Stress evolution and deformation behavior of thermoplastic composite stiffened structures during the forming process

The stress evolution and demolding deformation behavior of thermoplastic composite components are crucial for performance and precision. In this paper, the stress evolution and deformation behavior of I-stiffened structures during cooling were studied by numerical prediction and experimental verification. Taking the effect of resin crystallization behavior on modulus into consideration, a resin time-varying modulus model was established, and the simulation results were compared with the existing Path-dependent model. The forming experiment of I-stiffened structures was carried out, and the simulation accuracy was verified. The results show that the internal stress distribution in most areas is uniform except for the trigonum after cooling; the stress values of the feature points including skin, corner, and trigonum of the Crystallinity model are 84.5, 169.5, and 60.7 MPa, respectively. The Crystallinity model has higher simulation accuracy and can better predict stress evolution and demolding deformation behavior. The error of stress values and deformation between the Crystallinity model and the experimental values is 9.3% and 5.1%. The research provides a useful reference for the control of residual stress and deformation behavior of complex thermoplastic composite components.Highlights The stress evolution and deformation behavior of I-stiffened structures was studied. A resin modulus model considering resin crystallization behavior was established. The combination sensor of "Thermocouple + FBG" is used to realize the online monitoring. A useful reference for the control of residual stress and deformation is provided.