Optimisation of manufacturing parameters and morphology-based numerical analysis of nanocomposites

Abstract

In recent years, the usage of polymer nanocomposites has been increasing rapidly. However, although their functional properties are superior, often the relevant mechanical properties do not give sufficient consistency to satisfy the expectations of the users. In most cases, the property variations come from the manufacturing methods and the lack of knowledge of the individual parameter's effects.The present paper describes a comprehensive approach towards determining the optimised formulation, melt compounding of the nanomaterials and numerical simulation which is based on the microscopic image processing of real morphological structures of polypropylene (PP)/clay nanocomposites. In this study, first of all, PP/clay nanocomposites are investigated with respect to their manufacturing and resulting morphology. The manufacturing parameter optimisation is carried out by implementing the methodology of Taguchi design of experiments (DoE). Clay type and content, compatibiliser content and PP type are varied to produce the combinations of factors that maximise (not simultaneously) the tensile/ flexural moduli and strengths as well as the impact strengths of prepared nanocomposites. A global sub-optimised combination is found for producing nanocomposites that possess good individual mechanical properties. Subsequently, object-oriented finite element (OOF) technique is used to incorporate the acquired morphological images of final optimised nanocomposites into twodimensional finite element modelling. An understanding of the overall material behaviour is developed through the combination of real data from micro/nanostructures and the fundamental material characteristics of the constitutive phases. Captured morphological images, using either scanning electron microscopy (SEM) or transmission electron microscopy (TEM), are utilised to generate the geometric information regarding the nano/microstructures. The material properties, on the other hand, are obtained from conducted tests and published literature. The numerical results predicting the elastic moduli of polypropylene/clay nanocomposites are compared with the experimental data and the available composites theoretical models. Very good agreement has been shown to exist establishing the viability of this kind of numerical approach.