Fibre placement of 20% compared with the baseline cylinder, i.e. 589 kNm versus 488 kNm. The global response (Figure 5a) and the strain distribution, plotted as a function of the vertical coordinate in Figure 5b, showed good agreement between the finite-element analysis (FEA) and the experimental (Exp) results. The extreme tensile and compressive strain values of the variable-stiffness cylinder were lower than those of the baseline cylinder at any given load level. Strength constraints in the aerospace industry are often based on maximum strain values, which means that the variable-stiffness cylinder would have an advantage over the baseline cylinder. Conclusions Variable-stiffness laminates can be used to increase the structural efficiency of a composite structure by redistributing loads. A few variables are needed to design a variable-stiffness composite, which can be manufactured using fibre placement. Many challenges for the design, analysis and validation of variable-stiffness composites still exist, but the potential for weight reduction makes variablestiffness composites a candidate to become the composite aerospace structure of the future. Fig. 5: Analytical and experimental results of the variable-stiffness and the baseline cylinder More information: www.fokker.com No58 June - July 2010 / jec composites magazine 41http://www.fokker.com http://www.webindustries.com