Estimation of the axial tensile modulus of a particle-reinforced composite fiber with variable radius

The modulus of a fiber is difficult to measure, especially when the radius of the fiber changes along the length. The use of an arithmetic average radius or volume average radius to calculate fiber modulus leads to an underestimate of the modulus. A model for measuring and calculating the true tensile modulus of a fiber that has large radius variation is proposed. The model has been used to calculate the modulus of a Wollastonite particle-reinforced polypropylene fiber. The difference between the modulus calculated from the model and that from either the arithmetic or volume-average radius increases linearly as the coefficient of variation (CV) of the fiber radius increases, especially when CV< 5%. When the evenness of the fiber increases, i.e. CV → 0, the difference between the three methods for calculating the axial tensile modulus is negligible.