Accession Number : ADA329862
Title : Net Shape Forming of Tough Fibrous Monolithic Ceramics.
Descriptive Note : Final rept. 1 Apr 94-30 Mar 97,
Corporate Author : MICHIGAN UNIV ANN ARBOR DIV OF RESEARCH DEVELOPMENT AND ADMINISTRATION
Personal Author(s) : Halloran, John W.
PDF Url : ADA329862
Report Date : 25 AUG 1997
Pagination or Media Count : 105
Abstract : Significant dimensional changes involving linear expansion and shrinkage of 6% occur during heating of a thermoplastic SiC/ethylene vinyl acetate mixture. Thermal expansion occurs before weight loss begins, and can be quantitatively explained in terms of the thermal expansion behavior of the constituents and the crystallization or melting of the semicrystalline polymer. Irreversible anisotropic displacements occur during the first heating cycle due to relaxation of molding strains. These can be reduced by annealing for periods comparable to the viscoelastic relaxation of the ceramic/polymer system. Shrinkage occurs during the early stages of degradation of EVA. This shrinkage is quantitatively accounted for with volume losses resulting from removal of the EVA. Shrinkage continues as weight loss proceeds and stops only at the point the ceramic particles contact one another. Total displacement behavior is the sum of the shrinkage from weight loss plus the expansion from thermal expansion of the individual components, and can be quantitatively predicted for simple or multi-step heating schedules.
Descriptors : *CERAMIC MATRIX COMPOSITES, ANNEALING, POLYMERS, ETHYLENE, THERMAL EXPANSION, ANISOTROPY, THERMOPLASTIC RESINS, SILICON CARBIDES, PYROLYSIS, ACETATES, VINYL PLASTICS.
Subject Categories : Laminates and Composite Materials
Distribution Statement : APPROVED FOR PUBLIC RELEASE