Carbon-fiber-reinforced YMAS glass-ceramic-matrix composites - IV. Thermal residual stresses and fiber/matrix interfaces

Unidirectional composites consisting of a glass-ceramic matrix reinforced with continuous carbon fibers, fabricated by hot-pressing, exhibit different fracture behavior according to the sintering thermal cycle. The thermal residual stresses in composites are determined from the mismatch in coefficients of thermal expansion and the thermo mechanical characteristics of both fibers and matrix. An ultrasonic technique is used to determine the temperature at which, on cooling, residual stresses induce microcracking in the matrix. The influence of the mechanical stresses and physico-chemical reactions between the fibers and the matrix on the nature and the strength of the fiber/matrix interface is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.