Analysis of warping defect formation mechanisms in hot molding of CF/PEEK thin-wall structures and their influence on mechanical properties

The hot molding of carbon fiber-reinforced polyether ether ketone composites (CF/PEEK) thin-wall structures employs high cooling rates, which cause uneven material shrinkage across different parts and pronounced warping defects. This study fabricated CF/PEEK thin-wall laminates with a thickness of 1.2 mm through die-pressing technology and analyzed the effects of various cooling processes on plate warping. In addition, the study elucidated the formation mechanism of warping defects in CF/PEEK thin-wall structures and plotted a cooling rate curve to determine a strategy for effectively mitigating such defects. Notably, CF/PEEK hot molding warping involves an asynchronous contraction of molecular chains of crystalline polymers, leading to thermal residual stress. This study also investigated the effects of warpage on bending properties and stability. When warpage ranged from 10 to 15 mm, the maximum bending strength deviation along the plane was approximately 150 MPa, indicating that excessive warping substantially reduces bending strength. Moreover, laminates with minor warpage differences exhibited consistent performance stability. Overall, this study provides valuable insights for enhancing the forming quality of CF/PEEK, thereby promoting their application in advanced equipment.