Experimental and Numerical Assessment of Progressive Damage in CF / PEEK Laminates Under Monotonic and Progressive Cyclic Four‐Point Bending

ABSTRACT

Carbon‐fiber‐reinforced PEEK composites combine high specific strength, corrosion resistance, and damage tolerance, supporting their use in aerospace, energy, and offshore applications. This work presents an integrated experimental, analytical, and numerical investigation of CF/PEEK thermoplastic laminates under quasi‐static and progressive cyclic four‐point bending, considering four stacking sequences: [0] ₉ , [±35] ₅ , [±55] ₅ , and [90] ₉ . Classical lamination theory was used to predict bending stiffness and first‐ply failure, while a Hashin‐based progressive damage model, calibrated through intralaminar fracture energies, was used to capture stiffness degradation, load redistribution, and final collapse under monotonic loading. Maximum Strain and Hashin first‐ply failure predictions were also assessed. The calibrated model reproduced the experimental peak loads with deviations up to 4.3% for the [0] ₉ , [±55] ₅ , and [90] ₉ laminates, whereas the [±35] ₅ layup was overpredicted by 32.8%, reflecting the non‐linear shear response of the PEEK matrix that is not captured by the linear‐elastic Hashin formulation. For the nominal antisymmetric angle‐ply sequences, torsion‐free and torsion‐restrained CLT predictions coincide; B coupling changes bending stiffness by less than 1%. Cyclic tests revealed marked stiffness degradation in matrix‐dominated [±35] ₅ and [±55] ₅ layups, in contrast to the brittle response of fiber and matrix‐aligned configurations. The calibration provides a common parameter set for the three layups governed by fiber or transverse matrix stresses; the shear‐dominated [±35] ₅ response requires extended constitutive treatment.