Failure modes of a unidirectional ultra-high-modulus carbon-fiber/carbon-matrix composite

Journal Article · Wed Mar 01 04:00:00 EST 1995 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1995.tb08223.x· OSTI ID:79774

Zaldivar, R J; Rellick, G S ^[1]; Yang, J M ^[2]

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1. Aerospace Corp., El Segundo, CA (United States). Mechanics and Materials Technology Center
2. Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering

The objective of this study was to observe the effects of various microstructural features on the in situ, room-temperature tensile fracture behavior of an ultra-high-modulus, unidirectional carbon/carbon (C/C) composite as a function of processing heat-treatment temperature (HTT) over the range of 1,100 to 2,750 C. An in situ SEM flexural stage was used to observe the interactions between the advancing crack tip and the microstructural features in the frontal process zone. Following the lowest HTT of 1,100 C, failure is dominated by the well-bonded brittle matrix; a tortuous crack path in the E130 fibers appears to contribute to a relatively high utilization of fiber strength in spite of this brittle-matrix failure. Approximate calculations of the interfacial shear stress that might be generated by matrix shrinkage during pyrolysis of the polymer to carbon were compared to approximations of crack-tip interfacial shear stresses (IFSS) using the Cook-Gordon approach. The results suggest that the strong bonding in the 1,100 C HTT composite cannot be accounted for by friction alone, and, therefore, chemical bonding or some type of fiber-matrix mechanical interlocking must be involved. Higher HTTs lead to progressive weakening of the fiber-matrix interface, and, with heat treatment to 2,150 C, multiple matrix cracking (MMC) is observed. Heat treatments to 2,400 and 2,750 C led to longitudinal intramatrix cohesive failure, at 2,750 C, this damage is extensive and results in composites with strength utilizations approaching those of dry fiber bundles.

• Sponsoring Organization: USDOE
• OSTI ID: 79774
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 3 Vol. 78; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON
CARBON FIBERS
COMPOSITE MATERIALS
CRACK PROPAGATION
FRACTURE MECHANICS
FRACTURE PROPERTIES
HEAT TREATMENTS
INTERFACES
MICROSTRUCTURE
SCANNING ELECTRON MICROSCOPY
SHEAR PROPERTIES
TENSILE PROPERTIES