Volume 13, Issue 1, 2004

Joining Techniques for Fibre Ceramic Structures*

R. Kochendorfer, N. Lutzenburger, H. Weihs

German Aerospace Center, DLR, Institute of Structures and Design, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany

(Received 7/03; accepted 12/03)

Abstract

This paper shows three different joining methods for fibre ceramic materials. The so called in-situ joining method is an integral part of the manufacturing process for CMC structures via the liquid silicon infiltration (LSI) process. Stiffening elements, local patches within attachment areas, inserts etc. are permanently joined to shell structures, thus enabling highly integrated components to be realised with low manufacturing costs. Mechanical joining methods are required for the attachment of CMC thermal protection systems and the assembly of large structures which can not be manufactured as one part due to the limited size of manufacturing devices (e.g. autoclave, furnaces ). For these cases, two different principles are available. The first method takes advantage of interlocking effects of hardened castable ceramics for permanent joints and the so called ceramic rivet, which has similar properties to metallic rivets, however using only elastic and frictional properties of the CMC basic material. The last joining method presented within this paper deals with the attachment of hot structures to a cold substructure. To solve the problems associated with thermal mismatch, elastic or kinematic attachment systems, well adapted to the thermal expansion behaviour are suitable candidates.

Keywords: joining, in-situ, CMC, screws, rivets, interlocking, hot structures, elastic, kinematic, thermal mismatch, thermal expansion