Fracture process zone of brittle composites

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7288779

Yu, C

An experimental-numerical analysis was used to study the fracture process zone (FPZ) trailing the crack tip in brittle composites. Two major parts are included in this dissertation. Part 1 is a static mode 1 fracture analysis of ceramic matrix composites. Part 2 is a mixed mode 1 and mode 2 dynamic fracture analysis of concrete. In Part 1, the FPZ which trailed a stably growing crack in SiC(w)/Al2O3 ceramic matrix composite was investigated through a hybrid experimental-numerical analysis. Surface displacements on the sides of three-point bend and wedge loaded-double cantilever beam (WL-DCB) specimens with chevron notch starter cracks were measured with moire interferometry during crack growth. The three-point bend specimens were precracked by the single edge precrack bend (SEPB) method. The experimental data was then input to two and three dimensional finite element models of the three-point bend and WL-DCB specimens, respectively, to determine by an inverse analysis the crack closure stress (CCS) versus crack opening displacement (COD) relations for SiC(w)/Al2O3. Energy dissipation rates in the trailing process zone plus the matrix fracture and fiber breakage accounted for about 80 percent of the release energy rate with the remainder being dissipated through the frontal process zone. In Part 2, a hybrid experimental-numerical procedure was used to analyze rapid crack growth in an impact loaded three-point bend concrete specimen with an offset straight precrack. Two-beam dynamic moire interferometry was used to record eight sequential moire patterns of the horizontal or vertical displacements by a ultra-high speed camera with an exposure of 2 microseconds and a framing rate of 100,000 frames/sec. The fracture responses of ceramic composites and concrete were both characterized by FPZ models which are the dominant fracture energy dissipation mechanism in this type of brittle composite.

• Research Organization: Washington Univ., Seattle, WA (United States)
• OSTI ID: 7288779
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BRITTLENESS
BUILDING MATERIALS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
COMPOSITE MATERIALS
CONCRETES
CRACK PROPAGATION
FRACTURE PROPERTIES
MATERIALS
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
SILICON CARBIDES
SILICON COMPOUNDS