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A research program is underway to experimentally characterize the strain rate dependent deformation and failure response of polymer matrix composites subject to high strain rate impact loads and to develop strain rate dependent deformation and failure models for the analysis of these types of materials. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the effective mechanical and thermal response of the composite. Tensile stress-strain curves for a representative composite are obtained experimentally for strain rates ranging from quasi-static to several hundred per second. The developed numerical procedure is also used to compute the deformation response. The predictions compare favorably to the experimentally obtained values both qualitatively and quantitatively. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results.
polymer matrix composites, micromechanics, viscoplasticity, strain rate, constitutive equations, impact
Aerospace Engineer, Life Prediction Branch, NASA Glenn Research Center, Cleveland, OH
Professor, Ohio State University, Columbus, OH