Modelling of the in-plane shear behavior of uncured thermoset prepreg

The in-plane shear behavior of prepreg material is one of the key parameters that affect defect generation in composites manufacturing processes, like Automated Fiber Placement (AFP) and Thermoforming. Recently a new characterization method for the in-plane shear of uncured prepreg under processing conditions was proposed. A strong influence of test/deformation rate and temperature was revealed. The present contribution proposes a way forward for predictive modelling of the observed behavior. A phenomenological viscoelastic model at large deformation is proposed. Each of the model components relates to assumed physical micro-mechanical mechanisms such as friction between the fibers, tensile loading of the fibers, etc. The proposed model provides enough flexibility to be able to fit the experimental results well. It was then implemented into ABAQUS as a VUMAT user defined subroutine. Initial model verification was performed by comparing the FE prediction with the experimental data, which suggests that the model will be able to make accurate predictions of the in-plane shear behavior of prepreg under processing conditions for a wide range of temperatures and deformation rates.