Venkata P. Kommula

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.

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.

Mechanical Properties, Water Absorption, and Chemical Resistance of Napier Grass Fiber Strand–Reinforced Epoxy Resin Composites

Napier grass fiber strands were used as reinforcement to obtain composites with epoxy resin as matrix. To improve the surface, these fiber strands were treated with alkali solution. The composites were prepared by means of hand lay-up molding, then the effects of Napier grass fiber strand loading on mechanical properties such as tensile, flexural and impact, interfacial bonding, and chemical resistance were investigated. The composite with 20 wt.% Napier grass fiber strands gives excellent mechanical properties and chemical resistance, showing that it has the best bonding and adhesion of the composites. SEM micrographs of fractured and worn surfaces clearly demonstrate the interfacial adhesion between fiber and matrix. Alkali-treated Napier grass fiber strand–reinforced composites have better resistance to water and chemicals than the untreated fiber strand composites.

Exploration on the characteristics of cellulose microfibers from Palmyra palm fruits

ABSTRACT To obtain cellulose microfibers from Palmyra palm fruit fibers, a new succession of specific chemical treatments including acidified chlorination, alkalization, and acid hydrolysis have been developed. Cellulose microfibers obtained were characterized by different techniques. The chemical analysis indicated an increase in α-cellulose content and decrease in lignin and hemicellulose for the cellulose microfibers over raw fibers. Fourier transform infrared and 13C NMR spectra confirmed the removal of non-cellulosic (lignin and hemicellulose) components after chemical treatments. The X-ray diffraction results revealed that the cellulose I was partly transformed into cellulose II by chemical treatments and the crystallinity index of cellulose microfibers was significantly increased as compared to raw fibers owing to removal of non-cellulosic components. Thermogravimetric analysis results demonstrated that the thermal stability was enhanced noticeably for cellulose microfibers than for the raw fibers. The scanning electron micrographs illustrated cleaner and rough surfaces for the cellulose microfibers when compared to those of raw fibers.

Extraction and characterization of cellulose single fibers from native african napier grass

With increasing awareness of protecting the environment, the demand for renewable and environmental materials is increasing. In this work, the cellulose single fibers (CSFs) were extracted from the African native Napier grass fibers (NGFs) by chemical process. NGFs and CSFs were characterized for their chemical composition, structure, morphology, crystallinity and thermal properties using, chemical analysis, FTIR, 13C CP/MAS NMR, SEM, XRD and TGA techniques. The resulted CSFs had higher α-cellulose content, crystallinity and thermal stability than the pristine NGFs. SEM images showed cleaner and rough surfaces for the CSFs when compared to those of NGFs. About 69% of the extracted CSFs showed a diameter range between 4 and 10 μm. FTIR and 13C CP/MAS NMR spectra confirmed the removal of lignin and hemicellulose components after chemical treatments.

Reliability Optimization for the Complex Bridge System: Fuzzy Multi-criteria Genetic Algorithm

System reliability optimization often involves multiple fuzzy conflicting objectives, for instance, reducing system cost and reliability improvement. This paper presents a system reliability optimization problem for the complex bridge system. First, the problem is formulated as a fuzzy multi-criteria nonlinear program. Second, we propose a fuzzy multi-criteria genetic algorithm approach (FMGA) to solve the problem. Fuzzy evaluation techniques are used to handle fuzzy goals and constraints, resulting in a flexible and adaptable approach that provides high-quality solutions within reasonable computation times. Using fuzzy theory concepts, the preferences of the decision maker on the cost and reliability objectives are judiciously incorporated. Third, computational experiments results are presented based on benchmark problems in the literature. The computational results obtained show that the proposed method is encouraging.

Extraction and structural characterization of cellulose from milkweed floss

ABSTRACT The aim of this study was to investigate the utilization of milkweed fruit floss residues as a source for the isolation of cellulose. Cellulose was extracted by acidified sodium chlorite and sodium hydroxide treatments. Characterization of the pristine milkweed floss and extracted cellulose was performed by chemical composition analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The extracted cellulose had mainly α-cellulose as the other components hemicellulose and lignin were significantly removed during cellulose extraction process. The FTIR spectra also indicated that the chemical treatments extensively removed hemicellulose and lignin from the pristine milkweed floss. SEM technique was used to investigate the surface morphology of the pristine milkweed floss and extracted cellulose. The intensity of the crystalline peak in the X-ray diffractograms of the extracted cellulose was higher than that of pristine milkweed. Further, the XRD results indicated a structural transformation of cellulose I (pristine milkweed) to cellulose II (extracted cellulose) because of the chemical treatments. The extracted cellulose, which is a high biomass, had better thermal stability than the pristine milkweed floss owing to removal of non-cellulosic components.

Tracking Design Elements in a Mechanical Engineering Curriculum

Design activity is core to modern engineering practice. Some design experience is demanded by professional bodies that accredit degree engineering programmes (e.g. ABET and ECSA). The purpose of this paper is to track design related topics through the curriculum of the mechanical engineering degree programme at the University of Botswana. A questionnaire was designed and administered to staff teaching on the programme. The responses were used to map design components in the curriculum and assess the design experience of students. The results showed that design topics were delivered in various courses and the knowledge gained by students increased steadily from Year 3 to Year 5. Some observed deficiencies in the teaching of design included lack of industry recommended projects, negligible application of design software, and the use of only single discipline based problems (i.e. no multi disciplinary teaching approach). It was concluded that a programme review is needed to improve the pedagogy of design and enhance programme robustness. It is envisaged that the study will help in designing a new mechanical engineering curriculum to satisfy accreditation requirements.