2004 Volume 2004 Issue 213 Pages 134-139
An ablator system, made of a completely carbonized two-layer phenolic CFRP, is able to withstand severe aerodynamic heating during reentry. The surface heat shield material of the two-layer type ablator is made by a technique in which chopped prepreg pieces are compressed at a high temperature. The use of the two-layer type ablator is an epoch-making concept that can attain lighter weight compared with the ablator system using the conventional phenolic CFRP, which surely leaves the non-pyrolyzed layer (virgin layer) to function as a structural member. The chopped cloth ablator is recessed in the chemical reaction between the material surface and oxygen. Although this chopped cloth ablator expands by thermal movement, it gets shrunk by carbonization. After all, the characteristic of the change in temperature of the chopped cloth ablator thickness is unknown. Therefore, it is difficult to estimate the exact stress of the chopped cloth ablator. In this study, the expansion (or shrinking) of the chopped cloth ablator is clarified from the difference in measured isobaric specific heat Cp, and the isochoric specific heat Cv. Cv of the chopped cloth ablator can be predicted using the Einstein frequency v. The measured temperature characteristic of the chopped cloth ablator's thickness was well in agreement with the value estimated based on the difference in Cp, and Cv.
