Damage in Non-Crimp Fabric carbon fiber reinforced epoxy composites under various mechanical loading conditions

Composite materials have emerged in the recent years as a frontrunning lightweight replacement for metals for structural applications in lightweight automobiles. However, the key adoption criteria for composites in lightweight vehicles is their crashworthiness, i.e., the amount of energy a structure made with composites would absorb in a crash event. The energy is absorbed in composites through various damage modes such as matrix cracks, delamination, fiber breakage, etc. Therefore, adoption of a certain composite material system requires thorough understanding of the initiation and propagation of damage until failure in that system under various mechanical loading conditions, which is also the central theme of this study. The response of Non-Crimp Fabric (NCF) carbon fiber reinforced epoxy composites, manufactured using High Pressure-Resin Transfer Molding (HP-RTM), under quasi-static mechanical loads was thoroughly investigated in this study. The behavior of unidirectional lamina and four laminates, [0/±45/90]s, [90/±45/0]s, [±45/02]s and [±45/902]s, was characterized in this study. The engineering properties and interlaminar fracture toughness of the lamina and the laminates are first measured using standard test methods. An in-situ damage monitoring technique called as ‘edge replication’ and post-failure fractography were employed to understand the damage initiation and growth in the materials under quasi-static tension and compression. The role of stitching sites, which are the compliant areas formed due to stitching threads in the NCF architecture, in the initiation of damage was clearly understood in this study. The damage generally initiated in the form of localized cracks in the stitching sites at low strains, which then nucleated other damage modes in the laminates at higher strains. Influence of ply thickness and stacking sequence was also investigated. It was concluded that, although the stacking sequence had negligible influence on the global stress-strain response under tension, the rates and extents of damage were strongly dependent on the stacking sequence. The global compression response, measured engineering properties and the observed damage modes showed higher sensitivity to the laminate stacking sequence. Finally, the damage observed in the composites was correlated to the energy dissipated in the creation of damage in this study

Absolute distance (thickness) metrology using wavelength scanning interferometry

Wavelength scanning interferometry offers a new dimension in precision metrology by measuring the cavity length (thickness), the cavity length variation over the cavity area (flatness), and the optical homogeneity within a transparent cavity; without any mechanical movement by implementing a tunable laser. This property is useful when the physical movement of an optic is not feasible using traditional phase shifting methods employing piezoelectric transducers and for characterizing solid optical cavities which require movement of one surface relative to the other. The cavity length that can be measured is limited by the wavelength scanning range - a smaller cavity requires a larger tuning range. Tunable lasers are now available with very large tuning ranges in the near infrared, potentially extending the measurement range significantly. The use of Fourier analysis on the intensity (interference) time history as a post processing step enables the measurement of cavity lengths without any 2p phase ambiguity. This study demonstrates absolute length (thickness) measurements of various artifacts such as the thickness of a transparent window, gauge blocks, and the diameter of transparent spherical cavities such as a ball lens on a commercial wavelength scanning Fizeau interferometer. A mathematical model of the measurement process is demonstrated along with a software simulation model to understand the impact of dynamic parameters such as tuning rate on the thickness. Finally, a custom built wavelength scanning interferometer is designed from an existing wideband tunable laser in-house to demonstrate the thickness of sub-mm windows

Securing Web Accounts Using Graphical Password Authentication through MD5 Algorithm

Today, most Internet applications still uses traditional text based passwords for the authentication. Two conflict cases of traditional password i.e. if user choose simple password it will easy to guess by attacker. The other hand, if a password is strong then it is often hard to remember for user. Instead of a text password user will be choose graphical password scheme that uses MD5. In MD5 images that converted into binary code. Here binary code will be the password for user. Thus, graphical password is secure than existing graphical password techniques because every time user needs to enter different set of code for authentication i.e. every time new password gets generated making Dictionary attacks, Brute Force attack, and other attacks infeasible. Because of these advantages, there is a growing interest in graphical password. In addition user can use ?document sharing? feature after authentication process and also graphical passwords can be applied to workstation, web log-in applications, ATM machines and mobile device

The effect of restraints type on the generated stresses in gantry crane beam

This paper includes an analysis of the mechanical phenomena in the gantry crane beam, because the cranes are currently one of the most common devices for the transporting loads. Designing modern mechanical structures is a complex task that requires the use of appropriate tools. Such a modern tool is the numerical simulation, which uses different numerical methods. One of the best known methods is the finite element method, also used here. Simulations are limited to analysis of the strength of the gantry crane beam that was the loaded of the force load movement along its length. The numerical analysis was made to the gantry crane beam which cross-section was an I-beam and ends were fixed in different ways. As the result of numerical calculations, the stresses and displacements of the structure of gantry were obtained. The influence of the restraints type and changing the loading force position on generate the Huber-Misses stress in the gantry crane beam was estimated. The aim was to ensure that the maximum equivalent stress generated in the gantry crane beam was less than the strength of material, because then the construction is safe

Access to food source and food source use are associated with healthy and unhealthy food-purchasing behaviours among low-income African-American adults in Baltimore City

Although previous research has shown limited availability of healthy food in low-income urban neighbourhoods, the association between food source use and food-purchasing patterns has not yet been examined. We explored food-purchasing patterns in the context of food source use and food source access factors in low-income areas of Baltimore City. Cross-sectional survey. Predominantly low-income neighbourhoods in East and West Baltimore City. A total of 175 low-income African-American adult residents. Supermarkets and corner stores were the most frequently used food sources. Walking was the main form of transportation used by 57 % of all respondents, 97 % of corner-store shoppers and 49 % of supermarket shoppers. Multiple linear regression models adjusting for demographic factors, type of food source used and transportation type found that corner-store use was associated with obtaining more unhealthy food (P = 0·005), whereas driving to the food source was associated with obtaining more healthy food (P = 0·012). The large number of corner stores compared with supermarkets in low-income neighbourhoods makes them an easily accessible and frequently used food source for many people. Interventions to increase the availability and promotion of healthy food in highly accessed corner stores in low-income neighbourhoods are needed. Increased access to transportation may also lead to the use of food sources beyond the corner store, and to increased healthy food purchasing

Synthesis of silver nanostructures for biological and environmental applications

"Nanotechnology is probably, as a phenomenon, the single most important new emerging force in technology." - Charlie Harris, CEO, Harris & Harris Group As the above quote suggests nanotechnology is not only a technology it is a phenomenon that has taken science to cutting edge technology. Nanotechnology has opened a new era of science where scientists can manipulate at nano meter scale. Nanoparticles are applied in almost all walks of life ranging from cosmetics to health and medical diagnostics (Gupta K.A 2005), ceramics (G. Aharon 2007). In a project concerning nanoparticles there are three important phases, synthesis phase, characterization phase and application phase. In the synthesis phase nanoparticles are synthesised using various chemical and physical methods that usually involve a surfactant, capping agent and a reducing agent. In recent years there has been a lot of interest in synthesizing nanoparticles of various shapes ranging from cubes, rods, triangles and prisms. In this project we will be focusing on the synthesis of silver nanoprsims, which have a characteristic quadrupole surface plasmon mode and has therefore found itself applicable in Surface Enhanced Raman spectroscopy (Sherry J.L 2006), for single molecule detection. In the project we will also look at the stability of nanoparticles in biological and ecotoxicological media. We will be using Uv-Vis spectroscopy for the analysis of the results

A study of the systems CuSO<SUB>4</SUB>-NiSO<SUB>4</SUB>-H<SUB>2</SUB>O and CuSO<SUB>4</SUB>-CoSO<SUB>4</SUB>-H<SUB>2</SUB>O

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