5. Conclusions
The idea of high volume production of light weigh composites with no compromise in mechanical properties was verified by replacing part of the GF with CNC in GF/epoxy composites made using SMC manufacturing method. It was demonstrated that introducing small amount of CNC, i.e. 1 and 1.5 wt%, in epoxy resin used in the SMC manufacturing process allowed removing 10 wt% GF from SMC composites reducing the composite weight by 7.5% without any reduction in tensile and flexural properties. Enhancement in storage and rubbery moduli were also recorded for both CNC/epoxy and GF/CNC-epoxy SMC composites, demonstrating the stiffening effect of CNC. In addition, Tg of 25GF/CNC-epoxy SMC composites with 1.5 wt% CNC slightly increased compared to that of the corresponding composite with no CNC. Specifically, incorporation of 1 and 1.5 wt% CNC in 25GF/CNC-epoxy SMC composites increased the tensile and flexural modulus by 15% and 11% respectively and flexural strength by 14% with respect to the properties of the corresponding SMC composites with no CNC. Significantly, the enhanced properties of 25GF/CNC-epoxy SMC composites increased to the level of 35GF/epoxy SMC composites with no CNC, indicating that a 7.5% lighter (lower density) composite achieved the required mechanical properties of a composite with 10 wt% more GF. Further, it was found that introducing CNC does not alter the impact energy; however, taking out GF reduced the impact energy. The results of this study indicate that producing high volume lightweight SMC composites that meet industrial standards is feasible through using cellulose nanomaterials.
