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Failure Prediction of Countersunk Composite Bolted Joints Using Reduced Order Multiple Space-Time Homogenization



This paper presents the computational modeling and prediction of fastened composite joints using the Eigendeformation-based reduced order homogenization (EHM), as part of the Air Force Research Laboratory’s Composite Airframe Life Extension Tools for Assessing the Durability and Damage Tolerance of Fastened Composite Joints. The multiscale modeling approach is based on computational homogenization theory, which computes the effective stress-strain behavior of the composite by solving a boundary value problem defined over unit cells of the composite microstructure. The key feature of the proposed modeling approach is that nucleation and propagation of damage within the composite are tracked at the microstructure, and no macroscale phenomenological failure criterion is used [1]. To reduce computational cost, this approach evaluates the microstructure problem by employing a reduced approximation basis, expressing the microstructural variations by numerical Green’s functions, computed prior to macroscale analysis. Three experimental test setups are considered for prediction that consist of static tension and compression tests of open hole, filled hole, and single shear bearing configurations. Motivated by blind prediction results the model is enhanced by: (a) recalibration of the damage parameters to better fit the input composite properties consistent with the curing process used in these experiments; and (b) incorporation of a better modeling methods to improve the post-failure behavior of the constituents for bearing-dominated failure cases.

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