Characterization and modelling of cure-dependent properties and strains during composites manufacturing

The geometric stability of structural parts is a critical issue in the aeronautical industry. However, autoclave curing of primary structural composite parts may cause significant distortions and divergences between the mould nominal geometries and the final shapes of the parts. To be able to anticipate such distortions, a robust simulation tool is needed, which can be implemented only if the phenomena involved are properly understood and characterized. The thermo-kinetic behaviour of the M21EV/IMA prepreg is fully characterized in this paper. Thermal strains and chemical shrinkages are measured using Thermo-Mechanical Analysis during the cure and the experimental method developed allows the thermo-chemical strains to be obtained even during the early stages of the cure. An experimental setup is developed to measure the thermo-mechanical behaviour of the material during its cure. Thanks to these measurements, a new constitutive mechanical model, inspired from the CHILE model, is defined. These data are then used as inputs for an FEA simulation of the entire curing process. Finally, the model is validated using the cure degree, glass transition and temperature monitoring, and post-cure distortion measurements.