A theoretical model with experimental verification for bending stiffness of thermosetting prepreg during forming process

Capturing the out-of-plane properties using a suitable experimental method and combination of constitutive models and modelling techniques is required to improve forming simulation outcomes for composite prepregs, with the ultimate aim of predicting and optimizing forming processes. This paper proposes a theoretical model for bending behavior of woven fabric-based out-of-autoclave prepregs under conditions relevant to forming process. Time and temperature dependencies are considered by means of time-temperature superposition in a linear viscoelastic material model. A new approach for considering the testing rate and temperature with respect to a reference value is also established. Experimental tests are carried out for estimation of the model parameters and validation of the proposed model. A special bending test setup is utilized to allow for adequate control of testing rates and temperatures as well as viscoelastic investigations. A good agreement between the predicted bending stiffness and the experimental values was observed. The model and experimental results reveal that the processing temperature has the strongest influence on the bending property results.