International Workshop on Next-Generation Composite Materials and Structures 2026

Abstract

In 3D-printed continuous carbon fiber reinforced PLA, the carbon fiber sizing agent is formulated for epoxy resins, resulting in poor interfacial adhesion to the thermoplastic PLA matrix that limits the interlaminar and flexural performance. Exploiting the ability of green tea catechin to improve the wettability of carbon materials, we propose a simple treatment in which carbon fibers are ultrasonically cleaned in a commercial green tea beverage. Specimens were fabricated from the treated fiber using a double-nozzle 3D printer and tested mechanically. The treatment raised the interlaminar shear strength to about 1.4 times that of the untreated material and increased the flexural strength by up to about 13%, whereas the fiber-dominated tensile properties were unchanged. Scanning electron microscopy confirmed the improved adhesion between the carbon fiber and PLA, and FTIR analysis indicated a change in the ester carbonyl band that suggests transesterification between the gallate-type catechins and PLA at the interface. The green tea catechin treatment is thus a simple and effective interfacial treatment for enhancing the mechanical properties of environmentally friendly PLA composites.