Ceramic Matrix Composite based on sol-gel and wet lay-up technologies for high loads and high temperature applications

Noam Geblinger, Materials & Processes Engineering Department, Mlm Division, Israel Aerospace Industry, Beer-Yaakov, Israel
Ron Intrater, Materials & Processes Engineering Department, Mlm Division, Israel Aerospace Industry, Beer-yaakov, Israel

Ceramic Matrix Composites (CMC's) are composed of ceramic fibers in a ceramic matrix. As opposed to conventional technical ceramics that fractures easily under mechanical or thermo-mechanical loads in low stresses, CMC materials show dramatic increase in fracture toughness, crack resistance, elongation (up to 1-2%), thermal shock resistance, the ability to absorb dynamical loads and other anisotropic properties that are attributed to the fibers orientation.

There are many methods to produce CMC materials; most of them involve high temperature and extreme conditions. The method used in this work is based on sol-gel technology using monomers in aqueous solution as the sol precursor for resin in which layers of compatible ceramic fabric are impregnated with. The sol is polymerizes in base catalyzed hydrolysis reaction creating the gel. Using familiar lay-up methods from the composite materials industry, the material is cured at low temperatures (up to 200⁰C) in a press or autoclave to perform the ceramic matrix by simple evaporation of water. The method allowed us to get a structural component that can bear high temperatures up to 1000⁰C with minimal need for machining.

Using this method, flat laminates were produced and their mechanical and thermal properties were characterized. The flexure strength of the material is 64% higher and the flexural modulus is 63% lower than that of technical silica, which allowed the material to carry much higher stresses. The material showed no significant change in mass up to 1450⁰C, with very low thermal diffusivity (0.24 mm^2/sec). The work nowadays is focused in scale up to produce and characterize the properties of conical parts. 

# This work is sponsored by the MLM and IAI R&D HQ