Phase-field modeling of fatigue fracture in porous functionally graded materials

Porous Functionally Graded Materials (PFGM) exhibit complex damage behavior due to the presence of pores. This study presents a hybrid phase-field model to investigate fatigue crack growth in PFGM. The continuous variation of material properties is captured using the Voigt rule of mixtures with uniform porosity, while fatigue effects are incorporated through a fatigue degradation function in the energy functional. Using temperature as an analogous phase field parameter and adapting a staggered solution scheme to solve the coupled governing differential equations, the framework is implemented through a UMAT subroutine feature in ABAQUS. The methodology is validated with results available in the literature, demonstrating its accuracy and robustness. Numerical simulations explore the influence of porosity ratio, power law index, and material gradation on the fatigue fracture behavior under various loading conditions. From a systematic numerical study it is opined that higher porosity levels significantly influence crack propagation paths and load-bearing capacity. Understanding fatigue fracture in PFGM provides valuable insights for optimizing material selection, enhancing structural durability, and improving design strategies for fatigue-critical applications in aerospace and mechanical engineering.