Nanoindentation and mechanical properties of graphene oxide/poly (vinyl alcohol) composites

In order to investigate the effects of graphene oxide (GO) on the mechanical properties of polymer matrix composites, GO/poly (vinyl alcohol) (PVA) composites were prepared by solution mixing method firstly. Then, the structure, interfacial bonding properties, mechanical properties, creep behaviors and water swelling rate of GO/PVA composites were investigate by XRD, TEM, FTIR, DSC, nanoindentation and so on. The results show that GO can be dispersed well in the PVA matrix, both of them are mainly combined through hydrogen bond interaction which has higher interface bonding force. Comparing with that of pure PVA, the hardness and effective elastic modulus of 1wt% GO/PVA composite enhance by 28.9% and 23.3%, respectively, and the indentation creep depth declines by 19.8%. GO/PVA composites show the lower ratios of infinite shear modulus to instantaneous shear modulus, which indicates that GO improves the creep resistance of PVA. The addition of GO also improves the waterproofness of GO/PVA composites and decreases swelling factor. The experimental results of moisture absorption nanoindentation show that the mechanical properties of pure PVA decline with the moisture absorption time increasing, while the mechanical properties of GO/PVA composite almost remain the same after moisture absorption for 72 h. The obtained conclusions provide theoretic guidance for the research of graphene reinforced polymer matrix composites.