A coupled 3D hyper-viscoelastic constitutive model for thin woven composite prepregs in preforming and consolidation

The prepreg compression molding (PCM) has emerged as an effective method for mass production of woven composite parts with complex geometry. The two coupling effects between non-uniform thickness deformation and yarn angle variation, viscoelastic compaction modulus and yarn angle variation due to preforming, which are often neglected in existing models, are actually critical in correct prediction for quality of final composite parts. To address these issues, a coupled 3D hyper-viscoelastic constitutive model was developed, and its efficacy was validated through bias-extension tests, confirming its capability to account for the coupling effect related to initial thickness variations caused by yarn angle change. Additionally, out-of-plane compaction deformation tests demonstrated the model's ability to incorporate variations in compaction material properties under different yarn angles, further affirming its applicability. To further test performance of the constitutive model, benchmark single-dome PCM experiments were conducted with thin woven prepregs. Comparative analysis of experimental and modeling results revealed the superb prediction accuracy of the model for part geometry and yarn angle distribution, respectively, after PCM. Furthermore, this new model significantly decreases the relative error of thickness prediction to 11.7 % compared to that of 34.2 % of the previous decoupled model. As a result, this newly established model can effectively capture the coupled material responses throughout the preforming and consolidation stages, assisting more realistic representation of the PCM process.