Material Modeling and Dynamic Analysis Studies of CNT-polymer Nanocomposite Structures

Abstract

Remarkable elastic, thermal and physical properties of carbon nanotubes (CNTs) make them most attractive nanoscale reinforcing elements in polymeric materials. Material properties and structural characteristics drastically improve with introduction of small amounts of these nano fillers. Present work studies the different aspects of material modeling and dynamic behavior of CNT reinforced polymer nanocomposites. The effective material properties are estimated empirically by modified Halpin-Tsai’s formulation and numerically by finite element analysis approach using representative volume element (RVE) model of CNT polymer matrix. Various configurations including variable length of CNTs with different volume fractions as well as using interphase region between CNT and matrix domain are accounted to know the effects on stiffness and thermal properties of composite. Studies are conducted for single walled (SWCNTs) and multi-walled CNT (MWCNTs) reinforcement. Along with interphase, some other factors like agglomeration and waviness of CNTs also play an important role in CNT reinforced composite and need to be considered in material modeling. In this regard, the analytical improved models (including Halpin-Tsai and effective medium approximation model) have been proposed. A generalization framework towards intelligent modeling is illustrated using back propagationneural network for estimation of elastic modulus and thermal conductivity at different input conditions including processing parameters. The results are compared with few experimental studies for different weight fraction samples. Static bending, dynamic buckling and free vibration analyses are conducted for uniform and functional graded (FG) CNT-polymer composite beams with approximate and finite element methods. The functional grading considerations are accounted with the help of a new layerwise distribution concept of CNT weight fractions along the thickness direction for different distribution profiles. The governing equations of dynamic system are formulated based on general higher order shear deformation theory. For analysis of low aspect ratio FG composite structures, the dynamic modeling is carried-out using plate theory. The natural frequencies and transient dynamic responses for different boundary conditions are predicted. Modal properties of beam and plate samples at different CNT weight fractions are experimentally validated.