Scholarship & Research
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Item Toward the design and characterization of a dynamically similar artificial insect wing(Montana State University - Bozeman, College of Engineering, 2019) Reid, Heidi Elita; Chairperson, Graduate Committee: Mark JankauskiMicro air vehicles (MAVs) are a useful tool for numerous tasks, such as environmental mapping, search and rescue, and military reconnaissance. As MAV applications require them to operate at smaller and smaller length scales, traditional propulsion mechanisms (e.g. fixed wings, rotating propellers) cannot meet these demands. Conversely, flapping wing micro air vehicles (FWMAVs) can to realize flight at sub centimeter-lengths. However, FWMAVs face design challenges that preclude autonomous flight, including inefficient energetics and reliable on-board sensing. A comprehensive understanding of flying insect biomechanics may provide valuable design insights to help overcome the challenges experienced by FWMAVs. Insect wings have biological sensors that provide feedback to control attitude and wing deformation improves both inertial and aerodynamic power economy. Consequently, the insect wing can guide the design FWMAV-employed artificial insect wings. The present work aims to (1) dynamically characterize real insect wings via experimental modal analysis, and (2) develop dynamically similar artificial wings to be used on FWMAVs or in controlled studies. To our knowledge, no existing artificial insect wing models are isospectral and isomodal with respect to their biological counterparts. Isomodality and isospectrality imply they have identical frequency response functions and vibration mode shapes, and thus will deform similarly under realistic flapping conditions. We measured the frequency response function and vibration modes of fresh Manduca sexta forewings using an electrodynamic shaker and planar scanning vibrometer and estimated the wings' mass distribution via a cut-and-weigh procedure. Based upon our results, we designed and constructed the artificial wings using fused filament fabrication to print a polylactic acid vein structure, based upon the actual vein size and arrangement present in biological wings. Thin polymer films were manually layered over the vein structure and trimmed to fit the wing boundaries to produce a flat wing structure. We determined that the biological and artificial wings have nearly identical natural frequencies, damping ratios, gain, and shape for the first vibration mode. The second mode exhibited complex modal behavior previously unreported in literature, which likely has significant implications to flapping wing aerodynamics. We demonstrate the feasibility of fabricating economical, realistic artificial wings for robotic applications moving forward.Item Developments in electrically conductive bio-composites for use in additive manufacturing(Montana State University - Bozeman, College of Engineering, 2019) Arroyo, Jesse Whitney; Chairperson, Graduate Committee: Cecily Ryan; Cecily Ryan was a co-author of the article, 'Incorporation of carbon nanofillers tunes mechanical and electrical percolation in PHBV:PLA blends' in the journal 'Polymers' which is contained within this thesis.With the growth of rapid production methods, such as additive manufacturing, petroleum derived plastics are becoming ever more prevalent in consumer homes and landfills. As the industry grows, research into a more circular approach to designing and using materials is critical to maintaining sustainability. Bioplastics such as poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(lactic acid) (PLA) provide material properties comparable to petroleum derived plastics and are becoming more common in the additive manufacturing field. Biobased fillers, such as bio-derived cellulose, lignin byproducts, and biochar, can be used to modify the thermal, mechanical, and electrical properties of polymer composites. Biochar (BioC), in particular, is of interest for enhancing thermal and electrical conductivities in composites, and can potentially serve as a bio-derived graphitic carbon alternative for certain composite applications. In this work, we investigate a blended biopolymer system: PLA/PHBV, and addition of carbon black (CB), a commonly used functional filler as a comparison for Kraft lignin-derived BioC. We present calculations and experimental results for phase-separation and nanofiller phase affinity in this system, indicating that the CB localizes in the PHBV phase of the immiscible PHBV:PLA blends. The addition of BioC led to a deleterious reaction with the biopolymers, as indicated by blend morphology, differential scanning calorimetry showing significant melting peak reduction for the PLA phase, and a reduction in melt viscosity. For the CB nanofilled composites, electrical conductivity and dynamic mechanical analysis supported the ability to use phase separation in these blends to tune the percolation of mechanical and electrical properties, with a minimum percolation threshold found for the 80:20 blends of 1.6 wt.% CB. At 2% BioC (approximately the percolation threshold for CB), the 80:20 BioC nanocomposites had a resistance of 3.43x10 8 Omega as compared to 2.99x10 8 Omega for the CB, indicating that BioC could potentially perform comparably to CB as a conductive nanofiller if the processing challenges can be overcome. Investigations into alkaline and dealkaline lignin sources have shown that alkaline lignin experiences a significant effect on the thermal stability of PHBV eluding that alternate sources of lignin may provide a solution to the processing challenges mentioned. This work has helped to develop a understanding of the factors that aid in creating sustainable materials sourced from PLA,PHBV, and BioC.Item Parametric study of cyclic loading effects on the creep behavior of polymers and polymer based composites(Montana State University - Bozeman, College of Engineering, 2000) Schumacher, Shane ChristianItem Modeling and analysis of thin-film, piezoelectric actuators(Montana State University - Bozeman, College of Engineering, 2000) Childs, Ashley ErinItem Material characterization of poly (vinylidene fluoride) : a thin film piezoelectric polymer(Montana State University - Bozeman, College of Engineering, 1997) Holloway, Frank ConlyItem Static and dynamic behavior of stress coated membranes(Montana State University - Bozeman, College of Engineering, 2006) Nandurkar, Kuldeep Pandurang; Chairperson, Graduate Committee: Christopher H. M. JenkinsLarge space mirrors need to be made of ultra-lightweight materials (membranes) that have very low densities and high flexibility (compliance) for packaging. A coating application necessary for optical reflectivity may also impart to these ultra-lightweight materials a desired shape and to help maintain that shape in the harsh environment of space. When a coating is applied on the membrane substrate, stresses develop in the coating due to atomistic processes. These stresses are fundamental to the final shape of the substrate. Coatings applied to the substrate in order to maintain a particular shape are known as the 'stress coating prescription'. As there is no way one could directly measure stresses in the coatings experimentally, in this work it will be explained how finite element analysis (FEA) was used in estimating stresses in the coatings. This work mainly comprises static pressuredeflection tests (bulge tests) on the coated and uncoated membranes, and a comparison of the experimental results to FEA findings in order to estimate the stresses in the coatings. Before FEA results are matched with the experimental results, an analytical solution to the problem in hand will be derived. Uncertainties due to variation in coating thicknesses and difficulties in coating process have led to various uncertainties in this work, and these uncertainties are also discussed. The ability to use changes in vibration frequency as a measure of coating stress is also investigated.Item Ultrasonic repair of polymers : fundamentals and modeling for self-healing(Montana State University - Bozeman, College of Engineering, 2009) Sarrazin, John Cody; Chairperson, Graduate Committee: Christopher H. M. JenkinsAlthough current research focuses within self-healing materials are advancing, most pursuits are passive systems, unlike the active biological systems they aim to mimic. In this paper an active method utilizing ultrasonic energy is explored. Ultrasonic inspection has served as an effective means toward nondestructive damage detection for decades. Also, a recent method called time-reversed acoustics allows for the redirection of acoustic waves back towards the source. The active healing method utilizes ultrasonic nondestructive damage detection to locate and categorize damage, and then provide coordinates for the redirection of an amplified ultrasonic energy to heal the material. First, the temperature change as a result of ultrasonic treatment was measured, and then a variety of dogbone samples were tensile tested, including virgin samples, damaged samples, and damaged but ultrasonically treated dogbone samples. The ultrasonic treatment increased the ultimate stress of the ultrasonically treated dogbone samples, which was a result of increased crystallinity. The crystallinity was confirmed with differential thermal analyses. The ultrasonic influence of material temperature and effect of ultrasonically treated damaged samples versus just untreated damaged samples were replicated with finite element models as a means to predict future application and use.