OPTIMUM FIBER ANGLE OF UNIDIRECTIONAL COMPOSITES FOR LOAD WITH VARIATIONS

Optimum fiber orientations of unidirectional composite materials under probabilistic loading conditions are found to be different from those under deterministic loading conditions. A simple and intuitive method called the interior tangent ellipsoid (ITE) method is proposed for optimum design of composites under the action of loads with variations. This method uses an analytical approach and enables a clear interpretation of the optimum orientation angles for probabilistic conditions. A comparison between the ITE method and the advanced first-order second-moment (AFOSM) method is made, and good agreements on optimum fiber orientations are observed. The computation time for the ITE method is much less than the time for the AFOSM method. It is concluded that the proposed method is valid for determining the optimum fiber angles of unidirectional composites under probabilistic loading conditions and the resulting optimum designs are much different from those under deterministic conditions.