Abstract:
Brittle-matrix composites with matrices that were not totally electrically insulating were found to change electrical resistance upon loading such that reversible strain caused the resistance to change reversibly and damage caused the resistance to change irreversibly. This electromechanical behavior allows dynamic strain and fatigue damage to be monitored simultaneously without the use of embedded or attached sensors, as the composites are themselves sensors. This new technique has been demonstrated for carbon-matrix and cement-matrix composites. The carbon-matrix composite with continuous carbon fibers was particularly effective for damage sensing; even damage in the first cycle of tensile loading at a stress amplitude of just 20% of the fracture stress (in the elastic regime) was detected. The cement-matrix composite with short carbon fibers (0.2-0.5 vol.%) was particularly effective for strain sensing; the gage factor Fractional change in resistance per unit strain) was as high as 1000, compared to 10 for conventional strain gages.
(Ref. SXVIII-026-97)
Source: NDE of Ceramics '97 May 4-7, Symposium on Nondestructive Evaluation of Ceramics
at the American Ceramic Society 99th Annual Meeting, Cincinnati, Ohio.
Buying the Symposium Proceedings from the American Ceramic Society.
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