The effect of interfacial reactions on residual stress fields within composites

摘要

The study has been devoted to methodological aspects related to the design of fiber/matrix interfacial zone in refractory composites. Titanium matrix composites reinforced by SiC filaments were chosen to illustrate the various facets of the study. The high temperatures of processing and use lead to thermally induced residual stresses which play such an important and often unfavorable role in the composite behavior that designing new materials inevitably requires the evaluation of these stresses.Making use of a classical method, for computing these thermal stresses showed the interposition of a compliant carbon interphase between fiber and matrix is inefficient to release significant hoop stresses. Besides, submitting fiber/matrix interfaces tohigh temperature generally gives rise to chemical interactions whose effects are often unfavorable. However, the formation of new interphases is sometimes accompanied by volume reductions leading to chemically induced residual stresses. A method has beenproposed to compute these stresses. Considering various types of interactions which can be involved in titanium matrix composites (TiB{sub}2/Ti, C/Ti, C/Si) has shown that chemical interactions are able to generate significant compressive hoop stresses.Their control through high temperature treatments could be used to moderate thermally induced tensile stresses whose excessive levels in hoop direction initiate radial microcracking.