Design of Thermoformable Composites and Advanced Manufacturing: Linking Processing, Microstructure, and Service Life Performance

Abstract

Engineered materials continue to evolve at incredible rates, serving an expansive range of consumer, industrial, and research needs. Composites, specifically polymer composites, offer lightweight alternatives with nearly unlimited combinations of constituents for both niche and broad applications. In parallel, advanced manufacturing techniques expand to accommodate precise control over these novel materials. For instance, additive manufacturing (AM) has revolutionized the rapid production of component parts since the commercialization of stereolithography in the 1980s and is now hailed for design freedom in complex structures and low material waste. Originally conceived for polymers, all classes of materials are now being exploited and produced in tandem with additive processes to push the possibilities of engineered micro- and macro-structures. In the case of AM, as well as other manufacturing techniques, there is an opportunity to thoughtfully design multifunctional materials, especially composites, in which each element can provide specific functions for targeted applications. Bulk material properties are induced through careful selection of the matrix reinforcement elements and further property tuning can stem from refinement of component manufacturing parameters, such as production temperature or post-process treatment. However, despite being crucial towards the improvement of composite design, developing the interconnected knowledge for each composite system and/or manufacturing technique can be exhaustive. Through two unique composite systems, this research investigates the relationship between manufacturing parameters, microstructural elements, and physical performance to conclude generalizable correlations for future iterations. In the first system, we analyze a continuous carbon fiber reinforced polyphenylene sulfide filament for fused filament fabrication. Here, we characterize two generations of filament designs and modify print tooling in attempt to maximize composite mechanical performance and potential service life/reliability. While still stronger (in tension) than all commercially available polymer composite filaments, we find that the stiffness of carbon fibers combined with the severe deposition angle of current commercial 3D printers leads to inherent process induced defects, which reduce strength and reliability. We can begin to alleviate these defects with improvements to initial composite morphology and the extruder nozzle design. In the second system, we utilize a sustainable feedstock, algae, as a potential matrix platform for biodegradable biocomposites. A deep investigation into algal biomatter transformation informs our correlation between its thermomechanical manufacturing (hot-pressing) and mechanical/chemical properties. We explore the complete life cycle of our biocomposites, from feedstock composition to changes during thermomechanical processing and ultimately end-of-life degradation. That knowledge informs intentional manipulation of the service life in a targeted product application. While vastly different material systems, the findings from these efforts will provide both researchers and manufacturers critical and diverse knowledge as to how production processes influence the manufacturability and resulting mechanical behavior of both synthetic and natural composite structures. Armed with informed cause and effect, we can then lead production of a new generation of advanced composite materials.