Modelling the Non-linear fibre and matrix dominated compressive behaviour in unidirectional Fibre-reinforced composites

Abstract

The mechanical behaviour of unidirectional fibre-reinforced composites is typically assumed to be linear elastic before failure. However, these materials exhibit nonlinear responses while being loaded in the matrix and fibre dominated directions that are generally disregarded. This research explores alternative physically-inspired finite element based modelling approaches that are formulated after the mechanisms behind such nonlinearities. The effect of fibre waviness/misalignment on the elastic modulus corresponding to the fibre direction has been investigated developing a phenomenological model based on the fibre micro-buckling theory. This model has been combined with the localisation plane plasticity, which deals with the matrix-dominated nonlinear deformation, for a complete description of the material’s mechanical behaviour. The proposed combined approach in a single model has shown to be capable of predicting the compressive stress-strain fibre- and matrix-dominated responses of IM7/8552 coupons at various loading rates.