Mixed mode fracture properties of interface for composite MPC and cement concrete specimen with asymmetric semicircular bending beam

Abstract

This paper investigates the interface fracture behavior of composite magnesium phosphate cement (MPC) and concrete asymmetric semicircular bending beam (ASCB) specimens under various loading conditions including pure mode I, mixed mode I&II, and pure mode II. Initially, finite element simulations are employed to compute and analyze the basic geometric characteristics of the ASCB specimens.. Subsequently, experimental tests are performed to determine the flexural strengths for different pre-crack lengths, and the critical stress intensity factors of ASCB specimens are obtained through testing. Then, parameters for the interface cohesive model are derived. Finally, the interface cohesive model for the composite MPC and concrete ASCB specimen is validated through numerical simulation. The present work show that a pure mode I opening crack represents the weakest form of the structure, and the flexural strength decreases with an increase in precrack length. The crack resistance at the repair interface is approximately 60% lower than the bearing capacity of pure mode II fractures. Intensity factor envelope analysis reveals that mixed mode I&II fractures should be avoided in composite structures experiencing complex stress states. The cohesive model effectively captures the interfacial bonding performance. When combined with the extended finite element method (XFEM), the cohesive model facilitates accurate simulation of the specimen’s interface fracture, demonstrating consistency with experimental results.