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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorSamuel, Johnson
dc.contributorMishra, Sandipan
dc.contributorWalczyk, Daniel F.
dc.contributorRyu, Chang Yeol
dc.contributorSahni, Onkar
dc.contributor.authorPicha, Kyle C.
dc.date.accessioned2021-11-03T08:53:52Z
dc.date.available2021-11-03T08:53:52Z
dc.date.created2017-11-10T12:49:55Z
dc.date.issued2017-08
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2064
dc.descriptionAugust 2017
dc.descriptionSchool of Engineering
dc.description.abstractOn the modeling front, predicting the temporal shape evolution of a droplet can aid process planning in a 3D printing of FrSCs environment. Given the ellipsoidal shape of the droplets encountered during the 3D printing process, the three time-dependent output parameters of interest include the height of the droplet (H), and its two relevant diameters D// and D⊥ that are measured in the directions parallel and perpendicular to the fiber axis, respectively. The model calculations presented in this thesis start with a substrate parametrization step involving a characterization of the diameter of the fibers, fiber bundles and fiber spacing encountered in the printing zone. This coupled with the knowledge of the inkjet printing parameters and the fluid properties of the ink allow for the subsequent calculations. The droplet shape is parametrized as an ellipsoidal cap. For every discrete time-step calculation, the model uses the equations of energy and volume conservation as well as an experimentally calibrated relation for the ratio D_(//)/H. This temporal expression involves 13 calibrated constants that connect non-dimensional fluid numbers to relevant substrate characteristics. The model also involves a free energy barrier calculation at every time increment that checks for the pinning of the D⊥ diameter. The validation experiments involved single droplet impingement studies using three inks under distinctly different inkjet printing conditions and substrates profiles. In general, the model prediction errors are observed to be under 7%. The free energy barrier calculation is a critical component of the model. In some cases, it contributes to a ~ 50% reduction in the model prediction errors.
dc.description.abstractThe high speed imaging study presented in this thesis investigates the spreading characteristics of droplets when deposited on fibrous substrates, under conditions relevant to 3D printing of aligned FrSCs. Both single and multi-droplet impingement studies are conducted on substrates with varying fiber number densities. The findings enable an effective understanding of the process planning issues relevant to the 3D printing of FrSCs. The single droplet impingement studies on stationary substrates reveal that the presence of fibers promotes droplet spreading along the length of the fibers. Occasional surface energy variations in the fiber mats in the form of voids and fiber bundles are also seen to affect the droplet shape and the characteristic spreading times. In the case of a moving substrate, the droplets are seen to spread the most during in-line printing, i.e., when the direction of the printing velocity coincides with the direction of fiber alignment. They spread the least during orthogonal printing, i.e., when the direction of the printing velocity is perpendicular to the direction of fiber alignment. The printing of straight lines shows an interesting edge retraction phenomenon that gets accentuated the most in the case of in-line printing. The findings of the high-speed imaging studies have been confirmed by 3D printing comparable artifacts using UV curable inks. These studies indicate that for a given fiber mat and UV curable ink combination, the choice of the in-line or orthogonal printing strategy has implications for the overall printing time, fiber content, edge resolution and surface quality of the 3D printed FrSC part.
dc.description.abstractFiber-reinforced soft composites (FrSCs) are a new class of composite materials made up of hierarchical, polymer fiber networks embedded within another soft polymer matrix. The objective of this thesis is to fundamentally study the liquid-substrate interactions relevant to the 3D printing of these FrSCs. The novel, multimaterial additive manufacturing process presented in this thesis combines the conventional inkjet-based printing of ultraviolet (UV) curable polymers with the deposition of electrospun fiber mats in between each printed layer. The process has been proven to manufacture multimaterial laminated nanocomposites having different 3D geometries. The dimensional accuracy of the parts is seen to be a function of the interaction between the liquid and solid interfaces. The thermogravimetric analysis (TGA) reveals that improvements in the mechanical properties are obtained without drastically altering the thermal degradation pattern of the base polymer.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMechanical engineering
dc.titleLiquid-substrate interactions relevant to 3D printing of fiber reinforced soft composites
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid178600
dc.digitool.pid178603
dc.digitool.pid178601
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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