Fracture Toughness of Carbon/Carbon Composites.
Abstract
The fracture toughness parameter, K sub max, was used to measure the resistance of two dimensional and three dimensional carbon/carbon composites to crack initiation. K sub max as a function of geometry and thickness was measured for two 2D composites differing in fiber and matrix precursors, weave pattern and microdefect field. One composite, KKarb C was independent of geometry and thickness. The second, T300 HT had an average value of 16 MPa*m to the 1/2 power for the four-point bend and compact-tension geometries and a value of 26 MPa*to the 1/2 power for the single-edge notch configuration. The latter result occurs due to the composite strength and the interaction of the stress and microflaw fields. Also, the SEN samples had larger active zones leading to greater crack initiation resistance. Effects of notch orientation and depth were analyzed for the 3D material. Circumferential testing direction showed the highest K sub max values for all three notch depths because the crack front encountered the highest cross-sectional area of yarns. A PASCAL program was written to compute the crack diffusion model parameters gamma *, gamma sub min, and alpha. A higher value of gamma * for the 2D materials reflected the type, distribution, and size of defects for the 2D materials. The alpha parameter was lower for materials showing a high degree of fluctuation in their maximum load.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 27, 1991
- Accession Number
- ADA240200
Entities
People
- A. Moet
- J. Minick
Organizations
- Case Western Reserve University