Buckling and compressive strength of laminates with optimized fiber-steering and layer-stacking for aerospace applications

The primary objective of design in aerospace composites is to minimize weight for a given loading requirement. For thin laminates subject to compression, this means ensuring sufficient buckling stiffness while maintaining material strength in the presence of in-service damage. In effect, stress levels (i.e., applied running load/laminate thickness) are maximized subject to buckling and strength requirements. Where buckling stresses for lightly loaded (thin) panels are relatively low, increased stiffening could be used to reduce effective panel widths, but this comes with increased manufacturing costs. A new manufacturing technique that incorporates in-plane steering of fibers to achieve curved, elastically tailored, tows is shown to offer improved efficiency by increasing the load carried in the vicinity of supports. However, such design needs to satisfy damage tolerance requirements. The use of a simple, analytical approach to damage tolerance enables the selection of optimum stacking sequences and shows the potential scope of using nonstandard ply orientations for even greater improvement over the current design practice.