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

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

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

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

An experimental validation of numerical model for top-hat tubular structure subjected to axial crush

Vehicle crashworthiness is an important aspect to consider when designing a vehicle to ensure the safety of the occupants. Besides this, vehicles are also designed to reduce weight for better fuel economics. One possible approach to reducing weight without compromising vehicle safety is by looking at new designs and usage of composite materials, along with the usage of computational models to reduce time and cost. Hence, this paper displays the experimental results of a carbon fiber reinforced closed top-hat section subjected to both quasi-static and dynamic crushing loading. The results were used to validate the computational model developed in the study. The specimens were made of carbon composite prepregs MTM-44 sheets stacked at the alternative orientation of ±45° and 0°/90°, where 0° direction coincides with the axis of the member. The samples were prepared by using a mold and carbon prepregs under vacuum bagging followed by curing in an autoclave. Trigger initiation was applied to ensure the specimens demonstrated a stable crushing mode of failure during the test. Experimental investigations were carried out under the ambient conditions with different loading conditions, and different kinetic energy ranges (2, 3 and 6 kJ). Experimental data was used to validate the finite element analysis (FEA). The maximum errors obtained between experimental and FEA for mean load, mean energy absorption, and crushing displacement were 13%, 13% and 7%, respectively. The numerically obtained results were in strong agreement with the experimental data and showed that they were able to predict the failure of the specimens. The work also showed the novelty of using such structures for energy absorption applications.Acknowledgments: This investigation was supported by the Council for at Risk Academy (CARA). The authors would like to acknowledge the university of Warwick and Warwick manufacturing group (WMG) and staff for providing full support, equipment and all facilities to complete this research. Also, great appreciation for the Sika Power company for providing an adhesive which is necessary for this investigation. The authors would also like to acknowledge Qatar National Research Fund for providing financial assistance to publish this paper as open access.Scopu

Crowd Dynamics, Management and Control at Tourist Attractions during Special Events: A Case Study at Souq Waqif Using Pedestride® Crowd Simulation Tool

"Large crowds can be expected at famous tourist attractions, e.g., Souq Waqif, during special events such as the FIFA World Cup 2022. A comprehensive understanding of crowd dynamics is extremely important in order to ensure safety of crowds and efficiency of crowd flows at large gathering spots. Pedestrian crowd simulation tools can be used to evaluate crowd flows and to verify crowd management and control strategies at public infrastructure. The objective of this study is to evaluate safety and efficiency of crowd flows at Souq Waqif, both under normal and emergency situations using Pedestride® Crowd Simulation tool developed at Melbourne University. This simulation model has been calibrated and validated using empirical data collected through controlled experiments and real-world observations. By simulating the increased visitor demand at Souq Waqif as a case study, we aim to highlight any required design modifications and to recommend and verify crowd management strategies in order to mitigate any unfavorable situations, such as stampede during any emergency. The study shows that at increased demands and during emergency evacuation, crowds tend to take similar route. Further, increased demands could elevate the maximum crowd density up to 6 p/m2 at gates and junctions. In order to mitigate such unfavorable situations, dynamic exit signs are needed to direct flows to other clear exits to avoid herding effect.

Additive Manufacturing Technology for Spare Parts Application: A Systematic Review on Supply Chain Management

Additive manufacturing (AM) is gaining interest among researchers and practitioners in the field of manufacturing. One major potential area of AM application is the manufacturing of spare parts, which affects the availability of the operation and supply chain. The data show that the application and adoption of AM has contributed to a reduction in lead times and inventory, which also contributes to a reduction in holding costs. This paper provides a review of recent work on the application of AM technology specifically for spare parts. The review shows that there are supply chain opportunities and challenges to the adoption of AM in spare parts within various application sectors. Our research reviews both the quantitative and qualitative models used for analysis to meet the emerging needs of the industry. The review also shows that the development of technology and its application is still emerging; therefore, there will be further opportunities to develop better spare parts supply chains to support AM applications. This paper concludes with future research directions. 2022 by the authors. Licensee MDPI, Basel, Switzerland.Acknowledgments: This study was made possible by the Qatar University grant# M?QJRC?2020?6. The APC was made possible through student grant #QUST?1?CENG?2022?302. The findings of this study are solely the responsibility of the authors.Scopus2-s2.0-8512929378

Practicality of 3D Printed Personalized Medicines in Therapeutics

Technological advances in science over the past century have paved the way for remedial treatment outcomes in various diseases. Pharmacogenomic predispositions, the emergence of multidrug resistance, medication and formulation errors contribute significantly to patient mortality. The concept of "personalized" or "precision" medicines provides a window to addressing these issues and hence reducing mortality. The emergence of three-dimensional printing of medicines over the past decades has generated interests in therapeutics and dispensing, whereby the provisions of personalized medicines can be built within the framework of producing medicines at dispensaries or pharmacies. This plan is a good replacement of the fit-for-all modality in conventional therapeutics, where clinicians are constrained to prescribe pre-formulated dose units available on the market. However, three-dimension printing of personalized medicines faces several hurdles, but these are not insurmountable. In this review, we explore the relevance of personalized medicines in therapeutics and how three-dimensional printing makes a good fit in current gaps within conventional therapeutics in order to secure an effective implementation of personalized medicines. We also explore the deployment of three-dimensional printing of personalized medicines based on practical, legal and regulatory provisions. Copyright 2021 Amekyeh, Tarlochan and Billa.Scopu

Mechanical and Thermal Analysis of Classical Functionally Graded Coated Beam

The governing equation of a classical rectangular coated beam made of two layers subjected to thermal and uniformly distributed mechanical loads are derived by using the principle of virtual displacements and based on Euler-Bernoulli deformation beam theory (EBT). The aim of this paper was to analyze the static behavior of clamped-clamped thin coated beam under thermo-mechanical load using MATLAB. Two models were considered for composite coated. The first model was consisting of ceramic layer as a coated and substrate which was metal (HC model). The second model was consisting of Functionally Graded Material (FGM) as a coated layer and metal substrate (FGC model). From the result it was apparent that the superiority of the FGC composite against conventional coated composite has been demonstrated. From the analysis, the stress level throughout the thickness at the interface of the coated beam for the FGC was reduced. Yet, the deflection in return was observed to increase. Therefore, this could cater to various new engineering applications where warrant the utilization of material that has properties that are well-beyond the capabilities of the conventional or yesteryears materials. The Authors, published by EDP Sciences, 2018.Scopu