Low Density Ceramics Based on Open Cell Macrostructures Fabricated from Reticulated Polymer Substrates.
Abstract
Processing procedures, and resulting mechanical properties, of open cell low density (relative density less that 0. 1) ceramic macrostructures were investigated. These macrostructures were fabricated by slurry coating reticulated polymer substrates. Cracks in the powder coating, which were produced during the pyrolysis of the substrate, remained after powder densification at high temperatures and were the major cause of suboptimum properties. Additionally, lack of slurry drainage during the coating process could fill cells with powder which would differentially shrink during densification, leaving large regions within the macrostructure void of cell struts. This problem became increasingly pronounced with decreasing cell size. Mechanical properties were measured for a commercial transformation toughened AL203/Zr02 doped cell material fabricated using reticulated polymer substrates with cell sizes of 30, 65, and 100 pores per inch. Approximately half of the specimens were treated by the manufacturer in an attempt to heal the partially cracked struts. The relative density of all commercial materials ranged between 7 and 12% of theoretical. Mechanical properties appeared to be independent of cell size. The elastic modulus, which ranged between 1 and 5 GPa, increased with density and was higher for the healed materials. The critical stress intensity factor ranged between 10 and 80 kPam 1/2, increasing with elastic modulus. Tensile strength ranged from 0.1 to 0.8 MPa and appeared to be related to processing variations and defects, which included specimen to specimen density variations, cracks within the cell struts and large regions fo missing cells in the material with the smallest cell size.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1986
- Accession Number
- ADA172558
Entities
People
- F. F. Lange
- K. T. Miller