Evaluation of curing residual stresses in three-phase thin composite laminates considering micro-scale effects

Generally, in thin laminates, residual stresses are studied in two scales; micro mechanics and macro-mechanics. So far, no study has included both the micro- and macro-scale analysis for predicting the thermal residual stresses of composite laminates. In other words, no literature model is proper for both the micro and macro scale at the same time. This paper presents a procedure to integrate micro and macro thermal residual stresses in composite laminates. The combination of micromechanics-based analytical results and hole-drilling calibration factors leads to predict the macro thermal residual stresses of a unidirectional laminate. Classical lamination theory (CLT) is then employed to predict macroscopic thermal residual stress of each layer in laminated composites (with different orientations). Comparison of longitudinal, transverse and in-plane shear stresses between the proposed approach and published experimental results is made for glass/epoxy laminates in cross-ply and quasi-isotropic configurations. Available experimental data from incremental hole-drilling method show that the present combination procedure yields more precise residual stresses predictions in comparison with the state that the CLT is used only. In other words, the presented procedure which adds the micro residual scale results to the CLT, gives rise to a better prediction of residual stress fields. Consequently, ignoring the micro-mechanical effects may result in some uncertainties in thermal residual stress evaluation of thin composite laminates. Furthermore, while the CLT is not able to take into account the in-plane shear residual stresses for the cross-ply composites, the present procedure can provide an estimation of shear residual stress field.