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Table 12. Failure probability of specimens Specimen type Failure probability
000 0
001 0
002 0.419767
010 0
011 8.54E-06
012 0.977041
100 0
101 0
102 0.994935
110 0
111 0.00161082
112 1
The results of tensile test were used for FORM analysis of the tensile strength at which failure probability was estimated. As a result of FORM analysis, PLA material was used and printing in the x-axis direction, and the higher the infill rate, the higher the probability of having the ultimate tensile strength of 30 MPa or more.
43
5 CONCLUSIONIn this thesis, The experiments to analyze experimental parameters that can improve the mechanical properties of the FDM 3D printed products are conducted . More specifically, tensile tests are conducted on a single material and dual material specimen to identify the effect of the various experimental parameters that can add up to the enhancement of the mechanical properties of 3D printed products. Moreover, the composite filaments of the thermoplastic matrix and carbon materials for the FDM process are tested to verify the enhancement of tensile strength. As a result, The assessment of the mechanical properties improvement of the printed product by the FDM process can be presented although the FDM 3D printer which is used for this thesis is the entry-level printer.
Secondly, the statistical methods to estimate the maximum tensile strength of the 3D printed products before printing of the actual products are examined. The Gaussian process to estimate nonstationary mechanical properties and its uncertainties with respect to the infill rate can be used.
The reliability analysis software FERUM (Finite Element Reliability Using Matlab) also proposes the probability that the maximum tensile strength of the printed product exceeds a certain pre-defined value.
In conclusion, we can apply this thesis to the efficient multiple material printing and to save material and the printing time. Even if various materials are used in the same ratio, the efficiency of mechanical properties can be increased. Also, to find optimal parameters for a specific tensile strength and print quickly with fewer materials can be conducted. It is possible to design more improved stability in terms of structure using the estimated mechanical properties. When an excessive load is applied to a specific part, it can be used for safety device by designing it to break at a characteristic load or more.
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