Experimental and cohesive finite element investigation of interfacial behavior of CNT fiber-reinforced composites

The interfacial behavior of carbon nanotube fiber (CNT fiber) composites is studied by using an experiment of fiber pulling-out from a polymer microdroplet and cohesive finite element method. A clamping fixture based on nano-tensile test system was designed for the microdroplet test of interfacial properties of the composites. Force-displacement curves and shear strengths of the interface between CNT fibers and polymers were obtained. Then an experiment-based cohesive finite element model was established to simulate the debonding and slipping of interface between the CNT fiber and polymer. Calculated force-displacement curves for fiber pullout from microdroplet are comparable with the experimental data. The debonding strength and failure feature of the interface of CNT fiber composite were discussed. It is found that the looseness of CNT fiber assembled by CNT bundles and threads leads to relatively low interfacial strength, which is very different from the traditional continuum-block fiber composites.