Design, Fabrication and Testing of Fiber-Reinforced Cellular Structures with Tensegrity Behavior using 3D Printed Sand Molds
| dc.contributor.author | Jorapur, Nikhil Sudhindrarao | en |
| dc.contributor.committeechair | Williams, Christopher B. | en |
| dc.contributor.committeemember | West, Robert L. | en |
| dc.contributor.committeemember | Druschitz, Alan P. | en |
| dc.contributor.committeemember | Suchicital, Carlos T. A. | en |
| dc.contributor.department | Mechanical Engineering | en |
| dc.date.accessioned | 2018-08-10T06:00:41Z | en |
| dc.date.available | 2018-08-10T06:00:41Z | en |
| dc.date.issued | 2017-02-15 | en |
| dc.description.abstract | The overall goal of this work is to improve the structural performance of cellular structures in bending applications by incorporating tensegrity behavior using long continuous fibers. The designs are inspired by the hierarchical cellular structure composition present in pomelo fruit and the structural behavior of tensegrity structures. A design method for analyzing and predicting the behavior of the structures is presented. A novel manufacturing method is developed to produce the cellular structures with tensegrity behavior through the combination additive manufacturing and metal casting techniques. Tensegrity structures provide high stiffness to mass ratio with all the comprising elements experiencing either tension or compression. This research investigates the possibility of integrating tensegrity behavior with cellular structure mechanics and provides a design procedure in this process. The placement of fibers in an octet cellular structure was determined such that tensegrity behavior was achieved. Furthermore, using finite element analysis the bending performance was evaluated and the influence of fibers was measured using the models. The overall decrease in bending stress was 66.6 %. Extending this analysis, a design strategy was established to help designers in selecting fiber diameter based on the dimensions and material properties such that the deflection of the overall structure can be controlled. This research looks to Additive Manufacturing (AM) as a means to introduce tensegrity behavior in cellular structures. By combining Binder Jetting and metal casting a controlled reliable process is shown to produce aluminum octet-cellular structures with embedded fibers. 3D-printed sand molds embedded with long continuous fibers were used for metal casting. The fabricated structures were then subjected to 4 point bending tests to evaluate the effects of tensegrity behavior on the cellular mechanics. Through this fabrication and testing process, this work addresses the gap of evaluating the performance of tensegrity behavior. The overall strength increase by 30%. The simulation and experimental results were then compared to show the predictability of this process with errors of 2% for octet structures without fibers and 6% for octet structures with fibers. | en |
| dc.description.abstractgeneral | Cellular materials are a class of lightweight structures composed by a network of cells comprising inter-connected struts, which help in reducing the material present in the structure. These structures provide high stiffness for low mass, better shock-absorption, thermal and acoustic insulation. Best known examples in nature include honeycomb, bamboo and cedar. There is a constant desire to improve strength of the cellular structures while wanting low mass. This research aims to provide a new approach towards the enhancing structural performance of cellular structures for bending applications through designs featuring long continuous fibers to impose tensegrity behavior. The designs in this research are inspired by the structural composition of pomelo fruit and tensegrity arrangements, where continuous long fibers are observed to enhance structural performance. Tensegrity structures are another class of lightweight structures composed of compressive bars and pre-stressed strings/fibers such that the structural elements undergo either tension or compression. The absence of bending stress makes these structures more efficient. A design method for analyzing and predicting the behavior of the structures is presented. To address the imposing manufacturing challenges, a novel manufacturing method is developed, producing cellular structures with tensegrity behavior through the combination of Binder Jetting and metal casting techniques. Binder Jetting is an additive manufacturing process, which selectively binds sand, layer by layer to create molds of desired designs and metal can be cast into the printed molds to realize parts. The bending performance was evaluated and the influence of fibers was measured using the models. The overall decrease in bending stress was 66.6 %. The fabricated structures were then subjected to 4 point bending tests. The overall strength increased by 30%. The simulation and experimental results were then compared to show the predictability of this process with errors of 2% for octet structures without fibers and 6% for octet structures with fibers. This research takes another step towards creating efficient lightweight structures and adds to the efforts taken to build multifunctional hierarchical cellular materials, which can provide better performance while saving material. Potential applications of these structures include earthquake resistant wall panels, aircraft fuselage/interior supports, automotive chassis structure, beams for supporting roof loads, armor panels in battle tanks, ship building and packaging (electromechanical systems). | en |
| dc.description.degree | Master of Science | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:9637 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/84531 | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Additive manufacturing | en |
| dc.subject | Cellular Structure | en |
| dc.subject | Tensegrity Behavior | en |
| dc.subject | Fiber-Reinforcement | en |
| dc.subject | Binder Jetting | en |
| dc.subject | Sand Casting | en |
| dc.title | Design, Fabrication and Testing of Fiber-Reinforced Cellular Structures with Tensegrity Behavior using 3D Printed Sand Molds | en |
| dc.type | Thesis | en |
| thesis.degree.discipline | Mechanical Engineering | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |
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