Browsing by Subject "Nylon 12"
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Item Improvements and effects of thermal history on mechanical properties for polymer selective laser sintering (SLS)(2015-08) Wroe, William Walker; Beaman, Joseph J.; Fish, ScottThis thesis investigates the relationship between the thermal history and mechanical properties for Nylon 12 tensile bars manufactured using Selective Laser Sintering. The thermal history is recorded using infrared imaging. In addition this thesis examines a new closed loop thermal control strategy for pre-heating the powder surface in a 3DSystems Sinterstation.Item Size effects in out-of-plane bending in elastic honeycombs fabricated using additive manufacturing : modeling and experimental results(2011-12) Mikulak, James Kevin; Kovar, Desiderio; Taleff, Eric M.; Rodin, Gregory J.; Bourell, David L.; Haberman, Michael R.Size effects in out-of-plane bending stiffness of honeycomb cellular materials were studied using analytical mechanics of solids modeling, fabrication of samples and mechanical testing. Analysis predicts a positive size-effect relative to continuum model predictions in the flexure stiffness of a honeycombed beam loaded in out-of-plane bending. A method of determining the magnitude of that effect for several different methods of constructing or assembling square-celled and hexagonal-celled materials, using both single-walled and doubled-walled construction methods is presented. Hexagonal and square-celled honeycombs, with varying volume fractions were fabricated in Nylon 12 using Selective Laser Sintering. The samples were mechanically tested in three-point and four point-bending to measure flexure stiffness. The results from standard three-point flexure tests, did not agree with predictions based on a mechanics of solids model for either square or hexagonal-celled samples. Results for four-point bending agreed with the mechanics of solids model for the square-celled geometries but not for the hexagonal-celled geometries. A closed form solution of an elasticity model for the response of the four-point bending configuration was developed, which allows interpretation of recorded displacement data at two points and allows separation the elastic bending from the localized, elastic/plastic deformation that occurs between the loading rollers and the specimen’s surface. This localized deformation was significant in the materials tested. With this analysis, the four-point bending data agreed well with the mechanics of solids predictions.