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Interfacial debonding affects the mechanical behaviors of composite structures. In the present work, we developed a new phase-field-based cohesive zone model for modeling debonding at interfaces. The traction-separation law and evolution of phase-field considering the mixed-mode scheme of fracture toughness are given in a variational form. Besides, the present interfacial model can work with the phase-field cohesive zone model for the bulk region, in which a common phase-field value ϕ is shared for both regions. The interaction between the bulk region and interfacial cracking in both displacement, as well as phase-field, are taken into account directly to avoid the over-estimation of the free surface energy. The framework is implemented with the finite element method and validated with several numerical examples. The present work provides a unified approach for modeling quasi-brittle fracture in the bulk region and interfaces and shows its advantage in describing interactions between bulk and interfacial cracking. • A phase-field-based cohesive element is proposed for interfacial failure. • Srength and fracture toughness can be defined independently in different directions. • Closure effect of the interfacial crack can be modeled with given penalty stiffness. • Governing equation is given in a variational form. • Mixed-mode behaviors of interfacial fracture is also considered. • The interaction between interface and matrix is considered by a driving force term. [ABSTRACT FROM AUTHOR]

In rock-like materials, mode I and II fracture toughness are distinctive while the compressive strength is much greater than the tensile strength. Besides, mixed-mode fractures instead of pure mode I or II fractures occur under complicated load cases in those materials. Therefore, to capture the mixed-mode cracking process, we developed a mixed-mode phase-field cohesive zone model based on the unified phase-field theory proposed by Wu. The model was built based on a strain energy decomposition scheme and the softening behavior of each mode is controlled by an independent degradation function. Thus, independent values of strength and toughness can be given for different failure modes simultaneously. A simple mixture rule of fracture toughness was introduced to describe the transition between different failure modes. The model can keep variational consistency perfectly and governing equations for displacement- and phase-field, which was never reported in other works. Several numerical examples verified the effectiveness and flexibility of this work. The present work showed a simple but effective way to simulate mixed-mode fracture. • A modified phase-field cohesive zone model is developed for mixed-mode fracture. • A simple mixture rule is utilized to describe the transition between each fracture mode. • The present model can keep the variational consistency perfectly. • Several numerical cases verify the present model. [ABSTRACT FROM AUTHOR]

To gain a deeper insight into the anomalous yield behavior of Ni 3 Al, it is essential to obtain temperature-dependent formation Gibbs energies of the relevant planar defects. Here, the Gibbs energy of the complex stacking fault (CSF) is evaluated using a recently proposed ab initio framework [Acta Materialia, 255 (2023) 118986], accounting for all thermal contributions—including anharmonicity and paramagnetism—up to the melting point. The CSF energy shows a moderate decrease from 300 K to about 1200 K, followed by a stronger drop. We demonstrate the necessity to carefully consider the individual thermal excitations. We also propose a way to analyze the origin of the significant anharmonic contribution to the CSF energy through atomic pair distributions at the CSF plane. With the newly available high-temperature CSF data, an increasing contribution to the energy barrier for the cross-slip process in Ni 3 Al with increasing temperature is unveiled, necessitating the refinement of existing analytical models. [ABSTRACT FROM AUTHOR]