Abstract
Fiber waviness defects are found in the inner surface of the hat-shaped stringers manufactured by a process system. In order to establish the acceptance criterion for the stringers with the fiber waviness defects, experimental testing and numerical simulation were carried out in this study. Specially induced fiber waviness defects of four pre-defined severity levels were manufactured and tested. A maximum of a 58.1% drop in compressive failure load is observed for the most severe level in the experimental results. A finite element model with progressive damage method and cohesive zone technique was developed to simulate the failure process and the impact of fiber waviness defects. The numerical simulation results of compressive failure load have a good agreement with experimental results qualitatively and quantitatively. In addition, two simple parameters, i.e., aspect ratio A/H and the number of plies with fiber waviness, are proposed to characterize the influence of the fiber waviness on the compressive failure load for the purpose of fast engineering quality checks.
Highlights
The number of defects could be more than one in practice; we only introduced one fiber waviness defect for each specimen for our first investigation, either concave fold or convex fold of fibers
All the fiber waviness defects are placed at the top of the photographs
Aiming at the hat-shaped composite stringers in a civil aircraft, experimental testing and numerical simulations have been carried out to investigate the influence of out-of-plane waviness defects, which are commonly observed during their manufacturing process
Summary
In order to establish the acceptance criterion for the stringers with the fiber waviness defects, experimental testing and numerical simulation were carried out in this study. A maximum of a 58.1% drop in compressive failure load is observed for the most severe level in the experimental results. The numerical simulation results of compressive failure load have a good agreement with experimental results qualitatively and quantitatively. Fiber waviness defects are the most commonly observed manufacturing defects in the composite laminates, which are introduced unintentionally during the manufacturing process. Many studies have been carried out on the formation of fiber waviness defects and the influence of fiber waviness defects on the mechanical performance of fiber-reinforced composites. Recent studies were summarized in Alves et al [1] and Kulkarni et al [2]
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