Sensitive strain monitoring of SiC fiber/epoxy composite using electrical resistance changes

This paper presents a sensitive strain-monitoring composite as compared with carbon fiber reinforced plastics (CFRP) using electrical resistance method. Carbon fibers in CFRP are useful as sensors under tensile load to detect fiber fracture and strain of the composites using electrical resistance change. However, the electrical resistance change resulting from fiber breaks is not sensitive at low-strain regimes because of the electrical conduction among neighboring fibers. In this study, surface oxidized SiC fibers were applied to prevent electrical conduction resulting from contact of neighboring fibers. Model specimens were fabricated by embedding as-received or oxidized SiC fibers into epoxy resin. Then, electrical resistance changes were measured under monotonic and loading–unloading tensile tests. Consequently, electrical resistance of oxidized SiC fiber specimens increased remarkably with increasing strain in comparison to as-received SiC fiber specimens as well as CFRP. The fibers were isolated electrically from each other by the SiO2 layer on fiber surface. Cumulative fracture probabilities of oxidized fibers embedded in the model specimens were predicted from measured electrical resistance change. The strength distributions were analyzed based on Weibull statistics.