8. Time Dependent Response of Composite Materials to Mechanical and Electrical Fields

The object of this paper is to broaden the familiar concepts of viscoelasticity and viscoelastic behavior of polymeric materials to the discussion of the (highly) nonlinear mechanical behavior of composite materials and to introduce relationships between that time-dependent mechanical response and the dielectric character of those materials. The foundation of the paper is a discussion of damage accumulation as the introduction of a ‘second phase’ into heterogeneous material morphologies and the interpretation of the influence of that accumulation process on the time dependent mechanical and electrical properties and behavior of those materials. It is the principal objective of the paper to establish science based relationships between the mechanical behavior of heterogeneous/composite materials under high-strain conditions and the response of those materials to alternating current or voltage inputs. Applications of the concepts will be discussed, including “design-defected composite materials” such as batteries, fuel cells, and separation membranes, and “service-defected composite materials” such as the structural composites used in airplanes, vehicles, and bridges. The purpose of the present work is to provide some coherence to that subject and to provide a foundation for the design of composite material systems.