Thermo-mechanical properties of polymer CNT composites (PhD) : experimental and multi-scale modelling approach

Abstract

Carbon nano-tubes (CNTs) based composites have found their way into different industrial applications such as load bearing in sports industry, thermal in energy generation sector and thermo-mechanical in automotive industry. It is believed that few weight percentages of CNTs can remarkably improve the mechanical, thermal and thermo-mechanical properties of CNTs based composites. During their life cycle, these composites are subjected to mechanical and thermo-mechanical loadings. Therefore, a suitable mechanical and thermo-mechanical design analysis is necessary before putting them in realistic applications. In the proposed thesis, multi-scale approach has been employed to study the thermo-mechanical properties of microwave processed carbon-nano-tubes polymer composites. Fabricated composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), nano indentation, uniaxial tensile, and fracture toughness tests to study the thermal stability, crystallinity, morphology, and mechanical performance. Multi-scale modelling approach has been implemented to predict the effective anisotropic material properties of the composites at diverse constituent conditions. Anisotropic material properties have been presented with the consideration of all possible conditions of composite matrix like elastic, elasto-plastic, and interfacial behaviour. Mori-Tanaka (M-T) homogenization scheme has been implemented with the fi nite element method (FEM) approach to predict the effective material properties of the composites. Further, these properties have been used at macro-scale simulation for fracture analysis. Both experimental and computational studies have been presented for fracture behaviour of polymer composites. Apart from this, the meso-scale model is used for the analysis of a bio-composite. The effective elastic properties of the bio-composite have been studied for a special case of interpenetration of the voids. The research work proposed a novel fabrication process for nano-composites with low microwave power and less processing time. The nano-composites have remarkable mechanical and thermo-mechanical properties compared to pure matrix material. The numerical simulations successfully predicted the transversely isotropic properties of perfectly bonded CNT in a matrix. The multi-scale modelling technique proposed in the present work bridges the meso-scale and macro-scale effectively. Also, the macro-scale properties evaluated experimentally like tensile, fracture toughness, etc., are in good agreement with the properties evaluated using the multi-scale modelling.