Symmetric, balanced cross-ply and diagonal-ply laminates. Global elastic properties and internal stresses
Jan Lewiński, Andrzej Wilczyński
Quarterly No. 1, 2010 pages 41-45
DOI:
keywords: cross-ply laminate, constitutive equations, global constants of elasticity, conditions
abstract In the work, research has been taken up on the problem of lead elimination from presently very popular technical Journal Composites [1] presented a paper by T. Niezgoda and M. Klasztorny, giving predicted values of elastic constants for a special case of balanced laminates. The present paper is influenced by the idea from the mentioned work, where the described case can be obtained without the use full methods of the theory of lamination, employing instead simple engineering techniques, which in turn can be solved symbolically and can bring a better understanding of the problems of lamination. The relations given here show the step by step procedure of obtaining the necessary elasticity relations and stress values. The main aim in presenting this paper is twofold. Primarily the employed methods are easy to understand and useful in the cases of first contact with the theory of lamination. Secondly, the method of obtaining presented results for diagonal-ply laminates, using a simple rotation of coordinates, is unique and to the Authors knowledge has not been published up to now. There are also other reasons for presenting this paper for not only there are insufficient data to follow the original procedure but also there is an error in the called literature, which now here is presented as [2]. Unfortunately this paper obtained by personal communication does not help much. Another item in this presentation is giving the exact, useful values of material constants for a diagonal laminate, together with values of acting stresses for this case, which may be of further use. As a result the present paper gives a detailed explanation of the procedure used in the homogenization process, shows application of this method to another commonly used composite and presents useful values of internal stresses, which decide on strength of the structure.