An experimental study was conducted to determine the effect of complex geometries on the burning rate of materials made using additive manufacturing. Controlling heat release rate has applicability in limiting fire hazards as well as for designing fuels for optimal burning rate. The burning rate of a structure is a function of the material properties as well as the airflow through it, which is dictated by the geometry. This burning rate is generally proportional to the porosity for objects in which the flow is limited by the path constriction. The relations between porosity and burning rate are well studied for wood cribs, which are layers of wood sticks. Crib and other objects with various geometric features were constructed of ABS plastic and coal powder using additive manufacturing processes. A cone calorimeter using oxygen calorimetry was used to measure the heat release rate of the crib specimens. Within the flow limited burning regime, the burning rate of an object is proportional to the porosity factor. Porosity factors calculated from a 1-D theoretical burn rate model as well as from two empirical models were found to correlate the heat release rate results for the crib samples. The heat release rate results of the complex geometries generally correlated to the same porosity factor; however, the model was modified to account for differences between regularly shaped cribs and objects with different sized flow areas. Using the empirical models provides good correlation for the crib burning data and gives a clearer delineation between the flow-limited and surface area controlled regimes. / Master of Science / An experimental study was conducted to determine the effect of complex geometries on the burning rate of materials made using additive manufacturing. Burning rate of objects is dependent on material composition, as well as on the shape of the object itself. Controlling burning rate has applicability in limiting fire hazards in built environments, as well as in the design of fuels. The burning rate of a structure is related to the type of material and the capacity for airflow through it. This burning rate is generally proportional to a defined parameter called a porosity factor, which can encompass geometric and material properties. Relationships between porosity and burning rate for cribs, layered wood objects, have been established. In this work, cribs and more geometrically complex objects were constructed of red oak, ABS plastic and coal powder. The constructed specimens were burned and resulting data evaulated. These data were also used to compare empirical and theoretical crib porosity models. Burning rate results of the objects with complex geometries generally correlated to the same porosity factors; however, the models were modified to account for differences between regularly shaped cribs and objects with different sized flow areas. Using the empirical models provides good correlation for the burning rate data and requires less analytical effort than does the theoretical model.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77963 |
| Date | 08 June 2017 |
| Creators | Kraft, Stefan Marc |
| Contributors | Mechanical Engineering, Lattimer, Brian Y., Williams, Christopher B., Diller, Thomas E. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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