Numerical and experimental studies have been conducted to try to quantify the influence of Automated Fiber Placement (AFP) induced manufacturing defects on the quasi-static behavior of composite parts ranging, on the building block approach, from coupons to sub-structural parts. In more recent studies, researchers started to conduct the same investigations for fatigue load cases with the purpose of determining the influence of defects on damage initiation and propagation mechanisms. This document will present a review of both experimental and numerical studies conducted so far on the influence of AFP defects on laminate response and failure characteristics during fatigue loading. In the first section, a brief introduction of the types of AFP manufacturing defects identified will be presented before focusing on publications related to the influence of the aforementioned defects on the quasi-static behavior of composite laminates. Following, in the second section, we propose to detail the numerical investigations on the fatigue behavior of composite laminates. Then, the third section will present a combined experimental and numerical investigation of the influence of the manufacturing defects presented in the first section on the fatigue behavior studied in detail in the second section. Finally, the fourth section is dedicated to a comparison of the time cost associated with numerical and experimental approach.

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An experimental study of unstiffened graphite-epoxy cylindrical shells with cutouts subjected to bending load is presented. Two cylinders were tested: a classical laminated cylinder with constant-stiffness and a fiber-steered cylinder with variable stiffness in circumferential direction. Both cylinders were tested until collapse in displacement control. Displacements and strains were measured by displacement sensors, strain gauges, and two digital image correlation systems. Analysis of the test data indicates that the highest stressed area was the edges of the cutouts where local displacements created large compression strains. The experimental data were compared with progressive damage analysis results obtained with a finite element analysis that included measured geometrical imperfections. The research contributes to the knowledge of variable-stiffness composite structures and their applications in aircraft fuselages. @en