Electrical Resistance Reduction of Laminated Carbon Fiber Reinforced Polymer by Dent Made by Indentation without Cracking

Abstract

Laminated carbon fiber reinforced polymer (CFRP) composites have been used in many aircraft components. Because it is quite difficult to detect delamination cracking visually, many cracking monitoring methods have been proposed. One of these methods is the self-sensing method, where electrical resistance change is used to detect the damage to the laminated CFRP. For a thick CFRP plate, however, a delamination crack is usually accompanied by a dent. The dent causes a decrease in the electrical resistance of the CFRP plate. Although dent monitoring using this decrease in electrical resistance has been proposed, it is also important to clarify the mechanism of the decrease in electrical resistance. In this study, therefore, experimental investigations were undertaken to understand the mechanism of the decrease in electrical resistance induced by the dent. An elastic-plastic finite element analysis was also performed to confirm the material deformation under the dent. We found that a decrease in the fiber spacing in the thickness direction caused by plastic deformation causes contact between the fibers, and this causes the decrease in the electric resistance in the thickness direction.