Prediction of Fracture and Detection of Fatigue in Ceramic Composites from Electrical Resistivity Measurements

Abstract

Fracture prediction and fatigue detection techniques in ceramic composites were examined. Composites with an electric conduction path were fabricated with ceramics having different electrical resistivity, using calcium fluoride powder as the insulating matrix and silicon carbide whiskers as the conducting additive. When a bending load was applied to the test piece, the electrical resistivity of the composites increased up to fracture. When the test pieces were repeatedly loaded below the fracture limit, there was a gradual increase of electrical resistivity before fracture. These phenomena suggested the possibility of predicting fracture and detecting fatigue in ceramic composites. The movement of whiskers disconnecting the conduction path and leading to an increase in electrical resistivity was confirmed by scanning electron microscopy observation.

Piezoresistive Cement-Based Materials for Strain Sensing

“…Composite piezoresistive materials include polymermatrix composites containing continuous carbon fibers (Schulte and Baron, 1989;Prabhakaran, 1990;Schulte, 1993;Kaddour et al, 1994;Muto et al, 1995;Sugita et al, 1995;Ceysson, et al, 1996;Wang and Chung, 1996b, 1997a,b, 1998Irving and Thiagarajan, 1998;Abry et al, 1999), carbon black (Kost et al, 1984;Pramanik et al, 1990;Radhakrishnan et al, 1994), metal particles (Radhakrishnan et al, 1994), short carbon fibers (Pramanik et al, 1990;Taya et al, 1998), cement-matrix composites containing short carbon fibers Chung, 1993, 1996a,b;Fu and Chung, 1996a;Fu et al, 1997Fu et al, , 1998, and ceramicmatrix composites containing silicon carbide whiskers (Ishida et al, 1994). The sensing of reversible strain had been observed in polymer-matrix and cement-matrix composites (Kost et al, 1984;Chung, 1993, 1996a,b;Radhakrishnan et al, 1994;Fu and Chung, 1996a;Wang and Chung, 1996b, 19971998Fu et al, 1997Fu et al, , 1998Irving and Thiagarajan, 1998;Taya et al, 1998).…”

Self-monitoring of strain in silicon carbide whisker reinforced silicon nitride

“…Damage self-monitoring has been previously reported in ceramic-matrix composites, such as a CaF 2 -matrix SiCwhisker composite [5], as the volume electrical resistivity increased irreversibly upon damage (probably due to cracks, which are electrically insulating).…”

Improvement in Mechanoluminescence Intensity of Ca[sub 2]Al[sub 2]SiO[sub 7]:Ce by the Statistical Approach

“…To improve the low reliability, many researchers have studied smart structural materials. 1,2 The electrical characteristics of smart structural materials are generally measured by using electrodes and electric wires. 1,2 It is difficult to measure the characteristics of moving things such as a gas turbine.…”

“…1,2 The electrical characteristics of smart structural materials are generally measured by using electrodes and electric wires. 1,2 It is difficult to measure the characteristics of moving things such as a gas turbine. Therefore, we have investigated various fluorescent materials with mechanoluminescence ͑ML͒ characteristic, and have developed fracture detection and visualization of the stress distribution system using ML phenomena.…”