Mukul Shukla

Physico-chemical, Tensile, and Thermal Characterization of Napier Grass (Native African) Fiber Strands

This article presents the extraction and effect of alkali treatment on the physical, chemical, tensile, and thermal characteristics of fiber strands obtained from Napier grass, a renewable biomass. In order to improve these properties, the Napier grass fiber strands were treated with sodium hydroxide. The alkali treatment was carried out using NaOH solution at three different concentrations (5, 10, and 15%) for 2 h. Characterization of untreated and alkali-treated Napier grass fiber strands was carried out by studying the chemical composition, surface morphology, functional group variation, crystallinity, and tensile and thermal behavior. It was found that untreated fiber strands have lower cellulose content, crystallinity, tensile properties, and thermal stability than alkali-treated fiber strands. Napier grass fiber strands treated with 10% NaOH showed optimum tensile strength, modulus, and percentage elongation with an improvement of 51.9, 47.3, and 12.1% respectively. Based on the properties determined for alkali-treated Napier grass fiber strands, we expect that these fibers will be suitable for use as a reinforcement in natural fiber composites.

Finite element analysis of multi-particle impact on erosion in abrasive water jet machining of titanium alloy

Abrasive water jets (AWJs) are finding growing applications for machining a wide range of difficult-to-machine materials such as titanium alloys, stainless steel, metal matrix and fibre reinforced composites, etc. Current applications of AWJs include machining of Titanium alloys for aircraft components and bio-medical implants to removal of aircraft engine coatings. This paper presents the application of an elasto-plastic model based explicit finite element analysis (FEA) to model the erosion behaviour in abrasive water jet machining (AWJM). The novelty of this work includes FE modelling of the effect of multiple (twenty) particle impact on erosion of Grade 5 Titanium alloy (Ti-6Al-4V). The influence of abrasive particle impact angle and velocity on the crater sphericity and depth, and erosion rate has been investigated. The FE model has been validated for stainless steel and yields largely improved results. Further, the same FEA approach has been extended to model the multi-particle impact erosion behaviour of Titanium alloy.

Characterizing the Effect of Laser Power Density on Microstructure, Microhardness, and Surface Finish of Laser Deposited Titanium Alloy

This paper reports the effect of laser power density on the evolving properties of laser metal deposited titanium alloy. A total of sixteen experiments were performed, and the microstructure, microhardness and surface roughness of the samples were studied using the optical microscope (OP), microhardness indenter and stylus surface analyzer, respectively. The microstructure changed from finer martensitic alpha grain to coarser Widmastatten alpha grain structure as the laser power density was increased. The results show that the higher the laser power density employed, the smoother the obtained surface. The microhardness initially increased as the laser power density was increased and then decreased as the power density was further increased. The result obtained in this study is important for the selection of proper laser power density for the desired microstructure, microhardness and surface finish of part made from Ti6Al4V.

Mechanical Properties and Chemical Resistance of Short Tamarind Fiber/Unsaturated Polyester Composites: Influence of Fiber Modification and Fiber Content

In the present work, tamarind fibers were extracted from ripened fruits by the water retting process. Using these fibers as reinforcement and unsaturated polyester as matrix, composite samples were prepared by the hand lay-up technique. The effect of chemical surface treatments (alkali and silane) of tamarind fibers on the mechanical properties, chemical resistance, and interfacial bonding was studied. The mechanical properties of the composites with surface modified fibers were found to be higher than those with unmodified fibers. Morphological studies indicated improvement of interfacial bonding by alkali and silane coupling agent treatments of the fibers. The composites were found to be resistant to many chemicals.

Effect of sodium alginate modification of graphene (by ‘anion-π’ type of interaction) on the mechanical and thermal properties of polyvinyl alcohol (PVA) nanocomposites

Layered aligned dispersion of graphene in graphene/polyvinyl alcohol (PVA) nanocomposites is prepared in the form of films through simple solution processing route. The results indicate that there exist an interfacial interaction between PVA and graphene because of hydrogen bonding. This is responsible for the change in structure of PVA (such as decrease in the level of crystallization) and exhibiting ductile PVA nanocomposite film with improved tensile modulus, tensile strength, and thermal stability. Moreover, to improve the mechanical properties of PVA nanocomposites, graphene is successfully modified using a non-covalent modifier, sodium alginate (SA) and there exist an ‘anion-π’ type of interaction in between SA and graphene. The modification results in finer dispersion of the graphene in PVA/SA-m-graphene nanocomposites. In addition, there exist a hydrogen bonding in between PVA and SA. This has resulted in the remarkable improvement in mechanical properties of PVA/SA-m-graphene nanocomposites as compared to pure PVA and PVA/graphene nanocomposites. The increase in mechanical properties of PVA/SA-m-graphene nanocomposites is achieved through better load transfer from graphene to polymer matrix, despite decrease in crystallinity of PVA. Improvement in tensile modulus and tensile strength is highest at 0.5 wt.% of SA-modified graphene in PVA/SA-m-graphene nanocomposites because of finer dispersion of graphene and is 62 and 40% higher than that of pure PVA. Addition of SA-modified graphene also improves the thermal stability of PVA/SA-m-graphene nanocomposites remarkably as compared to unmodified graphene PVA nanocomposites.

Effect of Chemical Treatment and Fiber Loading on Mechanical Properties of Borassus (Toddy Palm) Fiber/Epoxy Composites

The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber–reinforced epoxy composites. Composites were prepared by the hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH) and alkali combined with silane (3-aminopropyltriethoxysilane) treatment of the fiber surface was carried out. Examinations through Fourier transform-infrared spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made with chemically modified and untreated Borassus fibers were studied using a universal testing machine. Based on the experimental results, it was found that the tensile properties of the Borassus-reinforced epoxy composites were significantly improved as compared with the neat epoxy. It was also found that the fiber treated with a combination of alkali and silane exhibited superior mechanical properties to alkali-treated and untreated fiber composites. The nature of the fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites.

Extraction, modification, and characterization of natural ligno-cellulosic fiber strands from napier grass

ABSTRACT Napier grass is a high-productivity perennial grass that is a very important forage for animals in the tropics. In this research work, fiber strands from Napier grass were extracted and the effect of acetic acid treatment on their chemical composition, morphological and structural changes, and tensile and thermal properties was studied. The acid treatment was carried out using glacial acetic acid solution at three different concentrations (5, 10, and 15%) for 2 h. Chemical analysis indicated lowering of amorphous hemicellulose content on acid treatment. FT-IR spectroscopic studies revealed variation of functional groups on acid treatment. Scanning electron micrographs indicated roughening of the surface of the fiber strands due to the removal of the hemicellulose layer on acid treatment. X-ray diffraction analysis indicated an increase in crystallinity of the fiber strands on acid treatment. The thermal stability and tensile properties of the fiber strands increased on acid treatment. This fiber has competitive advantages when evaluated with other natural fibers and can be developed further as a potential reinforcement in polymer matrix composites.

Evaluation of mechanical behavior of chemically modified Borassus fruit short fiber/unsaturated polyester composites

Natural fine fibers were extracted from Borassus fruits belonging to the Arecaceae family. To improve the surface, these fibers were treated with aq NaOH solution. Composites were prepared by the hand lay up process using both the untreated and alkali-treated Borassus fine fibers as reinforcement and unsaturated polyester resin as matrix. The effect of a coupling agent and alkali treatment of fibers on tensile, flexural and impact properties of the composites was studied. The mechanical properties and interfacial bonding were found to improve when surface modified fibers were employed in the composites. This is due to the improvement of chemical bonding between the treated fibres and polyester matrix as also supported by Fourier transform infrared results. Water absorption by the different composite types was also found to be negligible.

Three-phase carbon fiber amine functionalized carbon nanotubes epoxy composite: processing, characterisation, and multiscale modeling

The present paper discusses the key issues of carbon nanotube (CNT) dispersion and effect of functionalisation on the mechanical properties of multiscale carbon epoxy composites. In this study, CNTs were added in epoxy matrix and further reinforced with carbon fibres. Predetermined amounts of optimally amine functionalised CNTs were dispersed in epoxymatrix, and unidirectional carbon fiber laminateswere produced. The effect of the presence of CNTs (1.0 wt%) in the resin was reflected by pronounced increase in Youngs modulus, inter-laminar shear strength, and flexural modulus by 51.46%, 39.62%, and 38.04%, respectively. However, 1.5wt% CNT loading in epoxy resin decreased the overall properties of the three-phase composites. A combination of Halpin-Tsai equations and micromechanics modeling approach was also used to evaluate the mechanical properties of multiscale composites and the differences between the predicted and experimental values are reported. These multiscale composites are likely to be used for potential missile and aerospace structural applications.

A Comparative Study of Modified and Unmodified High-Density Polyethylene/Borassus Fiber Composites

In this work, composite samples were prepared using Borassus fibers and a high-density polyethylene matrix. Alternatively, a chemically modified matrix (maleic anhydride grafted HDPE) was also used to improve fiber-matrix compatibility. The effect of fiber loading on the mechanical properties was investigated. Borassus fiber/modified HDPE composites exhibited improved mechanical performance as compared to pure HDPE composites. SEM studies on the fractured specimens of unmodified HDPE fiber composites reveal the poor fiber-matrix interaction, whereas the interaction is strong with enhanced mechanical properties for modified HDPE fiber composites. This is due to an improvement of the chemical bonding between the modified HDPE matrix and the Borassus fiber as also supported by Fourier transform infrared spectroscopy results. Thermal stability was also found to be enhanced slightly for modified HDPE composites.