Fiber-reinforced composite materials have been used very widely and have emerged as a major class of structural materials in recent years and are either used or being considered as substitutes for metals in many weight-critical components in aerospace and other industries1. In most practical applications the material parameters vary considerably and are subject to uncertainties, mainly due to the uncontrollable aspects associated with the manufacturing process. The probabilistic methods cannot be applied easily since the probability distributions of the uncertain parameters are not known. Also, in some situations, the parameters of a composite material are known only in linguistic form. Hence fuzzy concepts are introduced in this work to model the uncertainties encountered in composite material mechanics, which may be described in linguistic terms or in imprecise form as fuzzy parameters. Numerical examples are given to demonstrate the feasibility and applicability of the approach presented.