Identification of stiffness properties of orthotropic lamina using the experimental natural frequencies and mode shapes
Gordis, Joshua H.
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Mechanical properties of advanced composite lamina are identified for better mathematical modeling of composite laminate for structural analysis. Each lamina is treated as an orthotropic material under plane stress state and are assumed to be transversely isotropic. Four stiffness properties, (E1, E2, n12, G12), are treated as design variables for minimization of a performance index. The differences between analytically obtained and experimental natural frequencies for the specimen, along with a proper weighting scheme for each mode, are minimized using the optimization routine, 'fmincon' in the MATLAB¬ optimization toolbox. The modal assurance criterion is utilized to construct the weighting to express the degree of correlation between mode shape vectors obtained experimentally and derived analytically. This study requires a series of experimental results; natural frequencies and corresponding mode shapes of the specimen. A computational tool has been developed as a result of this study. Numerical examples are investigated to demonstrate the performance of this approach. Further study with experiments may show practical benefit of current method for characterization of mechanical properties of advanced composite materials
NPS Report NumberNPS-MAE-07-003
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