexural strength modulus improved by 31.76% and 37.08%, respectively. Additionally, the interlaminar shear and impact strength enhanced by 40.95% and 47.51%, respectively. For SiC nanocomposites, improvements in flexural strength (12.79%) and flexural modulus (9.59%) were accomplished at 1.25 wt.% nanoparticle loading. Interlaminar shear strength was enhanced by 34.27%, and maximum impact strength was improved by 30.45%. Effective particle interactions with polymeric chains of epoxy, crack deflection, and crack arresting were the micromechanics accountable for enhancing the mechanical properties of nanocomposites.

The present work aims to study the effect of water sorption–desorption–resorption conditions on the mechanical properties of epoxy-nanoclay nanocomposites (ENNCs). To prepare ENNCs specimens, nanoclay and epoxy are mixed together by a stirrer and a sonicator. The nanoclay-epoxy and hardener mixture are moulded into specimens that meet the dimensions prescribed by the ASTM standards. The specimens fabricated are subjected to three conditions viz., water sorption, desorption and resorption for a total of 140 days. Water sorption–desorption–resorption effects on the mechanical properties of pure epoxy and ENNCs are studied by tensile and flexural tests. Results showed that the nanoclay presence improved the mechanical properties and lowered the percentage of water uptake. Tensile and flexural strengths of epoxy and ENNCs are reduced under sorption conditions and recovered to more than 90% of their original strengths under desorption conditions. The lowest tensile and flexural strengths were displayed by specimens subjected to resorption in comparison to specimens subjected to the other two conditions. The flexural and tensile strengths of epoxy are more severely affected compared to ENNCs under water sorption–desorption–resorption conditions. Scanning electron microscopy images are employed to learn the causes of specimen failure under a tensile load.

Waste eggshells were procured and processed to obtain uncarbonised eggshells and carbonised eggshells. Four variants of composites viz., unfilled, uncarbonised eggshell filled, carbonised eggshell filled and hybrid eggshell filled were fabricated using hand lay-up technique. All three variants of filled composites were added 10 wt.% of eggshells. The idea of hybridizing the uncarbonised and carbonised eggshell fillers was also carried out. A mechanical stirrer was utilised for mixing the eggshells with unsaturated polyester resin. All four variants of composites were subjected to tensile and flexural strength tests as per the respective American Society for Testing and Materials (ASTM) standards. The tests showcased that all eggshell filled composites possess better tensile and flexural strengths compared to unfilled composites. Carbonised eggshell filled composites exhibited the highest strengths among all the composite variants considered followed by hybrid composites and uncarbonised eggshell filled composites. The unfilled composites exhibited the least strength. The carbonised eggshell filled composites showcased 43.9 and 34.14% higher tensile and flexural strengths in comparison with unfilled composites. Microscopic analysis of the failed specimens was conducted using a scanning electron microscope (SEM). The SEM images revealed that the eggshell filler was responsible for crack deviations and crack arrests contributing to the strength of the composites.

Abstract. The importance of medium carbon steels as engineering materials is reflected by the fact that out of the vast majority of engineering grade ferrous alloys available and used in the market today, a large proportion of them are from the family of medium carbon steels. Typically medium carbon steels have a carbon range of 0.25 to 0.65% by weight, and a manganese content ranging from 0.060 to 1.65% by weight. Medium carbon steels are more resistive to cutting, welding and forming as compared to low carbon steels. From the last two decades a number of research scholars reported the use of verity of heat treatments to tailor the properties of medium carbon steels. Spheroidizing is the novel industrial heat treatment employed to improve formability and machinability of medium/high carbon low alloy steels. This exclusive study covers procedure, the effects and possible outcomes of various heat treatments on medium carbon steels. In the present work, other related heat treatments like annealing and special treatments for property alterations which serve as pretreatments for spheroidizing are also reviewed. Medium carbon steels with property alterations by various heat treatment processes are finding increased responsiveness in transportation, aerospace, space, underwater along with other variegated fields. Improved tribological and mechanical properties consisting of impact resistance, stiffness, abrasion and strength are the main reasons for the increased attention of these steels in various industries. In the present scenario for the consolidation of important aspects of various heat treatments and effects on mechanical properties of medium carbons steel, a review of different research papers has been attempted. This review may be used as a guide to provide practical data for heat treatment industry, especially as a tool to enhance workability and tool life.

The main concern of this research is to identify the effect of multistage solutionizing and artificial aging behaviour on tensile behavior of LM4 + Si3N4 (1, 2, and 3 wt.%) composites. A two-stage stir casting method was employed to produce composites, which minimized the necessity for a lengthy and high-temperature preheating treatment of reinforcement and resulted in homogeneous reinforcement distribution. Cast composites were subjected to single-stage and multistage solutionizing heat treatment (SSHT and MSHT) followed by aging at 100 and 200°C. Peak hardness of the LM4 and cast composites was noted during artificial aging. With the increase in wt.% of reinforcement, the hardness of the composites increased. Cast composites subjected to MSHT and aging at 100°C displayed maximum hardness when matched to other combinations. Compared to as-cast LM4 hardness (70 VHN), L3SN (with MSHT + aged at 100°C) composite attained 124% higher hardness (157 VHN). UTS values followed a similar trend, compared to as-cast LM4 UTS (149 MPa), L3SN (with MSHT + aged at 100°C) composite attained 54% higher UTS (230 MPa). Major reasons for the improvement in mechanical properties of heat-treated composites are due to the existence of hard Si3N4 particles and the formation of θ'-Al2Cu and θ"-Al3Cu (metastable) phases. From the fracture surface analysis of LM4 and L3SN composite, it was concluded that the type of fracture experienced by LM4 is of ductile nature and that of the composite is of mixed nature.