Predicting failure behaviour of short glass fiber reinforced PEEK composites using anisotropic elastoplastic constitutive model

Short glass fiber reinforced polyether-ether ketone (SGF/PEEK) composites exhibit significant mechanical anisotropy due to the preferential fiber orientation induced during processing. In this study, a constitutive model is developed to describe the anisotropic elastoplastic behavior of SGF/PEEK based on a comprehensive experimental investigation of SGF/PEEK composites under complex stress states. The experimental program includes uniaxial tensile tests on specimens with different orientations and biaxial tensile tests using optimized cruciform specimens. Based on the experimental data, three yield criteria were calibrated for incorporation into the constitutive model. The results indicate that the Yld2004-18p model provides the most accurate predictions of yield strength, plastic flow, and ultimate strength by effectively capturing mechanical anisotropy, with prediction errors for yield strength, tensile strength, and r-value all remaining below 2%. Subsequently, a maximum stress failure criterion was incorporated to further capture the fracture behavior. The coupled model predicted a biaxial tensile failure stress of 84 MPa. Validation against experimental results for biaxial tensile tests of both cruciform and notched specimens confirms that the framework effectively captures anisotropic elastoplastic deformation and fracture evolution, including crack initiation and propagation paths under complex stress states. This work provides a reliable simulation tool for performance assessment and failure prediction of SGF/PEEK structures under complex loading conditions, which expands its application prospects in demanding engineering environments.