Characterization of Carbon Nanofibre Reinforced Epoxy Composite using Nanoindentation and AFM/UFM Techniques

Abstract

Carbon nanofibre (CNF) reinforced epoxy composites were characterized using nanoindentation, Atomic Force Microscopy (AFM) and Ultrasonic Force Microscopy (UFM). These tests were supplemented with ultrasonic wave propagation and three-point bend test methods. CNFs were functionalised with oxygen to improve dispersion and adhesion in the epoxy matrix. The CNF/epoxy composites showed an improvement in modulus and hardness compared to those of neat epoxy resin. The improvement was dependent on the functionalisation treatment time; however, the increase was of a different magnitude when measured by three methods: nanoindentation, wave propagation method and three-point bend (TPB) test. Thus, the indention test technique is capable of providing mechanical properties from a limited size and/or quantity of nanocomposites, which is generally the case during the initial material development stage. Further, the AFM-UFM was able to characterize the dispersion behavior of CNFs in nanocomposites, which is an important factor to improve the mechanical properties of nanocomposites. However, UFM provided much clearer information about dispersion than AFM. Finally, AFM-UFM appears to be a promising technique for observing nanocomposites at nanoscale and it has potential for the mapping of the local surface stiffness at nanoscale.