Electrical resistance change in carbon fiber cement composites for nondestructive integrity monitoring.

摘要

The scope of this dissertation encompasses three major research focuses. The first involves the evaluation of the potential of carbon fiber reinforced concrete to serve as an intrinsically smart material capable of providing some information as to the conditions of internal stress, strain and cracking in the absence of any visible exterior signs of damage. The second concentration is an investigation on the applicability and the methodology for the use of electrical resistance measurements as the nondestructive means of extracting this information about physical integrity from the material. The third purpose of this dissertation is to provide arguments, on the basis of improved mechanical and durability properties, that carbon fiber-reinforced concrete could be utilized as structural concrete.; Among the major findings: Carbon fiber reinforced concrete has the ability to serve as a smart material and electrical resistance measurements can be used as a nondestructive means of evaluation. The signal that is manifested is a reversible change in resistance when cracking is not significant (for example, when stress-strain response is still elastic), and an irreversible increase in resistance when cracking takes place. Smart material capability exists even at low fiber volume contents (0.2% to 1.0%). The electrical resistance of the composite is very sensitive to changes in temperature. No detrimental effects are observed in compressive strength through the addition of carbon fibers. Significant improvements in the load at failure as measured through compact tension tests are observed for increased fiber volume contents.