Measurement and tailoring of composite electrical properties

Deep dielectric charging and subsequent electrostatic discharge in composit e materials are growing concerns as these materials are used ever more exte nsively in spacecraft. A previous study showed that electric properties are critical to this problem. The goals of the current investigation are 1) ex perimental measurements of the continuum electrical properties of a carbon fiber/epoxy composite and 2) the creation of a composite with electrical pr operties 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, ar e dominated by details of the composite microstructure, and should not be t reated as continuum properties. Conversely, a tailorable glass fiber/epoxy system was created by adding conductive carbon black to the epoxy. This mat erial has consistent and measurable properties. It has conductivity variabl e over three orders of magnitude, and dielectric constant variable by a fac tor of 16, with good dielectric strength and mechanical properties.