On the measurement of residual stresses in fibre metal laminates

During the manufacturing of fibre-reinforced laminates, undesired phenomena are produced, among which the residual stresses need investigation and analysis. The authors have previously presented the research done on the predictive modelling and measurement of the distortions happening during the manufacturing of fibre metal laminates (FML). In this paper, primary measurements of residual stresses are presented. First, the mechanisms governing the development of residual stresses in polymeric laminates are described. Then, the measurement techniques applicable to composite and hybrid materials are reviewed. The hole-drilling method is used to estimate the stress levels in the aluminium sheet of the FML. The results give a new understanding of the stress state in the FML. Comparisons made with the model predictions show the consistency of the results and indeed the need for further improvements for the model validations in terms of the residual stress values in the aluminium sheets.