Analysis of Longitudinal Compression Failure Behavior of Unidirectional CF/PEEK Composites

For the continuous carbon fiber-reinforced polyether ether ketone (CF/PEEK) composites fabricated via hot-press molding, its longitudinal compressive mechanical response and failure behavior are studied by combining tests and micromechanical finite element simulation approach. A finite element model incorporating matrix plasticity and damage, interfacial debonding, and fiber failure is developed to predict and analyze the stress-strain response, progressive damage evolution, and failure mechanisms of composite materials under longitudinal compression. The results indicate that the unidirectional CF/PEEK composite exhibits a nearly linear-elastic response up to the peak load, followed by rapid failure. Experimentally, the average compressive strength and elastic modulus are 915.4 MPa and 117.3 GPa, respectively. The finite element predictions show good agreement with the experimental data, with an error margin of approximately 10%, thereby verifying the accuracy and reliability of the established micromechanical model. The evolution of longitudinal compressive damage can be categorized into three stages: the elastic stage, the stage of matrix and interfacial damage development, and the final catastrophic failure stage. The ultimate failure mode is a mixed mechanism involving matrix cracking, interfacial debonding, and fiber shear fracture. As the primary load-bearing elements, the shear failure of fibers is identified as the dominant factor triggering the overall failure of the composite.