A Continuum Interface Debonding Model and Application to Matrix Cracking of Composites

Based on the internal variable theory of thermodynamics, a continuum interface constitutive model relating interface traction with interface separation was developed. An interface damage variable was introduced, and an evaluation equation was derived to characterize the degradation of interfacial rigidity with interface debonding. The present constitutive model was applied to fiber pullout from the matrix, and bridging matrix cracking of composites. Relatively simple closed form formulas were obtained for shear stress distribution along the interface, pulling stress of fiber from the matrix, and stress intensity factor of the small matrix crack tip with fiber bridging. The effects of interface parameters involved in the evaluation equation on interface shear stress distribution, and pulling stress of fiber were also discussed.