Laminate stiffness tailoring for improved buckling performance

Abstract

This article presents an algorithm to tailor bending stiffness properties for double angle-ply laminates. A database of orthotropic double angle-ply laminates is derived for non-crimp fabric configurations, highlighting the severity of this manufacturing constraint compared to the use of single unidirectional layers. The significance of the new algorithm is demonstrated through the development of a range of new laminate designs, all with matched isotropic bending stiffness properties, allowing the isolated effects of axial stiffness to be studied, in this case to improve the critical length at which the transition from local to overall mode instability occurs in thin walled columns. Many of the non-crimp fabric designs can be tapered in thickness, through ply terminations, without introducing undesirable thermo-mechanical coupling behaviour. These configurations can now be matched to either bending or extensional stiffness of equivalent balanced and symmetric laminate designs, which are shown to occupy only specific, ply number dependent regions within the design space. This is demonstrated for typical aircraft components, to identify configurations with improved buckling performance.