The 23rd Sagamore Army Materials Research Conference was held last week in upstate New York. The ... more The 23rd Sagamore Army Materials Research Conference was held last week in upstate New York. The theme was Nondestructive Characterization of Materials, and the intent of this meeting was to approach the subject with a broad brush treatment, including historical aspects, the assessment of significant advances in each topic area, important new capabilities, and discussion of some exploratory techniques as contrasted with the generally more focused and in-depth studies that have been reported here at Asilomar.
: In a series of projects dating back to 1984, the Defense Advanced Research Projects Agency (DAR... more : In a series of projects dating back to 1984, the Defense Advanced Research Projects Agency (DARPA) has instigated research in advanced polymers including such goals as thermally oxidatively stable matrix resins for 700 F composite applications, rigid molecular composites, liquid crystal displays, and piezoelectric sensors. Volume I of the present report reviews the history and accomplishments of the DARPA High Performance Polymer Program and presents highlights of the program review conducted by DARPA on 14-15 January 1992. Volume II, intended as a comprehensive reference source document, is an appendix which provides the program review agenda, a list of participants, and copies of selected presentation material. Correspondence from the presenters is included with the presentation material where appropriate.
: Progress in the development of new approaches to the analysis and experimental studies of the d... more : Progress in the development of new approaches to the analysis and experimental studies of the deformation, failure, and processing of structural materials under high loading rates has been reviewed. Advances in elucidation of the response of materials to high loading rates, with a focus on ceramics, are included. The field of shock synthesis and processing, and directions of future work, have been considered. Special emphasis has been given to materials deformation modes, other prefailure modes, and fracture mechanisms, since these are the concepts that are key to hydrocode development and accurate modeling of real material behavior under high loading-rate conditions.
: Unique opportunities are offered for new devices and systems through the use of advanced materi... more : Unique opportunities are offered for new devices and systems through the use of advanced materials, such as composites, ceramics, and intermetallics. Concurrent engineering approaches to the use of these materials are key to assuring successful applications. Generic steps in concurrent engineering with special reference to advanced materials are reviewed. Examples are provided of intelligent processing and net-shape processing, which provide routes to more reproducible materials. It is anticipated that a wide range of DARPA applications will be affected by the approaches described here, including the metal-matrix composites model factory, composite hulls and chassis for lightweight ground vehicles, and the polymer composite submarine hull.
: Superalloy filament formation by melt spinning has been demonstrated down to the 1.5-mil level ... more : Superalloy filament formation by melt spinning has been demonstrated down to the 1.5-mil level with orifice life greater than thirty minutes. Methods for successful filter operation have been established to achieve this performance. Filament formation rates of 1500 ft/min and higher were normally attained. Long filament lengths were obtained at the 2-mil level and streaming was sucessfully initiated down to the 0.7-mil level. Ultimate tensile strength increases of 50% were demonstrated by direct aging. With the direct aging process, good elongation (10%) was retained with the nickel-base alloys Rene 41, M-252, and Inconel 713LC. (Author, modified-PL).
: The effects of crystallite orientation upon the formation of deformation bands in alpha- iron a... more : The effects of crystallite orientation upon the formation of deformation bands in alpha- iron are determined, along with the influence of crystallite orientation and size upon strength of polycrystalline iron. The application of thermomechanical processing methods to semicrystalline polymers produces marked strengthening in bulk nylon 6/6, and several modes of fracture are related to the thermal and mechanical history. Attempts to form aluminum-alumina composites by deformation processing procedures do not prove feasible. Geometrical problems and those associated with thermal expansion and residual stresses are the major sources of difficulty. (Author-PL)
Thesis (M. Met. Engr.)--University of Oklahoma, 1963. Includes bibliographical references (leaves... more Thesis (M. Met. Engr.)--University of Oklahoma, 1963. Includes bibliographical references (leaves 72-75).
ABSTRACTStudies have been carried out on the structures and mechanical characteristics of an unus... more ABSTRACTStudies have been carried out on the structures and mechanical characteristics of an unusual family of sea sponges under the classification of Hexactinellida, genus Euplectella. The sponge spicules have been of interest to materials scientists because of their potentially important optical, coupled with mechanical, properties. The structures of the class Hexactinellida are characterized by a concentric ring appearance in the cross-section, which is a composite of hydrated silica, coupled with silicatein as a thin layer at the ring interfaces. The mechanical behavior and the toughness of the spicules have been examined with the aid of a special fiber testing method, coupled with scanning electrom microscopy (SEM) observations. It appears that there may be common mechanisms underlying toughness in rigid natural composites with high ratios of mineral/organic phase. In addition, novel pressurization tests of a portion of the sponge skeleton have provided information about the re...
Progress in molecular and subcellular biology, 2009
The unique mechanical response of spicules of Hexactinellid sponges, notably, Euplectella aspergi... more The unique mechanical response of spicules of Hexactinellid sponges, notably, Euplectella aspergillum, are reviewed and related to the structure, architecture, and failure modes of those natural rigid composite materials. In particular, exceptional levels of resilience, damping capacity, and the ability to dissipate mechanical energy prior to failure have been observed, all these properties greatly exceeding those of synthetic melt-fabricated glass. How these observations can be related to the design of new structural composites that are based on glass are described.
Diverse microstructures observed in rigid natural composites have been linked to mechanical prope... more Diverse microstructures observed in rigid natural composites have been linked to mechanical properties that are equal to and, at times, superior to those which have been designed into synthetic composite materials comprised of organic, metallic, and ceramic constituents. The constitution, properties, and microstructures of the natural and synthetic materials are described, along with what is known and what is unknown about the constituent components, and interfaces. Hierarchical approaches to designing with and the mechanical analyses of both natural and synthetic composites will be described.
Journal of the Mechanical Behavior of Biomedical Materials, 2015
This study focused on determining the presence of organic phases in the siliceous components of r... more This study focused on determining the presence of organic phases in the siliceous components of rigid marine composites ("glass" sponge spicules), and thereby clarifying how such composites dissipate significant mechanical energy. Through the use of imaging by helium ion microscopy in the examination of the spicules, the organic phase that is present between the layers of hydrated silica was also detected within the silica cylinders of the composite, indicating the existence therein of a network, scaffolding, or other pattern that has not yet been determined. It was concluded that the presence of an interpenetrating network of some kind, and tenacious fibrillar interfaces are responsible for large energy dissipation in these siliceous composites by viscoelastic and other mechanical deformation processes. This discovery means that future mechanics analyses of large deformation behavior of such natural rigid composites (that may also include teeth and bones) should be based on the presence of interpenetrating phases.
The roles of minor organic layers in influencing the mechanical response of such biomineralized c... more The roles of minor organic layers in influencing the mechanical response of such biomineralized composites as mollusk shells and sponge spicules have been investigated. The mechanisms whereby such minor constituents govern energy dissipation in rigid biomineralized structures are discussed, and a rationale for new modes of toughening that may relate more generally to families of ceramic- or glass/organic composites is offered. New results of simple torsional tests conducted on spicule fibers of a hexactinellid sponge, Euplectella aspergillum (Euplectella a.), compared with those done on melt-drawn glass fibers, showed an enhanced ability to resist failure in torsion, whereas the glass fibers did not. This behavior was attributed to the presence of a very thin adhesive viscoelastic phase between the siliceous layers of the spicule fibers, combined with the architectural and surface features of the spicule fiber.
A study of the structure and toughness of the spicules of the sponge Euplectella aspergillum (Ea)... more A study of the structure and toughness of the spicules of the sponge Euplectella aspergillum (Ea) under tension and bending was performed, and the results were compared with those of a silica glass. Very different fracture morphologies were observed in the spicules that failed in bending and in tension, and toughness of the spicules in bending and the toughness in
The 23rd Sagamore Army Materials Research Conference was held last week in upstate New York. The ... more The 23rd Sagamore Army Materials Research Conference was held last week in upstate New York. The theme was Nondestructive Characterization of Materials, and the intent of this meeting was to approach the subject with a broad brush treatment, including historical aspects, the assessment of significant advances in each topic area, important new capabilities, and discussion of some exploratory techniques as contrasted with the generally more focused and in-depth studies that have been reported here at Asilomar.
: In a series of projects dating back to 1984, the Defense Advanced Research Projects Agency (DAR... more : In a series of projects dating back to 1984, the Defense Advanced Research Projects Agency (DARPA) has instigated research in advanced polymers including such goals as thermally oxidatively stable matrix resins for 700 F composite applications, rigid molecular composites, liquid crystal displays, and piezoelectric sensors. Volume I of the present report reviews the history and accomplishments of the DARPA High Performance Polymer Program and presents highlights of the program review conducted by DARPA on 14-15 January 1992. Volume II, intended as a comprehensive reference source document, is an appendix which provides the program review agenda, a list of participants, and copies of selected presentation material. Correspondence from the presenters is included with the presentation material where appropriate.
: Progress in the development of new approaches to the analysis and experimental studies of the d... more : Progress in the development of new approaches to the analysis and experimental studies of the deformation, failure, and processing of structural materials under high loading rates has been reviewed. Advances in elucidation of the response of materials to high loading rates, with a focus on ceramics, are included. The field of shock synthesis and processing, and directions of future work, have been considered. Special emphasis has been given to materials deformation modes, other prefailure modes, and fracture mechanisms, since these are the concepts that are key to hydrocode development and accurate modeling of real material behavior under high loading-rate conditions.
: Unique opportunities are offered for new devices and systems through the use of advanced materi... more : Unique opportunities are offered for new devices and systems through the use of advanced materials, such as composites, ceramics, and intermetallics. Concurrent engineering approaches to the use of these materials are key to assuring successful applications. Generic steps in concurrent engineering with special reference to advanced materials are reviewed. Examples are provided of intelligent processing and net-shape processing, which provide routes to more reproducible materials. It is anticipated that a wide range of DARPA applications will be affected by the approaches described here, including the metal-matrix composites model factory, composite hulls and chassis for lightweight ground vehicles, and the polymer composite submarine hull.
: Superalloy filament formation by melt spinning has been demonstrated down to the 1.5-mil level ... more : Superalloy filament formation by melt spinning has been demonstrated down to the 1.5-mil level with orifice life greater than thirty minutes. Methods for successful filter operation have been established to achieve this performance. Filament formation rates of 1500 ft/min and higher were normally attained. Long filament lengths were obtained at the 2-mil level and streaming was sucessfully initiated down to the 0.7-mil level. Ultimate tensile strength increases of 50% were demonstrated by direct aging. With the direct aging process, good elongation (10%) was retained with the nickel-base alloys Rene 41, M-252, and Inconel 713LC. (Author, modified-PL).
: The effects of crystallite orientation upon the formation of deformation bands in alpha- iron a... more : The effects of crystallite orientation upon the formation of deformation bands in alpha- iron are determined, along with the influence of crystallite orientation and size upon strength of polycrystalline iron. The application of thermomechanical processing methods to semicrystalline polymers produces marked strengthening in bulk nylon 6/6, and several modes of fracture are related to the thermal and mechanical history. Attempts to form aluminum-alumina composites by deformation processing procedures do not prove feasible. Geometrical problems and those associated with thermal expansion and residual stresses are the major sources of difficulty. (Author-PL)
Thesis (M. Met. Engr.)--University of Oklahoma, 1963. Includes bibliographical references (leaves... more Thesis (M. Met. Engr.)--University of Oklahoma, 1963. Includes bibliographical references (leaves 72-75).
ABSTRACTStudies have been carried out on the structures and mechanical characteristics of an unus... more ABSTRACTStudies have been carried out on the structures and mechanical characteristics of an unusual family of sea sponges under the classification of Hexactinellida, genus Euplectella. The sponge spicules have been of interest to materials scientists because of their potentially important optical, coupled with mechanical, properties. The structures of the class Hexactinellida are characterized by a concentric ring appearance in the cross-section, which is a composite of hydrated silica, coupled with silicatein as a thin layer at the ring interfaces. The mechanical behavior and the toughness of the spicules have been examined with the aid of a special fiber testing method, coupled with scanning electrom microscopy (SEM) observations. It appears that there may be common mechanisms underlying toughness in rigid natural composites with high ratios of mineral/organic phase. In addition, novel pressurization tests of a portion of the sponge skeleton have provided information about the re...
Progress in molecular and subcellular biology, 2009
The unique mechanical response of spicules of Hexactinellid sponges, notably, Euplectella aspergi... more The unique mechanical response of spicules of Hexactinellid sponges, notably, Euplectella aspergillum, are reviewed and related to the structure, architecture, and failure modes of those natural rigid composite materials. In particular, exceptional levels of resilience, damping capacity, and the ability to dissipate mechanical energy prior to failure have been observed, all these properties greatly exceeding those of synthetic melt-fabricated glass. How these observations can be related to the design of new structural composites that are based on glass are described.
Diverse microstructures observed in rigid natural composites have been linked to mechanical prope... more Diverse microstructures observed in rigid natural composites have been linked to mechanical properties that are equal to and, at times, superior to those which have been designed into synthetic composite materials comprised of organic, metallic, and ceramic constituents. The constitution, properties, and microstructures of the natural and synthetic materials are described, along with what is known and what is unknown about the constituent components, and interfaces. Hierarchical approaches to designing with and the mechanical analyses of both natural and synthetic composites will be described.
Journal of the Mechanical Behavior of Biomedical Materials, 2015
This study focused on determining the presence of organic phases in the siliceous components of r... more This study focused on determining the presence of organic phases in the siliceous components of rigid marine composites ("glass" sponge spicules), and thereby clarifying how such composites dissipate significant mechanical energy. Through the use of imaging by helium ion microscopy in the examination of the spicules, the organic phase that is present between the layers of hydrated silica was also detected within the silica cylinders of the composite, indicating the existence therein of a network, scaffolding, or other pattern that has not yet been determined. It was concluded that the presence of an interpenetrating network of some kind, and tenacious fibrillar interfaces are responsible for large energy dissipation in these siliceous composites by viscoelastic and other mechanical deformation processes. This discovery means that future mechanics analyses of large deformation behavior of such natural rigid composites (that may also include teeth and bones) should be based on the presence of interpenetrating phases.
The roles of minor organic layers in influencing the mechanical response of such biomineralized c... more The roles of minor organic layers in influencing the mechanical response of such biomineralized composites as mollusk shells and sponge spicules have been investigated. The mechanisms whereby such minor constituents govern energy dissipation in rigid biomineralized structures are discussed, and a rationale for new modes of toughening that may relate more generally to families of ceramic- or glass/organic composites is offered. New results of simple torsional tests conducted on spicule fibers of a hexactinellid sponge, Euplectella aspergillum (Euplectella a.), compared with those done on melt-drawn glass fibers, showed an enhanced ability to resist failure in torsion, whereas the glass fibers did not. This behavior was attributed to the presence of a very thin adhesive viscoelastic phase between the siliceous layers of the spicule fibers, combined with the architectural and surface features of the spicule fiber.
A study of the structure and toughness of the spicules of the sponge Euplectella aspergillum (Ea)... more A study of the structure and toughness of the spicules of the sponge Euplectella aspergillum (Ea) under tension and bending was performed, and the results were compared with those of a silica glass. Very different fracture morphologies were observed in the spicules that failed in bending and in tension, and toughness of the spicules in bending and the toughness in
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