Multiphase Fea-Approach for Non-Linear Deformation Prediction and Fibre-Reinforced Plastics Failure

The study shows that the combination of several finite elements with different deformation models of continuum (elastic, elastic-plastic, isotropic and orthotropic) at common nodes makes it possible to predict complex nonlinear deformation of fibrous composites. There is considered only elastic deformation in the built-in libraries of anisotropic materials in well-known commercial FEA packages. Calculations of nonlinear mechanical behavior and failure under loading in the warp/weft and diagonal directions were performed on the example of fibreglass plastic STEF. Complex behavior of STEF is shown to be described by combining three phases with simple constitutive models: two brittle monotropic (imitate dry warp and weft fibers) and one isotropic elastic-plastic (imitate polymer). To determine the elasticity and fracture parameters of each model, it is proposed to apply experimental STEF stress-strain diagrams in the warp/weft and diagonal directions. The failure criteria for the above mentioned models are independent and are recorded in terms of strain. The strain mapping and damage development in STEF near the hole was studied by DIC and acoustic emission methods. ANSYS Workbench (Autodyn) software, critical distance theory, and failed finite element erosion technology were used to evaluate the fracture load of tensile specimens with a hole. The results of fracture loads and inelastic deformation fields calculations are in good agreement with the experimental data.