Dr. Geoffrey P. McKnight Profile

Dr. Geoffrey P. McKnight

Student at HRL Labs LLC

SPIE Involvement:

Author

Publications (17)

Proceedings Article | 27 May 2022 Presentation + Paper

Presentation + Paper

Curving of large-format infrared sensors

Mark O'Masta, Binh-Minh Nguyen, Alexander Gurga, Trevor Sasse, Brian Hempe, Christian Neuhaus, Eric Clough, Jacob Hundley, Pamela Patterson, James Jenkins, Mary Chen, Gregory Jacques, Scott Linton, Francisco Perez, Colin Van Ysseldyk, Esther Wang, Yan Tang, Kenta Niwa, Tobias Schaedler, Alexandros Kyrtsos, John Glennon, Andreu Glasmann, Enrico Bellotti, Geoff McKnight

Proceedings Volume 12107, 121071S (2022) https://doi.org/10.1117/12.2618122

KEYWORDS: Sensors, Staring arrays, Mid-IR, Infrared sensors, Infrared imaging, Silicon, Spherical lenses, Monochromatic aberrations, Infrared radiation, Imaging systems

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Proceedings Article | 1 April 2014 Paper

Paper

Theoretical and experimental investigation of architected core materials incorporating negative stiffness elements

Chia-Ming Chang, Andrew Keefe, William Carter, Christopher Henry, Geoff McKnight

Proceedings Volume 9057, 905723 (2014) https://doi.org/10.1117/12.2051036

KEYWORDS: Foam, Finite element methods, Neodymium, Composites, Electroluminescence, Performance modeling, Chemical elements, Surface conduction electron emitter displays, Solids, Vibration control

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Proceedings Article | 30 March 2012 Paper

Paper

Lightweight thermal energy recovery system based on shape memory alloys: a DOE ARPA-E initiative

Alan Browne, Andrew Keefe, Paul Alexander, Nilesh Mankame, Patrick Usoro, Nancy Johnson, Jan Aase, Peter Sarosi, Geoffrey McKnight, Guillermo Herrera, Christopher Churchill, John Shaw, Jeff Brown

Proceedings Volume 8343, 834306 (2012) https://doi.org/10.1117/12.913275

KEYWORDS: Shape memory alloys, Thermoelectric materials, Thermal efficiency, Energy efficiency, Prototyping, Combustion, Liquids, Neodymium, Thermodynamics, Standards development

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Proceedings Article | 29 March 2010 Paper

Paper

Active material based active sealing technology: Part 1. Active seal requirements vs. active material actuator properties

Christopher Henry, William Carter, Guillermo Herrera, Geoffrey McKnight, Alan Browne, Nancy Johnson, Imad Bazzi

Proceedings Volume 7645, 76450H (2010) https://doi.org/10.1117/12.843834

KEYWORDS: Polymers, Liquid crystals, Actuators, Manufacturing, Electrodes, Carbon, Shape memory alloys, Dielectrics, Electroactive polymers, Metals

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Proceedings Article | 1 April 2009 Paper

Paper

A reversibly deployable air dam: a bending approach based on embedded shape memory alloy actuators, Part II: technology demonstration

Geoffrey McKnight, Alan Browne, Nancy Johnson

Proceedings Volume 7290, 72900C (2009) https://doi.org/10.1117/12.812280

KEYWORDS: Shape memory alloys, Actuators, Ferroelectric materials, Control systems, Electromagnetism, Electronics, Electronic test equipment, Polymers, Photography, Roads

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Proceedings Article | 2 April 2008 Paper

Paper

Large strain variable stiffness composites for shear deformations with applications to morphing aircraft skins

G. McKnight, C. Henry

Proceedings Volume 6929, 692919 (2008) https://doi.org/10.1117/12.778888

KEYWORDS: Composites, Kinematics, Skin, Shape memory polymers, Photogrammetry, Resistance, Aerodynamics, Polymers, Temperature metrology, Prototyping

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Morphing or reconfigurable structures potentially allow for previously unattainable vehicle performance by permitting several optimized structures to be achieved using a single platform. The key to enabling this technology in applications such as aircraft wings, nozzles, and control surfaces, are new engineered materials which can achieve the necessary deformations but limit losses in parasitic actuation mass and structural efficiency (stiffness/weight). These materials should exhibit precise control of deformation properties and provide high stiffness when exercised through large deformations. In this work, we build upon previous efforts in segmented reinforcement variable stiffness composites employing shape memory polymers to create prototype hybrid composite materials that combine the benefits of cellular materials with those of discontinuous reinforcement composites. These composites help overcome two key challenges for shearing wing skins: the resistance to out of plane buckling from actuation induced shear deformation, and resistance to membrane deflections resulting from distributed aerodynamic pressure loading. We designed, fabricated, and tested composite materials intended for shear deformation and address out of plane deflections in variable area wing skins. Our designs are based on the kinematic engineering of reinforcement platelets such that desired microstructural kinematics is achieved through prescribed boundary conditions. We achieve this kinematic control by etching sheets of metallic reinforcement into regular patterns of platelets and connecting ligaments. This kinematic engineering allows optimization of materials properties for a known deformation pathway. We use mechanical analysis and full field photogrammetry to relate local scale kinematics and strains to global deformations for both axial tension loading and shear loading with a pinned-diamond type fixture. The Poisson ratio of the kinematically engineered composite is ~3x higher than prototypical orthotropic variable stiffness composites. This design allows us to create composite materials that have high stiffness in the cold state below SMP T_g (4-14GPa) and yet achieve large composite shear strains (5-20%) in the hot state (above SMP T_g).

Proceedings Article | 2 April 2008 Paper

Paper

3D FEA simulation of segmented reinforcement variable stiffness composites

C. Henry, G. McKnight, A. Enke, R. Bortolin, S. Joshi

Proceedings Volume 6929, 69290X (2008) https://doi.org/10.1117/12.778891

KEYWORDS: Composites, 3D modeling, Kinematics, Shape memory polymers, Finite element methods, Strain analysis, Matrices, Systems modeling, Homogenization, Aluminum

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Reconfigurable and morphing structures may provide significant improvement in overall platform performance through optimization over broad operating conditions. The realization of this concept requires structures, which can accommodate the large deformations necessary with modest weight and strength penalties. Other studies suggest morphing structures need new materials to realize the benefits that morphing may provide. To help meet this need, we have developed novel composite materials based on specially designed segmented reinforcement and shape memory polymer matrices that provide unique combinations of deformation and stiffness properties. To tailor and optimize the design and fabrication of these materials for particular structural applications, one must understand the envelope of morphing material properties as a function of microstructural architecture and constituent properties. Here we extend our previous simulations of these materials by using 3D models to predict stiffness and deformation properties in variable stiffness segmented composite materials. To understand the effect of various geometry tradeoffs and constituent properties on the elastic stiffness in both the high and low stiffness states, we have performed a trade study using a commercial FEA analysis package. The modulus tensor is constructed and deformation properties are computed from representative volume elements (RVE) in which all (6) basic loading conditions are applied. Our test matrix consisted of four composite RVE geometries modeled using combinations of 5 SMP and 3 reinforcement elastic moduli. Effective composite stiffness and deformation results confirm earlier evidence of the essential performance tradeoffs of reduced stiffness for increasing reversible strain accommodation with especially heavy dependencies on matrix modulus and microstructural architecture. Furthermore, our results show these laminar materials are generally orthotropic and indicate that previous calculations of matrix gap and interlaminar strains based on kinematic approximations are accurate to within 10-20% for many material systems. We compare these models with experimental results for a narrow geometry and material set to show the accuracy of the models as compared to physical materials. Our simulations indicate that improved shape memory polymer materials could enable a composite material that can accommodate ~30% strain with a cold state stiffness of ~30GPa. This would improve the current state of the art 5-10x and significantly reduce the weight and stiffness costs of using a morphing component.

Proceedings Article | 17 April 2007 Paper

Paper

Bill Armstrong memorial session: elastic modulus and strain recovery testing of variable stiffness composites for structural reconfiguration

Geoff McKnight, Robert Doty, Guillermo Herrera, Chris Henry

Proceedings Volume 6526, 652617 (2007) https://doi.org/10.1117/12.717287

KEYWORDS: Composites, Shape memory polymers, Polymers, Matrices, Polyurethane, Kinematics, Structural design, Glasses, Manufacturing, Prototyping

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Proceedings Article | 6 April 2006 Paper

Paper

Cellular variable stiffness materials for ultra-large reversible deformations in reconfigurable structures

C. Henry, G. McKnight

Proceedings Volume 6170, 617023 (2006) https://doi.org/10.1117/12.659633

KEYWORDS: Polymers, Finite element methods, Composites, Temperature metrology, Polonium, Carbon, Shape memory alloys, Structural engineering, Shape memory polymers, Magnetism

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Proceedings Article | 16 May 2005 Paper

Paper

Variable stiffness materials for reconfigurable surface applications

Geoff McKnight, Chris Henry

Proceedings Volume 5761, (2005) https://doi.org/10.1117/12.601495

KEYWORDS: Composites, Shape memory polymers, Prototyping, Structural design, Aluminum, Carbon, Kinematics, Data modeling, Chemical elements, Matrices

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Proceedings Article | 16 May 2005 Paper

Paper

Solid-state actuation based on reversible Li electroplating

William Barvosa-Carter, Cameron Massey, Geoffrey McKnight, Ping Liu

Proceedings Volume 5761, (2005) https://doi.org/10.1117/12.601493

KEYWORDS: Lithium, Plating, Ions, Electroplating, Thin films, Solid state electronics, Actuators, Thermodynamics, Temperature metrology, Metals

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Proceedings Article | 6 May 2005 Paper

Paper

Reversible work by electrochemical intercalation of graphitic materials

Cameron Massey, Geoffrey McKnight, William Barvosa-Carter, Ping Liu

Proceedings Volume 5759, (2005) https://doi.org/10.1117/12.601491

KEYWORDS: Ions, Diffusion, Actuators, Carbon, Electrodes, Polymers, Bromine, Temperature metrology, Solid state physics, Solid state electronics

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Proceedings Article | 5 May 2005 Paper

Paper

Miniature thin-film NiTi hydraulic actuator with MEMS microvalves

Geoff McKnight, Leslie Momoda, Don Croft, Dong Lee, Daniel Shin, Greg Carman

Proceedings Volume 5762, (2005) https://doi.org/10.1117/12.607307

KEYWORDS: Actuators, Thin films, Microelectromechanical systems, Silicon, Shape memory alloys, Etching, Manufacturing, Silicon films, Electronics, Nanolithography

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Proceedings Article | 14 August 2003 Paper

Paper

Thin-layer magnetostrictive composite films for turbomachinery fan blade damping

Wade Pulliam, Donggun Lee, Gregory Carman, Geoffrey McKnight

Proceedings Volume 5054, (2003) https://doi.org/10.1117/12.483725

KEYWORDS: Composites, Magnetism, Magnetostrictive materials, Fluctuations and noise, Finite element methods, Aluminum, Manufacturing, Thin films, Absorption, Iron

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Proceedings Article | 9 July 2002 Paper

Paper

Recent advances in magnetostrictive particulate composite technology

Wade Pulliam, Geoffrey McKnight, Gregory Carman

Proceedings Volume 4698, (2002) https://doi.org/10.1117/12.475074

KEYWORDS: Composites, Particles, Magnetism, Magnetostrictive materials, Amplifiers, Absorption, Crystals, Polymers, Manufacturing, Transducers

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Proceedings Article | 11 July 2001 Paper

Paper

Large magnetostriction in Terfenol-D particulate composites with preferred [112] orientation

Geoffrey McKnight, Gregory Carman

Proceedings Volume 4333, (2001) https://doi.org/10.1117/12.432754

KEYWORDS: Composites, Particles, Magnetostrictive materials, Optical proximity correction, Crystals, Magnetism, Polymers, Anisotropy, Data modeling, Crystallography

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Proceedings Article | 14 June 2000 Paper

Paper

Energy absorption in axial and shear loading of particulate magnetostrictive composites

Geoffrey McKnight, Gregory Carman

Proceedings Volume 3992, (2000) https://doi.org/10.1117/12.388240

KEYWORDS: Magnetism, Absorption, Composites, Particles, Magnetostrictive materials, Polymers, Anisotropy, Actuators, Sensors, Crystals

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Showing 5 of 17 publications

Conference Committee Involvement (14)

Smart Structures and NDE for Industry 4.0, Smart Cities, and Energy Systems

27 April 2020 | Online Only, California, United States

Smart Structures and NDE for Energy Systems and Industry 4.0

4 March 2019 | Denver, Colorado, United States

Smart Structures and NDE for Industry 4.0

5 March 2018 | Denver, Colorado, United States

Industrial and Commercial Applications of Smart Structures Technologies XI

26 March 2017 | Portland, Oregon, United States

Industrial and Commercial Applications of Smart Structures Technologies X

21 March 2016 | Las Vegas, Nevada, United States

Industrial and Commercial Applications of Smart Structures Technologies IX

9 March 2015 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies VIII

11 March 2014 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies VII

10 March 2013 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies VI

12 March 2012 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies V

7 March 2011 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies IV

8 March 2010 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies III

9 March 2009 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies II

10 March 2008 | San Diego, California, United States

Industrial and Commercial Applications of Smart Structures Technologies

19 March 2007 | San Diego, California, United States

Showing 5 of 14 Conference Committees

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