Determination of ply level residual stresses in a laminated carbon fibre-reinforced epoxy composite using constant, linear and quadratic variations of the incremental slitting method

Measurement of residual stresses in FRP composites is by no means a trivial task and there are no commonly applied or standardised methods currently available. As a result, characterisation of residual stresses is often avoided, resulting in the use of conservative safety margins, which has consequently resulted in structures being overdesigned. In the work described here, the incremental slitting method has been demonstrated to be a technique suitable for measuring residual stress in thin (∼0.3 mm) plies of a [0°2/90°2]4s carbon fibre-reinforced epoxy laminate. The stresses measured using a constant stress approximation approach provided the best agreement with measurements obtained using the layer removal technique and stresses predicted using a semi-coupled transient-thermal and structural model.