Failure prediction of a new sandwich panels based on flax fibres reinforced epoxy bio-composites

Abstract Flax fibres reinforced polymer composites are more and more used in various fields such as transportation due to the low density of flax paired up with good mechanical properties. This calls for a better understanding and prediction of the mechanical behaviour of such composites. In this study, the mechanical behaviour of flax fibres fabric reinforced polymer composites has been studied experimentally and numerically for composite laminates and for Omega stiffened Sandwich Panels. Composites laminates plies exhibited a strong non-linear mechanical behaviour due to the particular structure of flax fibres which is investigated. Likewise, the omega sandwich panels presented the same behaviour and high strength making them competitive with conventional glass fibres reinforced polymer composite sandwich panels used in aeronautics. A material model is proposed to describe the four phases non-linear behaviour that has been implemented to get a predictive finite element model (FE) .Different damage laws have been identified calibrated and implemented as a UMAT routine to get a predictive finite element model (FE). The composite flax ply model includes diffuse damage, failure damage and residual strain. The material model has been validated for many stacking sequences. The finite element model including the four phase behaviour up to damage and failure is demonstrate to reproduce the crack locations and buckling zones and amplitudes of the omega panel under tension and three points bending.