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Full-Text Articles in Engineering
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering, Mohammad Nur E Alam, Mikhail Vasiliev, Kamal Alameh
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering, Mohammad Nur E Alam, Mikhail Vasiliev, Kamal Alameh
Mikhail Vasiliev
A new class of magneto-optic garnet nanocomposite materials is prepared using two Bi-substituted iron garnet materials of composition types (Bi,Dy) 3(Fe,Ga)5O12 and Bi3Fe 5O12. A composition adjustment approach is applied by varying the radio frequency (RF) powers driving each sputtering target during the deposition process. This new class of nanocomposite materials exhibits simultaneously high specific Faraday rotation, MO figure of merit, and effective uniaxial magnetic anisotropy after being crystallized through optimized annealing processes. We demonstrate experimentally that the excellent combination of materials' properties obtained in this garnet nanocomposite is particularly advantageous for developing magneto-photonic crystals as well as optical sensors …
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering, Mohammad Nur E Alam, Mikhail Vasiliev, Kamal Alameh
New Class Of Garnet Nanocomposites For Use In Magnetic Photonic Crystals Prepared By Rf Magnetron Co-Sputtering, Mohammad Nur E Alam, Mikhail Vasiliev, Kamal Alameh
Mikhail Vasiliev
A new class of magneto-optic garnet nanocomposite materials is prepared using two Bi-substituted iron garnet materials of composition types (Bi,Dy) 3(Fe,Ga)5O12 and Bi3Fe 5O12. A composition adjustment approach is applied by varying the radio frequency (RF) powers driving each sputtering target during the deposition process. This new class of nanocomposite materials exhibits simultaneously high specific Faraday rotation, MO figure of merit, and effective uniaxial magnetic anisotropy after being crystallized through optimized annealing processes. We demonstrate experimentally that the excellent combination of materials' properties obtained in this garnet nanocomposite is particularly advantageous for developing magneto-photonic crystals as well as optical sensors …
Waveform-Based Selection Of Acoustic Emission Events Generated By Damage In Composite Materials, Emmanuel Maillet, Gregory Morscher
Waveform-Based Selection Of Acoustic Emission Events Generated By Damage In Composite Materials, Emmanuel Maillet, Gregory Morscher
Dr. Gregory N. Morscher
Acoustic emission (AE) has been shown to be a promising health monitoring technique for composite materials as it allows real-time location and identification of damage. When attempting to relate the recorded acoustic emission to a material׳s mechanical behavior, the relevance of results relies on an accurate selection of AE originating from material damage. Indeed, during mechanical tests most of the recorded AE is generated outside of the volume of interest and without proper filtering these AE signals can significantly affect the analysis. To date, there exists no common procedure for the selection of AE signals and therefore results can hardly …
Short Crack Growth Model In A Particulate Composite Using Nonlinear Elastic Fracture Mechanics, Ying Zhang, Tsuchin Chu, Ajay Mahajan
Short Crack Growth Model In A Particulate Composite Using Nonlinear Elastic Fracture Mechanics, Ying Zhang, Tsuchin Chu, Ajay Mahajan
Dr. Ajay Mahajan
The fracture mechanics model for a long crack does not work very well with short-crack propagation when the initial crack length is less than 5.1 mm (0.2 inch). In order to investigate the short crack effect, a series of tests of particulate composite specimens with long and short cracks were performed and the results recorded on a video tape. This test data was analyzed to determine the fracture parameters. Two initial crack lengths, 2.5 mm (0.1 inches) and 7.6 mm (0.3 inches) were used in the crack propagation tests. Based on the principle of linear elastic fracture mechanics (LEFM), the …
Determination Of Optimal Experimental Parameters For Transient Thermography Imaging Using Finite-Element Models, Tsuchin Chu, Ajay Mahajan, A. Digrgorio, S. Russell
Determination Of Optimal Experimental Parameters For Transient Thermography Imaging Using Finite-Element Models, Tsuchin Chu, Ajay Mahajan, A. Digrgorio, S. Russell
Dr. Ajay Mahajan
A study was conducted to determine the optimal inspection parameters such as range and time for finding defects in carbon/epoxy composite panels using IR thermography imaging. The present paper presents an innovative method for automatically selecting these parameters for evaluating composites based on a series of finite-element models. Such finite-element models of composite panels with flaws at different depth locations were constructed a priori and analysed to estimate the optimal operating parameters. The optimal inspection range and time were identified in the contour plots obtained from the appropriate finite-element analysis results. A graphite–epoxy composite panel with phantom defects at various …
Characterization Of Waviness In Wind Turbine Blades Using Air Coupled Ultrasonics, Sunil Kishore Chakrapani, Vinay Dayal, David K. Hsu, Daniel J. Barnard, Andrew Gross
Characterization Of Waviness In Wind Turbine Blades Using Air Coupled Ultrasonics, Sunil Kishore Chakrapani, Vinay Dayal, David K. Hsu, Daniel J. Barnard, Andrew Gross
Sunil Kishore Chakrapani
Waviness in glass fiber reinforced composite is of great interest in composite research, since it results in the loss of stiffness. Several NDE techniques have been used previously to detect waviness. This work is concerned with waves normal to the plies in a composite. Air‐coupled ultrasonics was used to detect waviness in thick composites used in the manufacturing of wind turbine blades. Composite samples with different wave aspect ratios were studied. Different wavy samples were characterized, and a three step process was developed to make sure the technique is field implementable. This gives us a better understanding of the effect …
Ultrasonic Testing Of Adhesive Bonds Of Thick Composites With Applications To Wind Turbine Blades, Sunil Kishore Chakrapani, Vinay Dayal, Ryan Krafka, Aaron Eldal
Ultrasonic Testing Of Adhesive Bonds Of Thick Composites With Applications To Wind Turbine Blades, Sunil Kishore Chakrapani, Vinay Dayal, Ryan Krafka, Aaron Eldal
Sunil Kishore Chakrapani
This paper discusses the use of pulse echo based ultrasonic testing for the inspection of adhesive bonds between very thick composite plates (thickness greater than 30 mm). Large wind turbine blades use very thick composite plates for its main structural members, and the inspection of adhesive bond-line is very vital. A wide gamut of samples was created by changing the thickness of plate and the adhesive. The influence of experimental parameters such as frequency on measurement is studied in this paper. Two different frequencies are chosen, and the measurement error bars are determined experimentally. T-Ray measurements were used to verify …
Inspection Of Helicopter Rotor Blades With The Help Of Guided Waves And "Turning Modes": Experimental And Finite Element Analysis, Daniel J. Barnard, Sunil Kishore Chakrapani, Vinay Dayal
Inspection Of Helicopter Rotor Blades With The Help Of Guided Waves And "Turning Modes": Experimental And Finite Element Analysis, Daniel J. Barnard, Sunil Kishore Chakrapani, Vinay Dayal
Sunil Kishore Chakrapani
Modern helicopter rotor blades constructed of composite materials offer significant inspection challenges, particularly at inner structures, where geometry and differing material properties and anisotropy make placement of the probing energy difficult. This paper presents an application of Lamb waves to these structures, where mode conversion occurs at internal geometric discontinuities. These additional modes were found to successfully propagate to the targeted regions inside the rotor and back out, allowing evaluation of the structure. A finite element model was developed to simulate wave propagation and mode conversion in the structure and aid in identifying the signals received in the laboratory experiment. …
In Situ Infrared Study Of The Role Of Peg In Stabilizing Silica-Supported Amines For Co2 Capture, Jak Tanthana, Steven Chuang
In Situ Infrared Study Of The Role Of Peg In Stabilizing Silica-Supported Amines For Co2 Capture, Jak Tanthana, Steven Chuang
Steven S.C. Chuang
The CO(2) capture capacity, adsorption mechanism, and degradation characteristics of two sorbents, silica-supported tetraethylenepentamine (TEPA/SiO(2)) and polyethylene-glycol-modified TEPA/SiO(2) (PEG/TEPA/SiO(2)), are studied by diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometry. The CO(2) capture capacities of TEPA/SiO(2) and PEG/TEPA/SiO(2) are determined to be 2087 and 1110 micromol CO(2) g(-1) sorbent, respectively. Both sorbents adsorb CO(2) as hydrogen-bonding species, NH(2)--O, and carbamate/carboxylate species. The CO(2) adsorption half-time increases with the number of CO(2) capture cycles. Infrared results suggest that the increased adsorption half-time is a result of diffusion limitation, caused by accumulation of TEPA and PEG species on the surface of …
Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru
Impact Mechanics And High-Energy Absorbing Materials: Review, Pizhong Qiao, Mijia Yang, Florin Bobaru
Florin Bobaru Ph.D.
In this paper a review of impact mechanics and high-energy absorbing materials is presented. We review different theoretical models (rigid-body dynamics, elastic, shock, and plastic wave propagation, and nonclassical or nonlocal models. and computational methods (finite-element, finite-difference, and mesh-free methods. used in impact mechanics. Some recent developments in numerical simulation of impact (e.g., peridynamics) and new design concepts proposed as high energy absorbing materials (lattice and truss structures, hybrid sandwich composites, metal foams, magnetorheological fluids, porous shape memory alloys. are discussed. Recent studies on experimental evaluation and constitutive modeling of strain rate-dependent polymer matrix composites are also presented. Impact damage …
Theoretical Analysis For Obtaining Physical Properties Of Composite Electrodes, Parthasarathy M. Gomadam, John W. Weidner, Thomas A. Zawodzinski, Andrew P. Saab
Theoretical Analysis For Obtaining Physical Properties Of Composite Electrodes, Parthasarathy M. Gomadam, John W. Weidner, Thomas A. Zawodzinski, Andrew P. Saab
John W Weidner
A theoretical analysis is presented that allows in situ measurements of the physical properties of a composite electrode, namely, the electronic conductivity, the ionic conductivity, the exchange-current density, and the double-layer capacitance. Use is made of the current-voltage responses of the composite electrode to dc and ac polarizations under three different experimental configurations. This analysis allows the physical properties to be obtained even when the various resistances in the composite (e.g., ionic, electronic, and charge-transfer) are of comparable values.
Velocity Effects On The Wear, Friction And Tribochemistry Of Aluminum Mmc Sliding Against Phenolic Brake Pad
A.S. Md Abdul Haseeb
Two aluminum metal matrix composites (MMC) reinforced with 13 vol.% of SiC or B4C particles were made by stir casting followed by hot extrusion. Effects of sliding velocity on the wear, friction and tribochemistry of the worn surfaces of both composites sliding against a commercial phenolic brake pad have been investigated under dry condition. The wear tests were carried out using a pin-on-disc type apparatus at two linear sliding speeds: 1.62 and 4.17 m s-1 under a constant contact pressure of 0.75 MPa for a sliding distance of 5832 m. The coefficient of friction was recorded and wear rate of …