Continuous carbon fiber polymer-matrix composites and their joints, studied by electrical measurements

Continuous carbon fiber polymer-matrix composites and their joints, as studied by DC electrical measurements, are reviewed. The resistance gives information on the microstructure and allows the self-sensing of strain, damage and temperature. In the case of composites with dissimilar fibers in adjacent laminae, the Seebeck effect allows temperature sensing, using the interface between laminae as a thermocouple junction. The resistance in the through-thickness direction can be apparently negative, due to entropy-driven electron backflow. The longitudinal resistance allows sensing of the glass transition and melting of the thermoplastic polymer matrix. The quality of composite-composite joints obtained by adhesion or fastening, and of composite-concrete joints obtained by adhesion, is revealed by resistance measurements.