In situ health monitoring and repair in composites using carbon nanotube additives

The authors demonstrate a simple, effective and real-time diagnostic, and repair technique featuring electrically conductive carbon nanotube additives that are infiltrated into the host structure. They show that by monitoring volume and through-thickness resistance, one can determine the extent and propagation of fatigue-induced damage such as crack and delamination growth in the vicinity of stress concentrations. The conductive nanotube network also provides opportunities to repair damage by enabling fast heating of the crack interfaces; the authors show up to 70% recovery of the strength of the undamaged composite. These advances could result in enhanced safety, reliability, and service life for polymer composites that are used in engineering applications. (C) 2007 American Institute of Physics.