Engineering Commons^™

Degradation Mechanism Of Expanded Polystyrene (Eps) Foam In Lost Foam Casting, Pips Approach For Synthesis And Novel Expansion Techniques For Cellular Foam, Indraneel Sen

Doctoral Dissertations

Lost Foam Casting (LFC) is a metal casting technology that facilitates fabrication of near-net shape metal castings using expanded polystyrene (EPS) foam patterns that are coated with refractory slurry and is effective for producing aluminum or iron castings of complicated geometry. However, the LFC process can produce considerable amount of scrap due to casting defects. Removing the EPS thermal decomposition products through the ceramic coating ahead of the advancing metal front during the liquid metal pour is a key factor in obtaining a defect free casting. Developing a fundamental understanding of foam degradation mechanism is essential in improving LFC process. …

Signaling Pathways Activated By Interleukin-2 And Interluekin-4 Receptors Mediate T Lymphocyte Clonal Expansion, Kristen K. Comfort

Chemical and Materials Engineering Faculty Publications

Cells sense and respond to chemical and physical stimuli through signal transduction pathways, which mediate cell proliferation, differentiation, migration, and survival. The cytokines interleukin-2 (IL-2) and interleukin-4 (IL-4) are key regulators of the adaptive immune system, particularly influencing the clonal expansion and differentiation of T cells. At least in culture, both synergistic and antagonistic effects of IL-2 and IL-4 co-stimulation have been reported; the antagonism, when observed, is thought to arise from the utilization of a common subunit shared by IL-2 and IL-4 receptors. We have sought to characterize IL-2 and IL-4 signaling at the level of intracellular pathways activated …

High Temperature Degradation Of 5250-4 Polymer Resin, Patrick E. Link

Theses and Dissertations

5250-4 bismaleimide resin is used in high performance polymer matrix composites with high temperature aeronautical applications. This thesis investigated the thermal and oxidative degradation of 5250-4 neat resin powder in argon, air, and oxygen environments. The powder was aged at 163 deg. C, 177 deg. C, and 190 deg. C in all environments for at least 250 hours. Isothermal thermo-gravimetric analysis demonstrated that weight loss was negligible for aging in the argon environment, indicating weight loss is the result of an oxidative process at these temperatures. The 5250-4 powder exhibited an initial period of weight gain before eventually losing weight …

Experimental Study On The Influence Of Foam Porosity And Pore Size On The Melting Of Phase Change Materials, Khalid Lafdi, Osama Mesalam Mesalhy, Shadab Shaikh

Chemical and Materials Engineering Faculty Publications

Experimental study was carried out to study the phase change heat transfer within a composite of phase change material (PCM) infiltrated high thermal conductivity foam. An experimental setup was built to measure the temperature profiles and capture the melting evolution of the PCM inside aluminum foams. Aluminum foams were used as the porous material, and low melting temperature paraffin wax was used as the PCM. It was observed from the results that the system parameters of the wax/foam composite had a significant influence on its heat transfer behavior.

By using higher porosity aluminum foam, the steady-state temperature was reached faster …

Thermal Conductivity Improvement In Carbon Nanoparticle Doped Pao Oil: An Experimental Study, Shadab Shaikh, Khalid Lafdi, Rengasamy Ponnappan

Chemical and Materials Engineering Faculty Publications

The present work involves a study on the thermal conductivity of nanoparticle-oil suspensions for three types of nanoparticles, namely, carbon nanotubes(CNTs), exfoliated graphite (EXG), and heat treated nanofibers (HTT) with PAO oil as the base fluid. To accomplish the above task, an experimental analysis is performed using a modern light flash technique (LFA 447) for measuring the thermal conductivity of the three types of nanofluids, for different loading of nanoparticles.

The experimental results show a similar trend as observed in literature for nanofluids with a maximum enhancement of approximately 161% obtained for the CNT-PAO oil suspension. The overall percent enhancements …

Effect Of Carbon Nanofiber Heat Treatment On Physical Properties Of Polymeric Nanocomposites—Part I, Khalid Lafdi, William Fox, Matthew Matzek, Emel Yildiz

Chemical and Materials Engineering Faculty Publications

The definition of a nanocomposite material has broadened significantly to encompass a large variety of systems made of dissimilar components and mixed at the nanometer scale. The properties of nanocomposite materials also depend on the morphology, crystallinity, and interfacial characteristics of the individual constituents. In the current work, vapor-grown carbon nanofibers were subjected to varying heat-treatment temperatures.

The strength of adhesion between the nanofiber and an epoxy (thermoset) matrix was characterized by the flexural strength and modulus. Heat treatment to 1800C∘ demonstrated maximum improvement in mechanical properties over that of the neat resin, while heat-treatment to higher temperatures demonstrated a …

Oxygen Plasma Treatment And Deposition Of Cnx On A Fluorinated Polymer Matrix Composite For Improved Erosion Resistance, Christopher Muratore, Andras Korenyi-Both, John E. Bultman, A. R. Waite, John G. Jones, T. M. Storage, Andrey A. Voevodin

Chemical and Materials Engineering Faculty Publications

The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CNx coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CNx was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the …

Influence Of Van Der Waals Forces On Increasing The Strength And Toughness In Dynamic Fracture Of Nanofibre Networks: A Peridynamic Approach, Florin Bobaru Ph.D.

Department of Engineering Mechanics: Faculty Publications

The peridynamic method is used here to analyse the effect of van der Waals forces on the mechanical behaviour and strength and toughness properties of three-dimensional nanofibre networks under imposed stretch deformation. The peridynamic formulation allows for a natural inclusion of long-range forces (such as van der Waals forces) by considering all interactions as ‘long-range’. We use van der Waals interactions only between different fibres and do not need to model individual atoms. Fracture is introduced at the microstructural (peridynamic bond) level for the microelastic type bonds, while van der Waals bonds can reform at any time. We conduct statistical …

Interfacial And Capillary Pressure Effects On The Thermal Performance Of Wax/Foam Composites, Mohammad Rajab Almajali, Khalid Lafdi, Shadab Shaikh

Chemical and Materials Engineering Faculty Publications

A numerical investigation study was performed to study the phase change behavior of wax/foam composite encapsulated in an aluminum casing. Two types of foam materials, namely, aluminum and carbon, were infiltrated with paraffin wax. The progress of melt interface and temperature distribution within the encapsulated composite was analyzed using computational fluid dynamics software (CFD). A two-energy equation model was implemented in the CFD software through the use of user-defined function (UDF). Interfacial effects influencing the heat transfer process at the casing-composite junction and between the wax-foam surfaces within the composite were addressed through the use of separate UDF. In addition, …

Investigation On Magnetorheological Elastomers Based On Natural Rubber, Lin Chen

Articles

Magnetorheological Elastomers (MR Elastomers or MREs) are a kind of novel smart material, whose mechanical, electrical, magnetic properties are controllable under applied magnetic fields. They have attracted increasing attentions and broad application prospects. But conventional MREs are limited to wide applications because their MR effects and mechanical performances are not high enough. This paper aims to optimize the fabrication method and to fabricate good natural rubber based MREs with high modulus by investigating the influences of a variety of fabrication conditions on the MREs performances, such as matrix type, external magnetic flux density, and temperature, plasticizer and iron particles. Among …

Microstructures And Viscoelastic Properties Of Anisotropic Magnetorheological Elastomers, Lin Chen

Articles

The microstructures and viscoelastic properties of anisotropic magnetorheological elastomers were investigated in this paper. The measurement results show that their mechanical properties are greatly dependent on the magnetic flux density applied in preparation. A finite-column model was proposed to describe the relations between the microstructures and the viscoelastic properties. The simulation results agree well with the experimental results.

Heating Methods And Detection Limits For Infrared Thermography Inspection Of Fiber-Reinforced Polymer Composites, Jeff R. Brown, H. R. Hamilton

Publications

The use of fiber-reinforced polymer (FRP) composites to strengthen existing civil infrastructure is expanding rapidly. Many FRP systems used to strengthen reinforced concrete are applied using a wet lay-up method in which dry fibers are saturated on site and then applied to the surface. This research investigated using infrared thermography (IRT) as a nondestructive evaluation (NDE) tool for detecting air voids and epoxy-filled holes in FRP systems bonded to a concrete substrate. Four small-scale specimens with FRP thicknesses ranging from 1 to 4 mm (0.04 to 0.16 in.) containing fabricated defects were constructed and inspected in a laboratory setting. Three …