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Analytical and Experimental Characterization of Thick-Section Fiber-Metal Laminates

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Final rept. 1 Sep 2011-30 Nov 2012

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Classical laminate theory, used in conjunction with the Ramberg-Osgood method accounts for plastic deformation, is a powerful tool for the determination of numerous static properties of fiber metal laminates. However, the method runs into limitations if the laminate is loaded in a direction other than one parallel to the fibers. This limitation necessitates a more robust method, able to fully account for fibers oriented at angles other than 0 deg and 90 deg as well as plastic deformation at an angle other than the rolling or transverse directions of the metal sheets. Various methods were investigated regarding plastic deformation of the metal layers. While each method was shown to be fairly accurate, the method chosen for this project uses a von Mises yield criterion and applies kinematic hardening to determine the stiffness of individual metal layers as loading increases. The off-axis deformation properties of the prepreg layers were modeled by using equivalent constraint models where the layer of interest is explicitly modeled and the adjacent, constraining layers are modeled as equivalent, smeared layers. Using this method the degraded stiffness of the prepreg layer is found. At each loading step the stiffness properties of individual layers are calculated. These individual stiffnesses are then combined using the standard CLT method, thereby providing the laminate stiffness matrix. While the model accurately predicts stress-strain curves on-axis, additional work is needed to study the local interactions between metal and prepreg layers as damage occurs in each layer.

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  • Laminates and Composite Materials

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