RESIDUAL THERMAL-STRESSES IN METALLIC AND INTERMETALLIC MATRIX COMPOSITES AFTER COOLING FROM PROCESSING TEMPERATURE

Thermal stresses induced during cooling from the fabrication to ambien t temperatures of SCS-6/Ti-6Al-4V and SCS-6/Ti-24Al-4Nb composites are analyzed applying the finite element method. The matrix is modeled as a bilinear elasto-plastic material with work and kinematic hardening. Thermo-mechanical properties of both the fiber and the matrix are tem perature dependent. Effects of the free surface of the composite are i ncluded in the analysis. It is shown that during cooling the matrix be havior may switch from elastic to elastoplastic and back to elastic. I n particular, for the Ti-6Al-4V matrix, the stresses remain below the yield limit and the cooling process is elastic at the beginning (at hi gh temperature) and also when approaching room temperature.