Effects of graphene functionalization on mechanical properties of carbon fiber laminate composites

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical EngineeringGraphene is a marvelous structure that has an incredible mechanical, electrical, and thermal properties. However, graphene fails to retain its outstanding properties during agglomeration due to its enormous specific surface area. To solve this problem, an established functionalization coating technique whereby silane molecules are applied to the pristine graphene surface improves its dispersion and stability in a polymeric composite. In this thesis, functionalized graphene was incorporated with a carbon fiber-reinforced polymer (CFRP) composite to improve its mechanical and viscoelastic properties. Successful integration of the 0.5 wt% silanized graphene in the CFRP composite leads to the improvement of ultimate tensile strength up to 58.41% from the base composite, with 8.44% improvement from the same amount of pristine graphene CFRP composite. In the evaluation of tensile strength, the 0.25 wt% and 1 wt% silanized graphene composites outperformed pristine graphene composites by 10.64% and 16.71%, respectively. Additionally, there was 7.35%, 9.97%, and 13.5% tensile modulus improvement in the 0.25 wt%, 0.5 wt%, and 1 wt% of silanized graphene, respectively, compared with pristine graphene composites. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests were used to characterize the graphene and silanized graphene, and C-scan was performed for the qualitative analysis of the manufactured CFRP nanocomposites. A further study using dynamic scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed a staggering glass transition temperature (Tg) shift of about 19.55oC for 0.25 wt% silanized graphene nanoinclusion. However, the highest amount (1 wt%) of graphene or silanized graphene degraded the mechanical strength but promisingly improved the viscoelastic characteristics of the CFRP composites. Therefore, the functionalized graphene proved to be a better candidate against pristine graphene in the development of graphene-filled CFRP nanocomposites