Premium
Notch Strength and Fracture Behavior of 2‐D Carbon‐Carbon Composites
Author(s) -
Griesheim Gary E.,
Pollock Peter B.,
Yen ShingChung
Publication year - 1993
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1993.tb05318.x
Subject(s) - composite material , materials science , fracture (geology) , reinforced carbon–carbon , tension (geology) , carbon fibers , fracture mechanics , strain energy , shear (geology) , composite number , ultimate tensile strength , structural engineering , finite element method , engineering
This study examined Mode I in‐plane fracture in two‐directional carbon‐carbon composites. Linear elastic fracture mechanics (LEFM) provided good predictions for the failure loads of the compact tension specimens, and consistent values of K IC were calculated. However, values for the strain energy release rate G IC were inconsistent. Analysis of loading/unloading cycles applied to the specimens showed that significant inelastic behavior occurred prior to fracture. Hence the J ‐integral method is not thought to be appropriate for fracture prediction. It was also found that the real crack tip stresses in carbon‐carbon composites are much lower than theoretical predictions. An interesting discovery is that cracks in carbon‐carbon composites appear to be naturally blunt. The lower limit on the crack tip diameter corresponds with the spacing of the woven fiber bundles. A significant conclusion from this study is that the material behavior can be modeled as the sum of two contributions: (i) a linear elastic solid, which fails according to LEFM, and (ii) an independent damage mechanism, which absorbs energy but does not alter the ultimate fracture load. Possible candidates for the damage mode are fiber pullout and inelastic deformations due to shear stresses.