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High Temperature Materials for Aerospace ApplicationsAdamczak, Andrea Diane 2010 May 1900 (has links)
Further crosslinking of the fluorinated polyimide was examined to separate the
cure reactions from degradation and to determine the optimum post curing conditions.
Glass transition/melting temperatures were ascertained using DSC, while weight loss
during curing and Td were determined using TGA. Furthermore, the mechanical
properties were measured using an Instron to relate to the thermal properties to find the
optimum curing conditions. The polyimide resin exhibited the best post-curing
conditions for further crosslinking for 8 hours at 410 degress C based on Tg, thermal stability,
and mechanical properties.
Blister temperatures, resulting from rapid heating, were obtained by monitoring
changes in transverse thickness expansion using two different techniques. Both
techniques employed showed similar blister temperatures in relation to the amount of
absorbed moisture, regardless of sample size. The polyimide resin exhibited blister
temperatures ranging from 225 - 362 degrees C, with 1.7 - 3.0 wt% absorbed moisture, and the
polyimide composite had blister temperatures from 246 - 294 degrees C with 0.5 - 1.5 wt%
moisture.
Weight loss of the fluorinated polyimide and its corresponding polyimide carbon
fiber composite under elevated temperature was examined. Weight loss as a function of
exposure temperature and time was measured using TGA and by pre- and post-weighing
of specimens treated in an oven. Both techniques showed similar weight loss trends as a
function of time and temperature, but TGA showed much greater weight loss due to
greater surface area to volume (i.e., small sample size). The neat polyimide resin and
carbon fiber composite exhibited negligible weight loss at temperatures below 430 degrees C
for exposure times up to 20 minutes.
Transition-metal carbides were initially synthesized by carbothermal reduction of
transition-metal halides and polymer precursor mixtures, at temperatures that range from
900 to 1500 degrees C in an argon atmosphere. TaC was synthesized from TaBr5, as a model
carbide for this process. Significant (> 40 vol%) amounts of TaC were formed at
reaction temperatures as low as 900 degrees C for one hour, with greater times and temperatures
leading to > 90 vol% yield. Universality of method was also proven by using other
various transition-metal halide salts (NbBr5, WCl4, and WCl6) with the polyimide.
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Abs/polyamide-6 Blends, Their Short Glass Fiber Composites And Organoclay Based Nanocomposites: Processing And CharacterizationOzkoc, Guralp 01 February 2007 (has links) (PDF)
The objective of this study is to process and characterize the compatibilized blends of
acrylonitrile-butadiene-styrene (ABS) and polyamide-6 (PA6) using olefin based
reactive copolymers and subsequently to utilize this blend as a matrix material in short
glass fiber (SGF) reinforced composites and organoclay based nanocomposites by
applying melt processing technique. In this context, commercially available epoxydized
and maleated olefinic copolymers, ethylene-methyl acrylate-glycidyl methacrylate
(EMA-GMA) and ethylene-n butyl acrylate-carbon monoxide-maleic anhydride
(EnBACO-MAH) were used as compatibilizers at different ratios. Compatibilizing
performance of these two olefinic polymers was investigated through blend
morphologies, thermal and mechanical properties as a function of blend composition and
compatibilizer loading level. Incorporation of compatibilizer resulted in a fine
morphology with reduced dispersed particle size. At 5 % EnBACO-MAH, the toughness
was observed to be the highest among the blends produced.
SGF reinforced ABS and ABS/PA6 blends were prepared with twin screw extrusion.
The effects of SGF concentration and extrusion process conditions on the fiber length
distribution, mechanical properties and morphologies of the composites were examined.
The most compatible organosilane type was designated from interfacial tension and
short beam flexural tests, to promote adhesion of SGF to both ABS and PA6. Increasing
amount of PA6 in the polymer matrix improved the strength, stiffness and also
toughness of the composites. Effects of compatibilizer content and ABS/PA6 ratio on
the morphology and mechanical properties of 30% SGF reinforced ABS/PA6 blends
were investigated. The most striking result of the study was the improvement in the
impact strength of the SGF/ABS/PA6 composite with the additions of compatibilizer.
Melt intercalation method was applied to produce ABS/PA6 blends based organoclay
nanocomposites. The effects of process conditions and material parameters on the
morphology of blends, dispersibility of nanoparticles and mechanical properties were
investigated. To improve mixing, the screws of the extruder were modified. Processing
with co-rotation yielded finer blend morphology than processing with counter-rotation.
Clays were selectively exfoliated in PA6 phase and agglomerated at the interface of
ABS/PA6. High level of exfoliation was obtained with increasing PA6 content and with
screw speed in co-rotation mode. Screw modification improved the dispersion of clay
platelets in the matrix.
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Mechanical characterization of DuraPulp by means of micromechanical modellingAl-Darwash, Mustafa, Nuss, Emanuel January 2015 (has links)
Södra DuraPulp is a relatively new eco-composite, made from natural wood fibers and polylactic acid (PLA), which comes from corn starch. Until now, there are only few applications for DuraPulp, mainly in the area of design. To find new fields of application, more knowledge about its mechanical material properties are of great interest.This study deals with characterizing the mechanical properties of DuraPulp in an analytical way by means of micromechanical modelling and evaluation with help of Matlab. The mechanical properties for PLA were taken from scientific literature. Not all properties of the wood fibers could be found in literature (particularly Poisson’s ratios were unavailable). Therefore, they partly had to be assumed within reasonable boundaries. These assumptions are later validated regarding their influence on the final product.Figures and tables were used to present and compare the in- and out-of-plane E-Moduli, shear moduli and Poisson’s ratios of DuraPulp. The calculated in-plane E-Moduli were then compared to those obtained from an earlier study, where DuraPulp was tested in tension. The results showed that experimental and analytical values are very similar to each other. / Södra DuraPulp är en relativt ny eco-komposit, tillverkat av naturliga trä fibrer och polylactic syra som kommer från majsstärkelser. I dagsläget finns det få användningsområden för DuraPulp, huvudsakligen används det inom design. För att expandera användningsområdet behövs det mer kunskaper angående de mekaniska egenskaperna för materialet. Studien handlar om att karakterisera de mekaniska egenskaperna för DuraPulp på ett analytiskt sätt i form av mikro-mekanisk modellering och evaluering med hjälp av Matlab. De huvudsakliga mekaniska egenskaperna för PLA kunde hämtas från flera vetenskapliga källor, men de motsvarande mekaniska egenskaperna för fibrer kunde inte alla valideras. Delvis antogs dem i rimliga gränser och deras inverkan validerades med hjälp av en parameter studie.Figurer och tabeller användes för att presentera och jämföra in- och ut-plan E-Moduler, skjuvmoduler och tvärkontraktionstalen av DuraPulp. De beräknade in-plan E-modulerna för DuraPulp jämfördes med motsvarande E-moduler från en tidigare studie där DuraPulp genomgick dragtest. Resultatet visade att analytiska och experimentella värden överensstämmer bra med varandra.
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[en] RELIABILITY-BASED DESIGN OF RC BEAMS STRENGTHENED WITH CFC / [pt] PROJETO BASEADO EM CONFIABILIDADE DE VIGAS EM CONCRETO ARMADO COM E SEM REFORÇO DE COMPÓSITOS DE FIBRAS DE CARBONONATHALY SARASTY NARVAEZ 21 January 2013 (has links)
[pt] No Brasil, o dimensionamento de estruturas de concreto armado segue as
recomendações da norma brasileira NBR 6118-2003. A norma brasileira, usa a
metodologia de dimensionamento semi-probabilístico que não quantifica a
probabilidade de falha de um elemento estrutural. A análise de confiabilidade de
estruturas é uma ferramenta que possibilita o cálculo da probabilidade de falha
associada a um estado limite e também um dimensionamento para uma determinada
probabilidade de falha denominada probabilidade de falha alvo. Este trabalho tem
como objetivo desenvolver uma metodologia que possibilite o dimensionamento
baseado em confiabilidade de seções de vigas de concreto armado sem e com
reforço com compósitos de fibras de carbono. Na análise de confiabilidade
desenvolvida foram consideradas como variáveis aleatórias o carregamento, as
resistências do aço e do concreto, e a resistência à tração dos compósitos de fibras
de carbono com propriedades estatísticas determinadas com base nos resultados dos
ensaios realizados no laboratório de Estruturas e Materiais do Departamento de
Engenharia Civil da PUC-Rio (LEM-DEC). Exemplos de dimensionamento de
seções de vigas de concreto armado submetidas à força cortante e à flexão foram
realizados inicialmente por métodos semi-probabilísticos e depois utilizando a
metodologia proposta baseada em confiabilidade. A análise dos resultados mostra a
viabilidade de um projeto baseado em confiabilidade usando um índice de
probabilidade de falha determinado para cada tipo de projeto aliando economia e
segurança. / [en] In Brazil, the design of reinforced concrete structures follows the
recommendations of Brazilian standard NBR 6118-2003. The Brazilian standard
uses the methodology of semi-probabilistic design that does not quantify the
probability of failure of a structural element. The reliability analysis of structures
is a tool that allows the calculation of probability of failure associated with a limit
state and also the design for a given probability of failure. This work aims to
develop a methodology that enables the Reliability-based-design of concrete
beams sections with and without strengthening with carbon fiber composites. In
the reliability analysis were considered as random variables the loads, the
compression concrete strenght, yield strenght, and tensile strength of carbon fiber
composites with certain statistical properties based on the results of tests
performed in the Structures and Materials laboratory at PUC-Rio (LEM-DEC).
Examples of reinforced concrete beams strengthened with CFC were performed
initially by semi-probabilistic methods and then using the proposed methodology
based on reliability. The analysis shows the feasibility of a Reliability-baseddesign
using a reliability index of failure probability determined for each type of
project combining economy and safety.
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Carbon Fiber Reinforced Lithium-Ion Battery Composites with Higher Mechanical Strength: Multifunctional Power Integration for Structural ApplicationsJadhav, Mayur Shrikant 08 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This study proposes and evaluates a multi-functional carbon fiber reinforced composite with embedded Lithium-ion battery for its structural integrity concept. The comparison of versatile composite structures manufactured conventionally, air-sprayed and electrospun multi walled carbon nano tubes in order to discover a better packaging method for incorporating lithium-ion batteries at its core is determined. In the electrospinning process recognized globally as a flexible and cost-effective method for generating continuous Nano filaments. It was incorporated exactly on the prepreg surface to obtain effective inter-facial bonding and adhesion between the layers. The mechanical and physical properties of carbon fiber reinforced polymers (CFRP) with electrospun multi walled carbon nano tubes (CNTs) have evidenced to possess higher mechanical strength incorporated between the layers of the composite prepreg than the traditional CFRP prepreg composite, At the same time the air sprayed CFRP with CNTs offers mechanical strength more than the traditional CFRP prepreg but lesser than the electrospun. This can be a design consideration from the economic feasibility viewpoint. They also contribute to efficient load transfer and structural load bearing implementation without compromising the chemistry of battery. The design validation, manufacture methods, and experimental characterization (mechano-electrical) of Multi-functional energy storage composites (MESCs) are examined. Experimental results on the electrochemical characterization reveal that the MESCs show comparable performance to the standard lithium-ion pouch cells without any external packaging and not under any loading requirements. The mechanical performance of the MESC cells especially electrospun CFRP is evaluated from three-point bending tests with the results demonstrating significant mechanical strength and stiffness compared to traditional pouch cells and conventional, air-sprayed CFRP and at lowered packaging weight and thickness. This mechanical robustness of the MESCs enable them to be manufactured as energy-storage devices for electric vehicles.
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Optimering av flexibel transmissionslänk till vinschbaserat vågkraftverk / Optimization of flexible transmission link to winch-based wave power plantStenhammar, Philip, Hård, Patrik January 2018 (has links)
Detta projekt undersöker olika alternativ av design utav transmissionskedja för ett vågkraftverk. Designen av koncepten kan delas in i två grupper, en grupp med styva länkar och rörliga leder och en annan grupp med stela leder och böjflexibla länkar. Analysen genomförs genom att undersöka olika tvärsnitt och olika material. De material som länkarna undersöks för är kolstål, rostfritt stål, aluminium, glas- och kolfiberkomposit. Analyserna utförs analytiskt för transmissioner med stela leder och böjflexibla länkar och för styva länkar med rörliga leder används Solidworks tillsammans med Ansys Workbench. En transmission med rörliga leder togs fram och idén baserades på en rullkedja. Denna design klarar de ställda kraven men det skapas problem i kontakteringen mellan kedjelederna där det blir koncentrationsspänningar och mycket slitage. I nuläget finns det inte några bussningar eller lager som klarar kraven som ställs på kedjan. I den andra gruppen med stela leder och böjflexibla länkar togs det fram två koncept. Den första har ett rektangulärt tvärsnitt och den andra ett runt. Den med det runda tvärsnittet klarar inte kraven då både böj- och dragspänningarna inte kan hållas tillräckligt låga samtidigt.Konceptet med det rektangulära tvärsnittet, som liknar ett band, klarar alla krav förutom utmattningskravet. Då bandet är tillverkat i stål blir bandets bredd för stor för bojen. Då bandet är tillverkat i aluminium uppfylls inte utmattningskravet. Fiberkompositer tappar mer än 50 % av sin styrka efter 10 miljoner repetitioner vilket gör att de måste bytas ut med jämna mellanrum för att undvika brott. / This project examines different options of designs of transmission chains for a wave power plant. The different designs can be divided into two groups, one group that contains chains with stiff links and moving joints and another group with stiff joints and bend flexible links. The analysis is carried out by examining different cross sections and different materials. The links are evaluated with carbon steel, stainless steel, aluminum, glass and carbon fiber composite. The analyses are preformed analytically for the group with stiff joints and bend flexible links and the group with stiff links and moving joints are examined with Solidworks together with Ansys workbench. One transmission with stiff links and moving joints was made inspired by a roller chain. This design meets the requirements, but problems occur in the contact between the links, where it appears concentration stresses and a lot of wear. At present there are no bearings that meet the demands on the chain.In the second group with stiff joints and bend flexible links, two designs were developed. The first one has a rectangular cross section and the other one has a round. The circular cross section does not meet the requirements, since both bending and tensile stresses cannot be kept low enough at the same time. The design with the rectangular cross section meets all the requirements except the fatigue requirement. After 10 million repetitions the fiber composites loses more than 50 % of its strength, which means that they needs to be replaced periodically to avoid fracture.
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Characterization of Dispersion and Residual Stress in Nanoparticle Reinforced Hybrid Carbon Fiber CompositesSelimov, Alex 01 January 2016 (has links)
Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of these photoluminescence emissions have been established to be stress dependent, which allows for in situ residual stress measurements. It is shown here that the application of silane coupling agents as particle surface treatments improves particle dispersion when compared to untreated samples. Reactive silane coupling agent (RSCA) treatments were found to provide for greater dispersion improvements when compared to non-reactive silane coupling agents (NRSCA). Higher resolution investigations into these samples found that treatment with a reactive coupling agent altered the stress state of particles concentrated around the fiber from a tensile stress state to a compressive stress state. This is proposed to result from bonding of the reactive groups on the coupling agent to the organic groups on the carbon fibers which adjusts the stress state of the particle. Future mechanical tests will verify the effects of the particle surface functionalization treatments on mechanical properties of the composites.
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Non-destructive Evaluation Measurements and Fracture Effects in Carbon/Epoxy Laminates Containing PorosityHakim, Issa A. 28 August 2017 (has links)
No description available.
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FIBER-COMPOSITE IN SITU FABRICATION: MULTILAYER COEXTRUSION AS AN ENABLING TECHNOLOGYJordan, Alex Michael 13 September 2016 (has links)
No description available.
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Effect of Large Holes and Platelet Width on the Open-Hole Tension Performance of Prepreg Platelet Molded CompositesGabriel Gutierrez (13875776) 07 October 2022 (has links)
<p>Carbon-fiber reinforced polymers (CFRPs) are often used in the aerospace and automotive industries for their high strength-to-weight ratios and corrosion resistance. A new class of composites – known as Prepreg Platelet Molded Composites (PPMCs) – offers further advantageous such as high forming capabilities with modest compromises in strength and stiffness. One such property of PPMCs that have garnered interest over the years is their apparent insensitivity to notches. Previous studies have researched the effect of specimen size and platelet length on its effect on the open-hole performance of PPMCs. Research however has focused on thinner samples with smaller hole sizes and neglected thicker samples with larger holes. Additionally, while platelet sizes have been investigated for unnotched samples, platelet width on notched samples is less clear from the literature. The present thesis offers some investigations to aid in filling this knowledge gap. </p>
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<p>The objective of this work is to study two parameters that could influence the performance of PPMCs under open-hole tension. First, thick (7.6 mm) specimens are subjected to large hole sizes (up to 19.08 mm) to investigate their behavior in comparison to the smaller sample sizes previously investigated in the literature. Through-thickness DIC measurements are taken to investigate strain gradients in these thicker specimens. Second, various platelet widths are tested to research their influence on notch insensitivity of open-hole tensile PPMC specimens. Lastly, a finite element based continuum damage mechanics model is implemented to predict macro-level structural properties using only material properties of the parent prepreg. It is found that large holes in thick samples increase notch sensitivity compared to other samples of similar diameter-to-width ratios. Narrower platelets were found to produce higher unnotched strengths, while wider platelets offered more notch insensitivity. Lastly, the finite element model developed was found to qualitatively replicate features and failure modes that are exhibited by PPMCs, though strength predictions became inaccurate at larger specimen sizes. Recommendations are made for future work on the basis of these findings. </p>
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