Shear Deformation and Forming Characteristics of Carbon Fiber Polypropylene Prepregs under Bias Extension Testing

The quality of molded fabric-reinforced thermoplastic composites with intricate geometries is significantly influenced by the in-plane shear properties of fabric prepreg. This study delves into the characterization of shear deformation during CF/PP prepreg forming. Initially, bias extension tests were conducted under varying temperature, loading rates, and layup configurations to elucidate the macroscopic shear forces and shear deformations of the prepreg. Subsequently, the shear deformation mechanism was then revealed based on experimental data, highlighting the diverse loading conditions. Finally, an analysis unveiled the influence of temperature, loading rate, and multilayered prepregs on shear deformation, revealing key mechanisms within the molding temperature range. Results indicated that within this range, prepreg shear deformation resistance increased with higher layup counts and loading speeds but decreased with elevated temperatures. When the temperature increased from 150 to 210 °C, the shear force to achieve shear lock decreased from 32.3 to 13.6N. When the loading speed increased from 5 to 20 mm/min, the shear force to achieve shear locking increased by 23%. Notably, the diminishing impact on shear deformation resistance followed the order: temperature, loading speed, and layup number. Furthermore, the bias-extension tensile test provided insights into the prepreg's shear deformation mechanism, offering crucial theoretical support for defect mitigation in the hot molding process of carbon fiber prepreg.