Manufacturing and evaluation of the tensile properties of 3D printed human hair reinforced composites

Abstract

This thesis proposes a novel method to 3D print human hair-based polymer composites. Human hair is a biological fiber whose microstructure is well-defined. It possesses high tensile strength, thermal insulation, a unique chemical composition, and elastic recovery, among other qualities. However, its delayed breakdown causes numerous environmental issues. Although there are many viable applications for hair, it is still regarded as biological waste. In light of this, this study aims to investigate the feasibility of producing a class of polymer composites reinforced with short human hair fibers and continuous human hair fibers using SLA 3D printing technique. The first study used short human hair fibers to 3D print polymer composites as a proof of concept. Short human hair fiber-reinforced composites in the weight percentage of 1,5,10,15, and 20 were fabricated, and a tensile test was performed to determine the ultimate tensile strength of the composites. Although the concept of 3D printing natural fibers using SLA 3D printing was successfully proved, the strength of the fabricated composite specimens was substantially low compared to the neat polymer specimen due to the presence of voids and poor interfacial adhesion between the fiber and the matrix. Hence in the second study, the focus was to develop effective surface treatment techniques to improve the interfacial adhesion between the fiber and the matrix. The second study also investigates using continuous human hair fibers instead of short human hair fibers to fabricate composites using 3D printing. Human hair fibers were modified by grafted with MA-POSS and cold air plasma treatment. The effect of the surface treatment was investigated by performing single-hair pull-out tests. Post surface modification, human hair fibers were used to 3D print tensile specimens using SLA 3D printing to determine the effect of surface treatment of the fibers. SEM and an optical microscope were used to study the surface morphology of the modified fibers. XPS was performed to confirm the grafting of MA-POSS on the human hair fibers. Voids, fiber volume, and fiber orientation were determined by performing Micro-CT.