Defects in Ceramic Matrix Composites and Their Impact on Elastic Properties (Postprint)
Interim rept. 29 Feb 2012-27 Jun 2013
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
Pagination or Media Count:
Defects created during the manufacture of an oxideoxide and two non-oxide SiCSiNC and MI SiCSiC ceramic matrix composites CMCs were categorized as follows 1 Intra-yarn defects such as dry fibers, 2 Inter-yarn defects such as those at crossover points, matrix voids, shrinkage cracks and interlaminar separation, and 3 Architectural defects such as layer misalignment. Their impact on elastic properties was analytically investigated using a stiffness averaging approach considering the defects to have volumetric and directional influences. In-plane tensile and shear moduli as well as the through-thickness compressive modulus were experimentally evaluated. Results of analytical model were around 7 on average from the mean value of the experimental data. It was observed that interlaminar separation drastically reduced the through-thickness modulus by about 63 for the SiCSiNC, 40 for the MI SiCSiC and around 32 for the oxideoxide composites. Shrinkage cracks in oxideoxide composite reduced the in-plane tensile and shear moduli by 14 and 8.8, respectively.
- Laminates and Composite Materials