Coupled large deformation phase-field and cohesive zone model for crack propagation in hard-soft multi-materials

This work presents a unified large deformation constitutive framework that couples the phase- field approach for bulk fracture with the potential-based Park-Paulino-Roesler cohesive zone model (PPR CZM) to study crack propagation in multi-material systems that contain interfaces. The phase-field component captures crack initiation and propagation within bulk constituents, whereas the PPR CZM captures failure mechanisms at the interface regions. The proposed unified framework is implemented via a user-element subroutine (UEL) within Abaqus and incorporates a large-deformation extension of the PPR CZM. The proposed coupled framework was used to examine fracture mechanisms in four scenarios: bi-layer hard-hard composite containing crack (notch) impinging on (1) a perpendicular interface and (2) an oblique interface, (3) tri-layer hard-soft multi-material composite containing crack perpendicular to interfaces, and (4) fiber-reinforced matrix composite with an interface and no notch. Results demonstrated that the unified framework successfully captured crack deflection and penetration in hard-hard bi-layers with dissimilar properties and both perpendicular and oblique interfaces, consistent with the expected response based on Linear Elastic Fracture Mechanics theroy. Furthermore, the large-deformation component of the framework was shown to provide an effective numerical tool for probing the underlying toughening mechanisms in hard-soft multi-material assemblies relative to their monolithic counterparts. Toughening in these composites was characterized by crack bridging and post-peak hardening in the force-displacement response. Finally, the framework accurately predicted complex fracture phenomena in fiber-reinforced composites, involving fiber-matrix debonding (via PPR CZM) and matrix cracking (via phase-field). The framework can inform the design of dissimilar hard-hard brittle materials and hard-soft composites, offering insights into fracture behavior and toughening mechanisms.