Characterization of direct print additive manufacturing process for 3D build of a carbon nanostructure composite

Abstract

This project is a focus on characterizing the process for actualizing three dimensional structures out of a carbon nanostructure composite via a direct print additive manufacturing process. Manufacturing parts additively enables for realization of geometrically complex shapes that often times cannot be manufactured any other way. The specificity of a material's properties have to be such, that the processing method can precisely place and bond material to itself in a highly repeatable manner. Commercial materials for additive manufacturing are have been optimized with these goals in mind and, therefore, often times lack the rigor and robustness for many applications.

The addition of nanomaterials is promising approach to enhance certain properties of AM materials without drastically altering their critical processing characteristics. This study looks into the reinforcing a commercial Stereolithography resin (DSM Somos™ Watershed 11122) with two types of carbon nanostructures (multi-walled carbon nanotubes and carbon nanofibers) in an attempt to improve mechanical characteristics of the bulk material. Related work has shown to not exceed concentrations over .5% (w/v) such that the material is still compliable with the AM technology. This study attempts to exceed these loading ratios, by attempting concentrations of: 1) 1% (w/v) 2) 2.5% (w/v) 3) 5% (w/v) 4) 10% (w/v).

A direct write system from nScrypt Inc. (Orlando, FL) is implemented as the extrusion method for the nanocomposite materials. An ultra-violet emitting radiation source is paired up with the nScrypt tool form a direct print additive manufacturing process that dispenses material then cures it right after. All the different processing characteristics and control variables are explained in great detail, as well as the design considerations for fabricating a part with this technique. The impact of the control parameters to dispensed features are observed and measured. Statistical data is generated from this for the design of parts to be built with the system.

Test specimens for mechanical evaluation are designed based off of the parameter measurements and observation of the material within the system. The test specimens are built from the different nanocomposite concentration and a control sample are evaluated until failure under tensile loads. The fractured specimens are imaged under a scanning electron microscope to analyze layer interfaces and fracture characteristics. A thermal evaluation with photo-DSC is done on the materials to document their behavior under elevated temperatures (0°C - 300°C).

Background on the technologies, materials, and processes is provided first. A through discussions general AM workflow, technology, and history is given. Then a focus into pertinent technologies (Stereolithography) is discussed in detail. A breadth of direct write technologies and applications are introduced with an emphasis in the one (nScrypt, DPAM) utilized in this study. Finally, carbon nanostructures are introduced.