Prediction of strength and modulus of discontinuous carbon fiber composites considering stochastic microstructure

Abstract

Modeling the mechanical behavior of discontinuous fiber composites has long been a challenge for the composites community and is of increasing interest due to recent interest for automotive lightweighting. Micromechanical models typically predict the stiffness accurately, but reliable strength models have been largely elusive due to the highly stochastic microstructure. This paper presents a stiffness and strength laminate analogy model for discontinuous fiber composites using stochastic fiber orientation, length, fiber volume fraction, and void volume fraction. For the first time, the master ply invariant approach has been applied to discontinuous fiber composites and shows good agreement in modeling the stiffness. A strain energy density-based laminate failure condition successfully predicts the tensile strength of these composites. This paper demonstrates accurate, first-order strength and stiffness predictions for discontinuous fiber composites using constituent properties readily obtained from material datasheets.