A comparison between the slitting method and the classical lamination theory in determination of macro-residual stresses in laminated composites

This research deals with the theoretical and experimental determination of curing-induced residual stresses in laminated polymer composites on the macro-mechanical level. The slitting method was employed to experimentally determine the residual stress as a function of depth for cross-ply and quasi-isotropic carbon/epoxy laminates. In order to estimate the non-uniform through-thickness residual stresses from strain data obtained by the slitting experiment, two calculation algorithms were used, including pulse method and series expansion method. Both methods led to generally similar calculated stress results. Series expansion method was adapted to treat discontinuous stress profiles in laminated composites. The thermal residual stresses were also calculated using the classical lamination theory (CLT). The results indicated that CLT overestimates residual stresses. The possible reasons for this discrepancy were discussed.