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Characterizing the Multiscale Elastic/Plastic/Rupture Response of Short Fiber Filled Plastics



To facilitate progressive failure structural simulation of short fiber filled injection molded parts, Autodesk has developed multiscale modeling methodology and software to seamlessly link the results of injection molding simulation with subsequent nonlinear multiscale structural response simulation. The key features of the methodology include: 1) Automated mapping of the predicted fiber orientation distribution onto the finite element mesh that will be used for the nonlinear structural response simulation, 2) Enhancement of the structural response simulation with a multiscale, progressive failure, constitutive model for short fiber filled plastic materials that accounts for plasticity and rupture of the matrix constituent material, resulting in a composite material that exhibits an anisotropic, nonlinear response that accounts for the observed differences between a tension dominated response and a compression dominated response, and 3) A robust, automated material characterization process that uses a minimal amount of simple uniaxial tensile and compression test data from the short fiber filled plastic material to fit the parameters of the multiscale, progressive failure, constitutive model. The injection molding process tends to produce specimens that exhibit a significant spatial variation of the fiber orientation tensor commensurate with the flow characteristics of the injection molding process. For relatively thin injection molded parts, the fiber orientation tensor exhibits a particularly strong variation in the thickness direction. Consequently, the typical uniaxial tension and compression specimens that are used to characterize the material model are more correctly viewed as structures rather than simple test coupons. In this paper, we propose an enhanced material characterization procedure that correctly accounts for the typical observed variation of the fiber orientation tensor through the thickness dimension of the test specimens that are used for material characterization. In this enhanced characterization process, the uniaxial tension and compression test data is supplemented with flexural test data to permit the material model coefficients and the fiber orientation tensor distribution to be determined simultaneously from the available test data.


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