Modeling of progressive high-cycle fatigue in composite laminates accounting for local stress ratios

TL;DR

The paper develops an XFEM-based progressive fatigue framework for multidirectional composite laminates, integrating Dávila's mixed-mode fatigue CZM with an implicit damage update and an adaptive cycle-jump scheme that accounts for local stress ratios under thermal residual stresses. By expanding the cycle-jump procedure to compute local $R$ during control cycles and transferring this information to cohesive points, the method captures distributed transverse matrix cracking and delamination with reduced computational cost. Validation against quasi-isotropic open-hole laminate experiments shows good agreement in fatigue life and damage evolution, and the study demonstrates that local stress ratios significantly influence damage progression and life predictions, especially at lower load levels. The framework requires only static material properties and a small set of fatigue parameters, offering a Paris-data-free alternative with stronger physical grounding for mode-mixity and residual-stress effects in virtual testing of composite structures.

Abstract

A numerical framework for simulating progressive failure under high-cycle fatigue loading is validated against experiments of composite quasi-isotropic open-hole laminates. Transverse matrix cracking and delamination are modeled with a mixed-mode fatigue cohesive zone model, covering crack initiation and propagation. Furthermore, XFEM is used for simulating transverse matrix cracks and splits at arbitrary locations. An adaptive cycle jump approach is employed for efficiently simulating high-cycle fatigue while accounting for local stress ratio variations in the presence of thermal residual stresses. The cycle jump scheme is integrated in the XFEM framework, where the local stress ratio is used to determine the insertion of cracks and to propagate fatigue damage. The fatigue cohesive zone model is based on S-N curves and requires static material properties and only a few fatigue parameters, calibrated on simple fracture testing specimens. The simulations demonstrate a good correspondence with experiments in terms of fatigue life and damage evolution.

Figures (15)

• Figure 1: Fatigue cohesive zone model: the traction-separation response under fatigue loading ($\textcolor{blue}{\bullet}$) is inside the quasi-static envelope
• Figure 2: S-N-based fatigue cohesive zone model
• Figure 3: XFEM crack insertion. The mixed-mode fatigue cohesive zone model is used in each cohesive integration point ($\bm{\bigotimes}$) for describing fatigue damage
• Figure 4: Cycle jump scheme with four phases: thermal load phase (in red), static ramp-up phase (in green), control cycle phase (in dark blue) and cycle jump phase (in light blue)
• Figure 5: Specimen dimensions (in mm) of the quasi-isotropic open-hole laminates. The fine mesh region is indicated in dark blue