Download or read book The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polyimide written by Lee M. Nicholson and published by . This book was released on 2001 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanical testing of the elastic and viscoelastic response of an advanced thermoplastic polyimide (LaRC-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The notched tensile strenght was shown to be a strong function of both molecular weight and temperature, whereas stiffness was only a strong function of temperature. A critical molecular weight was observed to occur at a weight-average molecular weight of ~22,000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure.
Download or read book The Role of Molecular Weight and Temperaturee on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polyimide written by Lee M. Nicholson and published by . This book was released on 2001 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Combined Influence of Molecular Weight and Temperature on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide written by Lee M. Nicholson and published by . This book was released on 2000 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC-SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of five materials of different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have higher creep compliance and creep rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of ~2500 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly. The short-term creep compliance data were used in association with Struik's effective time theory to predict the long-term creep compliance behavior for the different molecular weights. At long timescales, physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested.
Download or read book The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polymide written by Jerry M. Allen and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplastic Polymide written by Lee M. Nicholson and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy Polyimide written by Lee M. Nicholson and published by . This book was released on 1999 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Combined Influence of Molecular Weight and Temperature on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of molecular weight on the viscoelastic performance of an advanced polymer (LaRC-SI) was investigated through the use of creep compliance tests. Testing consisted of short-term isothermal creep and recovery with the creep segments performed under constant load. The tests were conducted at three temperatures below the glass transition temperature of five materials of different molecular weight. Through the use of time-aging-time superposition procedures, the material constants, material master curves and aging-related parameters were evaluated at each temperature for a given molecular weight. The time-temperature superposition technique helped to describe the effect of temperature on the timescale of the viscoelastic response of each molecular weight. It was shown that the low molecular weight materials have higher creep compliance and creep rate, and are more sensitive to temperature than the high molecular weight materials. Furthermore, a critical molecular weight transition was observed to occur at a weight-average molecular weight of M (bar) (sub w) 25000 g/mol below which, the temperature sensitivity of the time-temperature superposition shift factor increases rapidly. The short-term creep compliance data were used in association with Struik's effective time theory to predict the long-term creep compliance behavior for the different molecular weights. At long timescales, physical aging serves to significantly decrease the creep compliance and creep rate of all the materials tested.Nicholson, Lee M. and Whitley, Karen S. and Gates, Thomas S.Langley Research CenterAGING (MATERIALS); GLASS; MOLECULAR WEIGHT; TEMPERATURE EFFECTS; THERMOPLASTICITY; VISCOELASTICITY; POLYIMIDES; CREEP TESTS; ERROR ANALYSIS; TIME TEMPERATURE PARAMETER; GLASS TRANSITION TEMPERATURE; DURABILITY
Download or read book Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy Polyimide written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanical Testing of an advanced thermoplastic polyimide (LaRC-TM-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength were all determined as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. A critical molecular weight (Mc) was observed to occur at a weight-average molecular weight (Mw) of approx. 22000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Furthermore, inelastic analysis showed that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microstructural images supported these findings.Nicholson, Lee M. and Whitley, Karen S. and Gates, Thomas S. and Hinkley, Jeffrey A.Langley Research CenterMOLECULAR WEIGHT; MECHANICAL PROPERTIES; POLYIMIDES; ELASTIC PROPERTIES; THERMOPLASTICITY; TENSILE STRENGTH; DUCTILE-BRITTLE TRANSITION; TEMPERATURE DEPENDENCE; FRACTOGRAPHY; GLASS TRANSITION TEMPERATURE; STRESS-STRAIN DIAGRAMS; MODULUS OF ELASTICITY; MICROSTRUCTURE; POLYMER MATRIX COMPOSITES; NOTCHES; TENSILE TESTS
Download or read book The Role of Molecular Weight and Temperature on the Elastic and Viscoelastic Properties of a Glassy Thermoplasti Nasa written by United States. National Aeronautics and Space Administration and published by . This book was released on 2003* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book American Society for Composites written by Michael Hyer and published by DEStech Publications, Inc. This book was released on 2011-06-28 with total page 2760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Creep and Fatigue in Polymer Matrix Composites written by Rui Miranda Guedes and published by Elsevier. This book was released on 2010-11-29 with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt: Creep is the tendency of materials to deform when subjected to long-term stress, particularly when exposed to heat. Fatigue phenomena occur when a material is subjected to cyclic loading, causing damage which may progress to failure. Both are critical factors in the long-term performance and reliability of materials such as polymer matrix composites which are often exposed to these types of stress in civil engineering and other applications. This important book reviews the latest research in modelling and predicting creep and fatigue in polymer matrix composites. The first part of the book reviews the modelling of viscoelastic and viscoplastic behaviour as a way of predicting performance and service life. Part two discusses techniques for modelling creep rupture and failure. The final part of the book discusses ways of testing and predicting long-term creep and fatigue in polymer matrix composites. With its distinguished editor and international team of contributors, Creep and Fatigue in Polymer Matrix Composites is a standard reference for all those researching and using polymer matrix composites in such areas as civil engineering. Reviews the latest research in modelling and predicting creep and fatigue in polymer matrix composites A specific focus on viscoelestic and viscoplastic modelling features the time-temperature-age superposition principle for predicting long-term response Creep rupture and damage interaction is examined with particular focus on time-dependent failure criteria for lifetime prediction of polymer matrix composite structures illustrated using experimental cases
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 2003-07 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Combined Influence of Molecular Weight and Temperaturee on the Aging and Viscoelastic Response of a Glassy Thermoplastic Polyimide written by Lee M. Nicholson and published by . This book was released on 2000 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Introduction to Polymer Viscoelasticity written by Montgomery T. Shaw and published by John Wiley & Sons. This book was released on 2005-08-19 with total page 339 pages. Available in PDF, EPUB and Kindle. Book excerpt: A revised molecular approach to a classic on viscoelasticbehavior Because viscoelasticity affects the properties, appearance,processing, and performance of polymers such as rubber, plastic,and adhesives, a proper utilization of such polymers requires aclear understanding of viscoelastic behavior. Now in its third edition, Introduction to Polymer Viscoelasticityremains a classic in the literature of molecular viscoelasticity,bridging the gap between primers on polymer science and advancedresearch-level monographs. Assuming a molecular, rather than amechanical approach, the text provides a strong grounding in thefundamental concepts, detailed derivations, and particularattention to assumptions, simplifications, and limitations. This Third Edition has been entirely revised and updated to reflectrecent developments in the field. New chapters include: * Phenomenological Treatment of Viscoelasticity * Viscoelastic Models * Time-Temperature Correspondence * Transitions and Relaxation in Polymers * Elasticity of Rubbery Networks * Dielectric and NMR Methods With detailed explanations, corresponding equations, andexperimental methods, supported by real-life applications (as wellas the inclusion of a CD-ROM with data to support the exercises),this Third Edition provides today's students and professionals withthe tools they need to create polymers with more desirablequalities than ever.
Download or read book Viscoelastic Properties of Polymers written by John D. Ferry and published by . This book was released on 1961 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constitutive Modeling of Nanotube Reinforced Polymer Composites written by G. M. Odegard and published by . This book was released on 2002 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through the traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube lengths, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyimide composite systems.
Download or read book Proceedings of the ASME Applied Mechanics Division written by and published by . This book was released on 2004 with total page 678 pages. Available in PDF, EPUB and Kindle. Book excerpt:
