Barry Davidson | Syracuse University (original) (raw)

Papers by Barry Davidson

Abstract: Evaluative research was conducted on a distributed collaborative engineering design (CE... more Abstract: Evaluative research was conducted on a distributed collaborative engineering design (CED) course taught between two universities who used an online Advanced Interactive Discovery Environment (AIDE). The AIDE provided communication tools and ...

Online Submission, 2007

The purpose of this article is to compare institutions of higher learning in Poland and universit... more The purpose of this article is to compare institutions of higher learning in Poland and universities in Canada using an information technology conceptual framework consisting of three parts: participation, feedback and partnership. _________________________________________________________________________

Journal of Composite Materials, 1995

Results are presented from a study to determine energy release rate and mode ratio for a locally ... more Results are presented from a study to determine energy release rate and mode ratio for a locally buckled, compression loaded laminate which contains either a single delamination or two symmetrically located delaminations. It is shown that, at a given applied load or displacement, significantly different values of energy release rate and mode ratio may exist in the two configurations. In general, the rate-of-increase of energy release rate with increasing displacement, as well as the percentage of crack-tip shearing mode at a given displacement, are higher in the configuration which contains two delaminations.

ABSTRACT A four point bend, end notched flexure test is described for determining the mode II fra... more ABSTRACT A four point bend, end notched flexure test is described for determining the mode II fracture toughness of laminated composites. The test consists of a unidirectional laminate with a midplane delamination loaded in four point bending. The test configuration is analysed by beam theory and by finite element analysis. When the delamination front is in between the inner load ing rollers the energy release rate, expressed in terms of the applied load, is independent of delamination length. In addition, delamination growth is shown to be stable for a displacement controlled test. The advantages of this test over conventional mode II tests are the reduction of frictional effects and the ability to perform an experimental compliance calibration as the delamination advances. Further, an R-curve characterisation may be conducted. This results in a reduced time to conduct tests to generate mode II data compared with the tests currently used by industry.

Sensors and Actuators a Physical, Oct 1, 2009

A molecular layer deposition approach is reported that produces a new class of hybrid organic-ino... more A molecular layer deposition approach is reported that produces a new class of hybrid organic-inorganic thin films. These films have very low densities, and display typical atomic layer deposition characteristics: controllable linear growth, conformality, low roughness, and uniform composition. Because of their aluminum content, the alucone films cannot be dry etched with oxygen plasma. In accordance with their molecular structure, the new materials are completely removed in hydrochloric acid solutions. Since they can be etched with accurate control in acidic solutions, these hybrid materials are promising for the fabrication of MEMS/NEMS (Micro/Nano Electro Mechanical Systems) devices. Doubly supported structures with 120 nm air gaps are demonstrated using alucone materials as sacrificial layers.

Online Submission, 2007

This article attempts to determine whether the recent educational reforms in Poland are making it... more This article attempts to determine whether the recent educational reforms in Poland are making it more difficult for discipline to be maintained in schools. In general, changes have a negative impact upon school discipline because the likelihood of mixed-ability classes in junior secondary institutions is high. ________________________________________________________________________

Online Submission, 2006

The aim of this study was to compare Polish post-secondary vocational institutions with Canadian ... more The aim of this study was to compare Polish post-secondary vocational institutions with Canadian community colleges. The research concentrated upon programs in nursing, tourism and information technology delivered by the following three Polish schools Krakowska Szkola Medyczna, (Cracow, Poland), Policealne Studium Zawodowe (Cracow, Poland), Cracow School of Information Technology and four Canadian community colleges Red Deer (Red Deer, Alberta), Centennial (Scarborough, Ontario), Durham (Oshawa, Ontario) and Confederation (Thunder Bay, Ontario).

Advanced Materials and Processes

ABSTRACT

One dimensional delamination buckling and growth is analyzed using closed form cylindrical buckli... more One dimensional delamination buckling and growth is analyzed using closed form cylindrical buckling and crack tip element analyses. A cylindrical buckling analysis is utilized to determine the strains, curvatures, deflections, forces and moments in a buckled region bounded by the laminate free surface and a near-surface delamination. These results are used as input into a linear crack tip element analysis to obtain the total energy release rate and individual mode I and mode II components. Geometric nonlinearities are accounted for through the loading on the crack tip element. Total energy release rate and fracture mode ratio as found by this new technique are shown to agree with nonlinear finite element results.

Journal of Reinforced Plastics and Composites

A study is described that evaluated the effect of the mode mix used to create a precrack on the p... more A study is described that evaluated the effect of the mode mix used to create a precrack on the perceived delamination toughness of laminated composites. Mode I double cantilever beam, mode II end-notched flexure, and mixed-mode symmetrically delaminated single leg bending tests were first performed on unidirectional graphite/epoxy specimens with mode I precracks. The tests were then repeated on new unidirectional specimens with mode II precracks. Through an examination of the mechanisms involved, it is shown that toughness values for materials that do not exhibit fiber bridging will be most accurate, at all mode mixities, if test specimens are precracked at the same mode mix as the test itself.

International Journal of Solids and Structures, 1997

ABSTRACT An unsymmetric double cantilever beam test is described and its suitability for the dete... more ABSTRACT An unsymmetric double cantilever beam test is described and its suitability for the determination of interfacial fracture toughness is evaluated. The test specimen consists of a beam type geometry comprised of two materials, one ‘top’ and one ‘bottom’, with a crack at one end along the bimaterial interface. The specimen is loaded in a splitting fashion similar to that of a conventional double cantilever beam test. Due to the dissimilar in-plane and out-of-plane deformations of the two legs, the load vs deflection response of the specimen is found to be nonlinear. A nonlinear plate theory is used to predict the deformations of the specimen, and these results are used in a crack tip element analysis to determine energy release rate and mode mixity. The analytical predictions are verified by comparisons to results from two-dimensional, geometrically nonlinear finite element continuum analyses for a variety of typical materials and test geometries. It is shown that, by varying the relative thicknesses of the two materials, the unsymmetric double cantilever beam test can be used on most bimaterial pairs to determine interfacial fracture toughness over a reasonably wide range of mode mixities.

2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems, 2009

ABSTRACT In this paper we present a novel low temperature, CMOS compatible, direct top-down nano-... more ABSTRACT In this paper we present a novel low temperature, CMOS compatible, direct top-down nano-fabrication process employing ALD tungsten (WALD) as a structural material for nano-electro-mechanical systems (NEMS). Using this process doubly clamped suspended NEMS devices have been successfully fabricated and demonstrated. The devices have been observed to operate comparably to 2-terminal electrostatic carbon nanotube (CNT) switches, and MEMS tunneling devices. A lifetime in excess of 660,500 cycles has been observed under low-current-limited operating conditions. Under these conditions the device behavior is stable, reproducible and hysterisis free, resembling that of MEMS tunneling devices.

Major Accomplishments in Composite Materials and Sandwich Structures, 2009

ABSTRACT Existing interfacial toughness tests are evaluated for their accuracy and suitability fo... more ABSTRACT Existing interfacial toughness tests are evaluated for their accuracy and suitability for application to a wide range of sandwich structures and environments. It is shown that geometric nonlinearities and/or axial load coupling can cause errors in the perceived toughness as obtained by many of these tests and their associated data reduction methods. A previously proposed modified peel test is selected to eliminate the effect of axial load and a new, modified beam theory based method of data reduction is developed. Experiments and nonlinear finite element analyses are used to show that this approach produces highly accurate values of toughness, even in the presence of geometrically nonlinear behaviors. Mechanically attached loading tabs are described, allowing the test to be used for a wide variety of structures under various simulated usage environments.

Journal of Composites Technology and Research, 1998

ABSTRACT Energy release rates obtained by geometrically linear and geometrically nonlinear finite... more ABSTRACT Energy release rates obtained by geometrically linear and geometrically nonlinear finite element analyses of homogeneous, symmetrically delaminated single leg bending specimens are presented for a variety of materials, specimen geometries and fixture dimensions. It is shown that certain test geometries will exhibit strong nonlinear effects; thus, critical energy release rates obtained from tests of these geometries, using data reduction procedures that are based on linear theory, may contain significant errors. The nonlinear finite element results are used to develop empirical relationships between energy release rate as predicted by the nonlinear analyses and those predicted by linear analyses. These empirical relationships are shown to be valid over a wide range of specimen material properties, material property ratios (e.g., Young's modulus to shear modulus) and geometric properties of both the specimen and fixture, including fixture roller diameters. Thus, the empirical relationships may be used in a quantitative manner to design tests in order that significant nonlinear effects do not occur prior to fracture, and hence linear data reduction procedures remain valid. Alternatively, the empirical relationships may be used to interpret test results where nonlinear behavior occurs. Both uses are illustrated by example for typical laminated composite materials.

Journal of Composite Materials, 2015

ABSTRACT

Acoustical Imaging, 1992

ABSTRACT

Journal of Composite Materials, 2014

ABSTRACT

Sensors and Actuators A: Physical, 2011

ABSTRACT In this paper we present a novel low-temperature, CMOS compatible, top-down nanofabricat... more ABSTRACT In this paper we present a novel low-temperature, CMOS compatible, top-down nanofabrication process employing ALD tungsten (WALD) as a structural material for nano-electro-mechanical systems (NEMS). Using this process, doubly-clamped suspended NEMS switches/tunneling devices have been successfully fabricated and demonstrated. The devices have been observed to perform comparably to two-terminal electrostatic carbon nanotube (CNT) switches, graphene-based switches, and MEMS tunneling devices. A lifetime of ∼50,000 cycles has been observed when these devices are operated in full contact switching mode, and a lifetime in excess of 5×106 cycles has been observed under low-current-limited operating conditions. In the tunneling regime a work function of 0.0682eV has been calculated using experimental data coupled with finite element model (FEM) approximations. Under low-current-limited conditions the device behavior is stable and reproducible, resembling that of MEMS tunneling devices.

Abstract: Evaluative research was conducted on a distributed collaborative engineering design (CE... more Abstract: Evaluative research was conducted on a distributed collaborative engineering design (CED) course taught between two universities who used an online Advanced Interactive Discovery Environment (AIDE). The AIDE provided communication tools and ...

Online Submission, 2007

The purpose of this article is to compare institutions of higher learning in Poland and universit... more The purpose of this article is to compare institutions of higher learning in Poland and universities in Canada using an information technology conceptual framework consisting of three parts: participation, feedback and partnership. _________________________________________________________________________

Journal of Composite Materials, 1995

Results are presented from a study to determine energy release rate and mode ratio for a locally ... more Results are presented from a study to determine energy release rate and mode ratio for a locally buckled, compression loaded laminate which contains either a single delamination or two symmetrically located delaminations. It is shown that, at a given applied load or displacement, significantly different values of energy release rate and mode ratio may exist in the two configurations. In general, the rate-of-increase of energy release rate with increasing displacement, as well as the percentage of crack-tip shearing mode at a given displacement, are higher in the configuration which contains two delaminations.

ABSTRACT A four point bend, end notched flexure test is described for determining the mode II fra... more ABSTRACT A four point bend, end notched flexure test is described for determining the mode II fracture toughness of laminated composites. The test consists of a unidirectional laminate with a midplane delamination loaded in four point bending. The test configuration is analysed by beam theory and by finite element analysis. When the delamination front is in between the inner load ing rollers the energy release rate, expressed in terms of the applied load, is independent of delamination length. In addition, delamination growth is shown to be stable for a displacement controlled test. The advantages of this test over conventional mode II tests are the reduction of frictional effects and the ability to perform an experimental compliance calibration as the delamination advances. Further, an R-curve characterisation may be conducted. This results in a reduced time to conduct tests to generate mode II data compared with the tests currently used by industry.

Sensors and Actuators a Physical, Oct 1, 2009

A molecular layer deposition approach is reported that produces a new class of hybrid organic-ino... more A molecular layer deposition approach is reported that produces a new class of hybrid organic-inorganic thin films. These films have very low densities, and display typical atomic layer deposition characteristics: controllable linear growth, conformality, low roughness, and uniform composition. Because of their aluminum content, the alucone films cannot be dry etched with oxygen plasma. In accordance with their molecular structure, the new materials are completely removed in hydrochloric acid solutions. Since they can be etched with accurate control in acidic solutions, these hybrid materials are promising for the fabrication of MEMS/NEMS (Micro/Nano Electro Mechanical Systems) devices. Doubly supported structures with 120 nm air gaps are demonstrated using alucone materials as sacrificial layers.

Online Submission, 2007

This article attempts to determine whether the recent educational reforms in Poland are making it... more This article attempts to determine whether the recent educational reforms in Poland are making it more difficult for discipline to be maintained in schools. In general, changes have a negative impact upon school discipline because the likelihood of mixed-ability classes in junior secondary institutions is high. ________________________________________________________________________

Online Submission, 2006

The aim of this study was to compare Polish post-secondary vocational institutions with Canadian ... more The aim of this study was to compare Polish post-secondary vocational institutions with Canadian community colleges. The research concentrated upon programs in nursing, tourism and information technology delivered by the following three Polish schools Krakowska Szkola Medyczna, (Cracow, Poland), Policealne Studium Zawodowe (Cracow, Poland), Cracow School of Information Technology and four Canadian community colleges Red Deer (Red Deer, Alberta), Centennial (Scarborough, Ontario), Durham (Oshawa, Ontario) and Confederation (Thunder Bay, Ontario).

Advanced Materials and Processes

ABSTRACT

One dimensional delamination buckling and growth is analyzed using closed form cylindrical buckli... more One dimensional delamination buckling and growth is analyzed using closed form cylindrical buckling and crack tip element analyses. A cylindrical buckling analysis is utilized to determine the strains, curvatures, deflections, forces and moments in a buckled region bounded by the laminate free surface and a near-surface delamination. These results are used as input into a linear crack tip element analysis to obtain the total energy release rate and individual mode I and mode II components. Geometric nonlinearities are accounted for through the loading on the crack tip element. Total energy release rate and fracture mode ratio as found by this new technique are shown to agree with nonlinear finite element results.

Journal of Reinforced Plastics and Composites

A study is described that evaluated the effect of the mode mix used to create a precrack on the p... more A study is described that evaluated the effect of the mode mix used to create a precrack on the perceived delamination toughness of laminated composites. Mode I double cantilever beam, mode II end-notched flexure, and mixed-mode symmetrically delaminated single leg bending tests were first performed on unidirectional graphite/epoxy specimens with mode I precracks. The tests were then repeated on new unidirectional specimens with mode II precracks. Through an examination of the mechanisms involved, it is shown that toughness values for materials that do not exhibit fiber bridging will be most accurate, at all mode mixities, if test specimens are precracked at the same mode mix as the test itself.

International Journal of Solids and Structures, 1997

ABSTRACT An unsymmetric double cantilever beam test is described and its suitability for the dete... more ABSTRACT An unsymmetric double cantilever beam test is described and its suitability for the determination of interfacial fracture toughness is evaluated. The test specimen consists of a beam type geometry comprised of two materials, one ‘top’ and one ‘bottom’, with a crack at one end along the bimaterial interface. The specimen is loaded in a splitting fashion similar to that of a conventional double cantilever beam test. Due to the dissimilar in-plane and out-of-plane deformations of the two legs, the load vs deflection response of the specimen is found to be nonlinear. A nonlinear plate theory is used to predict the deformations of the specimen, and these results are used in a crack tip element analysis to determine energy release rate and mode mixity. The analytical predictions are verified by comparisons to results from two-dimensional, geometrically nonlinear finite element continuum analyses for a variety of typical materials and test geometries. It is shown that, by varying the relative thicknesses of the two materials, the unsymmetric double cantilever beam test can be used on most bimaterial pairs to determine interfacial fracture toughness over a reasonably wide range of mode mixities.

2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems, 2009

ABSTRACT In this paper we present a novel low temperature, CMOS compatible, direct top-down nano-... more ABSTRACT In this paper we present a novel low temperature, CMOS compatible, direct top-down nano-fabrication process employing ALD tungsten (WALD) as a structural material for nano-electro-mechanical systems (NEMS). Using this process doubly clamped suspended NEMS devices have been successfully fabricated and demonstrated. The devices have been observed to operate comparably to 2-terminal electrostatic carbon nanotube (CNT) switches, and MEMS tunneling devices. A lifetime in excess of 660,500 cycles has been observed under low-current-limited operating conditions. Under these conditions the device behavior is stable, reproducible and hysterisis free, resembling that of MEMS tunneling devices.

Major Accomplishments in Composite Materials and Sandwich Structures, 2009

ABSTRACT Existing interfacial toughness tests are evaluated for their accuracy and suitability fo... more ABSTRACT Existing interfacial toughness tests are evaluated for their accuracy and suitability for application to a wide range of sandwich structures and environments. It is shown that geometric nonlinearities and/or axial load coupling can cause errors in the perceived toughness as obtained by many of these tests and their associated data reduction methods. A previously proposed modified peel test is selected to eliminate the effect of axial load and a new, modified beam theory based method of data reduction is developed. Experiments and nonlinear finite element analyses are used to show that this approach produces highly accurate values of toughness, even in the presence of geometrically nonlinear behaviors. Mechanically attached loading tabs are described, allowing the test to be used for a wide variety of structures under various simulated usage environments.

Journal of Composites Technology and Research, 1998

ABSTRACT Energy release rates obtained by geometrically linear and geometrically nonlinear finite... more ABSTRACT Energy release rates obtained by geometrically linear and geometrically nonlinear finite element analyses of homogeneous, symmetrically delaminated single leg bending specimens are presented for a variety of materials, specimen geometries and fixture dimensions. It is shown that certain test geometries will exhibit strong nonlinear effects; thus, critical energy release rates obtained from tests of these geometries, using data reduction procedures that are based on linear theory, may contain significant errors. The nonlinear finite element results are used to develop empirical relationships between energy release rate as predicted by the nonlinear analyses and those predicted by linear analyses. These empirical relationships are shown to be valid over a wide range of specimen material properties, material property ratios (e.g., Young's modulus to shear modulus) and geometric properties of both the specimen and fixture, including fixture roller diameters. Thus, the empirical relationships may be used in a quantitative manner to design tests in order that significant nonlinear effects do not occur prior to fracture, and hence linear data reduction procedures remain valid. Alternatively, the empirical relationships may be used to interpret test results where nonlinear behavior occurs. Both uses are illustrated by example for typical laminated composite materials.

Journal of Composite Materials, 2015

ABSTRACT

Acoustical Imaging, 1992

ABSTRACT

Journal of Composite Materials, 2014

ABSTRACT

Sensors and Actuators A: Physical, 2011

ABSTRACT In this paper we present a novel low-temperature, CMOS compatible, top-down nanofabricat... more ABSTRACT In this paper we present a novel low-temperature, CMOS compatible, top-down nanofabrication process employing ALD tungsten (WALD) as a structural material for nano-electro-mechanical systems (NEMS). Using this process, doubly-clamped suspended NEMS switches/tunneling devices have been successfully fabricated and demonstrated. The devices have been observed to perform comparably to two-terminal electrostatic carbon nanotube (CNT) switches, graphene-based switches, and MEMS tunneling devices. A lifetime of ∼50,000 cycles has been observed when these devices are operated in full contact switching mode, and a lifetime in excess of 5×106 cycles has been observed under low-current-limited operating conditions. In the tunneling regime a work function of 0.0682eV has been calculated using experimental data coupled with finite element model (FEM) approximations. Under low-current-limited conditions the device behavior is stable and reproducible, resembling that of MEMS tunneling devices.