Abstract
The purpose of this study is to develop a methodology for separating and manipulating singular carbon fibers and conducting tensile pullout tests to investigate the micromechanics of additive manufactured short carbon fiber reinforced composites. The experimental procedure follows a four-step process for preparing the ink, separating the fibers, printing the DIW sample with embedded fiber, and conducting the pullout test. The pullout testing is conducted once the DIW samples are cured and utilizes a custom mount to hold the sample. Throughout the experiment one ink per fiber alignment is used, the nozzle diameter remains constant, the pullout testing parameters remain the same, and all inks are printed and cured within 7 days of adding the hardener (to eliminate any significant changes in viscosity.) The average rate for fiber separation is about 5-7 minutes per fiber and in less than 18-20 hours to fully fabricate, cure and test samples—5 to 10 samples fabricated and 15-24 hours for the mounting epoxy (JB Weld) to cure for pullout testing. Based on the results of the methodology, it is seen that randomly aligned fibers exhibit a greater interfacial shear strength when compared to aligned fibers. Furthermore, in pullout testing, the max load for debonding is multiple times greater than that of the aligned fibers—contradicting traditional composite theory.