A Viscoelastic‐Plastic Model for the Through‐Thickness Creep/Recovery Behavior of Dry Fiber Fabric Preforms Considering Ply‐Angle Difference Ratio

ABSTRACT In the manufacturing of fiber‐reinforced composites, different stacking configurations are commonly adopted in dry fabric preforming, while the resulting inter‐ply angle difference ratio can affect the through‐thickness deformation of the preform. Dry fabrics also exhibit time‐dependent and irreversible deformation during compaction, which should be considered for accurate prediction of preform thickness evolution. In this work, a unified viscoelastic‐plastic constitutive model is developed to describe the through‐thickness creep/recovery behavior of dry CF3031 twill‐weave fabric preforms by incorporating the ply‐angle difference ratio into the constitutive coefficients through a nonlinear weighting function. Creep/recovery tests were conducted on 21‐ply preforms with 20 inter‐ply interfaces at 0.3 MPa and 25°C, including 3 h creep and approximately 1 h stress‐free recovery. The proposed model was established by combining a Burgers viscoelastic representation with a Bingham element to account for recoverable time‐dependent deformation and irreversible compaction deformation, respectively. The identified constitutive parameters showed good agreement with the experimental results, with R 2 values ranging from 0.9846 to 0.9967. The model was further implemented in ABAQUS through a user‐defined material subroutine to simulate the complete loading, creep, unloading, and creep‐recovery process. The results demonstrate that the proposed model can capture the stage‐wise through‐thickness deformation evolution and the effect of ply‐angle difference ratio under the investigated conditions, providing a constitutive basis for the numerical analysis and process optimization of dry fabric preforming.