Hybrid Fiber Carbon-carbon Composites for Improved Compatibility With Oxidation Resistant Coatings

Period of Performance: 01/01/1985 - 12/31/1985

$391K

Phase 2 SBIR

Recipient Firm

Fiber Materials, Inc.
Biddeford Industrial Park
Biddeford, ME 04005
Principal Investigator

Abstract

CARBON-CARBON COMPOSITES ARE USEFUL HIGH TEMPERATURE STRUCTURAL MATERIALS. OPPORTUNITIES EXIST FOR THEIR USE IN HOT, OXIDIZING ENVIRONMENTS, BUT PROTECTION SYSTEMS HAVE TO BE DEVELOPED TO PREVENT OXIDATION WHICH POSES A SERIOUS PROBLEM ABOVE 400 DEG C. CONVENTIONAL OXIDATION RESISTANT COATING SYSTEMS EMPLOYING THIN LAYERS OF EITHER SiC OF Si3N4 CRACK WHILE UNDERGOING LARGE TEMPERATURE CHANGES DUE TO THE DIFFERENCE BETWEEN THEIR COEFFICIENTS OF THERMAL EXPANSIONS (CTE) AND THAT OF CARBON-CARBON. BASED ON IN-PROCESS THERMAL EXPANSION RESULTS OF PHASE I, THE NICALON HYBRID FIBER SYSTEM WILL UNDERGO FURTHER DEVELOPMENT AS A HIGH CTE COATING SUBSTRATE. THE EXPANDED PROGRAM WILL STUDY THE SUITABILITY OF A RESIN MATRIX OVER A PITCH MATRIX, THE ADDITION OF THERMALLY STABLE FIBERS, ALTERATION OF THE NICALON (SiC) WEAVE ARCHITECTURE, AND THE WEAVING OF HIGH CTE HOMOGENEOUS FIBER SYSTEMS. THE EVALUATION OF THESE VARIATIONS WILL RESULT IN AN OPTIMIZED COATING SUBSTRATE. AS IN PHASE I, CHEMICAL VAPOR DEPOSITED (CVD) SiC AND Si3N4 WILL BE APPLIED TO THE DENSIFIED COMPOSITES IN ORDER TO DETERMINE HOW THEIR DIFFERENT CTE'S AND ELASTIC MODULI WILL AFFECT THEIR PERFORMANCE AS PROTECTIVE COATINGS. COATED SPECIMENS WILL BE EVALUATED IN STATIC AIR OXIDATION TESTS, AND SUCCESSFUL SUBSTRATE-COATING COMBINATIONS WILL UNDERGO MECHANICAL TESTS.