Process-induced residual stresses in composite laminates by different constitutive laws and parametric investigation

This study invstigated and compared various constitutive laws, including a linear law, cure-hardening instantaneously linear elastic material (CHILE) law, a viscoelastic law, and a path dependent law on the development of the macroscale residual stress during manufacturing by finite element analysis. Considering the complexity of viscoelastic model, a simple model with various Maxwell elements was developed and validated against an analytical model to assess its accuracy. The simulations for composites using all the adopted models indicated that the development of residual stress mainly occurred during the cooling stage. The peak interlaminar normal residual stress (σ_zz) within the composites from different models were compared and analysed. Models using a viscoelastic law showed the most conservative residual stress in comparison with those based on the other three approaches. This difference was attributed to the simplification of the material behaviour used in the other laws. A parametric study based on the viscoelastic model was conducted to understand the influence of cure parameters on residual stress, which provided guidelines for optimising the cure protocol.