UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Author: search.filters.author.Armstrong, ConnorSubject: search.filters.subject.Direct Ink Writing

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    Dynamic Control of Fiber Orientation for Additive Manufacturing via a Soft-Actuating Nozzle
    (2019) Armstrong, Connor; Bigio, David I; Sochol, Ryan D; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Recently, additive manufacturing of fiber-reinforced composite hydrogels has been used to create self-assembling and self-folding structures through hydration-triggered shape change. Additive manufacturing of shape-changing structures has applications in spatially-limited environments such as in-vivo biological implants and components for space travel. Fiber orientation in composite hydrogels dictates the degree of anisotropic swelling deformation of hydrated structures. This thesis explores the impact of extrusion channel geometry on fiber orientation as well as the relationship between fiber orientation and swelling deformation of composite hydrogels. To study the impact of fiber orientation on swelling deformation, fiber orientation in composite hydrogels was varied using diverging extrusion dies of increasing divergence angles. It was found that increasing channel divergence angle reduced the number of fibers oriented in the direction of flow, which led to increasingly isotropic swelling deformations. To create a gradient of fiber orientations in extruded structures, an extrusion nozzle utilizing soft actuators to alter its divergence angle in real-time was developed. Hydrogels extruded through the soft-actuated dynamic nozzle exhibited similar fiber orientation and swelling behavior to those extruded through the fixed divergence angles. Spatially-varied swelling deformation characteristics promise to improve additive manufacturing of self-assembling and self-folding structures by increasing the complexity of controllable shape change geometries achievable in extruded composite polymer structures.