Due to the complex nature of fibre reinforced composite (FRC) materials, the onset of damage does not cause instantaneous failure of the entire structure. As a natural progress of the research in the area of modelling damage at multi-scales, a discrete element method (DEM) has been presented in this thesis to simulate and analyse the damage progression in FRC laminates which consists of interfacial debonding, transverse cracking, delamination, and transverse cracking and delamination under quasi-static tensile and/or thermalloadings. Regular and random packing schemes have been developed to assemble the particles to construct the DEM models of the composite materials in which two contact constitutive models, i.e. parallel bond model and contact softening model, are used to represent the linear elastic properties of the fibre and the plastic or cohesive behaviour of matrix and interface, respectively. The interlaminar delamination in composite laminates under mode I, mode II and mixed mode have been modelled and the extension of plastic zone in front of the crack tip has been predicted. The initiation and propagation of matrix cracking as well as the consequent fibre/matrix interfacial debonding process in single-fibre composite has been modelled and analysed by DEM. The effects of fibre distribution and fibre volume fraction on the transverse cracking path and the residual damage remaining in the composite lamina are studied by DEM. The progression of transverse cracking and delamination in cross-ply laminates, the cracking density as well as the stiffness degradation have been predicted by DEM and compared with those from other numerical models or experiments. A thermal expansion scheme has been developed in the DEM modelling of composite laminates, and the damage progression of matrix cracking, fibre/matrix debonding, transverse' cracking and delamination are included in the thermal-mechanical coupling DEM model with the consideration of material microstructures. The outcome of this research has validated the application of DEM in composite laminates in terms of its advantages in the modelling of damage progression and the prediction of cracking density and stiffness reduction, and also proved the potential of DE M in the future research of composite material design.
|Publication status||Published - 2011|