scott groves - Academia.edu (original) (raw)
Papers by scott groves
U.S. Department of Energy Office of Scientific and Technical Information - OSTI OAI, Jul 19, 2016
Advanced Composites Letters
The finite-strain-invariant criterion is applied to Toray 1000 / DER332 symmetrically balanced an... more The finite-strain-invariant criterion is applied to Toray 1000 / DER332 symmetrically balanced angle-ply laminates subjected to a uniaxial loading state. The results indicate that the initial failures are all in the matrix failure mode.
International Journal of Solids and Structures
A continuum mechanics approach is utilized herein to develop a model for predicting the thermomec... more A continuum mechanics approach is utilized herein to develop a model for predicting the thermomechanical constitution of elastic composites subjected to both monotonic and cyclic fatigue loading. In this model the damage is characterized by a set of second-order tensor valued internal state ...
An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composi... more An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0° to 90° to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles. 2 figs.
ABSTRACT The performance of commercial high-performance fibers is examined for application to fly... more ABSTRACT The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.
An interface structure for hub and mass attachment in flywheel rotors. The interface structure ef... more An interface structure for hub and mass attachment in flywheel rotors. The interface structure efficiently transmits high radial compression forces and withstands both large circumferential elongation and local stresses generated by mass-loading and hub attachments. The interface structure is comprised of high-strength fiber, such as glass and carbon, woven into an angle pattern which is about 45.degree. with respect to the rotor axis. The woven fiber is bonded by a ductile matrix material which is compatible with and adheres to the rotor material. This woven fiber is able to elongate in the circumferential direction to match the rotor growth during spinning.
An Achilles heel for the performance of thick-section, cylindrical fiber composite flywheels is t... more An Achilles heel for the performance of thick-section, cylindrical fiber composite flywheels is the poor interlaminar properties of the material. Methods that have been used to minimize or eliminate radial tensile stresses include prestressing concentric cylinders and mass loading. There can also be significant interlaminar shear stresses at the edges of mass-loaded flywheels and in flywheels for high-power density applications
As part of efforts to develop a three-dimensional failure model for composites, a study of failur... more As part of efforts to develop a three-dimensional failure model for composites, a study of failure and fatigue due to combined interlaminar stresses was conducted. The combined stresses were generated using a hollow cylindrical specimen, which was subjected to normal compression and torsion. For both glass and carbon fiber composites, normal compression resulted in a significant enhancement in the interlaminar shear stress and strain at failure. Under moderate compression levels, the failure mode transitioned from elastic to plastic. The observed failure envelope could not be adequately captured using common plylevel failure models. Alternate modeling approaches were examined and it was found that a pressure-dependent failure criterion was required to reproduce the experimental results. The magnitude of the pressure-dependent terms of this model was found to be material dependent. The interlaminar shear fatigue behavior of a carbon/epoxy system was also studied using the cylindrical specimen. Preliminary results indicate that a single S/N curve which is normalized for interlaminar shear strength may be able to reproduce the effects of both temperature and out-of-plane compression on fatigue life. The results demonstrate that there are significant gains to be made in improving interlaminar strengths of composite structures by applying out-of-plane compression. This effect could be exploited for improved strength and fatigue life of composite joints and other regions in structures where interlaminar stress states are critical.
A cumulative damage model for predicting the stiffness loss in crossply graphite/epoxy laminates ... more A cumulative damage model for predicting the stiffness loss in crossply graphite/epoxy laminates is obtained by applying a thermomechanical constitutive theory for elastic composites with distributed damage. The model proceeds from a continuum mechanics and thermodynamics approach wherein the distributed damage is characterized by a set of second-order tensor-valued internal-state variables. The internal-state variables represent globally averaged measures of matrix cracking and internal delaminations. The resulting model represents a set of damage-dependent laminate-plate equations. These are developed by modifying the classical Kirchhoff plate theory. The effect of internal delamination enters the formulation through modifications of the Kirchhoff displacements. The corresponding internal-state variable is defined, utilizing the kinematics of the internal delaminated region and the divergence theorem. This internal-state variable represents the components of the out-of-plane displacement modes created by the delamination. A local anisotropic stiffness is then defined to couple these out-of-plane displacements with the in-plane forces. The effect of the matrix cracking enters the formulation through alteration in the individual lamina constitution. The internal-state variable is related to the surface area of delamination by employing linear elastic fracture mechanics.
A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolu... more A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolute gap width by measuring axial strain in an orthogonal direction to the displacement/gap width. The gap gauge includes a preferably titanium base having a central tension bar with springs connecting opposite ends of the tension bar to a pair of end connector bars, and an elongated bow
The primary objective of this research has been to develop a multiaxial testing capability for co... more The primary objective of this research has been to develop a multiaxial testing capability for continuous fiber composites using the axial/torsion/internal pressurization of tubes. This capability enables one to generate the two-dimensional (in-plane) failure surface for these materials. The multiaxial test specimen consists of a 5.08 cm (2.0 in.) diameter composite tube with 15° cast epoxy end cones for gripping.
This is an informal report intended primarily for internal or limited external distribution. The ... more This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory.
Review of Progress in Quantitative Nondestructive Evaluation, 1996
fhisisapreprintofapapcrintended forpublication in ajoumilorproceedings. Since changes may be made... more fhisisapreprintofapapcrintended forpublication in ajoumilorproceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recornmendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER This document was prcparcd 3s an account of work sponsored by an agency of the Unitcd States Government. Neither the Unitcd States Government nor the University of California nor m y of thcir cmployces, makes any warranty, express or impiicd, or assumcs any legal liability or responsibility for the accuracy, completeness, or uscfulncss of any information, apparatus, product, or process disclosed, or represents that its LIW would not infringe privately owned rights. Refercncc herein to any specific commercial product, process, or service by trade name, trademark, rnanufacturcr, or otherwise, docs not nccessarily constitute or imply its endorscmcnt, rccommcndation, or favoring by the United States Govcrnmcnt or the Univcrsity of California. The views and opinions of authors cxprcsscd herein do not neccssarilv state or rcflcct those of the United States Government or thc University of Ciiifornia, and shall not be used for advertising or product cndorsemcnt purposes. I CHARACTERIZATION OF STATIC-AND FATIGUE-LOADED CARBON
A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent ... more A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent magnet to provide a magnetic field, and a magneto-optic material positioned in the magnetic field for rotating the plane of polarization of polarized light transmitted through the magneto-optic material. The magnet is independently movable relative to the magneto-optic material so as to rotate the plane
U.S. Department of Energy Office of Scientific and Technical Information - OSTI OAI, Jul 19, 2016
Advanced Composites Letters
The finite-strain-invariant criterion is applied to Toray 1000 / DER332 symmetrically balanced an... more The finite-strain-invariant criterion is applied to Toray 1000 / DER332 symmetrically balanced angle-ply laminates subjected to a uniaxial loading state. The results indicate that the initial failures are all in the matrix failure mode.
International Journal of Solids and Structures
A continuum mechanics approach is utilized herein to develop a model for predicting the thermomec... more A continuum mechanics approach is utilized herein to develop a model for predicting the thermomechanical constitution of elastic composites subjected to both monotonic and cyclic fatigue loading. In this model the damage is characterized by a set of second-order tensor valued internal state ...
An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composi... more An interlayer toughening mechanism is described to mitigate the growth of damage in fiber composite flywheel rotors for long application. The interlayer toughening mechanism may comprise one or more tough layers composed of high-elongation fibers, high-strength fibers arranged in a woven pattern at a range from 0° to 90° to the rotor axis and bound by a ductile matrix material which adheres to and is compatible with the materials used for the bulk of the rotor. The number and spacing of the tough interlayers is a function of the design requirements and expected lifetime of the rotor. The mechanism has particular application in uninterruptable power supplies, electrical power grid reservoirs, and compulsators for electric guns, as well as electromechanical batteries for vehicles. 2 figs.
ABSTRACT The performance of commercial high-performance fibers is examined for application to fly... more ABSTRACT The performance of commercial high-performance fibers is examined for application to flywheel power supplies. It is shown that actual delivered performance depends on multiple factors such as inherent fiber strength, strength translation and stress-rupture lifetime. Experimental results for recent stress-rupture studies of carbon fibers will be presented and compared with other candidate reinforcement materials. Based on an evaluation of all of the performance factors, it is concluded that carbon fibers are preferred for highest performance and E-glass fibers for lowest cost. The inferior performance of the low-cost E-glass fibers can be improved to some extent by retarding the stress-corrosion of the material due to moisture and practical approaches to mitigating this corrosion are discussed. Many flywheel designs are limited not by fiber failure, but by matrix-dominated failure modes. Unfortunately, very few experimental results for stress-rupture under transverse tensile loading are available. As a consequence, significant efforts are made in flywheel design to avoid generating any transverse tensile stresses. Recent results for stress-rupture of a carbon fiber/epoxy composite under transverse tensile load reveal that these materials are surprisingly durable under the transverse loading condition and that some radial tensile stress could be tolerated in flywheel applications.
An interface structure for hub and mass attachment in flywheel rotors. The interface structure ef... more An interface structure for hub and mass attachment in flywheel rotors. The interface structure efficiently transmits high radial compression forces and withstands both large circumferential elongation and local stresses generated by mass-loading and hub attachments. The interface structure is comprised of high-strength fiber, such as glass and carbon, woven into an angle pattern which is about 45.degree. with respect to the rotor axis. The woven fiber is bonded by a ductile matrix material which is compatible with and adheres to the rotor material. This woven fiber is able to elongate in the circumferential direction to match the rotor growth during spinning.
An Achilles heel for the performance of thick-section, cylindrical fiber composite flywheels is t... more An Achilles heel for the performance of thick-section, cylindrical fiber composite flywheels is the poor interlaminar properties of the material. Methods that have been used to minimize or eliminate radial tensile stresses include prestressing concentric cylinders and mass loading. There can also be significant interlaminar shear stresses at the edges of mass-loaded flywheels and in flywheels for high-power density applications
As part of efforts to develop a three-dimensional failure model for composites, a study of failur... more As part of efforts to develop a three-dimensional failure model for composites, a study of failure and fatigue due to combined interlaminar stresses was conducted. The combined stresses were generated using a hollow cylindrical specimen, which was subjected to normal compression and torsion. For both glass and carbon fiber composites, normal compression resulted in a significant enhancement in the interlaminar shear stress and strain at failure. Under moderate compression levels, the failure mode transitioned from elastic to plastic. The observed failure envelope could not be adequately captured using common plylevel failure models. Alternate modeling approaches were examined and it was found that a pressure-dependent failure criterion was required to reproduce the experimental results. The magnitude of the pressure-dependent terms of this model was found to be material dependent. The interlaminar shear fatigue behavior of a carbon/epoxy system was also studied using the cylindrical specimen. Preliminary results indicate that a single S/N curve which is normalized for interlaminar shear strength may be able to reproduce the effects of both temperature and out-of-plane compression on fatigue life. The results demonstrate that there are significant gains to be made in improving interlaminar strengths of composite structures by applying out-of-plane compression. This effect could be exploited for improved strength and fatigue life of composite joints and other regions in structures where interlaminar stress states are critical.
A cumulative damage model for predicting the stiffness loss in crossply graphite/epoxy laminates ... more A cumulative damage model for predicting the stiffness loss in crossply graphite/epoxy laminates is obtained by applying a thermomechanical constitutive theory for elastic composites with distributed damage. The model proceeds from a continuum mechanics and thermodynamics approach wherein the distributed damage is characterized by a set of second-order tensor-valued internal-state variables. The internal-state variables represent globally averaged measures of matrix cracking and internal delaminations. The resulting model represents a set of damage-dependent laminate-plate equations. These are developed by modifying the classical Kirchhoff plate theory. The effect of internal delamination enters the formulation through modifications of the Kirchhoff displacements. The corresponding internal-state variable is defined, utilizing the kinematics of the internal delaminated region and the divergence theorem. This internal-state variable represents the components of the out-of-plane displacement modes created by the delamination. A local anisotropic stiffness is then defined to couple these out-of-plane displacements with the in-plane forces. The effect of the matrix cracking enters the formulation through alteration in the individual lamina constitution. The internal-state variable is related to the surface area of delamination by employing linear elastic fracture mechanics.
A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolu... more A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolute gap width by measuring axial strain in an orthogonal direction to the displacement/gap width. The gap gauge includes a preferably titanium base having a central tension bar with springs connecting opposite ends of the tension bar to a pair of end connector bars, and an elongated bow
The primary objective of this research has been to develop a multiaxial testing capability for co... more The primary objective of this research has been to develop a multiaxial testing capability for continuous fiber composites using the axial/torsion/internal pressurization of tubes. This capability enables one to generate the two-dimensional (in-plane) failure surface for these materials. The multiaxial test specimen consists of a 5.08 cm (2.0 in.) diameter composite tube with 15° cast epoxy end cones for gripping.
This is an informal report intended primarily for internal or limited external distribution. The ... more This is an informal report intended primarily for internal or limited external distribution. The opinions and conclusions stated are those of the author and may or may not be those of the Laboratory.
Review of Progress in Quantitative Nondestructive Evaluation, 1996
fhisisapreprintofapapcrintended forpublication in ajoumilorproceedings. Since changes may be made... more fhisisapreprintofapapcrintended forpublication in ajoumilorproceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recornmendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER This document was prcparcd 3s an account of work sponsored by an agency of the Unitcd States Government. Neither the Unitcd States Government nor the University of California nor m y of thcir cmployces, makes any warranty, express or impiicd, or assumcs any legal liability or responsibility for the accuracy, completeness, or uscfulncss of any information, apparatus, product, or process disclosed, or represents that its LIW would not infringe privately owned rights. Refercncc herein to any specific commercial product, process, or service by trade name, trademark, rnanufacturcr, or otherwise, docs not nccessarily constitute or imply its endorscmcnt, rccommcndation, or favoring by the United States Govcrnmcnt or the Univcrsity of California. The views and opinions of authors cxprcsscd herein do not neccssarilv state or rcflcct those of the United States Government or thc University of Ciiifornia, and shall not be used for advertising or product cndorsemcnt purposes. I CHARACTERIZATION OF STATIC-AND FATIGUE-LOADED CARBON
A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent ... more A micro-position sensor and sensing system using the Faraday Effect. The sensor uses a permanent magnet to provide a magnetic field, and a magneto-optic material positioned in the magnetic field for rotating the plane of polarization of polarized light transmitted through the magneto-optic material. The magnet is independently movable relative to the magneto-optic material so as to rotate the plane