Open-source C++ user subroutines for extensible and robust cohesive-zone-model fracture analysis in Abaqus

We introduce open-source C++ subroutines — implemented as user element (UEL) and user material (UMAT) in Abaqus finite element (FE) software — for fracture analysis based on the cohesive zone model. Implemented in an object-oriented, modular architecture, the proposed framework leverages modern C++ features to enhance extensibility and functionality for general FE simulations. The Abaqus built-in cohesive element is susceptible to numerical instability; we introduce pragmatic modifications to the standard formulation — a total-secant scheme, strength retrieval, and brittle-failure enforcement — to improve numerical robustness and mitigate potential convergence issues. Model development, implementation details, and source code ( https://github.com/dpluxin ) are provided, together with guidance for integrating additional interfaces and third-party libraries. Validation against benchmark studies, including double cantilever beam (DCB), end-notched flexure (ENF), and mixed-mode bending (MMB) tests, demonstrates the accuracy and robustness of the presented scheme. • Open-source C++ subroutines for Abaqus: modular, object-oriented CZM implementation. • Extensible architecture for easy addition of new element types, material models, and third-party libraries. • Total-secant Newton–Raphson with failure-onset strategies for enhanced numerical robustness. • Validated by benchmark fracture tests—improved initiation/propagation predictions and FE stability.