Strain Rate Dependent Behavior of Glass/Nano Clay Filled Epoxy Resin Composite

It is believed that addition of small amount of nanoclays in the neat epoxy and fiber reinforced epoxy composite system can improve the mechanical properties. The mechanical properties of most of polymer matrix composites are sensitive to testing rate. However, most of the researches were concentrated on the behavior of the polymermatrix composites at high strain rates. The present research work is to investigate the role of clay on neat epoxy and glass–fiber reinforced epoxy composites, at low strain rates. The clay in terms of 1.5 wt%, 3 wt%, and 5 wt% are dispersed in the epoxy resin using mechanical stirring followed by sonication process. The corresponding glass/epoxy nanocomposites are prepared by impregnating the clay epoxy mixture by hand lay-up process. Characterization of the nanoclay is done by X-ray diffraction and Scanning Electron Microscopy. Tensile stress-strain curves are obtained at strain rates of 10-4 s-1, 10-3 s-1, 10-2 s-1, and 10-1 s-1 by a hydraulic  machine reporting that, even at low strain rates, the longitudinal strength and stiffness increase as strain rate increases for all clay loadings. It is observed that the tensile modulus increases as the clay loading increases for both epoxy and glass/epoxy nanocomposites. It is also noticed that the longitudinal tensile strength decreases as the clay loading increases. The failed specimens show marked changes in the fracture surface with increased strain rate. Scanning electron microscopy is used to study the fiber/matrix/clay adhesion in fracture surfaces.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 295-302, DOI:http://dx.doi.org/10.14429/dsj.64.733

Optimal Design of Filament Wound Grid-stiffened Composite Cylindrical Structures

An integral account of design and analysis of grid-stiffened cylindrical structures is presented. For convenience, a two-phase approach is adopted. In the initial phase, with a view to arriving at a few initial possible optimal configurations, parametric analysis through smeared stiffeners approach is utilised. The ribs, in a filament wound grid-stiffened structure, introduce several additional design elements that result in many possible design configurations; in the initial phase, these design options are efficiently reduced to a few numbers. Finite element modelling is used in the final design and analysis. Rib material is distinct from normal unidirectional composites and this aspect is inherently accounted for in the modelling approaches considered here.Defence Science Journal, 2011, 61(1), pp.88-94, DOI:http://dx.doi.org/10.14429/dsj.61.48

Perforation of Layered Composite Plates byImpactors of Different Nose Shapes

Conical and hemispherical nose-shaped cylindrical impactors have been used in drop weightimpact experiments on 3.1 mm CSM-polyester laminated plates. Based on experimental results,various failure mechanisms and energy absorbed in different failure modes are identified and calculated.It is found that the damage area beyond a certain value of impact energy does not increase. Theperforation geometry is the same as that of the impactor irrespective of increased crack length, andcomplete rotation of petals takes place at impactors radius. It is also observed that the crack lengthincreases with decrease in contact area. But, when the nose is sharp (5 mm hemispherical nose), thereis no extended crack beyond perforated region. Blunt nosed (truncated conical impactor with 10 mmnose dia) impactors cause more number of petals/cracks than 10 mm hemispherical nosed impactorand less than 5 mm hemispherical nosed impactor. The petals formed by a cylindrical impactor with40 mm hemispherical nose are unequal in size, whereas in the case of conical impactors, these areequal. At lower energies, blunt nosed impactors cause more delamination than the hemisphericalones, and at higher energy, it is the reverse. It is found that there exist many visible concentriccircular ring hinge mechanisms at the top surface of plates

Energy Absorption Characteristics of Metallic and Composite Shells

Metallic and composite shells of different sizes and tubes were subjected to axial compression in an Instron Machine. Their progressive failure modes and energy absorption capacities have been studied. In the case of metallic shells, analytical expressions are derived to find the mean collapse load and the fold length based on the formation of plastic hinges. Theoretical results have been compared with experimental results wherever possible. The effect of internal folding on the post-collapse behaviour of round tubes has been discussed and expressions for fold length and post-collapse load compression curves are derived as a function of internal folding. Based on the experimental observations, analysis has been carried out to find the progressive crushing load and crush length in a cycle of round and conical shells. The shells are infilled with polyurethane foam and subjected to axial compression. The effect of foam on the crushing behaviour is also studied. Conical shells of different cone angles varied from 8.5" to 45" and the effect of cone angle on the crushing mode of the conical shells has been studied. Also, a comparative study of metallic and composite shells has been carried out based on the deformation and energy absorption characteristics. The different parameters considered for analysis include effective crushing length and total energy absorbed during the crushing process and the Euler buckling length in metallic shells

Buckling Analysis of Composite Hexagonal Lattice Cylindrical Shell using Smeared Stiffener Model

Hexagonal lattice pattern formed by helical and circumferential ribs is the most common among different possible lattice patterns. An energy-based smeared stiffener model (SSM) is developed to obtain equivalent stiffness coefficients of a composite lattice cylindrical shell with such hexagonal lattice patterns. Using the equivalent stiffness coefficients, Ritz buckling analysis was carried out. Extensive finite element modelling covering different representative sizes have been carried out. SSM is validated by comparing the estimated buckling loads. Variation of material properties of rib unidirectional composites from those of normal unidirectional composites is accounted for in the energy  formulations.Defence Science Journal, 2009, 59(3), pp.230-238, DOI:http://dx.doi.org/10.14429/dsj.59.151

Ballistic Impact on Glass/Epoxy Composite Laminates

Glass/epoxy composite laminates are subjected to impact loading and the energy absorbing capacity of the laminates is studied. In the present study, laminates with four different orientations and thickness values are considered. Analytical study is carried out based on energy method and results are compared with FE results obtained from Abaqus/Explicit software. Results obtained from the analytical methods are showing good agreement with the FE results. It is found that cross-ply laminates are most efficient in ballistic resistance when compared with the laminates of other orientations. It is also noticed that the energy absorbing capacity is decreasing with increase in velocity of the projectile for a given lay-up and thickness value.Defence Science Journal, Vol. 64, No. 4, July 2014, pp. 393-399, DOI:http://dx.doi.org/10.14429/dsj.64.3882

Problems in Public Distribution System

To minimize the poverty level among general public, Government of India promoted Public distribution system for extending basic necessary goods at subsidized rates. But their primary motto has not been fulfilled due to numerous problems prevailing in PDS. Thus, an attempt has been made in this study to ascertain the Problems prevailing in PDS. The result of the study indicates that Adulteration, Distribution of inferior quality goods, Under Weighment are the common problems found in Public distribution system

Awareness and Usage of Electronic Resources by the Faculty Members - A Case Study

This paper aimed to explore the awareness and usage of online resources by the faculty members of Vivekanandha Arts and Science College for Women, Salem. The current study is rooted in primary data which were collected from the faculty members who are working in different departments of Vivekanandha Arts and Science College for Women. A total of 200 well structured and designed questionnaires were dispersed among the faculty members and we received only 179 filled questionnaires were returned out of 200 sample of population and the total response rate was 89.5%. The results of the study was observed and found the maximum number of 112 users (62.57%) was male distribution. Seventy percent of the faculty members were under the age group between 26 and 50 and 66.48 percent of the respondents were from rural area. It is observed the huge proportion of (42.46%) 76 faculty members were comes under Assistant professors and they ranked the first. It is noted the major portion of 91 (50.84%) faculty members were using the Internet in the central library for preparing research work. This study has recommended that more electronic journals and databases should be subscribed to, that awareness and training programmes for accessing electronic resources to be implemented, and the digital library infrastructure facilities to be enhanced

A Study on Quality of Work Life of Software Professionals in Bengaluru City

Purpose: The earning potential of software companies depends on their employees’ productivity. To improve productivity, the organizations have to provide their employees with a pleasant working environment.  By offering pleasant Quality of Work Life (QWL) a company may retain efficient employees and keep them preoccupied with work, thereby improving productivity.    Design / Methodology / Approach: Study being descriptive in nature. Data relevant to the study have been collected by employing well-structured questionnaire. By adopting convenience sampling technique software employees have been selected from Bengaluru city. Data have been gathered from select software professionals at Bengaluru city.  Questions relating to personal profile and quality of work life are included in the questionnaire.   Findings: Result of chi-square test discloses that gender, educational qualification, type of family and working hours significantly influences the perception of QWL of Software Professionals.   Practical Implications: The result of the study assist employers to understand their employees’ perception towards quality of work life and understand the employees’ expectations thereby, management are in a positon to fulfil the expectations of the employees.  Once employees’ expectations are fulfilled dedicated and committed employees may be retained at the workplace and efficient employees are attracted, thereby productivity and profitability of an institution may improve.   Social Implications: Offering better working environment at work place may motivate employees to be loyal and committed and to put their level best for the development of an organization as a whole.   Sincere and committed employees are an asset for the institution, their efforts not only contribute towards institution growth but also growth of a nation as a whole.   Originality / Value: Data collected through questionnaire are original in nature. Questionnaire assist in understanding the employees’ perception towards quality of work life at their work place