DEVELOPMENT OF HIGHLY FILLED BIO-BASED COMPOSITES FOR SUSTAINABLE, LOW-COST FEEDSTOCK: PROCESSING EFFECTS ON POROSITY AND FIBER ALIGNMENT

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Date

2023

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University of Texas at Austin

Abstract

A poly(lactic acid) composite with a high loading of bio-based fibers was developed using a combination of high-aspect ratio (AR) wood pulp and low-AR wood flour along with viscosity modifiers to maximize mechanical performance, maintain processability, and lower the cost and embodied energy of the resulting feedstock. An optimized composite formulation containing 40 wt.% of a blend of high- and low-AR natural fibers with a rice bran-based wax processing aid was scaled up to produce pellet feedstock using twin screw extrusion, and materials were compression and injection molded to investigate the effect of fiber alignment on material performance. The feedstock was then printed on the Big Area Additive Manufacturing system at Oak Ridge National Laboratory. Print parameters including temperature gradients, screw and gantry speeds, layer times, and nozzle designs were varied to minimize sharkskinning, warpage, and porosity of the final parts. A strong effect of the nozzle size on the resulting porosity was observed, and consistent trends between decreasing porosity, increasing fiber alignment, and increasing mechanical performance were identified after printing with different nozzles, compression molding, and injection molding.

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