FE-BASED PREDICTION OF PROCESS INDUCED DISTORTIONS AND RESIDUAL STRESSES FOR CFRP FRAMES

This paper deals with a simulation strategy for the prediction of process-induced distortions and residual stresses of composite frames. The mechanical material behavior is described by a viscoelastic material model depending on temperature and degree of cure. For the description of the reaction kinetic a phenomenological based model considering chemical and diffusion-controlled reactions is introduced. To this, reaction model parameters are fitted to isothermal and dynamic DSC measurements. The thermal expansion and chemical shrinkage are characterized by thermal mechanical analysis and using the contact angle measurement method. The required mechanical material parameters are derived by dynamic mechanical analyses. The simulation strategy is demonstrated for a CFRP frame of an aircraft fuselage. Based on a sequentially coupled temperature-displacement analysis temperature and degree of cure distributions are determined. Corresponding process-induced distortions and occurring residual stresses are calculated and analyzed. The results of the process-induced distortions are used to derive a compensated tooling design. An analogous simulation with the compensated design shows the applicability of this approach