Electrospinning was examined for its potential to create functional materials. Three distinct electroactive materials were electrospun into fibers and fiber mats and then characterized with the intent of determining their utility in aerospace and biomedical applications such as micro-air vehicles and the cardiovascular system. Electrospun Graft Elastomers demonstrated potential as actuators, as electromechanical strain testing showed comparable response to the film form of this material. Further improvement of electroactive response was realized with high dielectric inclusions and fiber orientation. Electrospin processing imparted piezoelectric properties to the fibers of poly(vinylidene fluoride). Differential scanning calorimetry and infrared spectroscopy indicated a degree of control over crystalline phase in poly(vinylidene fluoride) fibers based on electrospinning conditions. An increase in dielectric constant in the direction of fiber orientation proved that electrospinning also caused alignment of single-walled carbon nanotubes within the fibers. Ultem®/aligned single-walled carbon nanotube fiber nanocomposites were also fabricated; these showed evidence of enhanced piezoelectric strain response relative to fibers composed of the matrix alone. Thermal and static mechanical testing of all three types of fibers revealed no significant findings that would limit their use in abovementioned applications. Extract biocompatibility tests did not indicate severe adverse reaction of L929 mouse fibroblast cells to fiber mats for either Graft Elastomers or poly(vinylidene fluoride). These contributions prove that functional electroactive materials can be produced utilizing electrospinning as the processing method. This technique is simpler and cheaper to carry out, and resulting fiber mats showed comparable or improved properties and performance compared to other physical forms of the same materials.

The content of this diploma thesis is a design of construction and selection of suitable material for upper-carrier part used for racing vehicle, produced by FDM 3D printing with the alternative option to replace an existing part, which was produced by conventional technique of CNC machining. Various versions of the experimental part are analyzed by FEM and compared in terms of safety coefficient with target to select the most appropriate construction design. The chosen version of the model is at the end compared with already existing part, which was also analyzed by FEM.

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Extrusion additive manufacturing technologies may be utilized to fabricate complex geometry devices. However, the success of these additive manufactured devices depends upon their ability to withstand the static and dynamic mechanical loads experienced in service. In this study, quasi-static tensile and cyclic fatigue tests were performed on ULTEM 9085 samples fabricated by fused deposition modeling (FDM). First, tensile tests were conducted following ASTM D638 on three different build orientations with default build parameters to determine the mechanical strength of FDM ULTEM 9085 with those supplied by the vendor. Next, different build parameters (e.g. contour thickness, number of contours, contour depth, raster thickness, and raster angle) were varied to study the effects of those parameters on mechanical strength. Fatigue properties were investigated utilizing the procedure outlined in ASTM D7791. S-N curves were generated using data collected at stress levels of 80%, 60%, 30% and 20% of the ultimate tensile stress with an R-ratio of 0.1 for the build orientation XZY. The contour thickness and raster thickness were increased to 0.030 in. to determine the effect of those two build parameters on tension-tension fatigue life. Next, the modified Goodman approach was used to estimate the fully reversed (R=-1) fatigue life. The initial data suggested that the modified Goodman approach was very conservative. Therefore, four different stress levels of 25%, 20%, 15% and 10% of ultimate tensile stress were used to characterize the fully reversed fatigue properties. Because of the extreme conservatism of the modified Goodman model for this material, a simple phenomenological model was developed to estimate the fatigue life of ULTEM 9085 subjected to fatigue at different R-ratios. / Master of Science / Additive manufacturing (AM) is a revolutionary technology that is dramatically expanding the current manufacturing capabilities. The additive process allows the designers to create virtually any geometry by constructing the parts in layers. The layer-to-layer build technique eliminates many of the limitations imposed by traditional manufacturing methods. For example, machining is a common manufacturing technique that is used to create highly complex parts by removing material from a billet. The process of removing material to create a part is called subtractive manufacturing. Subtractive manufacturing requires sufficient clearance for tool access, in addition to complicated mounting fixtures to secure the part. These constraints often force engineers to design less optimized geometries to account for the manufacturing limitations. However, additive manufacturing allows the user greater design freedoms without a significant increase in resources. This innovative construction technique will push the boundaries of cutting-edge designs by removing many restrictions associated with traditional manufacturing technologies. Additive manufacturing is a relatively recent technology that evolved from rapid prototyping techniques that were developed in the 1960s. Rapid prototyping is used to create rapid iterations of physical models. However, additive manufacturing aims at creating functional end-use products. The layer-to-layer build process still poses many research challenges before it will be accepted as a reliable manufacturing technique. One of the current limitations with AM technologies is the availability of material properties associated with AM materials. The layer-to-layer build process and the toolpath creates different material properties that are dependent on the orientation of the applied load. Thus, further research is recommended to provide designers with a greater understanding of the mechanical characteristics of additive manufactured materials such as ULTEM 9085. This objective of this research is to characterize the static strength and fatigue characteristics of ULTEM 9085. The first part of the thesis focused on investigating the effects of the following build parameters on the strength of the component: build orientation, contour thickness, number of contours, contour depth, raster thickness, and raster angle. The second portion of this investigation determined the effects of fluctuating loads on the fatigue life of ULTEM 9085. Overall, the results of this investigation can be used to design more effective components using extrusion additive manufacturing technologies.

Nanometer thick layers of clay and polymer were formed on mica, silicon, and aluminum 2024-T3 alloy using alternating solutions of positively and negatively charged polymer and clay, respectively. Atomic force microscopy was used to observe the morphology of the composite films on mica and silicon. It was found that solution concentrations of clay above 0.02 weight percent lead to the uncontrolled deposition of clay platelets on the substrate's surface. By using solution concentrations of clay above 0.02 weight percent and ultrasonic agitation together it is possible to deposit a uniform monolayer of clay platelets on a mica substrate in £ 20 seconds. Ultrasonic agitation also produced crude patterns of montmorillonite platelets. Thin films of poly(diallydimethylammonium chloride) (PDDA) were made using concentrations ³ 2 weight percent of PDDA. It was found that the PDDA formed several unusual morphologies. Spherulites of PDDA were observed with AFM and the glass transition temperature of high molecular weight PDDA was measured using differential scanning calorimetry (DSC). Circular regions of positive charge were discovered on silicon wafers provided by three different sources. These areas of charge have never been reported in literature, but can easily be detected by placing wafers into solutions containing negatively or positively charged solutions of clay or polymer, respectively. The exact nature of these charged regions is unknown, but it is hypothesized that impurities on silicon wafers create the circular regions of positive charge. ISAM films made of a polyamide salt and a synthetic clay, Laponite RD®, demonstrated significant corrosion resistance on 2024-T3 Al alloys after 168 hours of salt spray testing. The ISAM films offered corrosion protection only if there was a significant layer of underlying surface oxide present, however. It was found that ISAM deposited films of polyarylic acid (PAA) and polyallylamine hydrochloride (PAH) may offer some corrosion resistance on 2024-T3 Al alloys, but these films' corrosion resistance is severely hampered by the presence of Cl- in the PAH solution. Funding from this project was gratefully received from the Materials Science and Engineering Department at Virginia Tech; Luna Innovations Inc; the American Chemical Society / Petroleum Research Fund #34412-G5 and the Environmental Protection Agency Contract #68-D-00-244. / Master of Science

The thesis deals with the dependence of mechanical characteristics on the anisotropy of polymers Nylon 12 and Ultem 9085 made by a 3D printing technology Fused Deposition Modeling (FDM). The evaluation of the material characteristics was performed on the basis of tensile and non-instrumental impact tests. It was proven that the material characteristics are strongly dependent on anisotropy, i.e. on layer thickness and raster angle for both types of polymers.