Relationship of dielectric property change to composite material state degradation

Polymer matrix composites are widely used in many industries, i.e. aerospace, microelectronics, energy storage etc., because of their unique properties and performance. During their service life, changes of material state caused by deformation and damage accumulation under combined mechanical, thermal and electrical fields requires fundamental understanding to support design of those material systems. Heterogeneous material systems are inherently dielectric as determined by their complex morphology. Dielectric properties of such materials are altered by many factors, e.g., electrical and structural interactions of the particles, and the shape, orientation and distribution of the constituents of the material system. When damage occurs, new phases are created as micro-defects, and grow progressively, interact, and accumulate. The dielectric properties of the composite system also change in a manner that uniquely reflects those details. In the present work we report a non-invasive, in-operando technique to study changes in dielectric properties during progressive damage accumulation in composite materials subjected to mechanical loading.