Natural fibre-based composites are replacing traditional materials in a wide range of structural applications that are used in different environments. Natural fibres suffer from thermal shocks, which affects the use of these composites in cold environment. Considering these, a goal was set in the present research to investigate the impact of cryogenic conditions on natural fibre composites. Composites were developed using polyester as matrix and jute-fibre and waste Teak saw-dust as reinforcement and filler, respectively. The effects of six parameters, viz., density of saw-dust, weight ratio of saw-dust, grade of woven-jute, number of jute layers, duration of cryogenic treatment of composite and duration of alkaline treatment of fibres on the mechanical properties of the composite was evaluated with an objective to maximise hardness, tensile, impact and flexural strengths. Taguchi method was used to design the experiments and response-surface methodology was used to model, predict and plot interactive surface plots. Results indicated that the duration of cryogenic treatment had a significant effect on mechanical properties, which was better only up to 60 min. The models were found to be statistically significant. The study concluded that saw-dust of density 300 kg/m³ used as a filler with a weight ratio of 13 wt.% and a reinforcement of a single layer of woven-jute-fibre mat of grade 250 gsm subjected to alkaline treatment for 4 h in a composite that has undergone 45 min of cryogenic treatment presented an improvement of 64% in impact strength, ca. 21% in flexural strength, ca. 158% in tensile strength and ca. 28% in hardness.

Opportunities for the fabrication of plant fiber hybrids using thermoplastics and thermosets may be found in a variety of industries, including automobiles and agriculture. This can lessen reliance on crude oil, which contributes to a number of sustainability problems. In the current study, calotropis gigantea fiber (CGF) and nanosilicon dioxide (SiO₂)-derived hybridized materials’ mechanical, dynamic mechanical, and water absorption properties were examined. Utilizing varying weight proportions of nanoSiO₂ (0, 1.5, 3, and 4.5 wt%) and 30 wt% of CGF, we manufactured the composite using the hand lay-up method. The moisture absorption of the manufactured composites was measured during periods of 500, 1000, and 2000 h. For composite materials containing 1.5 wt% SiO₂, the highest interlaminar shear strength (ILSS) failure point was 12.52 MPa for 500 h, which is 12.32% lower than the breaking strength for dried products (14.28 MPa). In comparison to the dry specimens, the bending strength of hybrids with 1.5% SiO₂ that were immersed in water for 500, 1000, and 2000 h decreased by 2.56%, 5.21%, and 9.65%, respectively. The storage modulus of the damp hybrids with 3% and 4.5 wt% SiO₂ was higher than that of the dry samples in terms of their dynamic mechanical properties. While the inclusion of nano-SiO₂ significantly reduced water absorption and moisture diffusion, especially for hybrid materials with 4.5 weight percent SiO₂, the water-absorption behaviour of hybrid natural fiber materials followed the Fickian law. With prolonged exposure time, the mechanical properties of the nanocomposite, both with and without nano-SiO₂, such as ILSS and bending strength, declined. Due to the effective distribution of filler in the matrices, the samples with 4.5 weight percent SiO₂ exhibited the smallest drop in strengths for both the flexural and interlaminar examinations, although all of them remained stronger than the CGF blends. The outcomes of the study point to potential applications in areas such as automobile manufacture, agriculture, construction, and general manufacturing.

This work aims to identify the pattern for the major output parameters, material removal rate (MRR) and surface roughness (R_a) of different combinations of Al6061-based composites. Based on the verification carried out on these patterns using analysis of variance (ANOVA) as the mathematical tool, the work predicts the mentioned output characteristics while machining Al6061 composites of different material compositions based on their hardness values. ANOVA was employed for the generation of equations of the particular composite. The equations were compared for the coefficients of each parameter employed in ANOVA. The work was carried out comparing the characteristic equation of different combinations of Al6061-based composite. The results indicate that the coefficients of the current show a drastic variation when compared to other coefficients for both the output parameters. It was observed that the current and its coefficients contribute to the output parameters based on the variation in hardness. For surface roughness, the constant of the characteristic equation was also found to influence the parameter for the change in hardness. The equation derived for both material removal rate (MRR) and surface roughness (R_a) were identified to be matching with the experimental result carried out for validation. The average variation observed was 9.3% for MRR and 7.2% for surface roughness.

The machining of composite materials has been an area of intense research for the past couple of decades due to its wide range of applications, from automobiles to air crafts or from boats to nuclear systems. Non-conventional machining, especially electric discharge machining (EDM), is found to be a good machining option for meeting the required outputs. To overcome the challenges of machining complex shapes, wire electric discharge machining (WEDM) was developed. Al6351 composites was observed to be extensively used in nuclear applications. Therefore, identifying the kerf width and surface roughness are important criteria for the dimensional accuracy of the final product. The present work aims at predicting the behavior of the two major machining parameters which are kerf width and surface roughness of Al6351 composites in wire EDM by creating a mathematical model using ANOVA for different combinations of the reinforcements and comparing the variations in the coefficients for different combinations of reinforcements. The developed model has been validated by conducting similar set of experiments in Al6351-5% SiC-1% B₄C hybrid composite. From the work, it was identified that pulse on time and current are the major contributing factor for kerf width and wire feed rate was observed to be contributing to the surface roughness. The validation results show an average variation of 8.17% for kerf width and 11.27% for surface roughness. The work can be successfully utilized for prediction of the kerf width and surface roughness of the composites manufactured with Al6351 as the base matrix material.

Solid particle erosion inevitably occurs if a gas–solid or liquid–solid mixture is in contact with a surface, e.g., in pneumatic conveyors. Nowadays, an erosive failure of the component after the usage of a long period has been gaining the interest of the researchers. In this research work, carbon fibre-reinforced polymer (CFRP) composites are prepared by varying the tow sizes of fibres, such as 5k, 10k, and 15k. The prepared composites are subjected to erosion studies by varying the process parameters, such as the impact angle (30, 60, and 90 degrees) and velocity (72, 100, and 129 m/s). The Taguchi orthogonal array design has been employed for the experimental plan and the erosion rate and surface roughness are observed for each run. The changes in the responses are reported for varying process parameters. The higher erodent velocity of 129m/s leads to higher erosion rates and forms poor surface quality. The minimum impact angle of 30 degrees provides higher erosion rates and higher surface roughness than the other impingement angles. Finally, the eroded surface of each sample is examined through microscopic and 3D profilometer images and the erosion mechanism is analysed at different conditions. The eroded particles supplied at lower speeds do not penetrate the composite surface. However, it is well-known that the lower the collision force, the harder the traces on the surface, yet no sign of fibre breaking or pull-out is observed. The passage of erodent particles on the composite caused surface waviness (flow trace), which prevents the surface from degrading.