Effect of Delamination on the Transverse Thermal Conductivity of a SiC-Fiber-Reinforced SiC-Matrix Composite

• Published in: Journal of the American Ceramic Society 1998-06, Vol.81 (6), p.1583-1588
• Main Authors: Donaldson, Kimberly Y., Trandell, Barbara D., Lu, Yangsheng, Hasselman, D. P. H., Maurer, Norb
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Structural ceramics; Technical ceramics
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.1998.tb02520.x

The effect of delamination on the transverse thermal conductivity of a biaxial multiweave SiC‐fiber‐reinforced chemical‐vapor‐infiltrated‐matrix composite was studied. The delamination process, induced by compressive loading, consisted of enlarging and widening pre‐existing interply cavities in the as‐received composite. Ultrasonic scanning suggested that the delamination process resulted in mechanical debonding between the plies. At room temperature, the delamination reduced the transverse thermal conductivity by a factor of ∼5. As a result of gaseous conduction in the interply cavities and/or delamination, the thermal conductivity was higher in air/nitrogen at atmospheric pressure than under vacuum, a difference that was especially pronounced in the delaminated sample. The thermal conductivity of the as‐received and delaminated samples exhibited a negative and positive temperature dependence, respectively, which resulted in almost‐equal values at temperatures >1000°C. Data analysis showed that the thermal conductivity of the delaminated composite was almost independent of the thermal conductivity of the plies themselves; instead, the thermal conductivity of the composite was controlled primarily by conduction across the delaminations at areas of direct contact, conduction through the gaseous phase within the delaminations, and radiation across the delaminations.