Material Extrusion Additive Manufacturing of Thermoset and Thermoplastic Composites
Open Access
- Author:
- Peeke, Lachlan M
- Graduate Program:
- Additive Manufacturing and Design (MS)
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 24, 2021
- Committee Members:
- Timothy Simpson, Program Head/Chair
Michael Anthony Hickner, Thesis Advisor/Co-Advisor
Nicholas Alexander Meisel, Committee Member - Keywords:
- 3D Printing
Additive Manufacturing
Silicone
Thermoplastics
Composite - Abstract:
- Additive manufacturing (AM) is a disruptive new manufacturing process that gives designers freedom for creating highly complex shapes through free-form fabrication. Through the layer-by-layer process, engineers have been able to mix and match different materials inside one geometry to create novel composites. One of the downsides of the current technology is the limited number of materials available for AM. The majority of polymers used in extrusion AM are thermoplastics because they are easy to process in affordable machines. While mechanically robust, thermoplastics are known to weaken with increases in temperature or exposure to solvents. Traditional manufacturing has a much larger variety of polymers available with a wide array of unique properties such as chemical resistance or biocompatibility. These unique properties can be achieved through different types of thermosetting polymers such as silicone. Silicone-based products can be found everywhere from medical devices to engine seals. With AM, a composite structure of thermoplastics and thermosets would yield an end product with mechanical strength and chemical properties that exceed the individual materials. This work consists of three main sections: (1) the processes developed to support the printing of the dual material composites, (2) tensile tests to demonstrate the result of thermoplastic reinforcement patterns in a silicone matrix, and (3) a study on the shear-thinning trends of silicones to describe ideal flow properties. The key innovation of this work is a new process that was developed to print reinforced silicone components. This process relied on a multi-material approach to place silicone and reinforcement in any desired location in the printed part. Although much research touches on the multi-material aspect of AM, the process presented manipulates two dissimilar materials in one system. Individually, thermoplastics and thermosets have been printed with similar thermoplastic and thermoset materials. The process hinges on the combination of a fused filament thermoplastic extruder and a pneumatic fluidic dispenser, both of which are mounted on a 3-axis gantry and controlled through software-generated machine code. Tensile data was collected by printing three-layer composite structures out of high viscosity silicone and patterned meshes of commonly used thermoplastics in AM. To complement the new process developed in this work for fabricating multi-material reinforced silicones, flow properties of various silicone feedstocks were identified through collection and observation of material throughput out of the fluidic dispenser under various pressure inputs to the system. By developing a dual extrusion 3D printer that can process common thermoplastics with commercially available thermosetting silicones, the end product can demonstrate the best mechanical and chemical properties of each material. This work sets the stage for generalizable direct ink writing and fused filament fabrication of architected elastomers where hard and soft components can be designed into the three-dimensional structure of the part.