Superior electrical, thermal, and mechanical properties of carbon nanotubes (CNTs) have made them effective filler for multifunctional polymer nanocomposites (PNCs). In this thesis work, an improved model has been developed to describe the CNT networks inside polymer matrix and thereby evaluated the PNCs c and . The new model accounts for the electrical conductance contributed by the continued CNT network across the boundary of adjacent representative volume elements. It more realistically represents the interconnectivity among CNTs and enhances the evaluation of the structure-to-property relationship of PNCs . Furthermore, comprehensive investigations on the piezoresistive behaviour of PNCs have been conducted using developed modeling framework. Quantitative analyses have revealed that piezoresistivity of PNCs is predominantly governed by the three mechanisms related to the strain-induced morphological evolution of the CNT network embedded in the polymer matrix.