STRC. 5
Preparation and characterization of date palm fibers and polypropylene matrix composites
1,2Omar Mortagy and 1,2Mahmoud Farag
1The Mechanical Engineering Department, the American University in Cairo, Egypt
2The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
Natural fibers, such as flax, hemp and jute, offer an environmentally more acceptable alternative to man-made fibers, such as glass and carbon fibers, in reinforcing plastics. This is because they need much less energy to grow, are renewable, and are bio-degradable after use. In addition to satisfying the increasingly stringent environmental criteria, natural fibers offer several other advantages, such as light weight and acoustic and thermal insulation because of their hollow and cellular structure. Because of these advantages, natural fiber reinforced plastics (NFRP) have replaced glass fiber reinforced plastic components in vehicles such as the Mercedes Benz A-Class and the Ford Model U hybrid-electric car.
This paper discusses the preparation and characterization of fibers extracted from date palm fruit carrying bunches and explores their use in strengthening polypropylene matrix composites. The fruit bunches are composed of predominantly cellulose fibers held together by hemicellulose and lignin matrix. The fibers are extracted by first mechanically crushing the fruit-bearing bunches, chemical treatment with NaOH at 90oC for two hours, and then separation of the fibers from the matrix using ultrasonic treatment for one hour at 50 oC. The density of the fibers was approximately 1.1 g/cc and diameter 180-270 μm. SEM studies showed that the fibers were made up of axially oriented fibrils of 5-7 μm diameter as well as large axial pores of about 30 μm diameter. Radial small pores of 3-6 μm diameter were also revealed.
The mechanical behavior of the fibers is being measured and compared with the properties of other natural fibers in the published literature. Different volume fractions of the fibers are also embedded in polypropylene matrix to determine the effect of preparation method and fiber volume fraction on mechanical behavior and water absorption.
If proved viable, the use of date palm fruit carrying bunches, which are currently discarded as agricultural waste, would be of great economic value since we have more than 7 million date palm trees in Egypt.
Processing of CNT-reinforced aluminum matrix composites
1,2Amal M. K. Esawi, 1,2Ahmed Abdel Gawad, 1,2Mostafa El Borady, and 1,2Mohamed Emara
1The Mechanical Engineering Department, the American University in Cairo, Egypt
2The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
In spite of varying reports in the literature on the exact properties of carbon nanotubes, both theoretical and experimental results confirm their possession of remarkable mechanical properties. Such properties have earned them serious consideration from both industry and research institutes as reinforcements for a number of material systems. Aluminum matrix composites have numerous attractive lightweight and structural applications. Reinforcing aluminum with nanotubes is expected to lead to exceptional new composites. However, some processing problems have first to be overcome; namely, (1) dispersion of the nanotubes within the matrix, and (2) controlling their alignment in the matrix. This work aims to overcome these problems by developing two novel techniques: one is the mechanical alloying of the nanotube/Al matrix powders to overcome the first problem and the second is the use of a powder rolling technique to produce thin strips of aligned CNT within the aluminum matrix.
Although observations of the fracture surface of the samples show that the CNTs are well dispersed and have not been damaged by the mechanical alloying process, the results so far are showing limited enhancement in mechanical properties. This could be attributed to two main reasons: (1) the use of catalytic CNTs of the cheapest variety available commercially and (2) poor interfacial bonding between the CNTs and the aluminum matrix. Further investigations are being carried out to: (1) Understand the local interfacial mechanics. The interface will be modified to promote bonding and the effect will be studied using nanoindentation techniques. (2) Study the effect of the processing temperature on the strength of the composite. It has been reported in the literature that higher processing temperatures result in the formation of aluminum carbide Al4C3 at defect sites on the nanotubes which may lead to a stronger interfacial bond between the nanotubes and the aluminum matrix. (3) Investigate the effect of using different aspect ratio CNTs on the mechanical properties.
Construction of consolidation maps for finite element material modeling of equal channel angular extrusion of hot compact nano and micron powders
1,2Ahmed Sadek and 1,2Hanadi G. Salem
1The Mechanical Engineering Department, the American University in Cairo, Egypt
2The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
The Equal Channel Angular Extrusion (ECAE) process is one of the most promising processes used for producing nanostructured consolidates making using of the severe plastic conditions that the powder particles experience during the extrusion. The intrinsic heat generated during extrusion in addition to 1.16 total strain imposed on the powder per passes can substitute for the elevated temperature required for sintering. The consolidation condition of the micro and nanopowders prior to ECAE influences significantly the structural evolution and hence mechanical properties of the produced bulk product. Building a model for such a process has become an essential requirement to allow several iterations and runs for obtaining optimal forming conditions that will produce best properties of the consolidate. Through the current research work consolidation maps of hardness and density variation for microscale and nanoscale Al-2124 powders hot compacts are obtained. The optimum consolidation condition will be selected for subsequent ECAE processing compared to the green compact condition. The consolidation behavior maps obtained for the micro and nanoscale powders will be used for the development of a finite element materials model of the ECAEed consolidates. A nanostructured microscale powders about 45µm and 87nm particle and internal structure average size, respectively hot compacts of height to diameter (h/d) ratio of 4 were obtained by combinations of temperatures (360, 420 and 480oC), durations (30, 60, and 90 minutes) ,and pressures (4, 5, and 6) multiples of the yield strength (sys) of as received Al-2124. A nanostructured nanoscale powders about 90nm and 15.6nm particle and internal structure average size, respectively were obtained by 36 hours of high energy ball milling. The nanoscale hot compacts were obtained using the same ranges of temperature and durations used for microscale ones, but with higher values of pressure (6, 7, and 8) multiples of the yield strength of as received Al-2124 powder. The nanoscale compacts exhibited hardness-values 3 to 4 times higher than that of microscale ones. For the microscale compacts, the optimal combination of compaction conditions was achieved for 60 minutes duration at 420-to-480oC range of temperatures, and 5-to-6sys range of stress. For the 30 and 90 minutes compaction durations the optimum properties were limited to 480oC over a stress range of 5.2 to 5.8s ys.
Effect of the compaction parameters and canning material of nanostructured Al-Powder consolidated via intense plastic straining process
1,2Mohamed Shamma and 1,2Hanadi G. Salem
1The Mechanical Engineering Department, the American University in Cairo, Egypt
2The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
Research groups around the world have reached common and contradicting conclusions regarding the behavior and properties of nanostructured materials. The aim of this research is to affirm the common findings by previous research, and support one of the currently proposed concepts of mechanical behavior based on in-depth testing and characterization of consolidated micro and nanopowders of aluminum processed by Equal Channel angular Extrusion (ECAE). The main challenge faced in processing nanostructured powders or bulk products is the retention of the internal nanoscale structures during the various processing stages. ECAE is classified as one of the intense plastic straining processes that are capable of producing bulk products with internal structure that is one order of magnitude smaller (200nm) than the conventional processing techniques (2.0µm). The ongoing project constitutes several activities such as (a) Design and manufacturing of the ECAE die for the consolidation of the micro and nanopowders into bulk billets, (b) Variation of the powder pre-extrusion condition including the powder canning materials, (c) variation of the extrusion parameters, and (d) characterization of the produced bulk consolidates before and after extrusion. Utilizing different "can" materials during extrusion has been investigated. The effect of variation of the processing parameters (compaction condition, extrusion temperature, strain rate) on the sample density, grain size, and hardness is studied. Al-2124 micro-powders with 87nm internal structure was consolidated through ECAE, which produced consolidated bulk rods with internal structure of 37nm in average size. The present study shows that ECAE is capable of producing consolidates form nanostructured-micro-powders, which opens a new venue for extensive investigation of the consolidation parameters for improved properties bulk nanocrystalline (NC) materials, as well as offering a new class of bulk materials for practical engineering applications.
Design of micro-lens arrays used for generation of diffraction-limited beams
1Joumana El-Rifai and 1,2Amr Shaarawi
1The Yousef Jameel, Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
2The Physics Department and the American University in Cairo, Egypt
Diffraction-limited beams can be generated using various methods. They can be produced using spherical lenses, conical lenses or annular slits that lie in the focal plane of a positive lens. The use of conical lenses in the production and generation of diffraction-limited beams is investigated in this work. The beam shaped by uniform illumination of a single conical lens is investigated using numerical simulations. The decay behavior and the focal depth of the beam are characterized in terms of the wavelength of the illumination and the radius of the axicon lens. The single lens is later expanded to an array of conical lenses packed in various shapes. The effects of the array shape on the focal depth of the field will be presented.
In the case a single conical lens is uniformly illuminated two equations describing the output beam were used to produce the simulations. The first equation was proposed by R.M. Herman and T. A. Wiggins (“Production and uses of diffractionless beams.” J. Opt. Soc. Am. A, 8 (6), 932-942 (1991)). The equation describes the production of a Bessel beam of the first kind using a conical lens. In their joint paper Herman and Wiggins adopted a mathematical approach, approximating their equation to prove that the output equation has a Bessel function lateral profile and thus the conical lens produces a Bessel beam. Within the scope of this study, we used a numerical approach rather than a mathematical one, where Herman and Wiggins’ original exact equation (before any approximations) was adopted
The simulations produced using the Herman and Wiggins approach only considered a conical lens placed at an origin (i.e., at ). In order to obtain simulations for a conical lens placed at any position on the xy-plane Herman and Wiggins expressions were modified to simulate the radiation from a conic lens placed at any arbitrary position ( and ). To examine the effect an array of conical lenses simulations of the radiated field for different configurations of the axicon lenses were carried out. It will be shown that the shape of the array has a direct influence on the decay behavior of the generated beams.
The preparation and characterization of catalytically viable micro/mesoporous mixed metallic oxides
1,2Jehane Ragai, 1,2Adham R. Ramadan, 1,2Nahed Yacoub, 2,3Christine Azer, 1,2Gehane Ghali, 1,2Malak Issa, 1,2Haguer Amin
1Chemistry Department, the American University in Cairo, Egypt
2The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
3Chemistry Department, Ain Shams University, Cairo, Egypt
The preparation and characterization of metal oxides and mixed metal oxides are carried out with the aim of investigating their catalytic and ion exchange properties. This is achieved by:
· Surface and bulk characterization using gas adsorption techniques for the determination of extent of surface area as well as porosity
· Measurement of acidic and basic properties of the prepared oxides and mixed oxides using different techniques differentiating between Lewis and Bronsted acidity/basicity.
· X-ray diffraction for crystalinity and phase determination
· Infrared spectrometry for the determination of different active groups in the oxide/mixed oxide matrices
· Thermal analyses for the establishment of the thermal behaviour of the oxides/mixed oxides, an important parameter for catalysts
· SEM imaging for shedding light on surface morphology
Doping is carried out with different cations and anions of different sizes and charges as their presence within the oxides/mixed oxides matrices is seen to affect the above parameters differently, with significant bearings on catalytic and ion exchange properties.
Enhancement design for a symmetrical decoupled MEMs-based gyroscope
1,2Abdelhameed Sharaf, 2,3Sherif Sedky, 1,4Mahmoud A. Ashour, 5Serag E.-D. Habib
1NCRRT, EAEA, 3 Ahmed Alzomor st., Naser city, Cairo, Egypt
2Yousef Jameel Science and Technology Research Center (STRC), Egypt
3Physics Department, the American university in Cairo, Egypt
4IC Design Center, EAEA, 3 Ahmed Alzomor st., Naser city Cairo, Egypt
5Electronics and Communications Dept., Faculty of Engineering, Cairo University, 12613, Giza, Egypt
This paper introduces an efficient design for symmetrical and decoupled micromachined gyroscope as shown in figure 1. The design utilizes all the silicon area in a more efficient way as compared to previously suggested designs (S. E. Alpe, and Tayfun Akin, “A single-crystal silicon symmetrical and decoupled MEMS gyroscope on an insulating substrate,” J. of MEMS, Vol. 14, No. 4, August 2005, PP. 707-717), increases the driving electrostatic force, and increases the sensing capacitance. Decoupling between sense and drive modes is achieved by separating the drive and sense masses. The decoupling is required to minimize the mechanical crosstalk, whereas matching the resonance frequencies is essential to increase the sensor sensitivities by the mechanical quality factor of the sense mode. A complete analytical analysis, based on the equations of motion, is performed. The analysis shows a resonance frequency of 4743 Hz for both modes, drive amplitude of 2.275 µm, and sense mode amplitude of 7.64nm. The mechanical and electrical sensitivities are 0.008 µm/(º/s) and 1.9 mV/(º/s) respectively. The change in the output capacitance is 0.13 aF/(º/s). The numerical analysis is preformed using finite element analysis (ANSYS). First a modal analysis is performed to extract the structure natural frequency. The resonance frequencies are 5385 Hz and 5382 Hz for drive and sense mode respectively, which has a frequency mismatch as low as 0.04%. The mode shapes for sense mode is derived. The mismatch between analytical and numerical results is 11.9%, which is mainly due to the higher accuracy of the numerical model as compared to the approximated analytical model. The frequency response of the drive mode indicates drive mode amplitude of 2.819 µm. Table I summarize the main results of this work. It is clear from the table that the proposed design has similar values to those reported for decoupled micromachined gyroscopes, but with more efficient use of area.