Monte Carlo simulations of electrical conductivity in short fiber composites.

摘要

The transport properties of conductive fiber composites are strongly dependent on the interactions between the conductive contents and their overall distribution, which is associated with the percolation and conduction of the relevant fibrous network. In this study, there are two models built to investigate the various factors that affect the effective electrical conductivity of short fiber reinforced conductive composites, via Monte Carlo simulations and finite element approaches.;First, a three-dimensional model was constructed to study the coated carbon fiberglass as the conductive filler. The fibers are modeled as randomly distributed three-dimensional cylinders with each cylinder consisting of a nonconductive core covered by a permeable conductive layer. By discretizing the interconnected surfaces of individual fibers, a finite element method is applied to evaluate the equivalent electrical conductivity of the entire system. In comparison with the model consisting of solid fibers, it has been shown that the coated structure can attain much higher conductivity.;Second, a reduced three-dimensional method was built to study general conductive fiber filler. Fibers are modeled as randomly distributed one-dimensional line segments in the three-dimensional space, and the contact conductivity between fibers are modeled by gap elements having the distances between fibers as their lengths and contact areas between fibers as their cross-section areas. This method can investigate the contact problem between fibers independently.;In both of the two models, Monte Carlo simulations are performed to quantify the relationships between the conductivity and many factors, to name a few: the fiber volume fraction, the fiber aspect ratio, and the distribution of fiber orientation angles. It has been shown that fairly reasonable results can be attained by both of the two models, and the reduced three-dimensional model provides a strong tool to study contact related problems in fibrous network. These findings can be used as guidance in designing the next generation of multiscale conductive composites.