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Stiffened composite panels have been extensively used thanks to their ability to withstand high load and large deflection. However, their nonlinear behavior and complex damage modes during the post-buckling regime remain challenging and still require research work to improve understanding. In the current study, the buckling and post-buckling responses of a hat-stiffened panel made with carbon fiber reinforced polymer composite material are investigated experimentally and numerically with identifying the damage process and its effect on the panel stiffness. The experimental analysis is achieved by performing quasi-static multi-step compressive loading up to failure with full displacement assessment. A Structural Health Monitoring strategy is also deployed for registering and localizing the Acoustic Emission (AE) activities during each run. Matrix data extracted from the AE waveforms are processed and classified with respect to damage mechanism. Additionally, this research proposes predictive Finite Element Model based on Progressive Failure Analysis. Modified Chang-Chang failure criteria is adopted and implemented using Ansys Usermat subroutine. Numerical and experimental data have been compared and good agreement is demonstrated.

Under dynamic loading conditions, damage in a plain weave Carbon Fiber Reinforced Polymer (CFRP) composite is a complex and multiscale process especially in the presence of a manufacturing flaw. In this context, this paper investigates the impact of an inserted flaw on the damage scenario and stiffness degradation over fatigue life. To achieve this objective, a full three-dimensional Finite Element Model (FEM) is developed to evaluate the stress distribution induced by the local defect. Fatigue tests are then performed on two configurations with and without inserted flaws with continuous monitoring by NDT techniques. The Acoustic Emission (AE) method is used for damage quantification and source localization while Digital Image Correlation (DIC) and Air-Coupled Ultrasonics (ACU) are applied to evaluate the stiffness degradation. The cross results obtained using the three monitoring techniques provide an insight into the damage process and stiffness degradation in woven composite with a simulated manufacturing flaw.

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