Assessment of damage initiation and progression in composite laminates with embedded electrically active plies is modeled. Utilizing electrically active layers embedded in composite laminates as damage sensors is proposed by several researchers and is mainly assessed experimentally. Sensing damage using embedded electrically active plies is generally preferred over the use of surface mounted PZT wafers since the range of the latter is limited to a very narrow area underneath the surface, while multiple damage mechanisms can generally be found in several plies of the laminate. The solution presented invokes two levels of analysis. Firstly, on the laminate level, applied membrane loads and/or bending moments induce stresses in the plies according to some distribution factors, which depend on the elastic properties and thickness fractions of the plies. To obtain these factors, the conventional lamination theory is implemented. Secondly, on the ply level, each unidirectional composite ply, whether electrically active or inactive, is modeled using the Mori-Tanaka averaging model. Both the fiber and matrix stresses are computed and a response in the form of electrical displacement is found in the electrically active plies. Upon damage in certain plies, some eignstresses are applied such that the stress components, which invoke the damage criteria vanish. These eignstresses affect not only the failed plies but also other plies and subsequently the overall behavior of the laminate. Deviations in the electric response of electrically active plies from that found in the undamaged state serves as a damage detector. This paper outlines a transformation field methodology which implements the above formulation and shows examples for laminates subjected to bending moments. Variation of the electric displacement with the progression of damage is examined in terms of the location of the electroactive ply within the laminate thickness.
Micheal, Amany and Bahei-El-Din, Yehia, "Detecting laminate damage using embedded electrically active plies – An analytical approach" (2017). Centre for Advanced Materials. 3.