Hygromechanical Response of Fibre Reinforced Polymers with Varying Fibre Topologies

Abstract

Vulnerability to environmental factors is a major concern for the reliability of fibre reinforced polymers (FRP). Life of FRP composites is limited to a great extent by the type and scale of service and environment factors viz. heat, moisture, mechanical load, alkalinity etc. The microstructural damage is the initial site of failure. The multi-scale analysis using the computer based finite element methods are becoming increasingly popular. The dissertation presents the micromechanics of FRP composites subjected to diffusion and hygromechanical conditions. A comprehensive analysis is undertaken to analyse the effect microstructural topological arrangement of fibres inside the matrix. To accomplish this several microstructures have been created with the variable topologies. The diffusion process is modelled by Fickian phenomenon. Effect of fibre clustering is reported on the diffusion kinetics. Several algorithms are written to create the microstructures with clustered fibre architectures. A number of statistical measures are employed to quantify the extent of fibre clustering. The statistical measures were helpful to predict the global characteristics of microstructures. The results show that the diffusivity of composites can be controlled through careful design of topology. Stresses due to the transient moisture distribution have been estimated through finite element modelling using appropriate displacement boundary conditions. Some fundamental topologies have been studied. Most important topological parameters have been identified. Utilising the results of fibre neighbourhood, interpretation of large microstructures has been discussed. Considerable interactions among neighbouring fibres can be observed in the stress build up. A major part of this study is conducted considering 2-dimensional microstructures. However the analysis is further extended in 3D to promote the understanding of diffusion and hygromechanical stress behaviour along the fibre axis. The observations should be helpful in designing optimum filament geometry with minimised stress concentration and impeded moisture ingress for improving the durability of FRP’s.