A Temperature-Dependent Visco-Hyperelastic Constitutive Model for Carbon Fiber/Polypropylene Prepreg

This study first heat-treats the surface of plain-woven carbon fibers to remove the surface sizing. The treated carbon fibers were then hot-pressed with polypropylene films to produce a carbon fiber/polypropylene prepreg. The resulting prepreg was subjected to uniaxial and off-axis tensile tests, providing fundamental data for constructing a constitute model for the carbon fiber/polypropylene prepreg. The relative error between the model predictions and experimental data is maintained within ±10%. Based on the experimental results, a temperature-dependent viscoelastic–hyperelastic constitutive model for carbon fiber/polypropylene is proposed. This model decomposes the unit volume strain energy function into four components: matrix isochoric deformation energy, fiber tensile strain energy, fiber–fiber shear strain energy, and fiber-matrix shear strain energy. The matrix energy is strain rate-dependent, exhibiting viscoelastic mechanical behavior. The material parameters of the constitutive model were identified by fitting the experimental data. The model was implemented in MATLABR2024a, and off-axis tensile tests were performed at temperatures ranging from 423 K to 453 K. Numerical simulations were compared with experimental results to validate the model. This work provides guidance for the development and validation of constitutive models for thermoplastic polypropylene prepregs.