A 3D elasto-plastic damage model for fiber-reinforced polymer composites with fiber kinking: Formulation and efficient numerical implementation

A 3D elasto-plastic damage (EPD) model for fiber reinforced polymer (FRP) composites has been developed in this study, which integrates a new fiber kinking criterion based on plastic deformation theory and employs an efficient formulation for elasto-plastic updates. The 3D hydrostatic pressure-sensitive plasticity model is embedded into the fiber kinking criterion based on the proportional loading condition, accounting for the objectivity and hydrostatic pressure sensitivity in fiber rotation calculations. Moreover, a transversely isotropic damage constitutive model is constructed with an exponential damage evolution law dependent on the matrix fracture angle. In the elasto-plastic update process of the 3D hydrostatic pressure-sensitive plasticity model, a novel one-equation integration algorithm is developed through the application of variable substitution in the backward Euler implicit scheme. Compared with the direct seven-equation integration algorithm, this oneequation integration algorithm is greatly more efficient, and it could easily improve convergence because it involves only one nonlinear equation. The 3D EPD model is employed to predict the open-hole compression (OHC) strengths and damage patterns of FRP composites, corresponding well with experimental data and providing better accuracy than the model without plasticity. Particularly, the parametric study exhibits that fiber initial misalignments greatly influence the OHC performance and should be calculated accurately.