Dissertations / Theses on the topic 'Fatigue of polymer foams'
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1
Le, Bail Jean-Baptiste. "Modélisation du comportement mécanique sous chargement d’une butée d’amortisseur en mousse de polyuréthane : vers une démarche de dimensionnement en fatigue." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0003.
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Les butées d’amortisseur en mousse de polyuréthane sont largement utilisées dans le milieu automobile. Leur principale fonction est d’amortir les chocs verticaux aux roues et de contribuer à l’intégrité de la suspension du véhicule. La réponse mécanique de ce type de pièces implique de prendre en considération différents mécanismes, allant du flambement des parois de la pièce à l’auto-contact en passant par les non-linéarités géométriques. La caractérisation actuelle de ces butées d’amortisseur en mousse de polyuréthane en fatigue est aujourd’hui limitée au cahier des charges du client et aux tests prédéfinis par celui-ci. L’objectif de cette thèse est de mener une caractérisation expérimentale complète du comportement mécanique afin d’aboutir à l’identification d’une loi de comportement type Hyperfoam. Cette caractérisation est effectuée en s’appuyant également sur des techniques d’imagerie, MEB et tomographique, afin de caractériser le lien entre la microstructure et le comportement mécanique de la butée d’amortisseur. Cette étude doit permettre au final, de définir une démarche globale pour le dimensionnement en fatigue des butées d’amortisseur en mousse de polyuréthanePolyurethane foam jounce bumpers are widely used in the automotive industry. Their main function is to absorb vertical shocks to the wheels and contribute to the integrity of the vehicle suspension. The mechanical response of this type of parts implies to take into account different mechanisms, from the buckling of the walls of the part to the self-contact through the geometrical non-linearities. The current characterization of these polyurethane foam jounce bumpers in fatigue is currently limited to the customer’s specifications and to the tests predefined by him. The objective of this thesis is to carry out a complete experimental characterization of the mechanical behavior in order to identify an Hyperfoam type behavior law. This characterization is also based on imaging techniques, SEM and tomographic, in order to characterize the link between the microstructure and the mechanical behavior of the jounce bumper. This study should allow to define a global approach for the fatigue design of polyurethane foam jounce bumper
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Fan, Haibo. "HfC structural foams synthesized from polymer precursors." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Dissertation/FAN_HAIBO_30.pdf.
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Bhattacharya, Subhendu, and subhendu bhattacharya@rmit edu au. "Development of macro/nanocellular foams in polymer nanocomposites." RMIT University. Civil, Environmental and Chemical Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20100122.114345.
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This thesis focuses on the generation of fine cell polymer foams using a heterogeneous nucleating agent (nanoclay), appropriate polymer blending strategies and accurate control of foam processing parameters. Foaming behaviour of HMSPP/ clay nanocomposites and HMS-PP/EVA/clay nanocomposite blends is studied using a batch and a continuous foam injection moulding system. Morphological studies using TEM and SEM led to a few interesting deductions. It is very difficult to attain complete exfoliation in case of HMS-PP/clay nanocomposites even at low clay loadings due to a non polar nature and low graft efficiencies of HMS-PP matrix. The addition of clay to an immiscible blend of HMS-PP/EVA results in compatibilization between the dispersed and the continuous phase. Nanocellular foams (290 nm) were subsequently generated in the batch process at a foaming temperature of 147oC and 25 seconds foaming time. The addition of immiscible EVA-28 to the HMS-PP matrix in presence of clay particles further results in reduction of foam cell sizes to 100 nm. The effect of gas concentration, foaming temperature, injection pressure, and foaming time on foam cell size was studied. It was found that the foam cell size was highly sensitive to the injection pressure at the mould gate (hence pressure drop rate) and foaming temperature. The cell size linearly decreased with increase in gas concentration and foaming time. The sensitivity of foam cell sizes to changes in processing parameters decreases with increase in clay concentration. The effect of addition of clay particle on gas solubility was modelled using the Guggenheims contact fraction approach and subsequently a new model to predict gas solubility was developed using statistical thermodynamic tools. Additionally the effect of shear and extensional rheology on foam cell morphology was modelled. It was found that the viscoelasticity of the polymer matrix greatly affects cell sizes as compared to extensional viscosity.
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Clarke, Alexander E. S. "Microwave techniques for the preparation of polymer foams." Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488321.
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Asik, Emin Erkan. "Characterization And Fatigue Behaviour Of Ti-6al-4v Foams." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614570/index.pdf.
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Porous Ti-6Al-4V alloys are widely used in the biomedical applications for hard tissue implantation due to its biocompatibility and elastic modulus being close to that of bone. In this study, porous Ti-6Al-4V alloys were produced with a powder metallurgical process, space holder technique, where magnesium powders were utilized in order to generate porosities in the range of 50 to 70 vol. %.
In the productions of Ti-6Al-4V foams, first, the spherical Ti-6Al-4V powders with an average size of 55 &mum were mixed with spherical magnesium powders sieved to an average size of 375 &mu
m, and then the mixtures were compacted with a hydraulic press under 500 MPa pressure by using a double-ended steel die and finaly, the green compacts were sintered at 1200
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Twite, Kabamba Eddy. "Polymer foams and composites recycling : Rheological and Macromolecular Investigations." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27578/27578.pdf.
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Talal, Sina. "Effect of long-term compression on rigid polymer foams." Thesis, Kingston University, 1999. http://eprints.kingston.ac.uk/20640/.
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The sponsors of this project have been using the rigid heavily-crosslinked polyurethane foam detailed in this study for load-bearing applications. One of the main requirements of this material is that it must possess excellent recovery properties following extensive compressive periods over several years. For such long loading regimes, there is need for detailed understanding of the compressive behaviour of this material, and its subsequent recovery upon release. More recently, there has been a growing interest in replacing the polyurethane foam with an alternative cellular plastic that possesses similar, if not identical, compressive recovery and behaviour. Attention was focused on the other primary polymer contingent, a polyethylene foam. A polyimide foam was also considered as it was already being used in applications similar to those of the polyurethane foam. The structures of the foams were investigated by means of Differential Scanning Calorimetry, Scanning Electron Microscopy and Image Analysis. The deformation mechanisms that occur during the application of a compressive force were examined visually via a scanning electron microscope compression rig. The mechanical analysis involved stress-strain testing whereby three stages of compression were identified (‘linear elastic, stress plateau and densification’), as described in the literature. Quadratic relationships were found to exist between the foam density and the ‘elastic modulus, plateau modulus and the compressive strength’ respectively. Such relationships had previously been found to exist in the literature, but not for the rigid variety of foam at such a broad range of densities. Further analysis included a detailed study of the recovery of the polyurethane (100 kg m[sup]-3 to 800 kg m[sup]-3) foams, a lightly-crosslinked polyethylene foam and a non-crosslinked polyimide foam. The foam samples were compressed by strains which spanned their linear elastic and stress plateau regimes i.e. by 2.5% to 35% for periods ranging from 3 days up to one year at ambient temperature. This analysis was also undertaken at elevated temperature as a means of accelerating the ageing process. Recovery of all of the samples was monitored for a minimum of 100 days at ambient temperature following release. Recovery of all of the foams tested was found to occur in two stages; an initial rapid recovery within the first day following release followed by a much slower recovery phase over a period of approximately 100 days. The initial rapid recovery was attributed to the recovery of the bulk polymer whilst the recovery of the cellular structure was associated with the ensuing slower recovery phase. In addition, recovery of the foams was found to be dependent more upon the compressive strain than on other parameters, such as compressive period and foam density. For compressive periods exceeding two weeks, recovery is almost independent of the latter parameters.
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Chen, Linling. "Developing Constitutive Equations for Polymer Foams Under Cyclic Loading." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1354739399.
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Shishesaz, Mohammad Reza. "Structure-property relationships in extruded plastics foams." Thesis, Brunel University, 1989. http://bura.brunel.ac.uk/handle/2438/5404.
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Physical properties and morphology of extruded semicrystalline polymers can be significantly affected by modification and change in die design and melt viscosity of the molten polymer. Further modifications to physical properties (i.e. density and open cell fraction) of foamed material occur, following the modification of melt viscosity by melt blending of polypropylene and high density polyethylene). The main object of this research project was to carry out a systematic examination of rheological properties of polymer/gas mixture, affect of die design, polymer molecular weight (melt viscosity), and processing conditions on density, open cell fraction, cell morphology (i.e. cell size and cell size distribution) and micromorphology of polyolefin foams. Also attention was given to method of stabilisation of extruded foam, where, it was found support of the extrudated foam (by adding a specially designed die adapter to the end of the die) prior to entering the cooling tank could result not only to a specimen with uniform cross section, but also due to drop in melt temperature, the cell walls are to some extent rigidized, hence, the collapse of bubbles are limited. From commercial point of view control of cell collapse, density and open cell fraction, will make these foamed materials valuable for their filtration characteristics. Microstructural analysis of polypropylene (unfoamed state) by X-ray diffraction and Differential Scanning Calorimetry revealed 13-spherulites are only formed in skin layer, and beneath the thickness of 500 pm from the surface, the crystal structure of this polymer is only consist of B-spherulites. On the other hand, the chemical blowing agent (Hydrocerol CF-20), was found to have nucleating affect on microstructure of polypropylene, where, it has resulted in reduction of size of spherulites together with a drop in recrystallisation temperature and formation of P and a spherulites through the thickness of extrudated foam. The foregoing chemical blowing agent was found to have no significant affect on the crystal structure of the high density polyethylene.
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Quell, Aggeliki [Verfasser]. "Monodisperse Emulsions as Template for Highly Structured Polymer Foams / Aggeliki Quell." Aachen : Shaker, 2017. http://d-nb.info/1138178152/34.
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Darr, Shehla. "Compression recovery of rigid polymer foams following confinement at elevated temperature." Thesis, Kingston University, 2007. http://eprints.kingston.ac.uk/20383/.
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Cellular materials are all around us. They can be found in nature as in bone, wood, leaves and even in our food. In the last fifty years, man has produced many synthetic cellular materials: firstly with polymeric foams and more recently with foamed metals, ceramics and glass. Polymer foams are used in a variety of applications ranging from coffee mugs to the feet of the Apollo Lunar Module, for which they were used as shock absorbers. This project was aimed at understanding the recovery from long-term compression of rigid polymer foams. Understanding the dynamics involved in the recovery process of foams is very important, especially in the automotive industry where it determines safety of the driver, passengers and pedestrians, for example, in car bumpers. In this study, foam samples were compressed by strains which spanned their linear elastic and stress plateau regions, i.e. 2.5% - 35% for one month at various temperatures. Recovery occurred in two stages, designated phase 1 and phase 2. Phase 1 is the initial recovery, which dominates the full recovery process and is complete within hours or days. Phase 2 is a lesser recovery occurring over a much longer period of approximately 100 days. The initial recovery is associated with the polymer itself, whilst phase 2 recovery is associated with the cellular structure. Recovery of all samples was monitored for a minimum of 100 days at ambient temperature. Tests were also carried out to see how the environmental surroundings affect the polymer recovery. The different polymer foams which were investigated were: • Polyethylene • Polyetherimide • Polyurethane • Polysulphone The polymers tested all showed very different responses to the changes in temperature. All polymers investigated at different compressive strains demonstrated reproducible Arrhenius plot slopes under different conditions and hence a reasonably reproducible set of values of recovery process. Analyses were based on the final total recovery of the thickness as the most reliable parameter of recovery. It has been demonstrated that the mechanism of polymer deformation and recovery probably does not involve chain scission but backbone vibration; that the best parameter for characterising the recovery process is the final total dimensional recovery of the sample; and that subtle environmental changes have a large effect on the recovery from compression, although temperature and humidity are not responsible.
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Zhong, Chong. "Pressure Chamber Experiments to Determine Triaxial Material Properties of Polymer Foams." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1556265641540063.
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Di, Prima Matthew Allen. "Thermo-mechanical and micro-structural characterization of shape memory polymer foams." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28178.
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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Gall, Ken; Committee Co-Chair: McDowell, David; Committee Member: Guldberg, Robert; Committee Member: Sanderson, Terry; Committee Member: Shofner, Meisha; Committee Member: Tannenbaum, Rina.
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Bonin, Michael. "An investigation into the properties of starch-based foams." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/6872.
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This thesis reports research to investigate the mechanical, thermal and acoustic properties of biodegradable foams in block forms based on wheat starch and developed at Brunel University's School of Engineering & Design, in order to exploit the potential environmental benefits of this renewable and biodegradable class of materials. Two emergent novel technologies have been developed based on a combination of the extrusion foaming of starch in conjunction with the natural adhesive characteristics of moistened starch to produce block foams. Regular Packing & Stacking (RPS), and Compression Bonded Loosefill (CBL), are foam fabrication technologies which have both demonstrated the potential to produce bulk foams based on wheat starch with unique structures and properties - a new class of foam materials in the form of macro-composites reinforced by a network of high-density bonding interfaces. This thesis, as part of a Department of Trade & Industry/Technology Strategy Board funded project, reports an investigation into the following areas to address the scientific and technical issues involved in the further development of the materials and their applications. - The basic properties of the raw materials used in the manufacture of CBL and RPS foams are outlined and the fabrication and preparation of these starch-based foams are described. The limitations of these production techniques are discussed with preliminary work and suggestions made for their enhancement. - Research into the mechanical properties of the CBL and RPS foams includes compression, tensile, creep and dynamic impact tests, whilst the mechanical behaviour of the foams subject to high temperature and high humidity conditions is also reported. - Research into the thermal properties of CBL and high density RPS foams includes testing of the material's thermal conductivity. This aspect of the research also involved a case study detailing the use of RPS in a commercial thermal insulation application. - Research into the acoustic properties of CBL and RPS foams includes tests for sound absorption coefficient and sound transmission loss. - Data obtained from these tests are benchmarked against data pertaining to the mechanical, thermal and acoustic properties of conventional polymer foams in order to provide a basis on which to identify the potential cushioning, thermal insulation and acoustic insulation applications of the starch-based materials. The research has demonstrated the following: - Potential cushioning applications include those limited to the range of static loads within the capabilities of the materials, taking into account the resilience of CBL and RPS which is likely to be compromised by successive impacts. - Tensile forces tend to exploit weaknesses in the macrostructure of these materials. By implication the behaviour of the materials under shear forces would be expected to be similarly compromised. - CBL and RPS exhibited dimensional shrinkage, density increase and significantly reduced mechanical properties under conditions of high temperature and humidity. This suggests that neither CBL nor RPS foams would be suitable for applications in regions where tropical conditions may be encountered unless used in conjunction with other protective materials which would not acutely increase the environmental burden of the products. - Low-density RPS and CBL foams exhibit lower thermal conductivities and hence higher thermal insulation properties compared to many commercially available polymer foams of similar densities. As such these foams have the potential to be used in applications in which a measure of thermal insulation is required. A case study based on an existing commercial application in which the temperature of chilled products must be maintained over a 24 hour period reinforced these findings. - The performance of CBL and RPS starch foams would not provide sufficient functionality to be employed in applications in which dedicated acoustic performance is required, although their sound absorption capabilities may facilitate overall marketability for applications in which a degree of acoustic performance is required if used in conjunction with other materials which demonstrate good acoustic performance. It is anticipated that this work will make significant contributions toward advances in the development of these novel technologies, specifically in terms of establishing an understanding of the properties of the starch-based materials and in identifying potential applications. The research results should thus provide a fundamental element in the basis for the industrial development of these renewable and biodegradable materials.
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Zeng, Changchun. "Synthesis, Structure And Properties Of Polymer Nanocomposites." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1078245607.
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Kohlhoff, Dominik. "Experimental Preparation of Microcellular Polymer Blend Foams by Exploiting Structural non-Homogeneity." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/165027.
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King, Nathan H. "Vapor-liquid Equilibrium of Polymer Solutions During Thermal Decomposition of Rigid Foams." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2538.pdf.
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Jovic, Kristina Julia. "New pathways to polymethacrylimide (PMI) foams." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/203746/1/Kristina_Jovic_Thesis.pdf.
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High-performance polymer foams such as polymethacrylimides are used to alleviate greenhouse gas emissions by decreasing the overall weight of vehicles. While these non-toxic, lightweight polymethacrylimide foams are time-proven products, their current production process faces several challenges, including toxic and expensive starting materials, insufficient knowledge into their formation mechanism as well as the requirement of high processing temperatures. The current PhD thesis addresses these problems by extending the base of suitable starting materials, developing advanced synthetic routes and establishing an in-depth understanding of the imidization mechanism to tune the thermal and mechanical properties of these versatile materials.
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Carroll, H. "Fatigue damage mechanisms in advanced polymer matrix composites." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597310.
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Recently, advances have been made in the design, manufacture and application of composite materials. A great deal of this progress has been made in the field of Fibre-Reinforced-Plastics (FRP). FRP often have greater strength to weight and stiffness to weight ratios than traditional materials such as metals, which makes them ideal for use in many application especially in aeronautical and aerospace sectors. For example Carbon-Fibre-Reinforced-Plastics (CFRP) are becoming more common in civil and military aircraft structures. However, there remain many unanswered questions regarding the behaviour of these materials especially under in-service conditions such as fatigue. There is an increasingly urgent need to gain an understanding of how FRPs behave. To fully understand the fatigue of a material it is necessary to gain an understanding of how damage initiates and accumulates and how the damage will affect the materials properties. It is also clear that to fully utilise FRPs it is necessary to be able to model the relationship between microstructural damage and the materials mechanical properties. This work has characterised the fatigue life of a quasi-isotropic carbon fibre reinforced composite, HS/919, at four R ratios. These are R=0.1 (tension-tension), R=+10 (compression-compression), R = -0.3 and R=-3.3 (both tension-compression). Those R ratios with a majority compression loading cycle experienced lower fatigue lives than those with a mainly tensile loading cycle. The work also highlighted the delaminations were a major damage mechanism. Post failure analysis of the fatigue specimens showed that the primary delamination, was occurring at different interfaces dependent on the loading cycle. With a mainly tensile loading cycle the delamination was occurring at the 0°/90° interface. While the mainly compressive loading cycle showed delaminations at the 0°/45° interface. This phenomenon was investigated using a modified mixed-mode bending technique developed by Reeder and Crews at Nasa. Static and fatigue tests were carried out on both the highlighted interfaces at three mixed-modes, MI/MII of 1/3, 1/1 and 3/1. Static tests showed that the 0°/45° interface was the weaker. In the fatigue tests two phenomena were observed, 1) that the strain energy release rate steadily decreased with crack length, 2) the strain energy release rate initially increased and then decreased. This is due to fibre bridging which was seen in both interface but was more apparent for the tests at the 0°/90° interface. There was a large amount of scatter in the fatigue data, especially at the 0°/45° interface. This made fitting a Paris type law to crack growth rates impossible for this interface. A Paris law was fitted to the 0°/90° data. It was hoped to transfer this knowledge to fatigue coupons with inserts.
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Kearney, Andrew V. "Fracture and fatigue of ultrathin nanoporous polymer films /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Wu, Jie. "Extraction of chitin nanofibers and utilization for sustainable composites and foams." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54006.
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Developing renewable materials to reduce the dependence on fossil fuel as a feedstock for a wide range of applications is becoming increasingly acknowledged as important in society. Chitin, the second most abundant biopolymer in nature, is an ideal candidate for diverse applications because of its remarkable properties, such as abundance, renewability, biodegradability, biocompatibility, antibacterial activity, chemical functionality, and high stiffness and strength. Despite these inherent advantages, chitin is currently still underutilized mainly due to its strong molecular interactions, which make it insoluble in common solvents. Currently, its major applications are limited to biomedical engineering, such as tissue engineering, wound dressing and sutures.
This thesis aims to explore and enable the potential utilization of chitin in other fields where it may serve as a renewable functional advanced material. Here, a number of novel chitin-based materials were developed successfully without employing chitin dissolution. These include chitin nanofibers (CNFs), porous chitin with tunable structures, chitin-reinforced polymer composites and chitin-stabilized aqueous foams. Moreover, the properties of these materials including interfacial, optical, thermal, and mechanical characteristics were determined, and their potential utilizations were demonstrated.
Briefly, in chapter 2, CNFs with diameters of ~20 nm were successfully extracted from crab α-chitin by a high pressure homogenization process. The produced CNFs were dispersed well in water without forming strong network structures due to their electrostatic repulsions. The obtained CNF film has a high residue amount (40%) when heated up to 1000 ˚C. Meanwhile, it exhibited high optical transparency as well as great gas barrier properties. In chapter 3, on the basis of the obtained CNFs in chapter 2, versatile porous structures including oriented sheets and three-dimensional aperiodic nanofiber networks were achieved by using a freeze drying technique. Since the formation of nanofibrous structures cannot be predicted by the widely-used particle encapsulation model, a modified structure formation mechanism was proposed. In chapter 4, the structure-property relationships of the CNF/poly(ethylene oxide)(PEO) nanocomposites were established. We demonstrated that the CNFs formed network structures in PEO matrix and had hydrogen bonding interaction with PEO. The CNFs can greatly enhance the mechanical properties of PEO, such as elastic modulus and tensile strength. In chapter 5, the aqueous foams stabilized by high-aspect-ratio CNFs were developed. The created foams exhibited strong hindrance on film drainage, coalescence and disproportionation. The fibrillated CNFs alone were not able to stabilize air bubbles, but the addition of small amounts of valeric acids in CNF dispersion can make chitin foamable. The results clearly showed that valeric acid modified CNFs reduced the surface tension of aqueous dispersion and were attached at the air-water interface.
Overall, this research has provided many new insights for the fabrication, characterization, and utilization of chitin, and has built a solid foundation for further exploiting chitin for diverse applications.
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Hossieny, Nemat. "Morphology and properties of polymer/carbon nanotube nanocomposite foams prepared by supercritical carbon dioxide." Tallahassee, Florida : Florida State University, 2010. http://etd.lib.fsu.edu/theses/available/etd-01062010-162530/.
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Thesis (M.S.)--Florida State University, 2010.Advisor: Changchun Zeng, Florida State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering. Title and description from dissertation home page (viewed on July 16, 2010). Document formatted into pages; contains xi, 75 pages. Includes bibliographical references.
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Graeber, Nadine. "A study of fundamentals in emulsion templating for the preparation of macroporous polymer foams." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/27245.
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This thesis describes a series of styrene (ST) and divinylbenzene (DVB) emulsion templated polymer foams prepared via low, medium and high internal phase emulsion templates (L/M/HIPE templates). The emulsion templates were stabilized using different commercially available technical surfactants and surfactant mixtures. Since the chemical nature of the chosen technical surfactants is unknown, the surfactants where characterized by means of Fourier Transform Infrared (FT-IR) and Nuclear Magnetic Resonance (NMR) spectroscopy, Electro Spray Ionization Mass- (ESI-MS) and Matrix-Assisted-Laser-Desorption-Ionization-Time-of-Flight-Mass Spectrometry (MALDI-TOF-MS). Additionally their adsorption at the water/ST:DVB interface was studied. The investigation regarding the preparation of surfactant stabilized emulsion templates and their polymerization products revealed that the most commonly used surfactant Span 80 is not the best suited surfactant to stabilize styrene/divinylbenzene emulsion templates which is why different surfactants were used in the thesis at hand. All successfully prepared poly(merized)HIPEs proved to have interconnected, open porous polymer foam structures. In contrast, the pore structure of polyMIPEs was open, closed or non-droplet shaped, depending on the surfactant used to stabilize the corresponding emulsion template. The mechanical compression properties of all prepared polyHIPEs were similar and independent of the HIPE formulation from which they were produced but the mechanical properties of polyMIPEs differed significantly. The influence of the surfactants on the morphology and mechanical properties of the resulting macroporous polymers will be discussed in detail. Furthermore, the relationship between the relative density (porosity) of the polymer foams and the mechanical response under compression was investigated. The semi-empirical models developed by Gibson and Ashby were applied and additionally modified to provide a more accurate description of the mechanical behaviour over a larger relative density range of polymer foams prepared via emulsion templating (polyL/M/HIPEs). This allows a prediction of the mechanical properties as a function of the relative density of the respective polymer foams and vice versa for the specified emulsion template formulation. It is obvious that the surfactant type and the internal phase volume ratio of the emulsion template used to produce macroporous polymer foams significantly determine their resulting mechanical properties, as clear transition states for polyH/M/LIPEs were identified in which the mechanical properties of these materials changed dramatically. The effect of the surfactant on the mechanical properties and the polymer foam morphology is discussed in terms of the surfactant's solubility in the polymer and thus in terms of its role as plasticizer. Finally, the influence of the pore size on the mechanical properties was investigated. It was found that the preparation process (emulsification and polymerization) of the emulsion templates is very crucial for the mechanical properties of the resulting polymer foams (reproducibility). More precisely, it was found out that the emulsion templates need to 'equilibrate' after emulsification. It was only for these emulsions that average pore sizes and mechanical properties could be reproduced.
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Hernodh, Svantesson Isabelle. "Thermally insulating carbon foams from carbonized kraft lignin." Thesis, KTH, Fiber- och polymerteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300749.
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Kolmaterial, såsom kolfibrer och kolskum, används som värmeisolatorer i applikationer vid höga temperaturer. För närvarande härleds dessa material från fossilbaserade källor, vilket tyder på ett behov av att hitta alternativa kandidater baserade på förnybara källor. Detta examensarbete undersökte möjligheten att använda kraftlignin som ett förnyelsebart startmaterial för framställning av kolskum med värmeisoleringsegenskaper. Två kraftligniner av barrträd med olika molekylvikter och ett kraftlignin av lövträd användes. De tre kraftligninerna karboniserades vid 1000°C efter att ha blandats i olika förhållanden och kombinationer (formuleringen av råmaterialet). Formuleringen av råmaterialet påverkade densiteten och porositeten hos de erhållna materialen, vilket i sin tur ledde till skillnader i kompressionsstyrkan och värmeledningsförmågan hos de erhållna kolskummen. Kolskummen hade olika värmeledningsförmåga (0,11-0,35 W/mK), porositet (80,55-97,53%) och densitet (0,08-0,42 g/cm3). För skummet med den högsta densiteten uppskattades krossstyrkan till cirka 10,03 MPa vilket är jämförbart med kommersiellt använda kolskum för högtemperaturisolerande applikationer. Kolskummens värmeledningsförmåga var inom omfånget för kommersiellt använda kolskum för högtemperaturapplikationer. Detta arbete visar möjligheten att tillverka kolskum från 100% kraftlignin som har liknande egenskaper som kommersiellt tillgängliga termiska isoleringsmaterial för högtemperaturapplikationer.Carbon materials, such as carbon fibres and carbon foams, are used as thermal insulators in high-temperature applications. At present, these materials are derived from fossil-based sources, which suggests a need of finding alternatives candidates based on renewables. This thesis work investigated the possibility of using kraft lignin as a renewable starting material for the preparation of carbon foams with thermal insulation properties. Two softwood kraft lignins with different molecular weights and a hardwood kraft lignin were used. The three kraft lignins were carbonized at 1000°C after being mixed in different ratios and combinations (precursor formulation). The precursor formulation affected the density and porosity of the obtained materials, which in turn led to differences in compression strength and thermal conductivity of the carbon foams derived. The obtained carbon foams had different thermal conductivities (0.11-0.35 W/mK), porosity (80.55-97.53%) and density (0.08-0.42 g/cm3). For the foam with the highest density, the crushing strength was estimated to approximately 10.03 MPa which is comparable to commercially used carbon foams for high-temperature insulating applications. The thermal conductivity of the prepared carbon foams was in the range of commercially used carbon foams for high-temperature applications. This work demonstrates the possibility of preparing carbon foams from 100% kraft lignin which has properties similar of commercially available insulating materials for high-temperature applications.
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Annapragada, Sriram Kiran. "Mechanism of Foaming on Polymer-Paperboard Composites." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19790.
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This thesis addresses a new technique of foaming on polymer-paperboard composites which combines the advantages of traditional polymeric foam with the environmental benefits of paperboard. Paperboard is sandwiched between two extruded polymeric layers of different densities. On application of heat, one face is foamed by the evaporating moisture in the board; the other face serves as a barrier. This work is directed at gaining a better understanding of the fundamental processes in foaming polymers on paperboard. The ultimate goal is to be able to produce uniform bubbles of a predetermined size on the surface so as to give optimum heat insulation and good tactile properties. Bubble growth was studied as a function of paperboard properties, polymer melt index, extrusion speed, polymer thickness, temperature and moisture content. The foam quality (thickness) is also related to the cell size distribution and various factors affecting it are identified. A combination of experimental techniques such as high speed imaging, infrared thermography and scanning electron microscopy is used for this purpose. Foaming on paper-polymer composites is caused by water vapor escaping through the pores present in the paperboard substrate and then foaming the polymer. The vapor driving force which dominates foaming and overcomes the less significant viscoelastic and surface tension opposition forces depends on the paperboard properties as well as on the ability of the polymer to bond with the paperboard. It was found that the bubble size distribution directly relates to the pore size distribution on the paperboard. The bubble size was also controlled by the thickness of the polymer layer and its ability to bond with the paperboard. Coalescence subsequently led to thicker foams due to the formation of larger sized bubbles.
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Islam, Md Zahirul. "Fatigue Behavior of Flax Fiber Reinforced Polymer Matrix Composites." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31577.
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Bio-based flax fiber polymer composites (FFPC) have the potential to replace metals and synthetic fibers in certain applications due to their unique mechanical properties. However, the long term reliability of FFPC needs to be better understood. In this study, the fatigue limit was evaluated using mathematical, thermographic, and energy-based approaches. Each approach determined fatigue limits around 45% load of ultimate tensile strength at a loading frequency of 5 Hz. Thermographic and energy-based approaches were also implemented at different loading frequencies (5, 7, 10, and 15 Hz) to define the effect of loading frequency on the fatigue life. Fatigue limit was found to decrease slowly with increasing loading frequency. Moreover, two forms of damage energy (thermal and micro-mechanical) during cyclic loading was separated using an experimental approach to pinpoint the main responsible damage energy for decreasing fatigue limit with increasing loading frequency.
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Dittenber, David Brian. "Fatigue of polymer composites life prediction and environmental effects /." Morgantown, W. Va. : [West Virginia University Libraries], 2010. http://hdl.handle.net/10450/10888.
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Thesis (M.S.)--West Virginia University, 2010.Title from document title page. Document formatted into pages; contains xii, 138 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-120).
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Nar, Mangesh. "Structural, Thermal and Acoustic Performance of Polyurethane Foams for Green Buildings." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699971/.
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Decreasing the carbon footprint through use of renewable materials has environmental and societal impact. Foams are a valuable constituent in buildings by themselves or as a core in sandwich composites. Kenaf is a Southeast USA plant that provides renewable filler. The core of the kenaf is porous with a cell size in a 5-10 micrometer range. The use of kenaf core in foams represents a novel multiscalar cellular structural composite. Rigid polyurethane foams were made using free foaming expansion with kenaf core as filler with loadings of 5, 10 and 15 %. Free foaming was found to negatively affect the mechanical properties. An innovative process was developed to introduce a constraint to expansion during foaming. Two expansion ratios were examined: 40 and 60 % (decreasing expansion ratio). MicroCT and SEM analysis showed a varying structure of open and closed cell pores. The mechanical, thermal insulation, acoustic properties were measured. Pure PU foam showed improved cell size uniformity. Introducing kenaf core resulted in decreasing the PU performance in the free expansion case. This was reversed by introducing constraints. To understand the combined impact of having a mixed close cell and open cell architecture, finite element modeling was done using ANSYS. Models were created with varying percentages of open, closed, and bulk cells to encompass entire range of foam porosities. Net zero energy building information modelling was conducted using EnergyPlus was conducted using natural fiber composite skins. Environmental impacts for instance global warming potential, acidification, eutrophication, fossil fuel consumption, ozone depletion, and smog potential of the materials used in construction was studied using life cycle assessment. The results showed improvement on energy consumption and carbon footprint.
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Kutay, Susan Michelle. "The physical and rheological properties of polymer-thickened foams in bulk and in porous media." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/NQ54795.pdf.
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Testouri, Aouatef. "Highly structured polymer foams from liquid foam templates using millifluidic lab-on-a-chip techniques." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00771862.
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Polymer foams belong to the solid foams family which are versatile materials, extensively used for a large number of applications such as automotive, packaging, sport products, thermal and acoustic insulators, tissue engineering or liquid absorbents. Composed of air bubbles entrapped in a continuous solid network, they combine the properties of the polymer with those of the foam to create an intriguing and complex material. Incorporating a foam into a polymer network not only allows one to use the wide range of interesting properties that the polymer offers, but also permits to profit from the advantageous properties of foam including lightness, low density, compressibility and high surface-to-volume ratio. Generally, the properties of polymer foams are strongly related to their density and their structure (bubble size and size distribution, bubble arrangement, open vs closed cells). Having a good control over foam properties is thus achieved by first controlling its density and structure.We developed a technique in which solid foams are generated essentially in a two-step process: a sufficiently stable liquid foam with well-controlled structural properties is generated in a first step, and then solidified in a second one. With such a two-step approach, the generation of solid foams can be divided into a number of well-separated sub-tasks which can be controlled and optimised separately. The transition from liquid to solid state is a sensitive issue of a great importance and therefore needs to be controlled with sufficient accuracy. It is essentially composed of three key steps: foam generation, mixing of reactants and foam solidification and requires the optimisation of foam stability in conjunction with an appropriate choice of both foaming time and solidification time. Furthermore, a good homogeneity of the polymer foam calls for a good mixing of the different reactants involved in the foaming and the polymerisation.A particularly powerful demonstration of the advantages of this approach is given by solidifying monodisperse liquid foams generated using millifluidic technique, in which all bubbles have the same size. In a liquid foam, equal-volume bubbles self-order into periodic, close-packed structures under gravity or confinement. As such, monodisperse foams provide simultaneous control over the size and the organisation of the pores in the final solid with an accuracy which is expected to give rise to a better understanding of the structure-property relationship of porous solids and to the development of new porous materials.We therefore aim to explore the new spectrum of properties, which polymer foams offer when we introduce an ordered structure into them since the most widely used polymer foams nowadays have disordered structures. The goal of our study is to demonstrate the feasibility of this two-step approach for different classes of polymers, including biomolecular hydrogel, superabsorbent polymer and polyurethane.For the generation of the structured polymer foams we use Lab-on-a-Chip technologies which allow the "shrinking" of large-scale set-ups to micro/millimetic scale. It permits also to perform "flow chemistry" in which the various liquid and gaseous ingredients of the foam are injected and mixed in a purpose-designed network of the micro- and millifluidic Lab-on-a-Chip. We adjust this approach according to the requirements of each polymer system, i.e. the foaming and the mixing techniques are chosen to fit the properties of each system, and can be exchanged to fit the properties of the studied systems.
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Tong, Xiaolong. "A Constitutive Model for Crushable Polymer Foams Used in Sandwich Panels: Theory and FEA Application." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1596806015399848.
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Forest, Charlène. "Preparation of nano-cellular foams from nanostructured polymer materials by means of CO2 foaming process." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10250.
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Cette étude porte sur l'élaboration de matériaux polymères nano-cellulaires via un procédé batch de moussage au CO2. Pour obtenir de tels matériaux, le moussage est provoqué dans des matériaux polymères nano-structurés afin de favoriser la nucléation hétérogène et d'obtenir des taux de nucléation et des densités de cellules élevées. Le moussage de terpolymères ABS et de PMMAs nanostructurés a été étudié, dans le but de produire des mousses nano-cellulaires avec une faible densité (inférieure à 0.3 g.cm-3) et une taille moyenne de cellules inférieure à 100 nm, correspondant aux morphologies de mousses requises pour obtenir des matériaux super isolants thermiquement. Le phénomène de nucléation, et donc la densité de cellules, sont apparus comme dépendant directement de la concentration et de la morphologie des agents nucléants, qui correspondent dans cette étude à des phases polymères immiscibles dispersées. L'élaboration de matériaux nano cellulaires a nécessité la compréhension des mécanismes de croissances de cellules, du rôle du CO2 en tant qu'agent gonflant et plastifiant ainsi que l'optimisation du procédé de moussage. Plus précisément, l'influence du comportement viscoélastique des matériaux polymères ainsi que celle des forces de surface sur la formation de cellules a également été étudié. Il a été montré que la formation de mousse se produisait dans un milieu viscoélastique, avec un comportement variant entre celui d'un solide et d'un liquide viscoélastique, et ce en fonction de la température et de la masses molaire des polymèresThis work focuses on the fabrication of nano-cellular polymer materials by means of a CO2 batch foaming process. To produce such materials, the foaming has to be induced in nano-structured polymer materials in order to favour heterogeneous nucleation and thus to obtain high nucleation rate and high cell density. The foaming of ABS terpolymers and nanostructured PMMAs was investigated, with the aim of producing nano-cellular foams with low density (lower than 0.3 g.cm-3) and an average cell size of 100 nm, which corresponds to required foam morphologies for super thermal insulating applications. It has been shown that nucleation, and thus cell density, directly depends on the content and morphology of nucleating agents, corresponding to dispersed polymer immiscible phases. The production of nano-cellular materials required the understanding of cell growth mechanisms, the role of CO2 as blowing agent and plasticiser and process optimisation. Specifically, the influence of viscoelastic behaviour of polymer materials and surface forces on cell formation was also investigated. It was found that the foaming occurred in viscoelastic media, with transitional behaviour between solid and liquid, depending on foaming temperature and molar mass of polymers
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Liu, Liu. "Durability of Polymer Composite Materials." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14002.
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The purpose of this research is to examine structural durability of advanced composite materials under critical loading conditions, e.g., combined thermal and mechanical loading and shear fatigue loading. A thermal buckling model of a burnt column, either axially restrained or under an axial applied force was developed. It was predicted that for a column exposed to the high heat flux under simultaneous constant compressive load, the response of the column is the same as that of an imperfection column; the instability of the burnt column happens. Based on the simplified theoretical prediction, the post-fire compressive behavior of fiberglass reinforced vinyl-ester composite columns, which have been exposed to high heat flux for a certain time was investigated experimentally, the post-fire compressive strength, modulus and failure mode were determined. The integrity of the same column under constant compressive mechanical loading combined with heat flux exposure was examined using a specially designed mechanical loading fixture that mounted directly below a cone calorimeter. All specimens in the experiments exhibited compressive instability. The experimental results show a thermal bending moment exists and has a significant influence on the structural behavior, which verified the thermal buckling model. The trend of response between the deflection of the column and exposure time is similar to that predicted by the model.
A new apparatus was developed to study the monotonic shear and cyclic-shear behavior of sandwich structures. Proof-of-concept experiments were performed using PVC foam core polymeric sandwich materials. Shear failure occurred by the extension of cracks parallel to the face-sheet/core interface, the shear modulus degraded with the growth of fatigue damage. Finite element analysis was conducted to determine stress distribution in the proposed specimen geometry used in the new technique.
Details for a novel apparatus used for the fatigue testing of thin films and face sheets are also provided.
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Svagan, Anna. "Bio-inspired cellulose nanocomposites and foams based on starch matrix." Doctoral thesis, KTH, Biokompositer, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9666.
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In 2007 the production of expanded polystyrene (EPS) in the world was over 4 million tonnes and is expected to grow at 6 percent per year. With the increased concern about environmental protection, alternative biodegradable materials from renewable resources are of interest. The present doctoral thesis work successfully demonstrates that starch-based foams with mechanical properties similar to EPS can be obtained by reinforcing the cell-walls in the foams with cellulose nanofibers (MFC). High cellulose nanofiber content nanocomposites with a highly plasticized (50/50) glycerol-amylopectin starch matrix are successfully prepared by solvent-casting due to the high compatibility between starch and MFC. At 70 wt% MFC, the nanocomposites show a remarkable combination of high tensile strength, modulus and strain to failure, and consequently very high work to fracture. The interesting combination of properties are due to good dispersion of nanofibers, the MFC network, nanofiber and matrix properties and favorable nanofiber-matrix interaction. The moisture sorption kinetics (30% RH) in glycerol plasticized and pure amylopectin film reinforced with cellulose nanofibers must be modeled using a moisture concentration-dependent diffusivity in most cases. The presence of cellulose nanofibers has a strong reducing effect on the moisture diffusivity. The decrease in zero-concentration diffusivity with increasing nanofiber content could be due to geometrical impedance, strong starch-MFC molecular interaction and constrained swelling due to the cellulose nanofiber network present. Novel biomimetic starch-based nanocomposite foams with MFC contents up to 40 wt% are successfully prepared by freeze-drying. The hierarchically structured nanocomposite foams show significant increase in mechanical properties in compression compared to neat starch foam. Still, better control of the cell structure could further improve the mechanical properties. The effect of cell wall composition, freeze-drying temperature and freezing temperature on the resulting cell structure are therefore investigated. The freeze-drying temperature is critical in order to avoid cell structure collapse. By changing the starch content, the cell size, anisotropy ratio and ratio between open and closed cells can be altered. A decrease in freezing temperature decreases the cell size and increases the anisotropy ratio. Finally, mechanical properties obtained in compression for a 30 wt% MFC foam prepared by freeze-drying demonstrates comparable properties (Young's modulus and yield strength) to expanded polystyrene at 50% RH and similar relative density. This is due to the reinforcing cellulose nanofiber network within the cell walls.QC 20100913
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Guzek, John S. (John Stephen). "Fatigue crack propagation along polymer-metal interfaces in microelectronic packages." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41401.
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Mortazavian, Seyyedvahid. "Fatigue Behavior and Modeling of Short Fiber Reinforced Polymer Composites." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1437787779.
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VanHouten, Desmond J. "Benign Processing of High Performance Polymeric Foams of Poly(arylene ether sulfone)." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/30014.
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This work is concerned with the production of high performance polymer foams via a benign foaming process. The first goal of this project was to develop a process and the conditions necessary to produce a low density (>80% density reduction) foam from poly(arylene ether sulfone) (PAES). Water and supercritical carbon dioxide (scCO2) were used as the blowing agents in a one-step batch foaming process. Both water and scCO2 plasticize the PAES, allowing for precise control on both the foam morphology and the foam density. To optimize the foaming conditions, both thermogravimetric analysis and differential scanning calorimetery (DSC) were used to determine the solubility and the reduced glass transition temperature (Tg) due to plasticization of the polymer. It was determined that 2 hours was sufficient time to saturate the PAES with water and scCO2 when subjected to a temperature of 220 oC and 10.3 MPa of pressure. Under these conditions, a combination of 7.5% of water and scCO2 were able to diffuse into the PAES specimen, correlating to ~60 oC reduction in the Tg of the PAES. The combination of water and scCO2 produced foam with up to an 80% reduction in density. The compressive properties, tensile modulus, and impact strength of the foam were measured. The relative compressive properties were slightly lower than the commercially available structural foam made of poly(methacrylimide).
The second objective of the dissertation was to enhance the compressive properties of the PAES foam, without concern for the foam density. Foam was produced over a range of density, by controlling the cell size, in order to optimize the compressive properties. Carbon nanofibers (CNFs) were also added to the PAES matrix prior to foaming to both induce heterogeneous nucleation, which leads to smaller cell size, and to reinforce the cell walls. Dynamic mechanical thermal analysis (DMTA), on saturated CNF-PAES, was used to determine the reduced Tg due to plasticization and establish the temperature for pressure release during foaming. DMTA proved to be more effective than DSC in establishing quantitative results on the reduction in the Tg. The CNF-PAES foam produced had compressive properties up to 1.5 times the compressive properties of the PAES foam.Ph. D.
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Salman, Marwan A. [Verfasser], and Siegfried [Akademischer Betreuer] Schmauder. "Multiscale modelling of nano-clay filled shape memory polymer foams / Marwan A. Salman ; Betreuer: Siegfried Schmauder." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/120659053X/34.
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Gallocher, Siobhain Lynn. "Durability Assessment of Polymer Trileaflet Heart Valves." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/54.
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The durability of a polymer trileaflet valve is dependent on leaflet stress concentrations, so valve designs that reduce stress can, hypothetically, increase durability. Design aspects that are believed to contribute to reduced leaflet stress include stent flexibility, parabolic coaptation curvature, and leaflet anisotropy. With this in mind, the purpose of this investigation was to elucidate what specific combinations of these parameters promote optimal acute and long-term valve function. A combination of four stent designs, seven leaflet reinforcement materials, and three coaptation geometries were evaluated through a combination of experimentation and modeling. Static tensile and Poisson’s ratio tests and dynamic tensile fatigue testing were used to evaluate the individual leaflet components; and hydrodynamic testing and accelerated valve fatigue was used to assess complete valve prototypes. The two most successful designs included a 0.40 mm thick knit-reinforced valve with a fatigue life of 10.35 years, and a 0.20 mm thick knit-reinforced valve with a 28.9 mmHg decrease in pressure drop over the former. A finite element model was incorporated to verify the impact of the above-mentioned parameters on leaflet stress concentrations. Leaflet anisotropy had a large impact on stress concentrations, and matching the circumferential modulus to that of the natural valve showed the greatest benefit. Varying the radial modulus had minimal impact. Varying coaptation geometry had no impact, but stent flexibility did have a marked effect on the stress at the top of the commissure, where a completely rigid stent resulted in a higher peak stress than a flexible stent (E = 385 MPa). In conclusion, stent flexibility and leaflet anisotropy do effect stress concentrations in the SIBS trileaflet valve, but coaptation geometry does not. Regions of high stress concentrations were linked to failure locations in vitro, so a fatigue prediction model was developed from the S/N curves generated during dynamic tensile testing of the 0.20 mm knit-reinforced leaflets. Failure was predicted at approximately 400 million cycles (10 years) at the top of the commissure. In vitro fatigue of this valve showed failure initiation after approximately 167 million cycles (4.18 years), but it was related to a design defect that is subsequently being changed.
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Uleck, Kevin R. "A hybrid model for fatigue life estimation of polymer matrix composites." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3312.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Haqu, Ziaul. "Fatigue behavior of plasma spray coatings on polymer matrix composite materials." Thesis, Wichita State University, 2008. http://hdl.handle.net/10057/2103.
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The majority of coated structural components are subjected to fluctuating internal and/or applied stress because of oscillating mechanical loads. The fatigue behavior of coatings and the overall cyclic failure response of coated structures have remained relatively unexplored. This study was an effort to investigate the fatigue behavior of plasma spray coatings on polymer matrix composite materials. Since no ASTM standard is available, we designed our own experiment to determine coatings suitability under cyclic loading, response in dynamic loading conditions, fatigue failure modes and fatigue life. Coatings were tested at different stress levels and frequencies. The stresses versus number of cycles (S-N) curves for the coatings were generated. The results indicate that the plasma spay coatings on polymer matrix composite materials are suitable for dynamic loading conditions.Wichita State University, College of Engineering, Dept. of Mechanical Engineering
Includes bibliographic references (leaves 42-43)
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Lancaster, I. M. "Influence of polymer modification on cracking and fatigue of asphalt mixtures." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3001738/.
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Efficient road networks are an integral aspect of the transport infrastructure of any modern economy and sound pavement design, along with effective maintenance programmes, are crucial to the continued quality and value of these assets. Polymer modification of the asphalt is frequently used to enhance the pavement durability performance. However, the benefits of polymer modification are not always clear to the designing engineer. Laboratory tests to assess asphalt performance often require large quantities of material, highly specialised test equipment and considerable amounts of time. Whilst the advantages of polymer modification on deformation resistance are well accepted, its impact on cracking and fatigue is less well defined. This research was therefore undertaken to quantify the effect of polymer modification on the cracking and fatigue performance of asphalt, and to develop methods to minimise the time and materials required to perform the laboratory assessments. A novel technique to analyse the performance of full asphalt mixtures utilising a standard laboratory dynamic shear rheometer (DSR) was developed using very small sample sizes. The technique was validated by comparing the results to existing testing geometries, with the new method shown to depict the viscoelastic behaviour of the asphalt. The asphalt’s fundamental fracture mechanics properties were investigated via the semi circular bending geometry, with the improved performance of the polymer modified asphalts in terms of fracture toughness and strain energy release rate demonstrated. A crack growth law based on the generalised J-integral was developed and used to determine characteristic material parameters which were used to predict pavement service life. Crack propagation of the semi-circular bending geometry under monotonic loading was modelled using the Extended Finite Element Method with the time dependent viscoelastic properties within the model determined using the small sample size technique, and modelled using a fractional viscoelastic element. ii The calibrated model was used to predict the load-displacement behaviour of specimens, and the improved crack resistance of the polymer modified asphalts verified. Binder fatigue behaviour was analysed using the DSR and the improved damage resistance of increasingly polymer modified binders verified. Asphalt fatigue was assessed using traditional large scale trapezoidal two point bending, cyclic semi-circular bending and small specimen sized tests on the DSR with the effect of polymer modification evaluated. Viscoelastic Continuum Damage (VECD) theory was successfully applied to the results with the potential for significant reductions in test durations using this approach demonstrated.
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Yari, Boroujeni Ayoub. "Fatigue, Fracture and Impact of Hybrid Carbon Fiber Reinforced Polymer Composites." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84223.
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The excellent in-plane strength and stiffness to-weight ratios, as well as the ease of manufacturing have made the carbon fiber reinforced polymer composites (CFRPs) suitable structural materials for variety of applications such as aerospace, automotive, civil, sporting goods, etc. Despite the outstanding performance of the CFRPs along their fibers direction (on-axis), they lack sufficient strength and performance in the out-of-plane and off-axis directions. Various chemical and mechanical methods were reported to enhance the CFRPs' out-of-plane performance. However, there are two major drawbacks for utilizing these approaches: first, most of these methods induce damage to the carbon fibers and, therefore, deteriorate the in-plane mechanical properties of the entire CFRP, and second, the methods with minimal deteriorating effects on the in-plane mechanical performance have their own limitations resulting in very confined mechanical performance improvements. These methods include integrating nano-sized reinforcements into the CFRPs' structure to form a hybrid or hierarchical CFRPs.
In lieu to all the aforementioned approaches, a relatively novel method, referred to as graphitic structures by design (GSD), has been proposed. The GSD is capable of grafting carbon nanotubes (CNTs) onto the carbon fibers surfaces, providing high concentration of CNTs where they are most needed, i.e. the immediate fiber/matrix interface, and in-between the different laminae of a CFRP. This method shows promising improvements in the in-plane and out-of-plane performance of CFRPs. Zinc oxide (ZnO) nanorods are other nano-sized reinforcing structures which can hybridize the CFRPs via their radially growth on the surface of carbon fibers. Among all the reported methods for synthesizing ZnO nanorods, hydrothermal technique is the most straightforward and least destructive route to grow ZnO nanorods over carbon fibers.
In this dissertation, the GSD-CNTs growth method and the hydrothermal growth of ZnO nanorods have been utilized to fabricate hybrid CFRPs. The effect of different ZnO nanorods growth morphologies, e.g. size distribution and alignment, on the in-plane tensile performance and vibration attenuation capabilities of the hybrid CFRPs are investigated via quasi-static tension and dynamical mechanical analysis (DMA) tests, respectively. As a result, the in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composite based on randomly oriented ZnO nanorods over the carbon fibers. The loss tangent of the CFRPs, which indicates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively.
While there are several studies detailing the effects of dispersed nanofillers on the fracture toughness of FRPs, currently, there are no literature detailing the effect of surface GSD grown CNTs and ZnO nanowire -on carbon fiber- on the fracture toughness of these hybrid composites. This dissertation probes the effects of surface grown nano-sized reinforcements on the fracture toughness via double cantilever beam (DCB) tests on hybrid ZnO nanorod or CNT grafted CFRPs. Results show that the surface grown CNTs enhanced the Mode I interlaminar fracture toughness (GIc) of the CFRPs by 22% and 32%, via uniform and patterned growth morphologies, respectively, over the reference composite based on untreated carbon fiber fabrics.
The dissertation also explains the basis of the improvements of the fracture toughness via finite element method (FEM). In particular, FEM was employed to simulate the interlaminar crack growth behavior of the hybrid CFRPs under Mode I crack opening loading conditions embodied by the DCB tests. These simulations revealed that the hybrid CFRP based on fibers with uniform surface grown MWCNTs exhibited 55% higher interlaminar strength compared to the reference CFRPs. Moreover, via patterned growth of MWCNTs, the ultimate crack opening resistance of the CFRPs improved by 20%. To mimic the experimental behavior of the various CFRPs, a new methodology has been utilized to accurately simulate the unstable crack growth nature of CFRPs.
Several investigations reported the effects of adding nanomaterials-including CNTs- as a filler phase inside the matrix material, on the impact energy absorption of the hybrid FRPs. However, the impact mitigation performance of CFRPs based on ZnO nanorod grafted carbon fibers has not been reported. The dynamic out-of-plane energy dissipation capabilities of different hybrid composites were investigated utilizing high velocity (~90 m/s) impact tests. Comparing the results of the hybrid MWCNT/ZnO nanorod/CFRP with those of reference CFRP, 21% and 4% improvements were observed in impact energy absorption and tensile strain to failure of the CFRPs, respectively.
In addition to elevated stiffness and strength, CFRPs should possess enough tolerance not only to monotonic loadings, but also to cyclic loadings to be qualified as alternatives to traditional structural metal alloys. Therefore, the fatigue life of CFRPs is of much interest. Despite the promising potential of incorporating nano-sized reinforcements into the CFRPs structure, not many studies reported on the fatigue behavior of hybrid CFRPs so far. In particular, there are no reported investigations to the effect of surface grown CNTs on the fatigue behavior of the hybrid CFRPs, due to fact that almost all the CNT growth techniques (except for the GSD method) deteriorated the in-plane performance of the hybrid CFRPs. The hybrid ZnO nanorod grafted CFRPs have not been investigated under fatigue loading as well. In this dissertation, different hybrid CFRPs were tested under tension-tension fatigue to reveal the effects of the different nano-reinforcements growth on the fatigue behavior of the CFRPs. A remarkable fatigue damage tolerance was observed for the CFRPs based on uniform and patterned grown CNT fibers. Almost two decades of fatigue life extension was achieved for CFRPs based on surface grown MWCNTs.Ph. D.
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Haqu, Ziaul Ahmed Ikram. "Fatigue behavior of plasma spray coatings on polymer matrix composite materials." A link to full text of this thesis in SOAR, 2008. http://hdl.handle.net/10057/2103.
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Dabrowski, Miriam Lucia [Verfasser], and Cosima [Akademischer Betreuer] Stubenrauch. "Tailor-made methacrylate-based polymer foams via emulsion and foamed emulsion templating / Miriam Lucia Dabrowski ; Betreuer: Cosima Stubenrauch." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-117101.
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Ofori-Abebresse, Edward Kwame. "Fatigue resistance of hot-mix asphalt concrete (HMAC) mixtures using the calibrated mechanistic with surface energy (CMSE) measurements approach." Thesis, Texas A&M University, 2006. http://hdl.handle.net/1969.1/4136.
Full textAbstract:
Fatigue cracking is one of the fundamental distresses that occur in the life of a Hot Mix Asphalt Concrete (HMAC) pavement. This load induced distress leads to structural collapse of the entire pavement ultimately and can only be remedied by rehabilitation. There is the need, therefore, for a total understanding of the phenomenon to be able to counter its occurrence. The fatigue resistance of hot mix asphalt concrete (HMAC) has been estimated using approaches ranging from empirical methods to mechanistic-empirical methods to purely mechanistic methods. A continuum mechanics based approach called the Calibrated Mechanistic with Surface Energy (CMSE) measurements was developed at Texas A&M University and recommended after comparison with other approaches in predicting fatigue lives of two Texas HMAC mixtures. The CMSE approach which includes fundamental material properties such as fracture, aging, healing, and anisotropy has been shown to effectively model the parameters that affect the performance of HMAC pavements exposed to repetitive traffic loads. Polymer modified asphalt (PMA) improves pavement performance by providing additional resistance to the primary distresses in flexible pavements, including permanent deformation or rutting, thermal cracking, and fatigue cracking. In this research, the CMSE approach was utilized to estimate the fatigue resistance of HMAC fabricated with asphalts modified with Styrene-butadiene-Styrene (SBS) co-block polymer. These HMAC mixtures were fabricated from materials used on three different road sections in Texas and one test pavement in Minnesota. The CMSE approach was validated as an effective approach for estimating the fatigue resistance of HMAC mixtures with PMA. The effect of oxidative aging on the fatigue resistance of the HMAC mixtures was also verified. Oxidative aging of the mixtures resulted in a corresponding decrease in mixture fatigue resistance. In addition, for two HMAC mixtures with the same binder content and aggregate gradation, the mixture with the softer of the two Performance Grade (PG) binders exhibited greater fatigue resistance. The use of the Utility Theory revealed the possible effects of aggregate geometric properties on the HMAC mixture properties and consequently on their fatigue resistance.
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Cartledge, Andrew. "The fatigue of carbon fibre composites containing interlaminar inkjet printed polymer droplets." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19374/.
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The objective of this research was to investigate a novel method of increasing the interlaminar toughening of prepreg composites to improve their fatigue performance, with particular emphasis on the retardation of delamination. Thermoplastic polymers droplets were deposited onto a composite prepreg using inkjet printing. Poly(methyl methacrylate) (PMMA) and polyethylene glycol (PEG) were dissolved in suitable solvents, creating polymer solutions that could be deposited onto prepreg substrates with excellent volume and position control. The prepreg laminae were then laid up to create complete laminates which contained the toughening polymers exclusively in their interlaminar regions, therefore leaving the bulk matrix properties unchanged. Both four point bending and tensile mechanical tests were used to evaluate the performance of printed composites. Results showed that multidirectional laminates printed with a solution of 10% by weight 20,000 molecular weight (Mw) PEG in deionised water exhibited significant retardation of delamination, being shown to reduce the rate of delamination by almost half in comparison to unprinted laminates. These laminates also showed increases of tensile strength and modulus of 4.9% and 12.3% respectively. Whilst laminates printed with PMMA and lower molecular weight PEG solutions were also shown to improve static mechanical properties, they also resulted in greatly increased rates of delamination in cyclic loading. Scanning electron microscopy was also used to analyse the delaminated surfaces of tensile samples. It was found that PMMA did not affect the bulk matrix properties in the interlaminar region. However, PEG was shown to result in increased matrix toughness and fibre/matrix bonding. PEG 20,000Mw was shown to exhibit the greatest increase of fibre/matrix bonding, whilst PEG 1,500Mw was shown to increase the ductility of the interlaminar matrix to an extent which was detrimental to the delamination resistance of laminates. The work presented in this thesis generated new understanding of the damage mechanisms operating at the interlaminar interface of cyclically loaded inkjet printed composites. It also demonstrated that such printed composites could potentially outperform unprinted laminates.
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Napiah, Madzlan B. "Fatigue and long term deformation behaviour of polymer modified hot rolled asphalt." Thesis, University of Leeds, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712012.
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Abu-Ragheef, Basil. "Polymer Aging Mechanics : An investigation on a Thermoset Polymer used in the Exterior Structure of a Heavy-duty Vehicle." Thesis, Linnéuniversitetet, Institutionen för skog och träteknik (SOT), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-88887.
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The use of plastic materials in the design of vehicle components is primarily driven by the need for vehicle weight and cost reduction. Additionally, these materials give design engineers freedom in creating appealing exterior designs. However, creating self-carrying exterior structures with polymers must fulfill long-term strength, creep and fatigue life requirements. Thus, the polymer polyDicyclopentadiene (pDCPD) has been chosen for this purpose. Its aging mechanics need to be understood by the design engineers to make the right decisions. This thesis has carried out mechanical tests such as uniaxial tensile testing, fatigue, and creep testing. Digital image correlation (DIC) system has been used to capture strain data from tensile tests. In the final analysis, DIC measurements proved more accurate than extensometer data retrieved from the testing machine. The rise in temperature has been captured using thermal imaging. Several degradation processes have been explored including physical aging, thermo-oxidation, photo-oxidation, chemical- and bio- degradations. Test results showed significant changes in mechanical properties after 17 years of aging. Additionally, severe thermal degradation has been observed in one of the tested panels of pDCPD. Temperature can rise to significant levels during cyclic loading at high stresses, which could have an impact on physical aging effects. Viscoelastic behavior has been explored and changes in dynamic and creep properties have been observed. The investigation also reviled that different defects caused by flawed manufacturing also can affect the material severely as one case has proved in this research.
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Cano, Camilo I. "Polyimide Microstructures From Powdered Precursors: Phenomenological and Parametric Studies on Particle Inflation." Akron, OH : University of Akron, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1123710711.
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Dissertation (Ph.D.)--University of Akron, Dept. of Polymer Engineering, 2005."August, 2005." Title from electronic dissertation title page (viewed 09/24/2005) Includes bibliographical references.