Secure tightening of a CMC fastener for the heat shield of re-entry vehicles

The results of static and hot tests of ceramic matrix composite fasteners for heat shield attachment to a re-entry vehicle are presented. Herein, the effect of the high temperature cycle occurring during atmospheric re-entry on the reduction of the tightening torque of the CMC fasteners is investigated. From cold testing, it is found that the Young's modulus of the material decreases with first-time loading and, therefore, previous loading of the fasteners before their application is recommended. In hot testing of a fully integrated fastener connection, the material temperatures within the connection are experimentally simulated. It is shown that with previous straining, a significant improvement of the fastener is achieved. The loosening torque is no longer reduced by thermally induced stretching of the fastener. (C) 2009 Elsevier Ltd. All rights reserved.