Estimation of axial compressive strength of unidirectional carbon fiber-reinforced plastic considering the variability of fiber misalignment

The analytical method to calculate the axial compressive stress-strain relation of a unidirectional carbon fiber -reinforced plastic (UD CFRP) was presented considering the variability of the fiber misalignment angle. Because the compressive load-bearing capability of fibers surrounded by a matrix was different depending on the fiber misalignment angle, fibers were grouped based on the misalignment angle. The contribution to the load bearing was calculated and summed based on the area ratio of the fiber groups. All fibers supported a compressive load in the initial loading. However, with increased loading, the load-bearing capabilities of the different fiber groups decreased more dramatically with greater misalignment angles. The fibers with a misalignment angle of 0.5 degrees showed a large load drop after their maximum loading, which triggered the ultimate failure. The variability of the fiber misalignment angle was indispensable to determining the axial compressive strength under the assumption of zero mean fiber misalignment angle.