Prediction of stiffness and strength of non-crimp fabric reinforced composites at multiscales

To predict the mechanical behaviors of non-crimp fabric reinforced composites, hexagonal unit cell (UC) and rectangular UC were developed to represent the fiber tow and composite, respectively. The equation boundary condition of the fiber tow UC was derived in detail. The macro-scale effective stiffness and strength of a non-crimp carbon fabric reinforced epoxy composite was obtained by calculating the effective elastic constants of the two UCs at different length scales. Finite element damage analyses were performed to study the progressive failure of the composite in tension. Results show that the initial damage occurs in either the resin pockets or the transverse tows. Damage develops within the resin pockets and transverse tows, and progresses into the longitudinal tows and causes the composite failure very quickly. The predicted value of tensile modulus of the non-crimp fabric reinforced composite is very close to experimental value, and the calculated value of tensile strength is slightly less than that of experimental value.