SUMMARY

Cellulose nanocrystals (CNC) are ideal candidates for reinforcement in polymers and polymer matrix composites due to their high specific modulus, and strength characteristics. In this study, the interfacial and mechanical properties of cellulose nanocrystals (CNC) coated glass fiber/epoxy composites were investigated as a function of the CNC content on the surface of glass fibers (GF). Chopped GF rovings were coated with CNC by immersing the GF in CNC (0-5 wt%) aqueous suspensions. In addition, the mechanical properties of short glass fiber/epoxy SMC composites containing cellulose nanocrystals (CNC) as an auxiliary component within the epoxy resin and made using sheet molding compound (SMC) manufacturing methos were investigated as a function of the CNC content. CNC up to 1.4 wt% were dispersed in the epoxy to produce the resin for SMC production. Single fiber fragmentation (SFF) tests showed that the interfacial shear strength (IFSS) increased by ~60% in composites produced with CNC coated GF as compared to uncoated GF, suggesting an enhancement of stress transfer across the GF/matrix interface. The role of CNC coatings on the tensile, flexural, and thermo-mechanical properties of the CNC-coated GF/epoxy composites was investigated. Incorporation of 0.17 wt% CNC in the composite resulted in increases of ~10% in both elastic modulus and tensile strength, and 40 % and 43 % in flexural modulus and strength respectively. The incorporation of 0.9 wt% CNC in the SMC composite resulted in increases in elastic modulus, tensile strength and elongation at break by ~25%, 30% and 22%, respectively and 44% and 33 % in flexural modulus and strength respectively. Concentrations of CNC up to 0.9 wt% in the SMC composite did not alter the impact energy. In conclusion CNC coatings on GF and CNC dispersion within an epoxy matrix alter the GF/matrix interface resulting in improvement of the mechanical performance of the corresponding composites.