Theoretical prediction, simulation and test validation of ultimate turning radius for prepregs in variable angle placement

The planar force model of prepreg, initially established based on the principle of minimum potential energy and the Rayleigh-Ritz method, was improved by considering the difference between the tensile and compressive moduli in the direction of the prepreg fibers. Compressive-tensile stress distribution coefficients were also established. Combined with tests on the effect of process parameters on interlayer tack, a theoretical prediction model for the turning radius related to process parameters was developed, and the impact of prepreg interlayer tack force on the minimum turning radius was analyzed. A finite element simulation model for prepreg curve placement was created to study the size and distribution patterns of folds generated during the prepreg turning process. A minimum turning radius test was conducted to establish evaluation criteria for surface defects in curve placement and verify the accuracy of the minimum turning radius prediction model. Based on this, a prediction method for the minimum turning radius of prepreg related to process parameters was established, providing constraints for the trajectory design of variable-stiffness placement composites.