Thermal stress concentration due to imperfect adhesion in fiber-reinforced composites

Thermal stress and strain analyses have been performed in unidirectional fiber-reinforced composites by considering the concept of an interphase between the fiber and matrix phases. The thermal and elastic material properties of the interphase are assumed to be variable and to depend on the degree of adhesion developed between fiber and matrix. An analytical approach is developed for the solution of the appropriate generalized plane strain steady-state thermoelastic problem. This approach is an extension of the homogeneous subdomain method, requiring appropriate discretization of the problem domain into an appropriate number of subdomains. Application of continuity and compatibility conditions for the temperature field and the thermoelastic stress potential result in a system of linear equations, the numerical solution of which supplies all necessary constants for evaluation of the solution of the problem. Numerical results are given for a wide range of the parameters involved, including material properties and imperfect adhesion coefficients. The introduction of the so-called degree-of-adhesion coefficients gives new insight into the failure mechanisms developed along the fiber/matrix interface. Application to the proposed model of imperfections in the adhesion between fiber and matrix shows very interesting results and explains the failure mechanisms for such materials. (C) 1997 Elsevier Science Limited.