Dielectric Assessment of Composite Damage States

Abstract

The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. Performance of composite materials is altered by the initiation, accumulation, and interaction of discrete micro-fracture events. Detecting eventual damage growth and predicting the onset of component failure is a challenging task. While a strong foundation of understanding has been established for damage initiation and accumulation during the life of composite materials and structures, an understanding of the nature and details that define fracture path development at the end of life has not been established. In the present research, we analyze nonlinear deformation and damage development in a model composite microstructure by deforming it using nonlinear, conformal incremental mechanics analysis followed by conformal dielectric simulation set on the deformed state. Our studies reveal inflection points in the predicted global dielectric response vs. strain that are related to changes in local damage growth rates and modes that clearly indicate impending fracture. Capabilities of the new method are discussed.