Prediction of Autoclave Curing of Aeronautical Composites Parts and of Resulting Spring-IN

Composite materials based on thermoset matrix are commonly used for manufacturing of aeronautics structures. These materials require after draping a polymerization in an autoclave. The curing stage done under controlled atmosphere induces internal stresses and geometrical distortions that can conduct to the part rejection.

This paper presents end to end simulation that takes into account the influence of the autoclave process and material phase evolution during curing on the quality of the final part.

The analysis is done in 2 phases: the first phase is a fluid dynamics analysis used to simulate gas flow and thermal exchange in the autoclave. The second phase is a thermo-chemical mechanical analysis where geometrical deformations and residual stresses are computed.

Thermal history of a composite part during its autoclave cycle will depend on many parameters like, gas flow velocity and gas temperature evolution, autoclave loading, thermal response of the tooling and exothermy of the reaction. Results of this first step simulation will be to generate an accurate thermal field history and degree of cure history in the composite part taking into accounts all these effects.

During curing step, generation of geometric distortions and residual stresses are directly linked to material thermal expansion and chemical shrinkage due to cross linking reaction. A biphase model is used which takes into account the change in material state (from rubbery to glassy) during the curing step. Material evolution is then used to compute expansionnal strains which can lead to residual stresses and shape distortion.

Results obtained with ESI composites simulation solution will then be compared to different cases manufactured using aeronautic process from SAMC.