The role of electrical anisotropy and effective conducting thickness in understanding and interpreting static resistance measurements in CFRP composite laminates

Abstract

This study is focused on (i) the experimental characterization of the anisotropic electrical resistivity of carbon fiber reinforced polymer (CFRP) composites and (ii) the development and experimental validation of predictive finite element (FE) models of the electrical response in CFRP laminates based on the concept of the effective conducting thickness. Two experimental methods have been developed to characterize the anisotropic electrical resistivities in three principle directions for the CFRP composite laminates using a direct current source. One method utilizes a traditional 6-probe resistance scheme and the alternative point-type 4-probe method is based on a handheld probe device similar to the JIS K7194 standard for homogenous plastics. An extensive experimental study has been conducted to characterize the anisotropic electrical resistivities of 16-ply unidirectional and 16-ply symmetric cross-ply IM7/977-2 and 32-ply unidirectional IM7/977-3 composites using the developed methods. Exploiting the concept of the effective conducting thickness, which describes the effective depth of current penetration through the thickness of an electrically anisotropic material, a unique methodology is developed for constructing FE models of these highly anisotropic CFRP materials. The concept of effective conducting thickness was identified as a critical component in achieving accuracy of the FE results as well as recovery of experimental resistivity from the alternative point-type 4-probe method. The FE models have been validated using the experimental results on the CFRP specimens of varying layup and thickness, and the techniques developed in this work may lead to advancements in non-destructive techniques in the areas of electrical characterization and damage sensing.

Electrically Conductive MXene-Coated Glass Fibers for Damage Monitoring in Fiber-Reinforced Composites

“…Additionally, SEM images of single fiber surfaces show loss of MXene coating due to friction from fibers sliding past one another during testing which adds to the increased electrical resistance observed. It is worth mentioning that fiber breakage within a composite system using DC measurements offers one failure mode within fiber-reinforced systems; however, to assess other types of failures, such as debonding or delamination, AC measurements can also be implemented [44][45][46]. Prior studies have shown MXenes can be incorporated into polymer matrices producing electrically conductive composites.…”

Determination of the anisotropic electrical conductivity of carbon fabric reinforced composites by the six-probe method

“…Hart and Zhupanska 33 developed a procedure to derive the anisotropic electrical conductivities from six-probe measurements on unidirectional composites. Their procedure expands upon work performed by Busch et al, 36 in which an analytical approximation is presented to measure the electrical conductivity of strongly anisotropic single crystals using the six-probe method.…”

“…In a more recent study, performed by Hart and Zhupanska, 33 the six-probe method, shown in Figure 2(e), has been investigated using uni-directional composites. In this method, an electrical current is applied through a line contact at positions A and B in the figure and voltages are measured in between these positions.…”