On fiber curvature effects in the analysis of unidirectionally reinforced composite structures

This paper studies the question whether or not neglecting fiber curvature e ffects in mean field methods - in particular the Mori-Tanaka method - used for describing the material laws of matrix-fiber composites leads to signif icantly erroneous results, when they are used in the analysis of axisymmetr ical composite structures or structures reinforced by curved aligned contin uous fibers. For comparison an exact analytical solution for a layered cylinder under th ermo-mechanical loading is derived, which can serve as a model for circumfe rentially reinforced cylindrical composite structures. For obtaining furthe r comparative results, classical lamination theory and a computational hexa gonal cell tiling concept are employed. It is shown that in most cases the micromechanical effects resulting from t he curvature of the fibers are negligible as far as the global, i.e., struc tural, thermo-mechanical behavior is concerned. Accordingly, the use of mic romechanical methods based on the Mori-Tanaka approach appears to be justif ied for composites with curved aligned reinforcements provided the radius o f curvature is very large in comparison with the fiber diameter, an assumpt ion which is fulfilled in nearly all cases. (C) 2000 Elsevier Science S.A. All rights reserved.