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A nonlinear hierarchical multiscale approach is proposed in this work, for the characterization of the mechanical and damping properties of carbon nanotube reinforced composites (CNT-RCs) considering slippage at CNT/polymer interface. The proposed numerical strategy encompasses various length scales, from nano to micro to macro. Individual CNTs are modeled at the nanoscale as space frame structures using the modified Molecular Structural Mechanics (mMSM) approach. Then the mMSM model is projected to an equivalent continuum beam element (EBE) which is subsequently used as the basic building block for the construction of full length straight CNTs at the microscale, embedded in a polymer matrix. The interfacial load transfer mechanism between the lateral surface of the CNT and the surrounding polymer is modeled with a nonlinear bond-slip friction-type model. This scheme provides with the finite element model of a Representative Volume Element (RVE) at the microscale in which a nonlinear homogenization scheme is implemented in order to compute effective material properties for the macrocontinuum. A Hill's anisotropic plasticity model is fitted onto the results of finite element analysis of the microstructured RVE model, so that anisotropic stiffness and energy dissipation mechanism, due to the directionality of the CNTs, can be captured by the equivalent macro model. Sensitivity analysis is performed with respect to various weight fractions (wf) of CNTs and interfacial shear strength (ISS) values. Global mechanical and damping properties for the homogenized models are assessed and compared with direct calculations on detailed fine scale models.

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