Buckling and compressive strength of laminates with optimized fibre-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 whilst 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 which incorporates in-plane steering of fibres 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 for which effective stress levels may approach those in high strength aluminium alloy.