A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Strategies For Enhancing Performance of Flapping Wing Aerial Vehicles Using Multifunctional Structures and Mixed Flight Modes(2018) Holness, Alex; Bruck, Hugh A; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biological flapping wing flight offers a variety of advantages over conventional fixed wing aircraft and rotor craft. For example, flapping propulsion can offer the speed of fixed wing aircraft at similar scales while providing the maneuverability of rotor craft. Avian species easily display feats of perching, payload carrying, endurance flying, and transition behavior. In light of these characteristics, emulating and recreating flapping flight in biomimetic or bioinspired work is important in the development of next generation aerial systems. Unfortunately, recreating flapping wing flight is not easily achieved despite numerous efforts to do so. This is in large part due to technological deficiencies. With emerging technologies, it has been possible to begin to unravel the intricacies of flapping flight. Despite technological advancements, offsetting weight with mechanical systems robust enough to provide power and torque while sustaining loading remains difficult. As a result platforms either have simple flapping kinematics with fair payload or have more complex kinematics with limited excess power which in turn limits payload. The former limits capabilities to mirror biological performance characteristics and the latter limits the energy available to power flight which ultimately negatively impacts mission capabilities. Many flapping wing systems are subpar to traditional flying vehicles. Flapping systems can become more competitive in achieving various mission types with increased system performance. In particular, if endurance is coupled with desirable features such as those displayed in nature, i.e., avian perching, they may become superior assets. In this work, four strategies for increasing performance were pursued as follows: (1) increases to maneuverability and payload via a mixed mode approach of flapping wing used in conjunction with propellers, (2) rapid deceleration and variation of flight envelope via inertial control using the battery, (3) increased endurance via integrated energy storage in the wings, and (4) providing endurance to the point of complete energy autonomy using a design framework considering flapping wings with integrated high efficiency solar cells.Item Determination of Mixed Mode Energy Release Rates in Laminated Carbon Fiber Composite Structures Using Digital Image Correlation(2012) Puishys, Joseph Francis; Bruck, Hugh A; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Carbon fiber composites have recently seen a large scale application in industry due to its high strength and low weight. Despite numerous beneficial attributes of composite materials, they are subject to several unique challenges; the most prevalent and troubling is delamination fracture. This research program is focused on developing an appropriate damage model capable of analyzing microscopic stress strain growth at the crack tip of laminated composites. This thesis focuses on capturing and identifying the varying stress and strain fields, as well as other microstructural details and phenomena unique to crack tip propagation in carbon fiber panels using a novel mechanical characterization technique known as Digital Image Correlation (DIC).