Micromechanical Analysis of Variable Angle Tow Composites Considering Uncertainties in Constituents

Fibre reinforced polymers are commonly used for hydrogen tanks, which operate under a range of temperatures, pressures, and levels of hydrogen permeation. This working environment can affect the mechanical properties of the composite mostly through the matrix. This study investigates the impact of uncertainties in constituents on the homogenised properties of fibre reinforced composite at the ply-scale. The uncertainties of the mechanical properties of individual carbon fibres and epoxy resin are incorporated into micromechanical analysis models to investigate the probabilistic distribution of the mechanical characteristics of unidirectional (UD) composites and variable angle tow (VAT) composites. The elastic moduli of composites determined from Ansys Representative Volume Element (RVE) models are compared to those derived from the rules of mixtures (ROM), modified rule of mixtures (MROM), Bridging micromechanics model, Halpin–Tsai, Mori–Tanaka, and macroscale experiments to verify the precision of simulations. The RVE models effectively predict the variation of UD and VAT stiffness. In addition, Young’s modulus of the VAT ply shows the most sensitivity to the uncertainty of matrix and fibre where the fibre angles range from 0° to 20° for E_x. Monte Carlo simulations for the UD composites show that E₁ (Elastic modulus aligned with the fibre) is more sensitive to the uncertainty of fibre while E₂ (Elastic modulus transverse to the fibre direction) is more sensitive to matrix variations.