The purpose of this paper is to investigate the use of equivalent-layer models for the analysis of finite-size carbon-fiber composite materials. A macroscopically equivalent model based on the homogenization technique, which is a more efficient method for analyzing fiber composite is investigated. Finite size composite slabs, consist of loose carbon fibers mixed with resins, are used to validate the equivalent models. Different thicknesses and sizes of the slabs, as well as relative volume of carbon fibers are considered. It is found that the breakdown frequencies of equivalent models vary significantly with the various geometries. It is important to validate the equivalent models of each finite-size composite block before simplifying them in the whole large structure model.