In the analysis of thick composite structures by the finite-element method there are some techniques which are used to determine the material properties. In order to determine material constants of a multi-layered composite element, the most commonly used method is to take an average value for element material properties. A finite-element analysis program was developed to analyze multi-layer composite beams and plates. In addition to the arithmetic average, a new method, called the weighted average method, was developed. By considering different loading conditions, one of the averaging methods was utilized. The effects of two averaging methods on the results were investigated. The results were compared with the analytical solutions. Both methods gave matching results for certain types of loading. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.