Enhanced Tensile Properties of Drilled Thermoplastic <scp>CF</scp>/<scp>PEEK</scp> Composite Laminate Using Heat Treatment Methods

ABSTRACT Thermoplastic carbon fiber reinforced polyetheretherketone (CF/PEEK) composite materials have broad application prospects in the aerospace field due to their unique recyclability and reusability. This paper proposes a novel heat treatment method aimed at enhancing the tensile properties of drilled CF/PEEK composite laminates based on crystallinity control. The crystallinity of the thermoplastic CF/PEEK composite plays a pivotal role in determining its mechanical properties. The nonisothermal crystallization kinetics of the CF/PEEK composite indicate that the composites have the longest crystallization time and the highest crystallinity at a cooling rate of 2°C/min, which provides a basis for the selection of furnace cooling for heat treatment. The combined heat treatment conducted at 320°C can increase the tensile load of the laminate by up to 25.68%. Digital image correlation technology is used to track the deformation and strain distribution in drilled CF/PEEK samples during the tensile process. Investigation of the tensile failure modes of the drilled laminate indicates fiber fracture and intralaminar failure as the primary mechanisms, with heat treatment effectively strengthening the polymer matrix and, consequently, enhancing the overall tensile performance of the laminates. This research provides valuable insights and practical guidance for optimizing the drilled thermoplastic composites in various industrial applications.