Apparatus, methodology, and modeling for continuous in-situ impregnation of dry carbon fiber tows with thermoplastic polymers for use in additive manufacturing

Authors
Garofalo, James, John
ORCID
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Other Contributors
Tichy, John
Narayanan, Shankar
Ozisik, Rahmi
Bucinell, Ronald
Walczyk, Daniel
Issue Date
2018-12
Keywords
Mechanical engineering
Degree
PhD
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute (RPI), Troy, NY. Copyright of original work retained by author.
Full Citation
Abstract
A novel co-extrusion system for continuous fiber reinforced thermoplastic composites was designed, fabricated, and tested. This new process, called In-Situ Impregnation, is a pultrusion process that impregnates continuous dry fiber reinforcement tows in-situ with thermoplastic for applications ranging from additive manufacturing using robotic manipulation to automated fiber placement. The performance goal was to design a co-extrusion system that directly uses raw materials (thermoplastic pellets and rolls of carbon fiber tow) instead of ‘prepreg’ tow in an effort to streamline and cut costs in advanced composites manufacturing and deliver fully customizable fiber orientation. Analytical and computational modeling was conducted to describe the flow rate of polymer through the system, impregnation of the fibers with polymer, heat transfer and temperature uniformity of the die system, friction and fiber tensioning, and the interfacial shear strength between the polymer and the fibers. Multiple experiments were conducted on the working pultrusion system varying polymer, exit geometry, die temperature, and volumetric flow rate of polymer from a thermoplastic screw extruder to gather process-ability and validate the models. A new test method was developed to evaluate the relative interfacial shear strength of a carbon fiber tow (bundle) and thermoplastic polymer, which was tested experimentally and results were obtained for the three polymers used. Microscopy techniques were employed to estimate the degree of impregnation and fiber volume fraction based on cross sections of the resulting composite tows. Future work includes commercialization of the technology, automation of the manufacturing system, and publishing the work in peer reviewed academic journals.
Description
December2018
School of Engineering
Department
Dept. of Mechanical, Aerospace, and Nuclear Engineering
Publisher
Rensselaer Polytechnic Institute, Troy, NY
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Rensselaer Theses and Dissertations Online Collection
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