Modelling stiffness-damage behaviour of (± 45/90)s and (90/±45)s glass fibre reinforced polymer laminates

The damage morphologies that occur in matrix dominated (± 45/90)s and (90/±45)s glass librc reinforced polymer laminates under quasi-static tensile loading and their effect on the laminate stiffness have been considered. Observations of the damage were made in situ and by microscopy of polished sections. The 90" and 45ʹʹ ply matrix cracking damage in the laminates was modelled using finite element analysis and hence predictions of the normalised stiffness as a function of increasing damage density were made for both laminates. Agreement between models and experiment was good and in particular the greater amount of stiffness reduction observed experimentally in the (90/±45)s laminate, associated with a ʹstaggeredʹ matrix cracking damage morphology, was modelled successfully. Information regarding the stress profiles in the 90° plies of the cracked laminates has also been obtained from the finite element analyses. There are distinct differences in the profiles between the stacking sequences, which are discussed with reference lo the experimental results and other analyses from the literature.