فهرست مطالب peyman mihankhah

Hypothesis: 

Fused filament fabrication (FFF) method is widely used in additive manufacturing due to its benefits, such as ease of use, cost-effectiveness, and availability. The mechanical properties of polylactic acid (PLA) printed by the FFF method can be significantly improved by combining them with nanomaterials such as nanoclay and optimizing the printing process parameters such as printing temperature and raster angle.

In order to investigate and optimize the multi-objective 3D printing process of PLA nanocomposite samples reinforced by nanoclay, the response surface method (RSM) was used as one of the methods of design of experiments. Nozzle temperature (190, 210 and 230°C), raster angle (0, 45 and 90°) and nanoclay weight percentage (0, 2 and 4% by wt) were studied to optimize output responses. Melt mixing of PLA with nanoclay particles was done using a twin-screw extruder machine and a granulator machine. The composite granules of PLA were prepared with 2 and 4% (by wt) of nanoclay. The prepared composite granules were entered into a single-screw extruder and composite filaments were produced.

The analysis of parameter participation in the density data reveals that the weight percentage of nanoclay and the nozzle temperature exhibit the most substantial influence, while raster angle has the least impact. Conversely, when considering tensile strength results, the weight percentage of nanoclay is the dominant factor, while the interaction between the weight percentage of nanoclay and raster angle has the smallest influence among the parameters under investigation. The multi-objective optimization results revealed that the optimal process conditions to achieve maximum strength are a nanoclay weight percentage of 4% (by wt), a nozzle temperature of 230°C, and a raster angle of about 25.5°. The tensile strength of the parts produced is 33.78 MPa, and their density is at least 1.089 g/cm3.

The importance of environmental issues has increased the use of biodegradable polymers which nowadays have become among main components in medical and biological applications. In the present study, a new combined method of fused filament fabrication (FFF) and batch foaming was introduced to improve the properties of poly lactic acid. For this purpose, FFF samples were produced with infill percentages of 100, 80 and 60 and then, foamed in batch process. Due to the importance and effect of the void fraction on structural and mechanical performance as well as the biodegradability of materials with porous structure, especially for medical purposes, void fraction and impact strength were evaluated. The results showed that the void fractions of FFF samples were 3%, 13% and 25% in infill percentages of 100, 80 and 60, respectively while after the foaming they reached to 14%, 19% and 30%. The findings revealed that the impact strength of FFF foamed samples was improved compared to FFF solid samples. For samples with 100 infill percentage, the impact strength improved from 207 to 506 J/m2 due to the foaming procedure with nano-sized cells created by the batch foaming.