Interlaminar Failure Behavior of Continuous Carbon Fiber Reinforced PEEK Composites Fabricated by Additive Manufacturing: Role of Failure Modes and Operating Temperature

Abstract

Continuous carbon fiber reinforced PEEK (CCF/PEEK) composites manufactured using material extrusion additive manufacturing (MEX) show great promise for aerospace applications. However, the interlaminar failure mechanisms under different failure modes and operating temperatures are still not fully understood. This study systematically investigates the interlaminar fracture behavior of MEXed CCF/PEEK composites using double cantilever beam (DCB), three-point end-notched flexure (3ENF), and mixed-mode bending (MMB) tests, covering pure Mode-I, pure Mode-II, and mixed-mode loading conditions. In addition, Mode-I interlaminar fracture behavior is evaluated at 130°C and 230°C to assess temperature effects. Furthermore, finite element analysis (FEA) models incorporating a cohesive zone method are developed, using a combined quadratic stress criterion and Benzeggagh–Kenane (B–K) fracture criterion to simulate interlaminar failure. The results show that at room temperature, the Mode-I and Mode-II interlaminar fracture toughness values (GIC and GIIC) are 0.63 and 1.22 N/mm, respectively. The mixed-mode fracture analysis yields a B–K material parameter of 0.73, allowing successful construction of the complete interlaminar fracture envelope. At elevated temperatures, GIC increases to 1.35 N/mm (130°C) and 1.32 N/mm (230°C), attributed to the PEEK matrix's improved plastic deformation capability. The calibrated FEA models effectively replicate the observed interlaminar fracture behavior, allowing reliable interlaminar failure analysis of MEXed composites.