Measurement and Tailoring of Composite Electrical Properties

Deep dielectric charging and subsequent electrostatic discharge in composite materials are growing concerns as these materials are used ever more extensively in spacecraft. A previous study showed that electric properties are critical to this problem. The goals of the current investigation are 1) experimental measurements of the continuum electrical properties of a carbon fiber/epoxy composite and 2) the creation of a composite with electrical properties that can be tailored without affecting its mechanical properties. The measurement of the conductivity and dielectric strength of carbon fiber/epoxy composites showed that these properties are difficult to measure, are dominated by details of the composite microstructure, and should not be treated as continuum properties. Conversely, a tailorable glass fiber/epoxy system was created by adding conductive carbon black to the epoxy. This material has consistent and measurable properties. It has conductivity variable over three orders of magnitude, and dielectric constant variable by a factor of 16, with good dielectric strength and mechanical properties.