Analysing thermally induced macro-scale residual stresses in tailored morphing composite laminates

An approach for predicting and extracting through-thickness residual stresses in tailored composite laminates (i.e. laminates with local variations in lay-up sequence and/or thickness) is presented. Tailored composite laminate configurations can be explored in some novel structural applications (e.g. morphing laminates) by incorporating unsymmetric laminate lay-up sequences. In such cases, the presence of and variation in through-thickness (i.e. macro-scale) residual stresses can considerably influence the structural geometry, strength and multi-stable behaviour of these laminates, and thus require consideration at a design stage. In this context, a combined numerical-experimental approach was used to analyse residual stresses in tailored laminates. Laminates with local unsymmetric cross-ply lay-ups and/or varying thicknesses were manufactured at elevated temperatures and experimental measurements (of cured shapes at room temperature) were used to develop laminate-level finite element models. The cured laminate shapes were measured using a full-field non-contact technique. The numerical models were calibrated and subsequently used to extract through-thickness residual stresses in the laminates. It was shown that the current approach can be successfully applied to predict the cured shapes of and the through-thickness residual stresses in tailored laminates.