Revisiting Rotating Bending Fatigue in FFF Polymer Specimens Using Geometry-Based Cross-Section Properties for Stress Estimation.

Abstract

The fatigue performance of polymer components fabricated by Fused Filament Fabrication (FFF) under cyclic loading is strongly influenced by their internal structure, defined by the infill pattern, density, and shell configuration, among others. Usual standard rotating bending fatigue procedures, such as those described in ISO 1143:2010, assume solid and homogeneous sections, leading to inaccurate stress estimations when applied to FFF specimens. In the absence of a specific fatigue standard for additive printed specimens, this work proposes and compares four analytical models for estimating the maximum surface stress in FFF-printed specimens subjected to rotating bending fatigue tests. The models vary in geometric fidelity, from a conventional solid-section assumption to an Analytical Geometry-Based model (AGB) that incorporates shell ovalization and non-uniform thickness. The accuracy of each method is evaluated by comparing the resulting S-N curves to experimental fatigue data obtained in this study and to results from existing literature.