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    Probabilistic analysis of composite stiffened panels including random AFP-produced defects towards enhanced design allowables
    (2023-06-01)
    Balokas, Georgios
    ;
    Heinecke, Falk
    ;
    Liebisch, Martin
    ;
    Wille, Tobias
    ;
    Kriegesmann, Benedikt
    Automated fiber placement introduces defects such as gaps and overlaps during production, which add uncertainty to the mechanical behavior of composite parts. This study describes a probabilistic methodology which allows the direct introduction of random defects to the composite part and the calculation of the allowable design values through probabilistic virtual testing. The method is applied on a stiffened panel and is based on measurements regarding the random defect magnitude. An offline database of knock-down factors for stiffness and strength properties is first generated via detailed defected FE models. The factors are then assigned to the panel FE model accordingly, and via a Monte Carlo procedure the statistical response sample of the part is calculated. The process is further accelerated by a machine learning technique able to emulate the relationship between the random input and the selected responses. Several parametric analyses reveal that the number of defects on the panel is often more sensitive than the defect size, while the intensity of the defect at the through-the-thickness direction and the affected plies have a rather strong effect. Moreover, the conservatism of the deterministic design approach based on safety factors is proven by a direct comparison to the described probabilistic approach.
    Publicationtype: Journal Article
      70
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    Uncertainty quantification of composite structures with manufacturing defects within the SuCoHS project
    (2022-06)
    Kriegesmann, Benedikt
    ;
    Balokas, Georgios
    ;
    Wille, Tobias
    Due to their high weight specific mechanical properties, fibre reinforced composite materials are increasingly utilized for high performance primary structures within aircraft wing and fuselage components. Yet, further exploitation is often limited due to rather high material and manufacturing costs including post-processing, concessions and rework. Additionally, very conservative engineering allowables are currently applied in order to account for uncertainties arising from manufacturing as well as operation phase. Further significant weight savings are expected for new structural components that are currently made from metals e.g. by reason of combined high thermal, mechanical or fire loading that cannot be bared by state-of-the-art composites. In order to maintain the leadership of the European aeronautics, the European funded project SuCoHS investigated potential weight and cost savings in expanding the use of composite materials in areas of demanding thermal conditions (temperature and fire). In particular, SuCoHS envisages new structural concepts with novel multi-material composites to provide high robustness against thermal, mechanical and fire loading. These developments also cater for high production rates, providing a cost competitive manufacturing process at minimum material and energy consumption, while reducing the requirement for visual inspection or rework. New solutions for structural health monitoring are considered within the structures to enable condition-based maintenance considering actual loading and structural conditions. The presentation will give an overview of the project and provide some detailed insight into the developed probabilistic sizing approach. For the latter, randomly occurring manufacturing defects (fibre tow gaps) as well as uncertain temperature distributions are taken into account in a probabilistic multiscale approach. The effect of fibre tow gaps is homogenized using meso-scale models and embedded into Monte Carlo simulations of the macro models using surrogate models.
    Publicationtype: Conference Presentation
      147
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