Design, Fabrication And Evaluation Of Composite Sandwich Panels For Crashworthiness

As time progressed, so did the technology of transportation and today we have a range of motorized vehicles that run on fossil fuel. The number of these vehicles is increasing year by year throughout the globe. There are two negative issues on this. First, the demand on fuel will increase and the second is that due to the increase of vehicles on road, the number of accidents and casualties has also increased the last two decades to an alarming figure. These accidents are a serious issue for the country in terms of economic losses. In 2003 alone, Malaysia had a total economic lost of RM 9.3 billion due to road accidents. One of the potential solutions to is to reduce the overall fuel consumption by reducing the overall mass of the vehicle. Reducing vehicle mass by material substitution may have implications for vehicle safety. Substitution of a lighter material of equal strength and energy absorbing capacity in the body structure can maintain the same level of kinetic energy absorption and passenger protection, while reducing overall vehicle mass. Hence the present work is dedicated to the design and evaluation of a new crashworthy composite sandwich structure design. The research methodology adopted in this thesis work comprises of two stages. The initial stage was an investigation to the axial crushing response of normal or conventional composite sandwich panels. The second stage was the designing stage of a potential candidate energy absorber based on inputs received from the initial stage of the thesis. All specimens were fabricated by using hand wet lay up. It was found in the first stage that all of these conventional panels failed in a global column buckling manner. None showed any signs of progressive failure as expected in a crush energy absorber devise. While maintaining the same amount of constituent materials used, several “new” sandwich panels were designed and tested quasi – statically in the second stage. From these designs, one particular design termed as “wrap” was found to be very promising as a potential candidate for crush energy absorber devise. To evaluate the true crush response, a drop hammer tower facility was designed and fabricated in this study. Through this study, dynamic crush response was investigated and as suspected, indeed the “wrap” specimen displayed satisfactory crashworthiness results. Specimens made from carbon fibers displayed good specific energy absorption as high as 34.7 kJ/kg, much higher in relation to conventional metals. In depth analysis on the macroscopic failure modes was done and its relation to the energy absorption capabilities of the specimens was studied. In general, four types of failure modes were observed. Several parameters were studied to further improve the crashworthiness of the “wrap” design. These parameters basically included the dimension, material configuration and the cross sectional topology. Based on these findings, the study had contributed significantly in the area of crashworthiness by producing a potential candidate for a crush element that could be used in automotive industries and also extended to other vehicles such as buses, trains and ships

Incorporating Data Governance Frameworks in the Financial Industry

Data governance frameworks are critical to reducing operational costs and risks in the financial industry. Corporate data managers face challenges when implementing data governance frameworks. The purpose of this multiple case study was to explore the strategies that successful corporate data managers in some banks in the United States used to implement data governance frameworks to reduce operational costs and risks. The participants were 7 corporate data managers from 3 banks in North Carolina and New York. Servant leadership theory provided the conceptual framework for the study. Methodological triangulation involved assessment of nonconfidential bank documentation on the data governance framework, Basel Committee on Banking Supervision\u27s standard 239 compliance documents, and semistructured interview transcripts. Data were analyzed using Yin\u27s 5-step thematic data analysis technique. Five major themes emerged: leadership role in data governance frameworks to reduce risk and cost, data governance strategies and procedures, accuracy and security of data, establishment of a data office, and leadership commitment at the organizational level. The results of the study may lead to positive social change by supporting approaches to help banks maintain reliable and accurate data as well as reduce data breaches and misuse of consumer data. The availability of accurate data may enable corporate bank managers to make informed lending decisions to benefit consumers

Magnetic-time model for seed germination

Germination of seed depends on several physico-chemical factors like temperature, water potential, light,  nitrate content, smoke, electric field and magnetic field. In the present work, effect of static magnetic field on black-gram seeds (Cicer arietinum L.) was described. Seeds of C. arietinum L. were exposed in batches to static magnetic fields of 0 to 226 mT strength in steps of 50 mT (approximately) for 1 h. Treatment of seeds in these magnetic fields increased the speed of germination, seedling shoot and root length under laboratory  germination tests. On the basis of this, a new germination model called magnetic time model is developed which was incorporated in hydrothermal model and hence nominated as hydrothermal magnetic time model which is proposed to incorporate the effect of magnetic field of different intensities on plants. Magnetic time constant ΘB is determined experimentally for different seeds population. The model is helpful in a way that it defines another constant called hydrothermal-magnetic-time constant, which is of great importance to  understand the behavior of induced magnetic field on seeds and plant growth.Key words: Magnetic-time model, hydro-thermal-magnetic-time model, Cicer arietinum L

Mechanical Response of Applying Different Parameters On Negative Stiffness Honeycomb Structure

It has become apparent that negative stiffness behavior may have potential applications in vibration isolation mechanisms, vibro-acoustic dampening materials, and mechanical switches. Unlike traditional honeycombs, due to these properties, a negative honeycomb can absorb substantial amounts of mechanical energy whilst maintaining a stable stress. The force threshold under displacement loading was investigated of three variables applied on different models of negative-stiffness honeycomb (NSH) structures. The three variables are material applied, honeycomb unit cell, and beam thickness of the negative honeycomb structure. Accordingly, nine models were developed, and the three varied materials were assigned repeatably to each model and then force threshold were studied after validating the model. The Finite element analysis (FEA) for formed model was validated and shows force value of 289 N with an error of 5% compared to the referenced model. In the 4- unit cell model, the highest force threshold of approximately 240 N was noticed during loading phase at the beam thickness of 19.05 mm for both nylon 11 and 12 material. Finally, the force threshold of 550 N during loading and unloading phases was observed for nylon 6/6 material at beam thickness of 19.05 mm. The results obtained confirm the negative stiffness behavior on the models and shows that the force threshold applied is reduced comparing to forces required in the conventional honeycombs models

Mechanical Response of Applying Different Parameters On Negative Stiffness Honeycomb Structure

It has become apparent that negative stiffness behavior may have potential applications in vibration isolation mechanisms, vibro-acoustic dampening materials, and mechanical switches. Unlike traditional honeycombs, due to these properties, a negative honeycomb can absorb substantial amounts of mechanical energy whilst maintaining a stable stress. The force threshold under displacement loading was investigated of three variables applied on different models of negative-stiffness honeycomb (NSH) structures. The three variables are material applied, honeycomb unit cell, and beam thickness of the negative honeycomb structure. Accordingly, nine models were developed, and the three varied materials were assigned repeatably to each model and then force threshold were studied after validating the model. The Finite element analysis (FEA) for formed model was validated and shows force value of 289 N with an error of 5% compared to the referenced model. In the 4- unit cell model, the highest force threshold of approximately 240 N was noticed during loading phase at the beam thickness of 19.05 mm for both nylon 11 and 12 material. Finally, the force threshold of 550 N during loading and unloading phases was observed for nylon 6/6 material at beam thickness of 19.05 mm. The results obtained confirm the negative stiffness behavior on the models and shows that the force threshold applied is reduced comparing to forces required in the conventional honeycombs models

Narrow QRS Tachycardia with Alternate Wide QRS Beats: What is the Mechanism?

A 44-year old lady underwent electrophysiology study for recurrent palpitations and documented narrow QRS regular tachycardia. The baseline ECG showed subtle preexcitation that was easily manifest on atrial pacing. The retrograde atrial activation sequence during ventricular pacing was eccentric suggesting retrograde conduction over the accessory pathway. A regular narrow QRS tachycardia with cycle length 280 ms was easily inducible on programmed atrial stimulation. The earliest ventricular activation during sinus rhythm & atrial pacing, and the retrograde atrial activation during ventricular pacing & tachycardia were diagnostic of left free wall accessory pathway and orthodromic atrioventricular reciprocating tachycardia (AVRT). During an episode of tachycardia, an ablation catheter was placed in the region of the lateral mitral annulus using retrograde trans-aortic approach. Once the ablation catheter was stabilized in that region, an interesting change in the AVRT was seen with appearance of wide QRS complexes of right bundle branch block (RBBB) morphology and left axis deviation in the alternate beats (Figure 1). The atrial activation sequence during both narrow and wide QRS beats was same with earliest activation in the distal coronary sinus. What is the mechanism of the alternate wide QRS beats during the AVRT

Energy absorption capability of thin-walled aluminium tubes under crash loading

This paper investigates the interaction of design factors such as tube thickness, tube length, and tube cross-sectional aspect ratio, along with friction and impacting mass on crashworthiness parameters such as specific energy absorption contact time, peak force and crush distance. The impact velocity is assumed to be constant at 15 m/s. The focus is on rectangular aluminium tubes and the analysis was carried out by using a validated finite element model. The analysis shows that the factors are not independent of each other and there is some degree of interaction between them. It was found that the trigger mechanism is a very important design factor to be included in the design of thin-walled tubes for energy absorption applications. The effect of the friction coefficient was found to be insignificant and finally, based on the interactions, it can be concluded that the most effective design would be a larger tube with small wall thickness, and a larger aspect ratio to avoid buckling.Universiti Tenaga Nasional, Malaysi

Application of Vehicle Restraint Systems (VRSs) in the State of Qatar: A Case Study from Northern Roads

Recent developments within Infrastructural Road Safety and especially in the Sector of Vehicle Restraint Systems (VRS) have enabled Transport Authorities to significantly reduce road fatalities and severe injuries. Predominantly, two authorities have established leading guidelines for VRS installation and maintenance, - the European Union (EU) and the United States. The guidelines for the State of Qatar are based on these two sources. This technical paper briefly reviews the aforementioned guidelines, highlights the additional items in the EU guidelines, and explains the evolution of the State of Qatar guidelines accordingly. Moreover, this paper explains the application of VRS guidelines to the road network of the State of Qatar by presenting evidences from a recent site visit to the highways/expressways in the Northern Part of the Qatari Road Network. The outcomes of the site visit mainly highlight the typical steel VRS applied alongside the road (lateral as well as in central reserve, median), crash cushions, and various terminal systems. The paper is aiming to support designers, planners, auditors, contractors and installers to improve road safety from the VRS point of view

Life Cycle Cost Analysis for Variable Refrigerant Flow (VRF) and Constant Refrigerant Flow (CRF) Air Conditioning Systems in Arid Climate: Case Study in Qatar

All over the world, there is a call to encourage sustainable energy thinking and implementation. In the heating, ventilation and air conditioning field, the rise of the variable refrigerant flow systems has made a big progress. This study presents a life-cycle cost analysis to evaluate the economic feasibility of constant refrigerant flow (CRF) in particular the conventional ducted unit air conditioning system and the variable refrigerant flow (VRF) system by using detailed cooling load profiles, initial, operating, and maintenance costs. Two operating hour scenarios are utilized and the present-worth value technique for life-cycle cost analysis is applied to an existing office building located in Qatar which can be conditioned by CRF and VRF systems. The results indicate that although the initial cost of the VRF system is higher than that of the CRF system, the present-worth cost of the VRF system is lower than that of the CRF system at the end of the lifetime due to lower operating costs. The implementation of these results on a national scale will promote the use of sustainable energy technologies such as the VRF system

The colloidal properties of fluorocarbon emulsions

Some of the colloidal aspects of perfluorochemical emulsions have been investigated. Particular attention was given to the influence of the nature of the oil phase on emulsion stability. Bulk emulsion stability was measured by an electron micrographic technique. Interfacial and single droplet rest-time data were also collected. A range of surfactants and perfluorochemicals were investigated. It was found that emulsion stability depends on the chemical nature of the oil phase and the emulsifier. The differences in stability could be rationalized in terms of the intermolecular forces between oil molecules, and oil and surfactant molecules. The effect on stability of a small amount of an additive incorporated into the oil phase was also investigated. It is postulated that although coalescence is the main mechanism by which fluorocarbon emulsions coarsen, molecular diffusion (Ostwald Ripening), in the more stable systems, is also important. Most stable emulsions were obtained by utilizing an emulsifier system comprising a small and a large molecular weight emulsifier. Accelerated stability testing and optimum storage conditions were also investigated. About 40C was found to be the optimum storage temperature. The problem of the fluoride ion production during emulsification could be minimised by sonicating in a carbon dioxide atmosphere. The oxygen uptake and release by fluorocarbon emulsions was rapid, reaching equilibrium within half a second. The in-vitro phagocytosis experiments showed that the phagocytosis rate of fluorocarbon emulsions was dependent on the droplet diameter and its surface characteristics. Investigation of methods to sterilize the fluorocarbon emulsions showed that filtration of constituents before emulsification coupled with autoclaving had the minimum effect on stability. A qualitative correlation between single droplet stability and bulk emulsion stability was found and it is concluded that the method could be a useful screening procedure to find an optimum system