Rapid Prototyping of Functionalized Polymer Composites
Michael Elia Aziz Dawoud;
Abstract
Polymers and polymer composites are nowadays used in several fields of application, such as in sporting, household goods, structural, and engineering applications. Prior to the large scale fabrication, product design; simulation, and prototype visualisation are common stages. Especially the latter stage is often very time consuming. In the l980’s, rapid prototyping techniques were developed to facilitate this modelling and visualisation of products. Several various technologies have accordingly evolved, making it possible to produce the three-dimensional model from different materials such as gypsum, wax, or even metals, ceramics, and polymers. The rapid development of technologies and materials has supported the desire to not only model the final product, but also to test it for functionality, such as load carrying characteristics, thermal, chemical, and physical behaviours.
The present thesis handles this specific challenge. For this purpose, the thesis is divided into four sections. In the first stage a Do-It-Yourself (DIY) 3D printing machine following the Fused Deposition Modelling (FDM) technique is designed, optimised, and constructed. In a following stage three different functional behaviours have been analysed: (1) Mechanical performance, (2) tribological behaviour and (3) electrical conductivity patterns. For each an experimental setup was designed to analyse the process-specific behaviour of the material. This implies the variation of the main process parameters; raster gap, and orientation. To improve the performance, the incorporation of additives, where appropriate, was considered. The following paragraphs describe in more detail the individual stages conducted throughout this study.
The FDM process simply builds up a 3D model by printing a sequence of stacked layers. The machine thus deposits a thermoplastic melt through a heated nozzle on a platform to form the individual layer. Then the nozzle moves up by the amount of the layer thickness, to build the next layer. This is repeated until the entire part is complete. The designed DIY machine comprises a 1200W heater that heats a bed of tempered glass. The printing nozzle has an opening of 1.0mm. The machine is further equipped with 3.0A stepper motors. The machine is controlled by an Arduino Mega control system. The initial design of the machine has been successively improved to enhance the accuracy of the printed products. The overall specifications of the machine are its printing speed of 30mm/s, a total working volume of 380×280×120mm. The machine is developed to process polymeric materials and their composites having melting temperatures up to 320°C.
To describe the mechanical performance of resulting 3D parts, acrylonitrile butadiene styrene (ABS) specimens with a raster angle varying from 0 to 75° at both negative and positive raster gap were printed. Thus process-specific material performance in terms of tensile, flexural, and impact properties were determined. As a reference, injection moulded parts of the same material were fabricated and similarly examined. This study shows that the use of negative raster gap nullifies the effect of the raster angle, where the internal structure of the printed specimen becomes comparable to that prepared by injection moulding. Applying positive gap, results into optimum properties at a printing angle of 45°. However, it is to be noted that 3D printing generally results in weaker mechanical properties when compared to injection moulding. Linking to the next experimental stage, the graphite flakes were added to the ABS matrix. This generally caused the deterioration of the mechanical properties which only started to increase at 10% weight concentration when compared to pure matrix.
The second examination of the behaviour includes the investigation of the tribological behaviour of the FDM fabricated specimens. To improve the frictional behaviour, graphite flakes in varying concentrations (ranging from 0 to 10 %Wt.) were added to ABS. In this respect, both material and process-specific properties were examined. Generally, a positive gap results in a higher coefficient of friction (COF) than with negative gap but accompanied by a higher specific wear rate. An angle of 15° results in the highest COF while an angle of 60° results in the lowest COF with acceptable wear rate. A
The present thesis handles this specific challenge. For this purpose, the thesis is divided into four sections. In the first stage a Do-It-Yourself (DIY) 3D printing machine following the Fused Deposition Modelling (FDM) technique is designed, optimised, and constructed. In a following stage three different functional behaviours have been analysed: (1) Mechanical performance, (2) tribological behaviour and (3) electrical conductivity patterns. For each an experimental setup was designed to analyse the process-specific behaviour of the material. This implies the variation of the main process parameters; raster gap, and orientation. To improve the performance, the incorporation of additives, where appropriate, was considered. The following paragraphs describe in more detail the individual stages conducted throughout this study.
The FDM process simply builds up a 3D model by printing a sequence of stacked layers. The machine thus deposits a thermoplastic melt through a heated nozzle on a platform to form the individual layer. Then the nozzle moves up by the amount of the layer thickness, to build the next layer. This is repeated until the entire part is complete. The designed DIY machine comprises a 1200W heater that heats a bed of tempered glass. The printing nozzle has an opening of 1.0mm. The machine is further equipped with 3.0A stepper motors. The machine is controlled by an Arduino Mega control system. The initial design of the machine has been successively improved to enhance the accuracy of the printed products. The overall specifications of the machine are its printing speed of 30mm/s, a total working volume of 380×280×120mm. The machine is developed to process polymeric materials and their composites having melting temperatures up to 320°C.
To describe the mechanical performance of resulting 3D parts, acrylonitrile butadiene styrene (ABS) specimens with a raster angle varying from 0 to 75° at both negative and positive raster gap were printed. Thus process-specific material performance in terms of tensile, flexural, and impact properties were determined. As a reference, injection moulded parts of the same material were fabricated and similarly examined. This study shows that the use of negative raster gap nullifies the effect of the raster angle, where the internal structure of the printed specimen becomes comparable to that prepared by injection moulding. Applying positive gap, results into optimum properties at a printing angle of 45°. However, it is to be noted that 3D printing generally results in weaker mechanical properties when compared to injection moulding. Linking to the next experimental stage, the graphite flakes were added to the ABS matrix. This generally caused the deterioration of the mechanical properties which only started to increase at 10% weight concentration when compared to pure matrix.
The second examination of the behaviour includes the investigation of the tribological behaviour of the FDM fabricated specimens. To improve the frictional behaviour, graphite flakes in varying concentrations (ranging from 0 to 10 %Wt.) were added to ABS. In this respect, both material and process-specific properties were examined. Generally, a positive gap results in a higher coefficient of friction (COF) than with negative gap but accompanied by a higher specific wear rate. An angle of 15° results in the highest COF while an angle of 60° results in the lowest COF with acceptable wear rate. A
Other data
| Title | Rapid Prototyping of Functionalized Polymer Composites | Other Titles | النمذجة السريعة لمؤلفات البوليمرات الموظفة | Authors | Michael Elia Aziz Dawoud | Issue Date | 2015 |
Attached Files
| File | Size | Format | |
|---|---|---|---|
| G12165.pdf | 211.65 kB | Adobe PDF | View/Open |
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