Macroscopic constitutive relationship is estimated by considering the microscopic particle/matrix interfacial debonding. For the interfacial debonding, the PPR potential-based cohesive model is utilized. The extended Mori–Tanaka model is employed for micromechanics, while a finite element-based cohesive zone model is used for the computational model. Both models (theoretical and computational) agree well each other in representing the macroscopic constitutive relationship on the basis of the PPR model. The microscopic interfacial cohesive parameters of the PPR model are estimated from macroscopic composite material behavior. In addition, different microscopic debonding processes are observed with respect to different macroscopic constitutive relationships (e.g. hardening, softening, and snap-back).