ECCM15 - 15 TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012 1 Electrical-based methods for locating damage in composite structures Athanasios Baltopoulos 1, *, Nick Polydorides 2 , Antonios Vavouliotis 1 , Vassilis Kostopoulos 1 1 Applied Mechanics Laboratory, University of Patras, Rio - Patras, 26504, Greece 2 Energy, Environment & Water Center, The Cyprus Institute, Nicosia, Cyprus *abaltop@mech.upatras.gr Keywords: NDI, Damage sensing, Electrical methods, Location search Abstract Based on the assumption that structural health is directly related to electricity conduction, in the case of conductive composite structures, the electric field has been proposed as a means for damage detection in electrically conductive laminates. Studies for locating the damage and monitoring its evolution using the local variation of the electrical conductivity have been rather sporadic. Here we present a strategy to collect electrical data in 2D following tomographic approaches (Electrical Tomography - ET) and two strategies to post-process the data and locate the development of damage in conductive composite structures; - the Effective Dipole (ED) - the Electrical Tomography Inverse Problem (ETIP) These approaches utilize voltage measurements on composite parts injected with electric current. ED delivers point estimates of the damage location while ET delivers conductivity maps. Within the frame of the present work, a basic but informative description of the theoretical background of the methods and their application strategy is provided. We apply them to static cases for damage localization in CFRP. We present experimental results and predictions using both ED and ETIP. The findings are supported by Finite Element simulations. The results indicate that both methods are capable of indicating the location of the developed damage. More specifically ED suppresses the damage location prediction envelope as far down as 7% of the total inspection area. ETIP provides a comprehensive conductivity map (similar to that of a C-scan) where correlations with damage are indicated. Secondary processing steps can be implemented to provide clearer damage characterization. Both can easily be implemented for the real time in-situ damage monitoring, while ED proves to be much faster. The present work contributes in the direction of damage location in conductive composites structures, using information from the electrical field. 1 Introduction to electrical sensing approaches Non-Destructive Inspection & Evaluation (NDI and NDE) of composites is of great importance for quality assurance as well as for Structural Health Monitoring (SHM) of composite structures. With the increasing use of composites in advanced structures, the demand for non-destructive inspections and, whenever possible, of on-line SHM will become a necessity. Apart from the more traditional techniques such as Ultrasonics and Thermography, alternative approaches based on different physical field have been proposed for use in composites, such as X-Rays and electrical properties. In this paper, we use the electrical field for NDE of composite structures. Among the initial works proposing the use of electrical conductivity for sensing strain and damage in conductive composites was the work by Baron and Schulte [1]. The idea of electrical conductivity/resistivity for damage assessment is based on the