Multi-level finite element analysis for progressive damage behavior of HA/PEEK composite porous structure

A three-dimensional multi-level finite element (FE) modeling approach has been developed to simulate mechanical response and progressive damage behavior of hydroxyapatite/polyetheretherketone (HA/PEEK) porous structures separately under tensile and compressive loadings. Moreover, the densification of the HA/PEEK porous structures under compressive loading was also simulated. Nonlinear constitutive relations of the HA/PEEK composites coupled with both matrix and interfacial debonding damage were determined by using a micro-level FE unit cell model. A Kelvin open-cell model composed of solid beams was used for constructing a meso-level FE model, which was the basic unit for building the porous structure. The relative density of the meso-level model was varied for mimicking different porosity levels. For simulating the progressive damage behavior of the porous structure from initiation to failure, a strain invariant failure criterion for the beams was incorporated into the meso-level FE model. A beam-to-beam self-contact model was adopted to describe the contact behaviors of the beam elements. Six case examples were used for investigating the effects of considering the micro-level composite damage behavior and failure criterion of the beam elements on the mechanical response of the porous structures separately under tensile and compressive loadings. With the proposed method considering both composite damage and beam failure, the predicted tensile and compressive stress-strain responses of the porous structure, including elastic, plateau and densification characteristics under compressive loading, agreed well with the related experimental data in open literature.