Lightweight aerospace structures have been sought after since humans took flight in 1903, making major strides in NASA's pursuit of the moon with the development of sandwich panel composites. Sandwich structures typically consist of two stiff phases (i.e., face sheets) separated by a lightweight phase (i.e., core), which are stacked together through adhesive layers. Such a structural arrangement provides a high stiffness-to-weight ratio and is often used in applications where weight saving is critical. Functionally Graded Materials (FGMs), refer to multifunctional materials, which contain a spatial variation of composition and/or microstructure for the specific purpose of altering thermal and structural properties. Recent advancements in Additive Manufacturing (AM), or 3D printing, drastically increased research capabilities. This thesis poses two novel concepts. First, sandwich beams manufactured as a single unit through additive manufacturing, eliminates the need for secondary bonding used in traditional sandwich structures. Second, with the introduction of a Functionally Graded (FG) core, sandwich structures offer enhanced flexural stiffness-to-weight ratio. To test these hypotheses, the design space of sandwich beams with FG cores is analytically explored by forming governing equations from existing methods and developing specific FG performance parameters. These equations are then exploited in MATLAB to map variation of the sandwich beam stiffness-to-weight ratio as a function of core relative density. Analytical estimations are verified for a particular design point of variable core density using the Finite Element (FE) models developed in the commercial FE program ABAQUS. Both the analytical and numerical results reveal a performance increase of approximately 31% of the stiffness-to-weight ratio for a variable core density. Finally, the selected design is additively manufactured using a poly-jet printer (Stratasys J55). The flexural modulus and strength of the additively manufactured sandwich beams are measured by the three-point bend test method. The experimental results clearly match the analytical and numerical estimations.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2020-2379 |
| Date | 01 January 2022 |
| Creators | Grondin, Timothy |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations, 2020- |
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