Experimental and Theoretical Study on the Viscoelastic Compression Properties of Unidirectional Prepreg Laminate

ABSTRACT The compression of composite preforms fabricated through automated layup techniques directly impacts fiber arrangement and geometric structure. To investigate how compression parameters affect unidirectional prepreg composites, this paper proposes two viscoelastic models. The first model features a variable‐stiffness spring and two Maxwell units to depict the compression‐relaxation behavior of layered unidirectional prepreg under pressure. The second model integrates a variable‐stiffness spring with two Voigt units to represent creep behavior. Unidirectional prepreg samples were prepared using automated fiber placement technology and subsequently subjected to compression experiments with varying ply thicknesses, orientations, compression strokes, speeds, forces, and material temperatures. These experiments affect the mechanical response of unidirectional preforms under pressure. The proposed method effectively captures stress and strain evolution during compression, accurately describing the response of automated layup preforms. Experimental results align closely with predictions, showing a correlation coefficient R ² over 0.98 and a root mean square error (RMSE) under 0.1, validating the model's accuracy. This approach offers a computational method for studying the mechanical response of automated layup preform deformation under compression.