The work presented in this thesis is a detailed study of impact damage subjected to
tensile and compressive loading to determine the stiffness reduction of the damage
region and identify the damage mechanisms and important parameters that control the
severity of the stiffness reduction. Once the important damage parameters had been
indentified a homogenised non-linear soft inclusion model was developed. This
represents the mechanical and material behaviour of an impact damage region under
tensile and compressive loading in a simple and easy to implement user material format.
The influence of different damage parameters was determined by building ply level
models of idealised impact damage with delaminations at every ply interface and fibre
fracture cracks within the plies. Parametric studies were conducted on the shape and
size of delaminations and on crack density and crack distribution under tensile and
compressive loading and these models were validated against experimental results. In
order to determine the influence of fractured fibres on the residual compressive stiffness
the fibres were modelled at the micro scale with individual fibres embedded in an
elastic-plastic matrix.