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Papers by Alan Gershon

biological inspiration during product development. Bionispiration and

ABSTRACT: Recently, it has become very important to rapidly characterize the processing-structure... more ABSTRACT: Recently, it has become very important to rapidly characterize the processing-structure-property relationships in polymer nanocomposites using mini-mal quantities of expensive nanoscale fillers. To address this issue, we present a new combinatorial approach developed for characterizing the variation in mechanical properties as a function of filler composition in polymer nanocomposites. The fun-damental basis for the combinatorial approach is the generation of compositional gradients through transient operation of a twin-screw extruder (TSE). The composi-tional variation in the specimens could be rapidly predicted a priori using a convo-lution process model and was verified a posteriori using pycnometry measurements and thermogravimetric analysis. To characterize the quasi-static mechanical proper-ties along the compositional gradient, sub-scale specimens that are proportional in size to ASTM type I specimens but with a gage section that is a factor of 10 smaller, were test...

The ability to control the structure of polymer composites at multiple length scales is now being... more The ability to control the structure of polymer composites at multiple length scales is now being exploited to enhance the energy absorbing capabilities of these composites in dynamic applications, such as armor structures. This research focuses on elucidating on the dynamic and static mechanical behavior of hierarchically-structured and nano-structured polymer composites that are now being developed using carbon micro- and nano-fiber reinforcement.. It was determined from tests conducted on small-scale tensile specimens of polymer nanocomposites obtained using a combinatorial approach based on Twin Screw Extrusion, that the tensile modulus and strength increases linearly with composition, while the strain to failure decreases linearly. Nanoindentation measurements made on the microstructure of the polymer nancomposites indicated that agglomerates behaved as micro-sized highly filled regions in the polymer nanocomposite that contributed to the bulk modulus in a linear rule-of-mixtur...

The development of hierarchical structure in synthetic materials is a new approach to enhancing m... more The development of hierarchical structure in synthetic materials is a new approach to enhancing multifunctional properties in a manner that is similar to natural materials. One means for achieving hierarchical structure is to add nanoscale ingredients to polymers that can either self-assemble in a "bottomup" approach or can be added to polymer with microscale reinforcement through engineered-assembly in a "top-down" approach. In order to better understand synthetic hierarchical structures developed through the nanoenhancement of polymers and those occurring in natural materials, multiscale characterization techniques and models are developed to elucidate the structure-property relationship due to hierarchical structure, and the control of

The development of hierarchical structure in synthetic materials is a new approach to enhancing m... more The development of hierarchical structure in synthetic materials is a new approach to enhancing multifunctional properties in a manner that is similar to natural materials. One means for achieving hierarchical structure is to add nanoscale ingredients to polymers that can either self-assemble in a “bottom-up ” approach or can be added to polymer with microscale reinforcement through engineered-assembly in a “top-down ” approach. In order to better understand synthetic hierarchical structures developed through the nano-enhancement of polymers and those occurring in natural materials, multi-scale characterization techniques and models are developed to elucidate the structure-property relationship due to hierarchical structure, and the control of this relationship through processing in synthetic materials. A combinatorial approach is applied for rapid characterization of the processing-structure-property relationships that develop in nano-enhanced thermoplastic polymers associated with...

Design And Nature III: …, 2006

The use of bio-inspiration to create new products and devices requires the development of new des... more The use of bio-inspiration to create new products and devices requires the development of new design tools and manufacturing technologies, as well as the education of students capable of using them. At the University of Maryland, we have developed new educational tools that emphasize bioinspired product realization. These tools include the development of a bioinspired design repository, a concurrent fabrication and assembly technology that focuses on the use of multi-piece, multi-stage molds to affordably manufacture large numbers of bio-inspired products, and a series of undergraduate curriculum enhancements. This paper provides an overview of these two technologies and describes how these technologies are integrated into the Mechanical Engineering curriculum. The new educational tools provide students with the fundamental design and manufacturing principles needed in bio-inspired product and device development. The curriculum changes culminate in an elective course undertaken in their senior year.

Journal of Materials Science, Jun 22, 2010

Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced ... more Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced polymers and polymer composites Alan L. Gershon • Daniel P. Cole • Arun K. Kota • Hugh A. Bruck Received: 30 January ...

Journal of materials science, 2010

Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced ... more Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced polymers and polymer composites Alan L. Gershon • Daniel P. Cole • Arun K. Kota • Hugh A. Bruck Received: 30 January ...

Solid Mechanics and Its Applications, 2009

Page 1. In Situ Characterization and Modeling of Strains near Embedded Electronic Components Duri... more Page 1. In Situ Characterization and Modeling of Strains near Embedded Electronic Components During Processing and Break-in for Multifunctional Polymer Structures Alan L. Gershon, Lawrence S. Gyger, Jr., Hugh A. Bruck, and Satyandra K. Gupta ...

International Journal of Solids and Structures, 2002

Información del artículo Three-dimensional effects near the interface in a functionally graded Ni... more Información del artículo Three-dimensional effects near the interface in a functionally graded Ni–Al<f>₂</f>O<f>₃</f> plate specimen.

Experimental Mechanics, Apr 8, 2008

In this paper, in situ experiments have been designed using the full-field deformation technique ... more In this paper, in situ experiments have been designed using the full-field deformation technique of Digital Image Correlation (DIC) to characterize non-uniform shrinkage in thermoplastic polymers commonly used in traditional and emerging molding processes. These experiments are capable of characterizing the differences in strains that develop due to thermal gradients and stiction as the polymer shrinks from the molten to the solid state during molding processes. The experimental set-up consists of simulated open molds, a heating stage, thermocouples for temperature measurements, and a video imaging system for DIC. From these experiments, it has been shown that there is a large increase in shrinkage strain associated with the transition of the polymer from the molten to the solid state in a mold with reduced side rigidity, and as it is cooled below the Vicat softening point. Changing the cooling rate from air-cooled to quasi-steady state can eliminate the transition at the Vicat softening point. Furthermore, substantial decreases in shrinkage strain are observed when the polymer is melted in an open mold without mold release, while using mold release produces results similar to that observed with reduced side rigidity. A simple one-dimensional model reasonably explains and predicts the observed trends in the shrinkage behavior due to temperature differences through the thickness of the polymer melt when using high conductivity molds as well as constraint in the polymer melt near the mold resulting from stiction.

The ability to control the structure of polymer composites at multiple length scales is now being... more The ability to control the structure of polymer composites at multiple length scales is now being exploited to enhance the energy absorbing capabilities of these composites in dynamic applications, such as armor structures. This research focuses on elucidating on the dynamic and static mechanical behavior of hierarchically-structured and nano-structured polymer composites that are now being developed using carbon micro-and nano-fiber reinforcement. . It was determined from tests conducted on small-scale tensile specimens of polymer nanocomposites obtained using a combinatorial approach based on Twin Screw Extrusion, that the tensile modulus and strength increases linearly with composition, while the strain to failure decreases linearly. Nanoindentation measurements made on the microstructure of the polymer nancomposites indicated that agglomerates behaved as micro-sized highly filled regions in the polymer nanocomposite that contributed to the bulk modulus in a linear rule-of-mixture formulation using a modulus for the CNFs of 15 GPa obtained from extrapolating the small-scale tensile measurements. When there are no agglomerates, the modulus is predicted to increase only 8%, which indicates that the presence of agglomerates may not be as detrimental as previously postulated. Laminated unidirectional carbon-fiber epoxy specimens were prepared using the polymer nanocomposites. Three point bend tests conducted on these specimens indicated a 25% increase in the maximum flexural energy density and a 25% decrease in the strength of the laminated composite specimens bonded with the 10 wt. % CNF polymer nanocomposite relative to the single composite layer. Bonding with the pure polymer resulted in a 50% decrease in both strength and the maximum flexural energy density relative to the single composite layer. Izod tests conducted on these specimens indicated a 125% increase in the impact energy when bonding with the 10 wt. % polymer nanocomposites instead of the pure polymer and a 20% increase over the single unidirectional carbon-fiber/epoxy composite layer, consistent with the three point bend tests and indicating that there was not much change in sensitivity at higher strain rates. The dynamic compressive behavior of hierarchically-structured polymer composites formed from CNFs and CMFs also indicated a rule-of-mixture effect from adding CNFs to a CMF-reinforced polymer composite, with an increase in the strength of the composite being 7 times greater for the CMF reinforcement relative to the CNF reinforcement.

Innovations in Engineering Education: Mechanical Engineering Education, Mechanical Engineering/Mechanical Engineering Technology Department Heads, 2004

Bio-inspired products and devices take their inspiration from nature [Gold00]. Current mechanical... more Bio-inspired products and devices take their inspiration from nature [Gold00]. Current mechanical engineering curricula do not cover manufacturing techniques and principles needed to develop such products and devices. We have been enhancing the mechanical engineering undergraduate curriculum by integrating recent advances in the manufacturing of bioinspired products and devices through the following activities:

Macromolecules, 2007

ABSTRACT

Polymer, 2008

The addition of multi-walled carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs) to polymeric m... more The addition of multi-walled carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs) to polymeric melts offers a convenient route to obtain highly conductive plastics. However, when these materials are melt processed, their conductivity can be lost. Here, it is shown that conductivities can be recovered through melt annealing at temperatures above the polymer's glass transition temperature (T g ). We demonstrate these results for both MWCNT and CNF-based composites in polystyrene (PS). The mechanism behind the conductivity increase is elucidated through modeling. It involves a transition from aligned, unconnected particles prior to annealing to an interconnected network after annealing through viscoelastic relaxation of the polymer. Such re-arrangement is directly visualized for the case of the CNFbased composites using confocal microscopy. The annealing-induced increase in particle connectivity is also reflected in dynamic rheological measurements on both MWCNT and CNF composites as an increase in their elastic moduli at low frequencies.

Modelling and Simulation in Materials Science and Engineering, 2007

A high-fidelity generalized method of cells (HFGMC) model for the micromechanical behavior of por... more A high-fidelity generalized method of cells (HFGMC) model for the micromechanical behavior of porous and composite microstructures has been previously developed. Based on this model, a new approach has been developed to optimize porous microstructures for ‘porous materials by design’. This approach uses a combination of genetic algorithms (GA) (stochastic), coarse (periodic) and Newton–Raphson (gradient) optimization methods. In order to

Materials Science and Engineering: C, 2010

... Author Contact Information , E-mail The Corresponding Author , Shaowen Xu b , Michael A. Sutt... more ... Author Contact Information , E-mail The Corresponding Author , Shaowen Xu b , Michael A. Sutton b and Vikrant Tiwari b. ... Understanding of the dynamic and static structure–property relationship in Palmetto wood can facilitate the development of new hierarchically structured ...

Macromolecules, 2007

ABSTRACT

biological inspiration during product development. Bionispiration and

ABSTRACT: Recently, it has become very important to rapidly characterize the processing-structure... more ABSTRACT: Recently, it has become very important to rapidly characterize the processing-structure-property relationships in polymer nanocomposites using mini-mal quantities of expensive nanoscale fillers. To address this issue, we present a new combinatorial approach developed for characterizing the variation in mechanical properties as a function of filler composition in polymer nanocomposites. The fun-damental basis for the combinatorial approach is the generation of compositional gradients through transient operation of a twin-screw extruder (TSE). The composi-tional variation in the specimens could be rapidly predicted a priori using a convo-lution process model and was verified a posteriori using pycnometry measurements and thermogravimetric analysis. To characterize the quasi-static mechanical proper-ties along the compositional gradient, sub-scale specimens that are proportional in size to ASTM type I specimens but with a gage section that is a factor of 10 smaller, were test...

The ability to control the structure of polymer composites at multiple length scales is now being... more The ability to control the structure of polymer composites at multiple length scales is now being exploited to enhance the energy absorbing capabilities of these composites in dynamic applications, such as armor structures. This research focuses on elucidating on the dynamic and static mechanical behavior of hierarchically-structured and nano-structured polymer composites that are now being developed using carbon micro- and nano-fiber reinforcement.. It was determined from tests conducted on small-scale tensile specimens of polymer nanocomposites obtained using a combinatorial approach based on Twin Screw Extrusion, that the tensile modulus and strength increases linearly with composition, while the strain to failure decreases linearly. Nanoindentation measurements made on the microstructure of the polymer nancomposites indicated that agglomerates behaved as micro-sized highly filled regions in the polymer nanocomposite that contributed to the bulk modulus in a linear rule-of-mixtur...

The development of hierarchical structure in synthetic materials is a new approach to enhancing m... more The development of hierarchical structure in synthetic materials is a new approach to enhancing multifunctional properties in a manner that is similar to natural materials. One means for achieving hierarchical structure is to add nanoscale ingredients to polymers that can either self-assemble in a "bottomup" approach or can be added to polymer with microscale reinforcement through engineered-assembly in a "top-down" approach. In order to better understand synthetic hierarchical structures developed through the nanoenhancement of polymers and those occurring in natural materials, multiscale characterization techniques and models are developed to elucidate the structure-property relationship due to hierarchical structure, and the control of

The development of hierarchical structure in synthetic materials is a new approach to enhancing m... more The development of hierarchical structure in synthetic materials is a new approach to enhancing multifunctional properties in a manner that is similar to natural materials. One means for achieving hierarchical structure is to add nanoscale ingredients to polymers that can either self-assemble in a “bottom-up ” approach or can be added to polymer with microscale reinforcement through engineered-assembly in a “top-down ” approach. In order to better understand synthetic hierarchical structures developed through the nano-enhancement of polymers and those occurring in natural materials, multi-scale characterization techniques and models are developed to elucidate the structure-property relationship due to hierarchical structure, and the control of this relationship through processing in synthetic materials. A combinatorial approach is applied for rapid characterization of the processing-structure-property relationships that develop in nano-enhanced thermoplastic polymers associated with...

Design And Nature III: …, 2006

The use of bio-inspiration to create new products and devices requires the development of new des... more The use of bio-inspiration to create new products and devices requires the development of new design tools and manufacturing technologies, as well as the education of students capable of using them. At the University of Maryland, we have developed new educational tools that emphasize bioinspired product realization. These tools include the development of a bioinspired design repository, a concurrent fabrication and assembly technology that focuses on the use of multi-piece, multi-stage molds to affordably manufacture large numbers of bio-inspired products, and a series of undergraduate curriculum enhancements. This paper provides an overview of these two technologies and describes how these technologies are integrated into the Mechanical Engineering curriculum. The new educational tools provide students with the fundamental design and manufacturing principles needed in bio-inspired product and device development. The curriculum changes culminate in an elective course undertaken in their senior year.

Journal of Materials Science, Jun 22, 2010

Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced ... more Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced polymers and polymer composites Alan L. Gershon • Daniel P. Cole • Arun K. Kota • Hugh A. Bruck Received: 30 January ...

Journal of materials science, 2010

Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced ... more Page 1. IMEC 2009 Nanomechanical characterization of dispersion and its effects in nano-enhanced polymers and polymer composites Alan L. Gershon • Daniel P. Cole • Arun K. Kota • Hugh A. Bruck Received: 30 January ...

Solid Mechanics and Its Applications, 2009

Page 1. In Situ Characterization and Modeling of Strains near Embedded Electronic Components Duri... more Page 1. In Situ Characterization and Modeling of Strains near Embedded Electronic Components During Processing and Break-in for Multifunctional Polymer Structures Alan L. Gershon, Lawrence S. Gyger, Jr., Hugh A. Bruck, and Satyandra K. Gupta ...

International Journal of Solids and Structures, 2002

Información del artículo Three-dimensional effects near the interface in a functionally graded Ni... more Información del artículo Three-dimensional effects near the interface in a functionally graded Ni–Al<f>₂</f>O<f>₃</f> plate specimen.

Experimental Mechanics, Apr 8, 2008

In this paper, in situ experiments have been designed using the full-field deformation technique ... more In this paper, in situ experiments have been designed using the full-field deformation technique of Digital Image Correlation (DIC) to characterize non-uniform shrinkage in thermoplastic polymers commonly used in traditional and emerging molding processes. These experiments are capable of characterizing the differences in strains that develop due to thermal gradients and stiction as the polymer shrinks from the molten to the solid state during molding processes. The experimental set-up consists of simulated open molds, a heating stage, thermocouples for temperature measurements, and a video imaging system for DIC. From these experiments, it has been shown that there is a large increase in shrinkage strain associated with the transition of the polymer from the molten to the solid state in a mold with reduced side rigidity, and as it is cooled below the Vicat softening point. Changing the cooling rate from air-cooled to quasi-steady state can eliminate the transition at the Vicat softening point. Furthermore, substantial decreases in shrinkage strain are observed when the polymer is melted in an open mold without mold release, while using mold release produces results similar to that observed with reduced side rigidity. A simple one-dimensional model reasonably explains and predicts the observed trends in the shrinkage behavior due to temperature differences through the thickness of the polymer melt when using high conductivity molds as well as constraint in the polymer melt near the mold resulting from stiction.

The ability to control the structure of polymer composites at multiple length scales is now being... more The ability to control the structure of polymer composites at multiple length scales is now being exploited to enhance the energy absorbing capabilities of these composites in dynamic applications, such as armor structures. This research focuses on elucidating on the dynamic and static mechanical behavior of hierarchically-structured and nano-structured polymer composites that are now being developed using carbon micro-and nano-fiber reinforcement. . It was determined from tests conducted on small-scale tensile specimens of polymer nanocomposites obtained using a combinatorial approach based on Twin Screw Extrusion, that the tensile modulus and strength increases linearly with composition, while the strain to failure decreases linearly. Nanoindentation measurements made on the microstructure of the polymer nancomposites indicated that agglomerates behaved as micro-sized highly filled regions in the polymer nanocomposite that contributed to the bulk modulus in a linear rule-of-mixture formulation using a modulus for the CNFs of 15 GPa obtained from extrapolating the small-scale tensile measurements. When there are no agglomerates, the modulus is predicted to increase only 8%, which indicates that the presence of agglomerates may not be as detrimental as previously postulated. Laminated unidirectional carbon-fiber epoxy specimens were prepared using the polymer nanocomposites. Three point bend tests conducted on these specimens indicated a 25% increase in the maximum flexural energy density and a 25% decrease in the strength of the laminated composite specimens bonded with the 10 wt. % CNF polymer nanocomposite relative to the single composite layer. Bonding with the pure polymer resulted in a 50% decrease in both strength and the maximum flexural energy density relative to the single composite layer. Izod tests conducted on these specimens indicated a 125% increase in the impact energy when bonding with the 10 wt. % polymer nanocomposites instead of the pure polymer and a 20% increase over the single unidirectional carbon-fiber/epoxy composite layer, consistent with the three point bend tests and indicating that there was not much change in sensitivity at higher strain rates. The dynamic compressive behavior of hierarchically-structured polymer composites formed from CNFs and CMFs also indicated a rule-of-mixture effect from adding CNFs to a CMF-reinforced polymer composite, with an increase in the strength of the composite being 7 times greater for the CMF reinforcement relative to the CNF reinforcement.

Innovations in Engineering Education: Mechanical Engineering Education, Mechanical Engineering/Mechanical Engineering Technology Department Heads, 2004

Bio-inspired products and devices take their inspiration from nature [Gold00]. Current mechanical... more Bio-inspired products and devices take their inspiration from nature [Gold00]. Current mechanical engineering curricula do not cover manufacturing techniques and principles needed to develop such products and devices. We have been enhancing the mechanical engineering undergraduate curriculum by integrating recent advances in the manufacturing of bioinspired products and devices through the following activities:

Macromolecules, 2007

ABSTRACT

Polymer, 2008

The addition of multi-walled carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs) to polymeric m... more The addition of multi-walled carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs) to polymeric melts offers a convenient route to obtain highly conductive plastics. However, when these materials are melt processed, their conductivity can be lost. Here, it is shown that conductivities can be recovered through melt annealing at temperatures above the polymer's glass transition temperature (T g ). We demonstrate these results for both MWCNT and CNF-based composites in polystyrene (PS). The mechanism behind the conductivity increase is elucidated through modeling. It involves a transition from aligned, unconnected particles prior to annealing to an interconnected network after annealing through viscoelastic relaxation of the polymer. Such re-arrangement is directly visualized for the case of the CNFbased composites using confocal microscopy. The annealing-induced increase in particle connectivity is also reflected in dynamic rheological measurements on both MWCNT and CNF composites as an increase in their elastic moduli at low frequencies.

Modelling and Simulation in Materials Science and Engineering, 2007

A high-fidelity generalized method of cells (HFGMC) model for the micromechanical behavior of por... more A high-fidelity generalized method of cells (HFGMC) model for the micromechanical behavior of porous and composite microstructures has been previously developed. Based on this model, a new approach has been developed to optimize porous microstructures for ‘porous materials by design’. This approach uses a combination of genetic algorithms (GA) (stochastic), coarse (periodic) and Newton–Raphson (gradient) optimization methods. In order to

Materials Science and Engineering: C, 2010

... Author Contact Information , E-mail The Corresponding Author , Shaowen Xu b , Michael A. Sutt... more ... Author Contact Information , E-mail The Corresponding Author , Shaowen Xu b , Michael A. Sutton b and Vikrant Tiwari b. ... Understanding of the dynamic and static structure–property relationship in Palmetto wood can facilitate the development of new hierarchically structured ...

Macromolecules, 2007

ABSTRACT