Application of micromechanical models for elasticity and failure to short fibre reinforced composites. Numerical implementation and experimental validation

This paper deals with numerical modelling of the mechanical behaviour of short fibre reinforced plastic composites manufactured by the injection moulding process. First of all, an experimental program has been carried out in which the local fibre orientation distribution has been measured in an 80x80x2mm injected plate by means of polished cut sections, analysed with SEM and image processing software. Tensile and three-point bending tests have been performed to obtain the elastic and strength response of the material in different locations along the plate and at two directions (parallel and normal to the flow direction). Analytical micromechanical models and averaging procedures have been implemented to relate the local fibre orientation distribution with the effective local anisotropic response of the material (elastic and strength). The models are validated by means of the finite element simulation of the performed characterisation tests. Finally, the methodology is applied to an injection moulded component with complex geometry. Fibre orientation data predicted with mould-flow software has been used to determine the local effective elastic stiffness and strength coefficients. A FE simulation of the functional behaviour of the component has been carried out. Results indicate that the proposed variable stiffness/strength anisotropic model predicts a lower load for onset of failure than when applying an equivalent isotropic material model.