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Damage Tolerance of Composite Sandwich Structures

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Final rept.

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The use of sandwich structures with composite facesheets in commercial aviation is increasing. Such structures provide redundant load paths and high specific bending stiffness. Because of their structural efficiency, light-weight designs result in thin facesheets that are susceptible to impact damage. This study concentrated on the modeling aspects of damage tolerance of thin-gage composite sandwich structures. As such, it is a companion work to the FAA report Review of Damage Tolerance for Composite Sandwich Airframe Structures, DOTFAAAR-9949, August 1999, which contains a literature review and describes current technical challenges. Current analytical attempts to assess the damage tolerance of composite sandwich structures first characterize the damage state. Based on the type and extent of damage, models are constructed to determine the stress and strain distributions. A failure criterion is then implemented with the calculated stress and strain state. Often components of the damage are neglected to simplify the model of the sandwich structure. Two models to be developed are proposed. The first is a model to determine the extent of load transfer around a damaged area. Localized stiffness reductions will result in a shift in the neutral axis as well as load transfer in the damaged facesheet and to the undamaged facesheet. The amount of load transfer coupled with detailed models of facesheet stability and strength will provide a methodology to determine damage tolerance. The second model is of the specific damage resulting from low-speed impacts. This model will provide a methodology to predict the growth of such damage.

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  • Commercial and General Aviation

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