Prediction on electrical resistivity of thin‐ply unidirectional composites considering electric tunnel effect

This article presents a model for equivalent conductive paths to predict the resistivity of thin‐ply carbon fiber reinforced unidirectional laminate (UDL), which incorporates electric tunnel effect. A statistical method was used to calculate the effective intra‐laminar conductive contact ratio and the number of inter‐laminar conductive pathways. Resistivities of four samples with ply thickness varying from 0.02 to 0.1 mm were calculated. A detailed comparison between the predicted and measured resistivities in the longitudinal, transverse and thickness directions validates the present model, which reveals the influence of ply thickness on the resistivity of the samples. Analysis of the model indicates that the resistivity of UDLs in the fiber direction is mainly dependent on the volume fraction, and the resistivities in their transverse and thickness directions are related to both the volume fraction of fibers and the microstructure of UDLs. Unidirectional laminates made from ply prepreg aretypical structural units of the carbon fiber‐reinforced composites, and the electricalproperties of composite laminates are inevitably affected by their microstructures.The equivalent conductive paths were used to predict the resistivity ofunidirectional composite laminates. The ultra‐thinning of the ply was found tohave size effects on the improvement of conductivities in their transverse andthickness directions of the composited laminates.