Abstract: A three-phase model for the thermal expansion coefficient and t ransformation strain coefficient of the
shape memory alloy composite was developed , in which the composite was considered as the austenitic phase , the product phase ( martensite phase ) and the mat rix phase. The common expressions for the thermal expansion coefficient and t ransformation strain coefficient of the shape memory alloy composite were derived based on the micromechanical analysis. The expressions can be fit for fibers with various shapes. Compared with the t raditional method , non-linearity of shape memory alloy need not be considered. Not only was the method simple , but also the interaction among the three phases was considered. As an application of the model , the at tention was paid to the effects of the fiber geometry , various shapes and volume ratio of fibers in the composite on the effective thermal expansion coefficient and t ransformation strain coefficient of the composite. By comparing with references , it is shown that the results are credible. It is helpful to the design of intelligent composites.