Functionalized Cellulose Nanocrystal Sizing to Enhance Mechanical Properties of Glass Fiber–Reinforced Epoxy Laminates

ABSTRACT This study investigates the effects of chemically functionalized cellulose nanocrystal (CNC) coatings on glass fiber (GF)‐epoxy laminate properties. Different types of modified CNCs, including sulfated, ion‐exchanged with MePh ₃ P, silylated with (3‐Aminopropyl)triethoxysilane, oxidized and oligomerized with tannic acid, and grafted with hexadecylamine, are slot die coated onto unidirectional GF fabrics prior to laminate fabrication. The CNC coatings are examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and contact angle measurements to evaluate the functionalization, morphology, and changes to hydrophobicity. The effect of CNC coatings on interfacial adhesion is determined using single fiber fragmentation tests, and their effect on mechanical properties is characterized using flexural and interlaminar shear strength tests. It is found that the hexadecylamine grafted CNC coating strengthens the GF‐matrix interface by up to 19%, and this enhancement provides additional improvement to the laminate flexural modulus and strength by 36% and 30%, respectively, in comparison to commercially sized (GF)‐epoxy laminates with no added CNC. This work demonstrates the potential of using CNC in GF sizing, as well as the importance of CNC surface chemistries on enhancing GF‐epoxy interfaces and composite performance.